DESCARTES/IlUSTRACIÓN

FUENTE http://www.csudh.edu/phenom_studies/western/lect_8.html
1. The relation of Descartes to the philosophy of Enlightenment
In France and in England, all the philosophical thoughts from the middle of 17th century through the 18th century were under Descartes’s influences.
Fontenelle (1657-1757)
The admirer of Descartes’ physics and his radical rationalism threatened the Christianity and the established Church. Fontenelle’s philosophy did not accept the Cartesian spiritualism and overemphasized the positive elements of the Cartesian philosophy. Thus, Fontenelle merely criticized the Ancient oracles as superstition, but this was immediately applied to the miracles of Christianity.
Bayle (1647-1706)
Starting with the Cartesian rationalism, Bayle considered that to believe in Christianity means to abandon Reason and the human rationality and to surrender to the miraculous phenomena. The opposition between philosophy (rationalism) and religion set up by Bayle created an anti-religious movement against Christianity as well as prepared for the development of the 18th Century philosophy.
The Enlightenment Movement in France is a synthesis of the Cartesian philosophy of the mechanistic understanding of nature and the British Empiricism.
In the 17th century, British philosophers such as Bacon, Hobbes and Locke came to France and were strongly influenced by the French Philosophies. In the 18th century, the French philosophers visited England and were strongly influenced by the British Empiricism and advocated empiricism rather than idealism in France upon their return.

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Published in: on January 18, 2012 at 10:14 pm  Leave a Comment  

sociedad del siglo XVII en tiempos de Descartes

http://www.genbriand.com.ar/siglo_17.htm

(FRagmento) Sí, en el período comprendido entre 1601 y 1700 todavía mucha gente creía que la Tierra era el centro del Universo. Y que todos los cuerpos celestes giraban alrededor. La gente creía en la astrología, que aún no estaba muy separada de la astronomía, y la química apenas se diferenciaba de la alquimia. La evolución del ser humano no tenía otra alternativa que el creacionismo bíblico. Esas cosas ni siquiera se discutían. Sin embargo, es en este siglo donde se da el gran salto hacia la modernidad, hacia el principio de lo que hoy es la ciencia. Es un siglo de mentes brillantísimas e ilustres, en todos los ámbitos. No corresponden a un movimiento filosófico homogéneo, son más individualistas que los renacentistas, pero comienzan a plantearse el mundo sobre bases firmes. El Renacimiento había traído el fin de las viejas estructuras, de una sociedad teocrática, totalmente regida por la Iglesia. Al poner una nueva visión del mundo con acento especial en el ser humano, deja también un gran vacío. Si nada se puede explicar tan fácilmente por la fé, entonces, cuáles es la real interpretación de la naturaleza? Es por eso que en este siglo comienza a funcionar el motor de los grandes cerebros, hacia la fundación de los cimientos de la ciencia. Descartes, Galileo, Leibnitz, Hume, Torricelli, Sir Isaac Newton, son sólo algunos de los nombres que comenzarán a revolucionar el mundo del conocimiento moderno. Es un siglo en el que todo se plantea de nuevo: las formas adquieren más elaboración, más detalles. Nace el barroco, en música y en arquitectura. El hombre comienza a dar sus primeros más importantes pasos en la comprensión de su universo. Ahora, guiados por un principio básico: la confianza en la Razón humana.

Published in: on January 18, 2012 at 10:04 pm  Leave a Comment  

filosofía moderna, conceptos básicos

FUENTE http://fr.wikipedia.org/wiki/Histoire_de_la_philosophie

Una “filosofía moderna”, que cubre lo que los historiadores llaman la Edad Moderna (desde 1.492 hasta 1.789). Esta filosofía es, en primer lugar, el heredero del pensamiento antiguo de muchas maneras. Los escritores modernos están lejos de haber roto todas las relaciones con la filosofía de los antiguos, que conocían perfectamente el contrario, a veces prestado su vocabulario. Por otro lado, los modernos a menudo han diseñado su propio trabajo como una mejora de lo que los filósofos de la antigüedad ya había hecho, que a veces les llevó a oponerse a ellos.
Este deseo de volver a la filosofía de los antiguos parece mejorar, desde el Renacimiento, a través del movimiento humanista. Se continúa en el siglo XVII, cuando la ciencia moderna surgió, y donde los grandes filósofos a menudo se aprenden en la ciencia (Descartes, Pascal, Leibniz), es entonces los principales enfoques de conocimiento que distinguen a los dos las principales tendencias que son el racionalismo (Descartes, Leibniz) y el empirismo (Hume, Locke). Durante el mismo período, la expansión de la filosofía política moderna, empezando por el hombre tal cual es y no lo que debería ser (Maquiavelo, Hobbes, Spinoza).
Pero también incluye la filosofía moderna, desde finales del siglo XVII, la Ilustración, que se adjunta a disipar las tinieblas del oscurantismo y la ignorancia por el triunfo de la razón y educar a la gente, especialmente a través del proyecto enciclopédico (en Alembert, Diderot), sino también por la elaboración de una filosofía política que hace hincapié en la democracia, la tolerancia y la soberanía del pueblo (Spinoza, Locke, Rousseau Voltaire). Esto creará la filosofía política del liberalismo y el republicanismo.
El Renacimiento [editar]

Published in: on January 18, 2012 at 9:43 pm  Leave a Comment  
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contexto de Descartes

FUENTE http://www.cvm.qc.ca/encephi/CONTENU/ARTICLES/modernit%C3%A9.htm

La modernité philosophique et le projet moderne

par Martin Godon, du cégep du Vieux Montréal

Introduction

Au XVIIe siècle, on assiste à divers bouleversements dans le monde de la pensée. On remet alors en question les autorités du passé ainsi que la tradition. Dans ce contexte, les croyances religieuses et les superstitions prennent une nouvelle dimension. Désormais, elles ne concernent que la vie personnelle. En conséquence, les dogmes de la foi n’ont plus à intervenir dans le cadre du développement de la pensée. Cette révolution est le fruit d’un lent et long processus qui s’amorce dès la fin du Moyen Âge, s’accélérant et se précisant à la Renaissance, et il conduit certains penseurs modernes à s’opposer à ceux qui veulent rester fidèles aux idéaux du passé.

Principales caractéristiques

Chronologiquement, l’époque moderne succède à la Renaissance. Le mot « moderne » vient du latin modernus et signifie : qui est récent. L’attitude intellectuelle qui caractérise la pensée moderne joue encore un rôle dominant dans notre société. Mais la modernité est tout d’abord un phénomène de civilisation caractérisé par une révolution intellectuelle majeure, elle-même stimulée par un développement technologique sans précédent. Les progrès du transport, l’apparition de l’imprimerie et l’urbanisation vont faciliter la circulation des connaissances. Dès lors, la référence à la tradition va prendre un sens nouveau. Ainsi, les penseurs modernes vont jusqu’à s’opposer explicitement aux idées religieuses ou traditionnelles qui dominaient à l’époque précédente.

Ouvert à la nouveauté, on tente alors de construire une représentation du monde à partir de nouveaux fondements, de nouveaux paradigmes (paradigme: modèle). Par exemple, on abandonne la représentation géocentrique du cosmos (Système de Ptolémée) pour une construction héliocentrique de l’univers (N. Copernic). Bref, la terre n’est plus le centre du monde.

Les progrès technologiques qui caractérisent la naissance de la modernité vont également favoriser la transformation de la vie économique, sociale et politique. Graduellement, une économie industrielle va se développer. Cette forme de production et de distribution s’inspire d’une des principales valeurs de la pensée moderne : l’efficacité. Sur le plan proprement philosophique, la notion relativement nouvelle d’individu rationnel et autonome, affirmant de plus en plus sa liberté de conscience (Luther) et d’action face au féodalisme religieux d’abord, politique ensuite, constitue un terreau favorable à la vision industrielle et capitaliste du monde.

La pensée moderne va trouver de nouveaux fondements dans ces valeurs d’efficacité technique et instrumentale et de liberté. Elle va notamment valoriser particulièrement les pouvoirs de notre raison. C’est donc en elle-même que la pensée moderne va trouver les nouveaux fondements métaphysiques qu’elle cherche. Cela signifie qu’on attribue à la subjectivité un rôle fondamental dans le processus de la connaissance. Autrement dit, la vérité ne correspond plus ni à une révélation divine ou mystique, ni à une croyance très ancienne. Dorénavant, on admet comme vérité uniquement ce qui peut faire l’objet d’un examen critique par la raison, par suite d’une démonstration strictement rationnelle. Le concept de modernité philosophique désigne cette nouvelle manière de penser ainsi que la nouvelle hiérarchie de valeur qui en découle. On peut donc dire de cette époque qu’elle est l’ère de la raison triomphante.

Qu’on pense à René Descartes (1596-1650), Thomas Hobbes (1588-1679), John Locke (1632-1704), Baruch Spinoza (1632-1677), Gottfried Wilhelm Leibniz (1646-1716), David Hume (1711-1776) et bien d’autres encore, les philosophes modernes sont préoccupés à un très haut degré par le sens de leur démarche et par la rigueur et l’exactitude de leur système. Dans ce contexte, les mathématiques puis les sciences de la nature vont souvent monopoliser les énergies. Les modernes croient, parfois aveuglément, au pouvoir libérateur de la science. Voilà pourquoi c’est à cette dernière qu’on va demander de produire une société d’individus libres de toutes contraintes.

La raison

Parce qu’ils ne tiennent plus compte de la révélation, de la foi et de la croyance religieuse comme critère de vérité, les penseurs modernes ne considèrent plus l’univers comme un monde rempli de mystères insondables. Concrètement, la pensée moderne n’accepte que les explications qui sont rationnelles. Cette autonomie de la raison constitue la principale caractéristique de la pensée moderne. Le monde n’est plus une structure sacrée, mais une réalité intelligible dont on peut découvrir les lois par une observation rigoureuse et méthodique. Bref, on croit que l’univers obéit à des lois rationnelles. C’est-à-dire que les lois qui déterminent la nature sont conformes aux lois qui déterminent la pensée. Par ailleurs, les penseurs modernes considèrent que chaque être humain possède la capacité de raisonner. Toute personne, en principe, peut donc comprendre les lois qui gouvernent la nature. Pour cela, il suffit de se donner la peine de réfléchir rationnellement, de bien conduire sa raison pour trouver quelque vérité, comme dit Descartes.

Puisque chaque individu possède la capacité de raisonner convenablement, les penseurs modernes vont croire que tous les humains sont égaux. En conséquence, ils vont inviter chaque humain à se servir de sa pensée afin de se libérer du pouvoir de toute forme d’autorité arbitraire. Par sa raison, l’individu possède donc une dignité qui lui est propre et en vertu de laquelle on ne lui demande plus d’être immolé au profit de puissances qui le dépassent. Pour le penseur moderne, le moi (ou encore l’individu ou la subjectivité) et tout ce qui s’y rattache prend donc une valeur primordiale, presque sacrée.

Cependant, il ne faut pas croire que les intellectuels modernes ont inventé la raison ou la rationalité. Il ne faut pas oublier que depuis leur naissance, la philosophie et les sciences favorisent la pensée rationnelle. Mais, soit la raison était un outil parmi d’autres, soit la raison obéissait, du moins en partie, à d’autres principes que les siens propres. Ce qui est distinctif de la pensée moderne c’est l’invention d’une nouvelle attitude intellectuelle selon laquelle la raison obéit exclusivement à des règles qu’elle s’est données elle-même en toute rigueur dans le but d’établir des liens indubitables entre les causes et les effets observables dans la nature ou entre les idées et les réalités auxquelles elles correspondent. On nomme cette attitude intellectuelle le rationalisme et il va susciter un grand enthousiasme pour toute une catégorie de penseurs. Le rationalisme conduit le penseur à chercher des certitudes qui peuvent être expliquées rationnellement hors de tout doute, tandis que dans les siècles passés, les penseurs cherchaient souvent, tant par l’usage de la raison que par d’autres outils, des vérités révélées de type interprétatif.

Pour le rationalisme cartésien, la nature est uniquement composée de matière et elle fonctionne comme une machine, c’est-à-dire que l’univers est strictement régi par des forces mécaniques qui sont également soumises aux lois de la raison. On peut dire que la raison semble avoir pris possession de tout dans l’univers tel qu’il est conçu par les rationalistes. Ceux-ci découvrent aussi que les lois de la nature peuvent être exprimées en langage mathématique. Autrement dit, on prend conscience que la matière et les forces mécaniques à l’œuvre dans la nature sont mesurables. Ainsi, grâce aux mathématiques on va pouvoir lire le grand livre de la nature.

Le projet moderne

Nicolas Copernic (1473-1543), Johannes Kepler (1571-1630), Isaac Newton (1642-1723), Galilée (1564-1642) et tous les scientifiques modernes cherchent à comprendre l’univers dans un but bien précis. Il s’agit de devenir, selon l’expression de Descartes, maître et possesseur de la nature par l’usage de la raison, cela afin d’améliorer le sort des êtres humains. On peut parler du projet moderne : par le progrès des sciences et des arts, les penseurs modernes souhaitaient libérer l’humain de ses souffrances et de ce qui l’aliène. On influence donc le développement des forces productives en vue d’une domination des phénomènes naturels par la science et la technique. Les philosophes et les scientifiques modernes croyaient que ce développement du savoir et de la technologie devait nécessairement produire une amélioration de nos conditions sociales et politiques. Le projet moderne est donc à la fois philosophique, scientifique et sociopolitique. Ce désir de libération grâce aux bienfaits de la science et de la technologie donne lieu à un renouveau scientifique sans précédent. Trois éléments caractérisent ce renouveau :

a) Un travail d’observation méthodique : afin de comprendre et de dominer la nature, il faut travailler avec rigueur, ce qui signifie l’observation méthodique des phénomènes naturels. S’ajoute à cela la validation des théories et des hypothèses par un travail méticuleux d’expérimentation. L’exactitude des conceptions théoriques doit permettre de dominer tout processus naturel ou social qui asservit l’être humain.

b) L’unité des sciences : par l’usage commun des mathématiques, les scientifiques modernes envisagent les sciences comme un arbre. Ainsi, puisque les sciences partagent le même langage, on en vient à imaginer un ordre hiérarchique des sciences et des connaissances, les mathématiques constituant le tronc auquel se rattachent les branches des diverses sciences.

c) Des progrès et inventions multiples : grâce à l’observation méthodique et un travail rigoureux, on assiste à de nombreuses découvertes théoriques qui vont souvent conduire à diverses inventions pratiques ayant pour but d’améliorer le sort de la condition humaine. Ici s’incarne l’idée maîtresse du projet moderne, celle d’un « Progrès Libérateur ». Dans ce contexte, l’efficacité et la productivité sont des valeurs extrêmement positives. Les penseurs modernes ne concevaient pas le côté déshumanisant que l’on attribue souvent à ces valeurs aujourd’hui.

Il ne faut surtout pas oublier que c’est l’usage rigoureux de la raison qui seul peut rendre possible ce progrès libérateur. On utilise désormais le concept de rationalité instrumentale pour désigner cette attitude de la pensée qui est exclusivement orientée vers le développement technoscientifique.

Conclusion

Finalement, la modernité va transformer la vie politique occidentale. Puisque tous sont aptes à se servir de leur raison, tous doivent avoir le droit de s’exprimer et doivent se partager les rênes du pouvoir. Les modernes vont donc, peu à peu, essayer de remplacer les formes de pouvoir fondées sur la violence et l’arbitraire par la démocratie.

Dans presque toutes les activités scientifiques, artistiques et intellectuelles de cette époque, on va assister à une lutte féroce entre ceux qui défendent les traditions et ceux qui font la promotion des idées nouvelles. Cette opposition a culminé en littérature dans ce que les historiens ont appelé la querelle des Anciens et des Modernes. Du côté des Anciens on compte Nicolas Boileau (1636-1711), Jean de Lafontaine (1621-1695), Jean Racine (1639-1699), Jean de La Bruyère (1645-1696), tandis qu’on peut classer Charles Perrault (1628-1703), Thomas Corneille (1625-1709) et Fontenelle (1657-1757) dans le rang des Modernes.

Sommairement, on peut dire que l’ère moderne s’achève au début du vingtième siècle. Cependant, dès le début du dix-neuvième siècle, des philosophes vont rejeter le projet moderne. Durant le vingtième siècle, les critiques vont devenir de plus en plus radicales. Ceux qu’on nomme parfois les penseurs postmodernes vont chercher à montrer que si la pensée rationnelle a produit le progrès promis, en revanche, ce progrès ne s’est pas avéré libérateur; que la raison ne peut pas être totalement fiable, digne de confiance; que la pensée moderne a rendu notre monde terne et gris, qu’elle est donc responsable du désenchantement du monde.

© CVM, 2003

Published in: on January 18, 2012 at 9:37 pm  Leave a Comment  
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epistemología de Descartes ( inglés )

FUENTE http://plato.stanford.edu/entries/descartes-epistemology/
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Descartes’ Epistemology
First published Wed Dec 3, 1997; substantive revision Tue Jul 20, 2010

René Descartes (1596–1650) is widely regarded as the father of modern philosophy. His noteworthy contributions extend to mathematics and physics. This entry focuses on his philosophical contributions in the theory of knowledge. Specifically, the focus is on the epistemological project of Descartes’ famous work, Meditations on First Philosophy. Upon its completion, the work was circulated to other philosophers for their comments and criticisms. Descartes responded with detailed replies that provide a rich source of further information about the original work. He indeed published the first edition (1641) of the Meditations together with six sets of objections and replies, adding a seventh set with the second edition (1642).

* 1. Conception of Knowledge
o 1.1 Analysis of Knowledge
o 1.2 Internalism and Justification
o 1.3 Indefeasibility in Context
o 1.4 Methodist Approach
o 1.5 Innate Ideas
* 2. Methods: Foundationalism and Doubt
o 2.1 Foundationalism
o 2.2 Method of Doubt
* 3. First Meditation Doubting Arguments
o 3.1 Dreaming Doubt
o 3.2 Evil Genius Doubt
* 4. Cogito Ergo Sum
o 4.1 The First Item of Knowledge
o 4.2 But is it Knowledge?
* 5. Epistemic Privilege and Defeasibility
o 5.1 Our Epistemic Best: Clear and Distinct Perception and its Defeasibility
o 5.2 The Epistemic Privilege of Judgments About the Mind
* 6. Cartesian Circle
o 6.1 Establishing the Divine Guarantee of the C&D Rule
o 6.2 Circularity and the Broader Argument
* 7. Proving the Existence of the External Material World
o 7.1 The Case for the Externality of the Causes of Sensation
o 7.2 The Case for the Materiality of the Causes of Sensation
* 8. Proving that One is Not Dreaming
* Bibliography
* Other Internet Resources
* Related Entries

1. Conception of Knowledge
1.1 Analysis of Knowledge

Famously, Descartes defines knowledge in terms of doubt. While distinguishing rigorous knowledge (scientia) and lesser grades of conviction (persuasio), Descartes writes:

I distinguish the two as follows: there is conviction when there remains some reason which might lead us to doubt, but knowledge is conviction based on a reason so strong that it can never be shaken by any stronger reason. (1640 letter, AT 3:64–65)

Elsewhere, while answering a challenge as to whether he succeeds in founding such knowledge, Descartes writes:

But since I see that you are still stuck fast in the doubts which I put forward in the First Meditation, and which I thought I had very carefully removed in the succeeding Meditations, I shall now expound for a second time the basis on which it seems to me that all human certainty can be founded.

First of all, as soon as we think that we correctly perceive something, we are spontaneously convinced that it is true. Now if this conviction is so firm that it is impossible for us ever to have any reason for doubting what we are convinced of, then there are no further questions for us to ask: we have everything that we could reasonably want. … For the supposition which we are making here is of a conviction so firm that it is quite incapable of being destroyed; and such a conviction is clearly the same as the most perfect certainty. (Replies 2, AT 7:144–45)

These passages (and others) clarify that Descartes understands doubt as the contrast of certainty. As my certainty increases, my doubt decreases; conversely, as my doubt increases, my certainty decreases. The requirement that knowledge is to be based in complete, or perfect certainty, amounts to requiring a complete absence of doubt — an indubitability, or inability to undermine one’s conviction. Descartes’ methodic emphasis on doubt, rather than on certainty, marks an epistemological innovation. This so-called ‘method of doubt’ will be discussed below (Section 2).

The certainty/indubitability of interest to Descartes is psychological in character, though not merely psychological — not simply an inexplicable feeling. It has also a distinctively epistemic character, involving a kind of rational insight. During moments of certainty, it is as if my perception is guided by “a great light in the intellect” (Med. 4, AT 7:59). This rational illumination empowers me to “see utterly clearly with my mind’s eye”; my feelings of certainty are grounded — indeed, “I see a manifest contradiction” in denying the proposition of which I’m convinced. (Med. 3, AT 7:36)

Should we regard Descartes’ account as a version of the justified true belief analysis of knowledge tracing back to Plato? The above texts (block quoted) are among Descartes’ clearest statements concerning the brand of knowledge he seeks. Yet they raise questions about the extent to which his account is continuous with other analyses of knowledge. Prima facie, his characterizations imply a justified belief analysis of knowledge — or in language closer to his own (and where justification is construed in terms of unshakability), an unshakable conviction analysis. There’s no stated requirement that the would-be knower’s conviction is to be true, as opposed to being unshakably certain. Is truth, therefore, not a requirement of Descartes’ brand of strict knowledge?

Many will balk at the suggestion. For in numerous texts Descartes writes about truth, even characterizing a “rule for establishing the truth” (Med. 5, AT 7:70, passim). It might therefore seem clear, whatever else is the case, that Descartes conceives of knowledge as advancing truth. Without denying this, let me play devil’s advocate. It is not inconsistent to hold that we’re pursuing the truth, even succeeding in establishing the truth, and yet to construe the conditions of success wholly in terms of the certainty of our conviction. Thus construed, to establish a proposition just is to perceive it with certainty; the result of having established it — i.e., what gets established — is the proposition’s truth. Note again that Descartes says, of the perfect certainty he seeks, that it provides “everything that we could reasonably want,” adding (in the same passage):

What is it to us that someone may make out that the perception whose truth we are so firmly convinced of may appear false to God or an angel, so that it is, absolutely speaking, false? Why should this alleged “absolute falsity” bother us, since we neither believe in it nor have even the smallest suspicion of it? (Replies 2, AT 7:144–45)

On one reading of this remark, Descartes is explicitly embracing the consequence of having defined knowledge wholly in terms of unshakable conviction: he’s conceding that achieving the brand of knowledge he seeks is compatible with being — “absolutely speaking” — in error. If this is the correct reading, the interesting upshot is that Descartes’ ultimate aspiration is not absolute truth, but absolute certainty.

On a quite different reading of this passage, Descartes is clarifying that the analysis of knowledge is neutral not about truth, but about absolute truth: he’s conveying that the truth condition requisite to knowledge involves truth as coherence.

A definitive interpretation of these issues has yet to gain general acceptance in the literature. What is clear is that the brand of knowledge Descartes seeks requires, at least, unshakably certain conviction. Perhaps this seeming preoccupation with having the right kind of certainty — including its being available to introspection — is linked with an internalist conception of knowledge.
1.2 Internalism and Justification

One way to divide up theories of justification is in terms of the internalism-externalism distinction. Very roughly: a theory of epistemic justification is internalist insofar as it requires that the justifying factors are accessible to the knower’s conscious awareness; it is externalist insofar as it does not impose this requirement.

Descartes’ internalism requires that all justifying factors take the form of ideas. For he holds that ideas are, strictly speaking, the only objects of immediate perception, or conscious awareness. (More on the directness or immediacy of perception in Section 5.2.) Independent of this theory of ideas, Descartes’ methodical doubts underwrite an assumption with similar force: for almost the entirety of the Meditations, his meditator-spokesperson — hereafter referred to as the ‘meditator’ — adopts the assumption that all his thoughts and experiences are occurring in a dream. This assumption is tantamount to requiring that justification come in the form of ideas.

An important consequence of the interpretation here being developed — namely, a traditional representationalist reading of Descartes — is that rigorous philosophical inquiry must proceed via an inside-to-out strategy. This strategy is assiduously followed in the Meditations, and it endures as a hallmark of many early modern epistemologies. Ultimately, all judgments are grounded in an inspection of the mind’s ideas. Philosophical inquiry is, properly understood, an investigation of ideas. The methodical strategy of the Meditations has the effect of forcing readers to adopt this mode of inquiry.

In recent years, some commentators have questioned this traditional way of understanding the mediating role of ideas in Descartes’ philosophy. Noteworthy in this regard is John Carriero’s outstanding commentary on the Meditations (2009) which provides a challenge to the kind account developed in the present essay.
1.3 Indefeasibility in Context

In characterizing knowledge as “incapable of being destroyed,” Descartes portrays knowledge as enduring. Our conviction must be, writes Descartes, “so strong that it can never be shaken”; “so firm that it is impossible for us ever to have any reason for doubting.” Descartes wants a brand of certainty/indubitability that is of the highest rank, both in terms of degree and durability. He wants knowledge that is utterly indefeasible. (Sceptical doubts count as defeaters.)

This indefeasibility requirement implies more than mere stability. A would-be knower could achieve stability simply by never reflecting on reasons for doubt. But this would result in mere undoubtedness, not indubitability. Referring to such a person, Descartes points out that although a reason for “doubt may not occur to him, it can still crop up if someone else raises the point or if he looks into the matter himself” (Replies 2, AT 7:141).

Many readers conclude that Descartes’ standards of justification are too high, for they have the consequence that almost nothing we ordinarily count as knowledge measures up. Before jumping to this conclusion, we should put the indefeasibility requirement into context.

Descartes is a contextualist in the sense that he allows that different standards of justification are appropriate to different contexts. This is not merely to say the obvious: that depending on the context of inquiry, knowledge-worthy justification will sometimes be needed, but other times not. It’s to say something stronger: that depending on the context of inquiry, the standards of knowledge-worthy justification might vary. For example, a contextualist might accept that ‘knowledge’-talk is equally appropriate whether one is describing the best achievements of empirical science, or the best achievements of mathematics, while acknowledging that the former rest on weaker standards of proof than the latter. This example is potentially misleading, in that Descartes appears loath to count mere empirical evidence as knowledge-worthy justification. But upon ramping up the standard to what he finds minimally acceptable, the standard admits of context dependent variation.

Descartes’ minimum standard targets the level of certainty arising when the mind’s perception is both clear and distinct. (For Descartes, clarity contrasts with obscurity, and distinctness contrasts with confusion.) He allows that judgments grounded in clear and distinct perception are defeasible (at least, for those who’ve not yet read the Meditations). But he regularly characterizes defeasible judgments at this level of certainty using terminology (e.g., ‘cognitio’ and its cognates) that translates well into the English ‘knowledge’ (and its cognates).

In the context of inquiry at play in the Meditations, Descartes insists on indefeasibility. (Typically, he reserves the term ‘scientia’ for this brand of knowledge, though he uses ‘cognitio’ and its cognates for either context.) Descartes’ aim is, once and for all, to lay a lasting foundation for knowledge. To achieve this, he contends that we “cannot possibly go too far in [our] distrustful attitude” (Med. 1, AT 7:22). Better to have a standard that excludes some truths, than one that justifies some falsehoods.

An interesting thesis emerges — call it the ‘No Atheistic Knowledge Thesis’. Descartes maintains that though atheists are quite capable of impressive knowledge, including in mathematics, they are incapable of the indefeasible brand of knowledge he seeks:

The fact that an atheist can be “clearly aware [clare cognoscere] that the three angles of a triangle are equal to two right angles” is something I do not dispute. But I maintain that this awareness [cognitionem] of his is not true knowledge [scientiam], since no act of awareness [cognitio] that can be rendered doubtful seems fit to be called knowledge [scientia]. Now since we are supposing that this individual is an atheist, he cannot be certain that he is not being deceived on matters which seem to him to be very evident (as I fully explained). (Replies 2, AT 7:141)

Hereafter, I refer to the indefeasible brand of knowledge Descartes seeks as ‘Knowledge’ (uppercase ‘K’).
1.4 Methodist Approach

How is the would-be Knower to proceed in identifying candidates for Knowledge? Distinguish particularist and methodist responses to the question. The particularist is apt to trust our prima facie intuitions regarding particular knowledge claims. These intuitions may then be used to help identify more general epistemic principles. The methodist, in contrast, is apt to distrust our prima facie intuitions. The preference is instead to begin with general principles about proper method. The methodical principles may then be used to arrive at settled, reflective judgments concerning particular knowledge claims.

Famously, Descartes is in the methodist camp. Those who haphazardly “direct their minds down untrodden paths” are sometimes “lucky enough in their wanderings to hit upon some truth,” but “it is far better,” writes Descartes, “never to contemplate investigating the truth about any matter than to do so without a method” (Rules 4, AT 10:371). Were we to rely on our prima facie intuitions, we might suppose it obvious that the earth is unmoved, or that ordinary objects (as tables and chairs) are just as just as they seem. Yet, newly emerging mechanist doctrines of the 17th century imply that these suppositions are false. Such cases underscore the unreliability of our prima facie intuitions and the need for a method by which to distinguish truth and falsity.

Descartes’ view is not that all our pre-reflective intuitions are mistaken. He concedes that “no sane person has ever seriously doubted” such particular claims as “that there really is a world, and that human beings have bodies” (Synopsis, AT 7:16). But pre-reflective such judgments may be ill-grounded, even when true.

The dialectic of the First Meditation features a confrontation between particularism and methodism, with methodism emerging the victor. For example, the meditator (while voicing empiricist sensibilities) puts forward, as candidates for the foundations of Knowledge, such prima facie obvious claims as “that I am here, sitting by the fire, wearing a winter dressing-gown, holding this piece of paper in my hands, and so on” — particular matters “about which doubt is quite impossible,” or so it would seem (AT 7:18). In response (and at each level of the dialectic), Descartes invokes his own methodical principles to show that the prima facie obviousness of such particular claims is insufficient to meet the burden of proof.
1.5 Innate Ideas

Descartes’ commitment to innate ideas places him in a rationalist tradition tracing back to Plato. Knowledge of the nature of reality derives from ideas of the intellect, not the senses. An important part of metaphysical inquiry therefore involves learning to think with the intellect. Plato’s allegory of the cave portrays this rationalist theme in terms of epistemically distinct worlds: what the senses reveal is likened to shadowy imagery on the wall of a poorly lit cave — what the intellect reveals is likened to a world of fully real beings illuminated by bright sunshine. The metaphor aptly depicts our epistemic predicament on Descartes’ own doctrines. An important function of his methods is to help would-be Knowers redirect their attention from the confused imagery of the senses, to the luminous world of the intellect’s clear and distinct ideas.

Further comparisons arise with Plato’s doctrine of recollection. The Fifth Meditation meditator remarks — having applied Cartesian methodology, thereby discovering innate truths within: “on first discovering them it seems that I am not so much learning something new as remembering what I knew before” (Med. 5, AT 7:64). Elsewhere Descartes adds, of innate truths:

[W]e come to know them by the power of our own native intelligence, without any sensory experience. All geometrical truths are of this sort — not just the most obvious ones, but all the others, however abstruse they may appear. Hence, according to Plato, Socrates asks a slave boy about the elements of geometry and thereby makes the boy able to dig out certain truths from his own mind which he had not previously recognized were there, thus attempting to establish the doctrine of reminiscence. Our knowledge of God is of this sort. (1643 letter, AT 8b:166–67)

The famous wax thought experiment of the Second Meditation is supposed to illustrate (among other things) a procedure to “dig out” what is innate. The thought experiment purports to help the meditator achieve a “purely mental scrutiny,” thereby apprehending more easily the innate idea of body. (Med. 2, AT 7:30–31) According to Descartes, our minds come stocked with a variety of intellectual concepts — ideas whose content derives solely from the nature of the mind. This storehouse includes ideas in mathematics, logic, and metaphysics. Interestingly, Descartes holds that even our sensory ideas involve innate content. On his understanding of the new mechanical physics, bodies have no real properties resembling our sensory ideas of colors, sounds, tastes, and the like, thus implying that the content of such ideas draws from the mind itself. Unlike purely intellectual concepts, however, the formation of these sensory ideas depends on sensory stimulation. Elsewhere (2006), I argue that on Descartes’ official doctrine, ideas are innate insofar as their content derives from the nature of the mind alone, as opposed to deriving from sense experience. This characterization allows that both intellectual and sensory concepts draw on native resources, though not to the same extent.

Though the subject of rationalism in Descartes’ epistemology deserves careful attention, the present essay generally focuses on Descartes’ efforts to achieve indefeasible Knowledge. Relatively little attention is given to his doctrines of innateness, or, more generally, his ontology of thought.

Further reading: On the internalism-externalism distinction, see Alston (1989) and Plantinga (1993). For a partly externalist interpretation of Descartes, see Della Rocca (2005). For coherentist interpretations of Descartes’ project, see Frankfurt (1970) and Sosa (1997a). For a stability interpretation of Descartes, see Bennett (1990). On the indefeasibility of Knowledge, see Newman and Nelson (1999). On contextualism in Descartes, see Newman (2004). On the methodism-particularism distinction, see Chisholm (1982). On Descartes’ rationalism, see Adams (1975), Jolley (1990), and Newman (2006).
2. Methods: Foundationalism and Doubt

Of his own methodology, Descartes writes:

Throughout my writings I have made it clear that my method imitates that of the architect. When an architect wants to build a house which is stable on ground where there is a sandy topsoil over underlying rock, or clay, or some other firm base, he begins by digging out a set of trenches from which he removes the sand, and anything resting on or mixed in with the sand, so that he can lay his foundations on firm soil. In the same way, I began by taking everything that was doubtful and throwing it out, like sand … (Replies 7, AT 7:537)

The theory whereby items of knowledge are best organized on an analogy to architecture traces back to ancient Greek thought — to Aristotle, and to work in geometry. That Descartes’ method effectively pays homage to Aristotle is, of course, welcome by his Aristotelian audience. But Descartes views Aristotle’s foundationalist principles as incomplete, at least when applied to metaphysical inquiry. I suggest that his method of doubt is intended to complement foundationalism. The two methods are supposed to work in cooperation, as conveyed in the above quotation. Let’s consider each method.
2.1 Foundationalism

The central insight of foundationalism is to organize knowledge in the manner of a well-structured, architectural edifice. Such an edifice owes its structural integrity to two kinds of features: a firm foundation and a superstructure of support beams firmly anchored to the foundation. A system of justified beliefs might be organized by two analogous features: a foundation of unshakable first principles, and a superstructure of further propositions anchored to the foundation via unshakable inference.

Exemplary of a foundationalist system is Euclid’s geometry. Euclid begins with a foundation of first principles — definitions, postulates, and axioms or common notions — on which he then bases a superstructure of further propositions. Descartes’ own designs for metaphysical Knowledge are inspired by Euclid’s system:

Those long chains composed of very simple and easy reasoning, which geometers customarily use to arrive at their most difficult demonstrations, had given me occasion to suppose that all the things which can fall under human knowledge are interconnected in the same way. (Discourse 2, AT 6:19).

It would be misleading to characterize the arguments of the Meditations as unfolding straightforwardly according to geometric method. But Descartes maintains that they can be reconstructed as such, and he expressly does so at the end of the Second Replies — providing a “geometrical” exposition of his central constructive steps, under the following headings: definitions, postulates, axioms or common notions, and propositions (AT 7:160ff).

As alluded to above, the Meditations contains a destructive component that Descartes likens to the architect’s preparations for laying a foundation. Though the component finds no analogue in the method of the geometers, Descartes appears to hold that this component is needed in metaphysical inquiry. The discovery of Euclid’s first principles (some of them, at any rate) is comparatively unproblematic: such principles as that things which are equal to the same thing are also equal to one another (one of Euclid’s axioms) accord not only with reason, but with the senses. In contrast, metaphysical inquiry might have first principles that conflict with the senses:

The difference is that the primary notions which are presupposed for the demonstration of geometrical truths are readily accepted by anyone, since they accord with the use of our senses. Hence there is no difficulty there, except in the proper deduction of the consequences, which can be done even by the less attentive, provided they remember what has gone before. … In metaphysics by contrast there is nothing which causes so much effort as making our perception of the primary notions clear and distinct. Admittedly, they are by their nature as evident as, or even more evident than, the primary notions which the geometers study; but they conflict with many preconceived opinions derived from the senses which we have got into the habit of holding from our earliest years, and so only those who really concentrate and meditate and withdraw their minds from corporeal things, so far as possible, will achieve perfect knowledge of them. (Replies 2, AT 7:156–57)

Among Descartes’ persistent themes is that such preconceived opinions can have the effect of obscuring our mental vision of innate principles; that where there are disputes about first principles, it is not “because one man’s faculty of knowledge extends more widely than another’s, but because the common notions are in conflict with the preconceived opinions of some people who, as a result, cannot easily grasp them”; whereas, “we cannot fail to know them [innate common notions] when the occasion for thinking about them arises, provided that we are not blinded by preconceived opinions” (Prin. 1:49–50, AT 8a:24). These “preconceived opinions” must be “set aside,” says Descartes, “in order to lay the first foundations of philosophy” (1643 letter, AT 8b:37). Unless they are set aside, we’re apt to regard — as first principles — the mistaken (though prima facie obvious) sensory claims that particularists find attractive. Such mistakes in the laying of the foundations weaken the entire edifice. Descartes adds:

All the mistakes made in the sciences happen, in my view, simply because at the beginning we make judgements too hastily, and accept as our first principles matters which are obscure and of which we do not have a clear and distinct notion. (Search, AT 10:526)

Though foundationalism brilliantly allows for the expansion of knowledge from first principles, Descartes thinks that a complementary method is needed to help us discover genuine first principles. He devises the method of doubt for this purpose — a method to help “set aside” preconceived opinions.
2.2 Method of Doubt

Descartes opens the First Meditation asserting the need “to demolish everything completely and start again right from the foundations” (AT 7:17). The passage adds:

Reason now leads me to think that I should hold back my assent from opinions which are not completely certain and indubitable just as carefully as I do from those which are patently false. So, for the purpose of rejecting all my opinions, it will be enough if I find in each of them at least some reason for doubt. (AT 7:18)

In the architectural analogy, we can think of bulldozers as the ground clearing tools of demolition. For Knowledge building, Descartes construes sceptical doubts as the ground clearing tools of epistemic demolition. Bulldozers undermine literal ground; doubt undermines epistemic ground. Using sceptical doubts, the meditator shows us how to find “some reason for doubt” in all our preexisting opinions.

Descartes’ ultimate aims, however, are constructive. Unlike “the sceptics, who doubt only for the sake of doubting,” Descartes aims “to reach certainty — to cast aside the loose earth and sand so as to come upon rock or clay” (Discourse 3, AT 6:28–29). Bulldozers are typically used for destructive ends, as are sceptical doubts. Descartes’ methodical innovation is to employ demolition for constructive ends. Where a bulldozer’s force overpowers the ground, its effects are destructive. Where the ground’s firmness resists the bulldozer’s force, the bulldozer might be used constructively — using it to reveal the ground as firm. Descartes’ innovation is to use epistemic bulldozers in this way. He uses sceptical doubts to test the firmness of candidates put forward for the foundations of Knowledge.

According to at least one prominent critic, this employment of sceptical doubt is unnecessary and excessive. Writes Gassendi:

There is just one point I am not clear about, namely why you did not make a simple and brief statement to the effect that you were regarding your previous knowledge as uncertain so that you could later single out what you found to be true. Why instead did you consider everything as false, which seems more like adopting a new prejudice than relinquishing an old one? This strategy made it necessary for you to convince yourself by imagining a deceiving God or some evil demon who tricks us, whereas it would surely have been sufficient to cite the darkness of the human mind or the weakness of our nature. (Objs. 5, AT 7:257–58; my italics)

Here, Gassendi singles out two features of methodic doubt — its universal and hyperbolic character. In reply, Descartes remarks:

You say that you approve of my project for freeing my mind from preconceived opinions; and indeed no one can pretend that such a project should not be approved of. But you would have preferred me to have carried it out by making a “simple and brief statement” — that is, only in a perfunctory fashion. Is it really so easy to free ourselves from all the errors which we have soaked up since our infancy? Can we really be too careful in carrying out a project which everyone agrees should be performed? (Replies 5, AT 7:348)

Evidently, Descartes holds that the universal and hyperbolic character of methodic doubt is helpful to its success. Further appeal to the architectural analogy helps elucidate why. Incorporating these features enables the method to more effectively identify first principles. Making doubt universal and hyperbolic helps to distinguish genuine unshakability from the mere appearance of it.

Consider first the universal character of doubt — the need “to demolish everything completely and start again right from the foundations” (Med. 1, AT 7:17). The point is not merely to apply doubt to all candidates for Knowledge, but to apply doubt collectively. Descartes offers the following analogy:

Suppose [a person] had a basket full of apples and, being worried that some of the apples were rotten, wanted to take out the rotten ones to prevent the rot spreading. How would he proceed? Would he not begin by tipping the whole lot out of the basket? And would not the next step be to cast his eye over each apple in turn, and pick up and put back in the basket only those he saw to be sound, leaving the others? In just the same way, those who have never philosophized correctly have various opinions in their minds which they have begun to store up since childhood, and which they therefore have reason to believe may in many cases be false. They then attempt to separate the false beliefs from the others, so as to prevent their contaminating the rest and making the whole lot uncertain. Now the best way they can accomplish this is to reject all their beliefs together in one go, as if they were all uncertain and false. They can then go over each belief in turn and re-adopt only those which they recognize to be true and indubitable. (Replies 7, AT 7:481)

That even one falsehood would be mistakenly treated as a genuine first principle — say, the belief that the senses are reliable, or that ancient authorities should be trusted — threatens to spread falsehood to other beliefs in the system. A collective doubt helps avoid such mistakes. It ensures that the method only approves candidate first principles that are unshakable in their own right: it rules out that the appearance of unshakability is owed to logical relations with other principles, themselves not subjected to doubt.

How is the hyperbolic character of methodic doubt supposed to contribute to the method’s success? The architectural analogy is again helpful. Suppose that an architect is vigilant in employing a universal/collective doubt. Suppose, further, that she attempts to use bulldozers for constructive purposes. A problem nonetheless arises. How big a bulldozer is she to use? A light-duty bulldozer might be unable to distinguish a medium-sized boulder, and immovable bedrock. In both cases, the ground would appear immovable. The solution lies in using not light-duty, but heavy-duty tools of demolition — the bigger the bulldozer, the better. The lesson is clear for the epistemic builder: the more hyperbolic the doubt, the better.

A potential problem remains. Does not the problem of the “light-duty bulldozer” repeat itself? No matter how firm one’s ground, would it not be dislodged in the face of a yet bigger bulldozer? This raises the worry that there might not be unshakable ground, but only that which is yet unshaken. Descartes’ goal of utterly indubitable epistemic ground may simply be elusive.

Perhaps the architectural analogy breaks down in a manner that serves Descartes well. For though there is no most-powerful literal bulldozer, perhaps epistemic bulldozing is not subject to this limitation. Descartes seems to think that there is a most-powerful doubt — a doubt than which none more hyperbolic can be conceived. The Evil Genius Doubt (and equivalent doubts) is supposed to fit the bill. If the method reveals epistemic ground that stands fast in the face of a doubt this hyperbolic, then, as Descartes seems to hold, this counts as epistemic bedrock if anything does.

Hence the importance of the universal and hyperbolic character of the method of doubt. Gassendi’s suggestion that we forego methodic doubt in favor of a “simple and brief statement to the effect that [we’re] regarding [our] previous knowledge as uncertain” misses the intended point of methodic doubt.

Before turning attention to the First Meditation demolition project, I want to address what I believe are significant misconceptions about the method of doubt. Two of these are suggested in a passage from the pragmatist Peirce:

We cannot begin with complete doubt. We must begin with all the prejudices which we actually have when we enter upon the study of philosophy. These prejudices are not to be dispelled by a maxim [viz., the maxim that the philosopher “must begin with universal doubt”], for they are things which it does not occur to us can be questioned. Hence this initial skepticism will be a mere self-deception, and not real doubt … A person may, it is true, in the course of his studies, find reason to doubt what he began by believing; but in that case he doubts because he has a positive reason for it, and not on account of the Cartesian maxim. Let us not pretend to doubt in philosophy what we do not doubt in our hearts. (1955, 228f)

It is a misconception that universal doubt is intended to result from the mere effort to adhere to the maxim — as if by sheer effort of will. To the contrary, Descartes introduces sceptical arguments precisely in acknowledgement that we need reasons for doubt:

I did say that there was some difficulty in expelling from our belief everything we have previously accepted. One reason for this is that before we can decide to doubt, we need some reason for doubting; and that is why in my First Meditation I put forward the principal reasons for doubt. (Replies 5, appendix, AT 9a:204)

Another misconception is suggested by Peirce’s reference to a “doubt in our hearts.” Distinguish two kinds of doubt, in terms of two kinds of ways that doubt can defeat knowledge. Some doubts purport to undermine one’s conviction or belief — call these ‘belief-defeating doubts’. Other doubts purport to undermine one’s justification (whether or not they undermine belief) — call these ‘justification-defeating doubts’. What Peirce calls a ‘doubt in our hearts’ is suggestive of a belief-defeating doubt. The resulting misconception is that only belief-defeating doubts can undermine knowledge. Longstanding traditions in philosophy acknowledge that there may be truths we believe in our hearts (as it were), but which we do not know. This is one of the lessons of methodic doubt. The sceptical doubts are supposed to help us appreciate that though we believe that 2+3=5, and believe that we’re awake, and believe that there is an external world, we may nonetheless lack Knowledge. Justification-defeating doubts are sufficient to undermine Knowledge, and this is the sort of doubt that Descartes puts forward.

A related misconception has the method calling not merely for doubt, but for disbelief or dissent. One of Gassendi’s objections reads in this manner. He seems to take Descartes to be urging us, quite literally, to “consider everything as false,” a strategy which, as he says to Descartes, “made it necessary for you to convince yourself” of the sceptical hypotheses (Objs. 5, AT 7:257–58). But Descartes’ method does not require us to dissent from the beliefs it undermines. Surely the spirit (even if not always the letter) of the invocation to doubt is that we are to “hold back [our] assent from opinions which are not completely certain and indubitable just as carefully as [we] do from those which are patently false” (Med. 1, AT 7:18).

Finally, a common misconception has it that the universality of doubt undermines the method of doubt itself, since the sceptical hypotheses themselves are so dubious. But this misses the point of the method: namely, to extend doubt universally to candidates for Knowledge, but not also to the very tools for founding Knowledge. As Descartes concedes: “there may be reasons which are strong enough to compel us to doubt, even though these reasons are themselves doubtful, and hence are not to be retained later on” (Replies 7, AT 7:473–74).

Further reading: On foundationalism: for Descartes’ treatment, see Discourse, First Meditation, and Seventh Objections and Replies; for its treatment by ancients, see Euclid (1956) and Aristotle (Posterior Analytics); by interpreters of Descartes, see Sosa (1997a) and Van Cleve (1979). On Cartesian inference, see Gaukroger (1989) and Hacking (1980). On methodical doubt: for Descartes’ treatment, see Rules, Discourse, First Meditation, and Seventh Replies; by commentators, see Frankfurt (1970), Garber (1986), Newman (2006), Williams (1983), and Wilson (1978). On needing reasons for doubt (nonvoluntarism), see Newman (2007). On the analysis-synthesis distinction (closed related to issues of doubt and methodology): see the Second Replies (AT 7:155ff); see also Galileo (1967, 50f), Arnauld (1964, 4:2–3), Curley (1986), and Hintikka (1978).
3. First Meditation Doubting Arguments
3.1 Dreaming Doubt

Historically, there are at least two distinct dream-related doubts. The one doubt undermines the judgment that I am presently awake — call this the ‘Now Dreaming Doubt’. The other doubt undermines the judgment that I am ever awake (i.e., in the way normally supposed) — call this the ‘Always Dreaming Doubt’. A textual case can be made on behalf of both formulations being raised in the Meditations.

Both doubts appeal to some version of the thesis that the experiences we take as dreams are (at their best) qualitatively similar to those we take as waking — call this the ‘Similarity Thesis’. The Similarity Thesis may be formulated in a variety of strengths. A strong Similarity Thesis might contend that some dreams are experientially indistinguishable from waking, even subsequent to waking-up; a weaker thesis might contend merely that dreams seem similar to waking while having them, but not upon waking. Debates about precisely how similar waking and dreaming can be, have raged for more than two millennia. The tone of the debates suggests that the degree of qualitative similarity may vary across individuals (or, at least, across their recollections of dreams). Granting such variation, dreaming doubts that depend on weaker versions of the Similarity Thesis are (other things equal) apt to be more persuasive. I want to consider a textually defensible formulation that is relatively weak. (Note, however, that some texts suggest a strong thesis: “As if I did not remember other occasions when I have been tricked by exactly similar thoughts while asleep” (Med. 1, AT 7:19, my italics).)

The relatively weak thesis I have in mind is this: that the similarity between waking and dreaming is sufficient to render it thinkable that a dream experience would seem realistic, even when reflecting on the experience, while having it. As Descartes writes: “every sensory experience I have ever thought I was having while awake I can also think of myself as sometimes having while asleep” (Med. 6, AT 7:77). This version of the Similarity Thesis is endorsable by those who never recollect dreams that seem, on hindsight, experientially indistinguishable from waking; indeed, it’s endorsable even by those who simply do not remember their dreams to any significant degree.

This weak Similarity Thesis is sufficient to generate straightaway the Now Dreaming Doubt. Since it is thinkable that a dream would convincingly seem as realistic (while having it) as my present experience seems, then, for all I Know, I am now dreaming.

Recall that Descartes’ method requires only a justification-defeating doubt, not a belief-defeating doubt. The method requires me to appreciate that my present belief (that I’m awake) is not sufficiently justified. It does not require that I give up that belief. (I might continue to hold it on some merely psychological grounds.) Nor does the belief need to be false — I might, in fact, be awake. The Now Dreaming Doubt does its epistemic damage so long as it undermines my reasons for believing I’m awake — i.e., so long as I find it thinkable that a dream would seem this good. The First Meditation makes a case that this is indeed thinkable. As Descartes writes: “there are never any sure signs by means of which being awake can be distinguished from being asleep” (Med. 1, AT 7:19).

The conclusion — that I don’t Know that I’m now awake — has widespread sceptical consequences. For if I don’t Know this, then neither do I Know that I’m now “holding this piece of paper in my hands,” to cite an example the meditator had supposed to be “quite impossible” to doubt. Reflection on the Now Dreaming Doubt changes his mind. He comes around to the view that, for all he Knows, the sensible objects of his present experience are mere figments of a vivid dream.

Much ado has been made about whether dreaming arguments are self-refuting. According to an influential objection, Similarity Theses presuppose that we can reliably distinguish dreams and waking, yet the conclusion of dreaming arguments presupposes that we cannot. Therefore, if the conclusion of such an argument is true, then the premise stating the Similarity Thesis cannot be. Some formulations of the thesis do make this mistake. Of present interest is whether all do — specifically, whether Descartes makes the mistake. He does not. Interestingly, his formulation presupposes simply the truism that we do in fact distinguish dreaming and waking (never mind whether reliably). He states his version of the thesis in terms of what we think of as dreams, versus what we think of as waking: “every sensory experience I have ever thought I was having while awake I can also think of myself as sometimes having while asleep” (Med. 6, AT 7:77). This formulation avoids the charge of self-refutation, for it is compatible with the conclusion that we cannot reliably distinguish dreams and waking.

Does Descartes also put forward a second dreaming argument, the Always Dreaming Doubt? I believe there is strong textual evidence to support this, though it is by no means the standard interpretation. (I make a case for this interpretation in my 1994.) The conclusion of the Always Dreaming Doubt is generated from the very same Similarity Thesis, together with a further sceptical assumption, namely: that for all I Know, the processes producing what I take as waking are no more veridical than those producing what I take as dreams. As Descartes writes:

[E]very sensory experience I have ever thought I was having while awake I can also think of myself as sometimes having while asleep; and since I do not believe that what I seem to perceive in sleep comes from things located outside me, I did not see why I should be any more inclined to believe this of what I think I perceive while awake. (Med. 6, AT 7:77)

The aim of the Always Dreaming Doubt is to undermine not whether I’m now awake, but whether “sensation” is produced by external objects even on the assumption I’m now awake. For in the cases of both waking and dreaming, my cognitive access extends only to the productive result, but not the productive process. On what basis, then, do I conclude that the productive processes are different — that external objects play more of a role in waking than in dreaming? For all I Know, both sorts of experience are produced by some subconscious faculty of my mind. As Descartes has his meditator say:

[T]here may be some other faculty [of my mind] not yet fully known to me, which produces these ideas without any assistance from external things; this is, after all, just how I have always thought ideas are produced in me when I am dreaming. (Med. 3, AT 7:39)

The sceptical consequences of the Always Dreaming Doubt are even more devastating than those of the Now Dreaming Doubt. If I do not Know that “normal waking” experience is produced by external objects, then, for all I Know, all of my experiences might be dreams of a sort. For all I Know, there might not be an external world. My best evidence of an external world derives from my preconceived opinion that external world objects produce my waking experiences. Yet the Always Dreaming Doubt calls this into question:

All these considerations are enough to establish that it is not reliable judgement but merely some blind impulse that has made me believe up till now that there exist things distinct from myself which transmit to me ideas or images of themselves through the sense organs or in some other way. (Med. 3, AT 7:39–40)

The two dreaming doubts are parasitic on the same Similarity Thesis, though their sceptical consequences differ. The Now Dreaming Doubt raises the universal possibility of delusion: for any one of my sensory experiences, it is possible (for all I Know) that the experience is delusive. The Always Dreaming Doubt raises the possibility of universal delusion: it is possible (for all I Know) that all my sensory experiences are delusions (say, from a God’s-eye perspective).
3.2 Evil Genius Doubt

Though dreaming doubts do significant demolition work, they are light-duty bulldozers relative to Descartes’ most power sceptical doubt. What further judgments are left to be undermined? Following the discussion of dreaming, the meditator tentatively concludes that the results of empirical disciplines “are doubtful” — e.g., “physics, astronomy, medicine,” and the like. Whereas:

[A]rithmetic, geometry and other subjects of this kind, which deal only with the simplest and most general things, regardless of whether they really exist in nature or not, contain something certain and indubitable. For whether I am awake or asleep, two and three added together are five, and a square has no more than four sides. It seems impossible that such transparent truths should incur any suspicion of being false. (Med. 1, AT 7:20)

In the final analysis, Descartes holds that such transparent truths — along with demonstrable truths, and many judgments of internal sense — are indeed Knowable. To become actually Known, however, they must stand unshakable in the face the most powerful of doubts. The stage is thus set for the introduction of another sceptical hypothesis.

The most famous rendering of Descartes’ most hyperbolic doubt takes the form of the Evil Genius Doubt. Suppose I am the creation of a powerful but malicious being. This “evil genius” (or deceiving “God, or whatever I may call him,” AT 7:24) has given me flawed cognitive faculties, such that I am in error even about epistemically impressive matters — even the simple matters that seem supremely evident. The suggestion is unbelievable, but not unthinkable. It is intended as a justification-defeating doubt that undermines our judgments about even the most simple and evident matters.

Many readers of Descartes assume that the Evil Genius Doubt draws its sceptical force from the “utmost power” attributed to the deceiver. This is to misunderstand Descartes. He contends that an equally powerful doubt may be generated on the opposite supposition — namely, the supposition that I am not the creature of an all-powerful being:

Perhaps there may be some who would prefer to deny the existence of so powerful a God rather than believe that everything else is uncertain. … yet since deception and error seem to be imperfections, the less powerful they make my original cause, the more likely it is that I am so imperfect as to be deceived all the time. (Med. 1, AT 7:21).

Descartes makes essentially the same point in a parallel passage of the Principles:

[W]e have been told that there is an omnipotent God who created us. Now we do not know whether he may have wished to make us beings of the sort who are always deceived even in those matters which seem to us supremely evident … We may of course suppose that our existence derives not from a supremely powerful God but either from ourselves or from some other source; but in that case, the less powerful we make the author of our coming into being, the more likely it will be that we are so imperfect as to be deceived all the time. (Prin. 1:5, AT 8a:6)

Descartes’ official position is that the Evil Genius Doubt is merely one among multiple hypotheses that can motivate the more general hyperbolic doubt. Fundamentally, the doubt is about my cognitive nature — about the possibility that my mind is flawed. Descartes consistently emphasizes this theme throughout the Meditations (italics added):

God could have given me a nature such that I was deceived even in matters which seemed most evident. (Med. 3, AT 7:36)

I can convince myself that I have a natural disposition to go wrong from time to time in matters which I think I perceive as evidently as can be. (Med. 5, AT 7:70)

I saw nothing to rule out the possibility that my natural constitution made me prone to error even in matters which seemed to me most true. (Med. 6, AT 7:77)

What is essential to the doubt is not a specific story about how I got my cognitive wiring; it’s instead the realization — regardless the story — that I can worry that my cognitive wiring is flawed. Elsewhere, I have suggested that we name the underlying doubt ‘Meta-Cognitive Doubt’, to make clear that it is fundamentally about the implications of having a flawed cognitive nature, rather than of being made by an omnipotent creator. (Carriero makes a similar point with the name ‘imperfect-nature doubt’ (2009, 27).) Even so, I regularly speak in terms of the evil genius (following Descartes’ lead), as a kind of mnemonic for the more general doubt about our cognitive nature.

Having introduced the Evil Genius Doubt, the First Meditation program of demolition is not only hyperbolic but universal. As the meditator remarks, I “am finally compelled to admit that there is not one of my former beliefs about which a doubt may not properly be raised” (Med. 1, AT 7:21). As will emerge, the early paragraphs of the Third Meditation clarify a further nuance of the Evil Genius Doubt — a nuance consistently observed thereafter. Descartes clarifies there that the Evil Genius Doubt operates in an indirect manner, a topic to which we return (in Section 5.1).

Further reading: On Descartes’ sceptical arguments, see Bouwsma (1949), Curley (1978), Newman (1994), Newman and Nelson (1999), Williams (1986 and 1995). For a contrary reading of the Evil Genius Doubt, see Gewirth (1941) and Wilson (1978). For a more general philosophical treatment of dreaming arguments, see Dunlap (1977).
4. Cogito Ergo Sum
4.1 The First Item of Knowledge

Famously, Descartes puts forward a very simple candidate as the “first item of knowledge.” The candidate is suggested by methodic doubt — by the very effort at thinking all my thoughts might be mistaken. Early in the Second Meditation, Descartes has his meditator observe:

I have convinced myself that there is absolutely nothing in the world, no sky, no earth, no minds, no bodies. Does it now follow that I too do not exist? No: if I convinced myself of something then I certainly existed. But there is a deceiver of supreme power and cunning who is deliberately and constantly deceiving me. In that case I too undoubtedly exist, if he is deceiving me; and let him deceive me as much as he can, he will never bring it about that I am nothing so long as I think that I am something. So after considering everything very thoroughly, I must finally conclude that this proposition, I am, I exist, is necessarily true whenever it is put forward by me or conceived in my mind. (Med. 2, AT 7:25)

As the canonical formulation has it, I think therefore I am. (Latin: cogito ergo sum; French: je pense, donc je suis.) This formulation does not expressly arise in the Meditations.

Descartes regards the ‘cogito’ (as I shall refer to it) as the “first and most certain of all to occur to anyone who philosophizes in an orderly way” (Prin. 1:7, AT 8a:7). Testing the cogito by means of methodic doubt is supposed to reveal its unshakable certainty. As earlier noted, the existence of my body is subject to doubt. The existence of my thinking, however, is not. The very attempt at thinking away my thinking is indeed self-stultifying.

The cogito raises numerous philosophical questions and has generated an enormous literature. In summary fashion, I’ll try to clarify a few central points.

First, a first-person formulation is essential to the certainty of the cogito. Third-person claims, such as “Icarus thinks,” or “Descartes thinks,” are not unshakably certain — not for me, at any rate; only the occurrence of my thought has a chance of resisting hyperbolic doubt. There are a number of passages in which Descartes refers to a third-person version of the cogito. But none of these occurs in the context of establishing the actual existence of a particular thinker (in contrast with the conditional, general result that whatever thinks exists).

Second, a present tense formulation is essential to the certainty of the cogito. It’s no good to reason that “I existed last Tuesday, since I recall my thinking on that day.” For all I Know, I’m now merely dreaming about that occasion. Nor does it work to reason that “I’ll continue to exist, since I’m now thinking.” As the meditator remarks, “it could be that were I totally to cease from thinking, I should totally cease to exist” (Med. 2, AT 7:27). The privileged certainty of the cogito is grounded in the “manifest contradiction” (cf. AT 7:36) of trying to think away my present thinking.

Third, the certainty of the cogito depends on being formulated in terms of my cogitatio — i.e., my thinking, or awareness/consciousness more generally. Any mode of thinking is sufficient, including doubting, affirming, denying, willing, understanding, imagining, and so on (cf. Med. 2, AT 7:28). My non-thinking activities, however, are insufficient. For instance, it’s no good to reason that “I exist, since I am walking,” because methodic doubt calls into question the existence of my legs. Maybe I’m just dreaming that I have legs. A simple revision, such as “I exist since it seems I’m walking,” restores the anti-sceptical potency (cf. Replies 5, AT 7:352; Prin. 1:9).

Fourth, a caveat is in order. That Descartes rejects formulations presupposing the existence of a body commits him to no more than an epistemic distinction between mind and body, but not yet an ontological distinction (as in so-called mind-body dualism). Indeed, in the passage following the cogito, Descartes has his meditator say:

And yet may it not perhaps be the case that these very things which I am supposing to be nothing [e.g., “that structure of limbs which is called a human body”], because they are unknown to me, are in reality identical with the “I” of which I am aware? I do not know, and for the moment I shall not argue the point, since I can make judgements only about things which are known to me. (Med. 2, AT 7:27)

Fifth, and related to the foregoing quotation, is that Descartes’ reference to an “I”, in the “I think”, is not intended to presuppose the existence of a substantial self. In the very next sentence following the initial statement of the cogito, the meditator says: “But I do not yet have a sufficient understanding of what this ‘I’ is, that now necessarily exists” (Med. 2, AT 7:25). The cogito purports to yield certainty that I exist insofar as I am a thinking thing, whatever that turns out to be. The ensuing discussion is intended to help arrive at an understanding of the ontological nature of the thinking subject.

More generally, we should distinguish issues of epistemic and ontological dependence. In the final analysis, Descartes thinks he shows that the occurrence of thought depends (ontologically) on the existence of a substantial self — to wit, on the existence of an infinite substance, namely God (cf. Med. 3, AT 7:48ff). But Descartes denies that an acceptance of these ontological matters is epistemically prior to the cogito: its certainty is not supposed to depend (epistemically) on the abstruse metaphysics that Descartes thinks he eventually establishes.

If the cogito does not presuppose a substantial self, what then is the epistemic basis for injecting the “I” into the “I think”? Some critics have complained that, in referring to the “I”, Descartes begs the question by presupposing what he means to establish in the “I exist.” Among the critics, Bertrand Russell objects that “the word ‘I’ is really illegitimate”; that Descartes should have, instead, stated “his ultimate premiss in the form ‘there are thoughts’.” Russell adds that “the word ‘I’ is grammatically convenient, but does not describe a datum.” (1945, 567) Accordingly, “there is pain” and “I am in pain” have different contents, and Descartes is entitled only to the former.

One effort at reply has it that introspection reveals more than what Russell allows — it reveals the subjective character of experience. On this view, there is more to the experiential story of being in pain than is expressed by saying that there is pain: the experience includes the feeling of pain plus a point-of-view — an experiential addition that’s difficult to characterize except by adding that “I” am in pain, that the pain is mine. Importantly, my awareness of this subjective feature of experience does not depend on an awareness of the metaphysical nature of a thinking subject. If we take Descartes to be using ‘I’ to signify this subjective character, then he is not smuggling in something that’s not already there: the “I”-ness of consciousness turns out to be (contra Russell) a primary datum of experience. Though, as Hume persuasively argues, introspection reveals no sense impressions suited to the role of a thinking subject, Descartes, unlike Hume, has no need to derive all our ideas from sense impressions. Descartes’ idea of the self does ultimately draw on innate conceptual resources.

Sixth, much of the debate over whether the cogito involves inference, or is instead a simple intuition (roughly, self-evident), is preempted by three observations. One observation concerns the absence of an express ‘ergo’ (‘therefore’) in the Second Meditation account. It seems a mistake to emphasize this absence, as if suggesting that Descartes denies any role for inference. For the Second Meditation passage is the one place (of his various published treatments ) where Descartes explicitly details a line of inferential reflection leading up to the conclusion that I am, I exist. His other treatments merely say the ‘therefore’; the Meditations treatment unpacks it. A second observation is that it seems a mistake to assume that the cogito must either involve inference, or intuition, but not both. There is no inconsistency in the view that the meditator comes to appreciate the persuasive force of the cogito by means of inferential reflection, while also holding that his eventual conviction is not grounded in inference. A third observation is that what one intuits might well include an inference: it is widely held among philosophers today that modus ponens is self-evident, and yet it contains an inference. There is no inconsistency in claiming a self-evident grasp of a proposition with inferential structure — a fact applicable to the cogito. As Descartes writes:

When someone says “I am thinking, therefore I am, or I exist,” he does not deduce existence from thought by means of a syllogism, but recognizes it as something self-evident by a simple intuition of the mind. (Replies 2, AT 7:140)

4.2 But is it Knowledge?

There are interpretive disputes about whether the cogito is supposed to count as indefeasible Knowledge. (That is, about whether it thus counts upon its initial introduction, prior to the arguments for a non-deceiving God.) Many commentators hold that it is supposed to count, but the case for this interpretation is by no means clear.

There is no disputing that Descartes characterizes the cogito as the “first item of knowledge [cognitione]” (Med. 3, AT 7:35); as the first “piece of knowledge [cognitio]” (Prin. 1:194, AT 8a:7). Noteworthy, however, is the Latin terminology (‘cognitio’ and its cognates) that Descartes uses in these characterizations. As discussed in Section 1.3, Descartes is a contextualist in the sense that he uses ‘knowledge’ language in two different contexts of clear and distinct judgments: the less rigorous context includes defeasible judgments, as in the case of the atheist geometer (who can’t block hyperbolic doubt); the more rigorous context requires indefeasible judgments, as with the brand of Knowledge sought after in the Meditations.

Worthy of attention is that Descartes characterizes the cogito using the same cognitive language that he uses to characterize the atheist’s defeasible cognition. Recall that Descartes writes of the atheist’s clear and distinct grasp of geometry: “I maintain that this awareness [cognitionem] of his is not true knowledge [scientiam]” (Replies 2, AT 7:141). This alone does not prove that the cogito is supposed to be defeasible. It does, however, prove that calling it the “first item of knowledge [cognitione]” doesn’t entail that Descartes intends it as indefeasible Knowledge.

Bearing further on whether the cogito counts as indefeasible Knowledge — prior to having refuted the Evil Genius Doubt — is the No Atheistic Knowledge Thesis (cf. Section 1.3 above). Descartes makes repeated and unequivocal statements implying this thesis. Consider the following texts, each arising in a context of clarifying the requirements of indefeasible Knowledge (all italics are mine):

For if I do not know this [i.e., “whether there is a God, and, if there is, whether he can be a deceiver”], it seems that I can never be quite certain about anything else. (Med. 3, AT 7:36)

I see that the certainty of all other things depends on this [knowledge of God], so that without it nothing can ever be perfectly known [perfecte sciri]. (Med. 5, AT 7:69)

[I]f I did not possess knowledge of God … I should thus never have true and certain knowledge [scientiam] about anything, but only shifting and changeable opinions. (Med. 5, AT 7:69)

And upon claiming finally to have achieved indefeasible Knowledge:

Thus I see plainly that the certainty and truth of all knowledge [scientiae] depends uniquely on my awareness of the true God, to such an extent that I was incapable of perfect knowledge [perfecte scire] about anything else until I became aware of him. (Med. 5, AT 7:71)

These texts make a powerful case that nothing else can be indefeasibly Known prior to establishing that we’re creatures of an all-perfect God, rather than an evil genius. These texts make no exceptions. Descartes looks to hold that hyperbolic doubt is utterly unbounded — that it undermines all manner of propositions, including therefore the proposition that “I exist.”

By contrast, other texts seem to support the interpretation whereby the cogito counts as indefeasible Knowledge. For example, we have seen texts making clear that it resists hyperbolic doubt. Often overlooked, however, is that it is only subsequent to the introduction of the cogito that Descartes has his meditator first notice the manner in which clear and distinct perception is both resistant and vulnerable to hyperbolic doubt: the extraordinary certainty of such perception resists hyperbolic doubt while it is occurring; it is vulnerable to hyperbolic doubt upon redirecting one’s perceptual attention away from the matter in question. This theme is developed more fully in the next Section below.

As will emerge, there are two main kinds of interpretive camps concerning how to deal with the so-called Cartesian Circle. The one camp contends that hyperbolic doubt is utterly unbounded. On this view, the No Atheist Knowledge Thesis is taken quite literally. The other camp contends that hyperbolic doubt is bounded; that is, that the cogito, and a few other special truths, are in a lockbox of sorts, utterly protected from even the most hyperbolic doubt. This view allows that atheists can have indefeasible Knowledge. These two kinds of interpretations are developed in Section 6.

Further reading: For important passages in Descartes’ handling of the cogito, see the second and third sets of Objections and Replies. In the secondary literature, see Beyssade (1993), Broughton (2002), Carriero (2009), Cunning (2007), Hintikka (1962), Markie (1992) Sarkar (2003), and Vinci (1998).
5. Epistemic Privilege and Defeasibility

The extraordinary certainty and doubt-resistance of the cogito marks an Archimedean turning point in the meditator’s inquiry. Descartes builds on its impressiveness to help clarify further epistemic theses. The present Section considers two such theses about our epistemically privileged perceptions. First, that clarity and distinctness are, jointly, the mark of our epistemically best perceptions (notwithstanding that such perception remains defeasible). Second, that judgments about one’s own mind are epistemically privileged compared with those about bodies.
5.1 Our Epistemic Best: Clear and Distinct Perception and its Defeasibility

The opening four paragraphs of the Third Meditation are pivotal. Descartes uses them to codify the phenomenal marks of our epistemically best perceptions, while clarifying also that even this impressive epistemic ground falls short of the goal of indefeasible Knowledge. This sobering realization leads to Descartes’ infamous efforts to refute the Evil Genius Doubt, by proving a non-deceiving God.

The first and second paragraphs portray the meditator attempting to build on the success of the cogito by identifying a general principle of certainty: “I am certain that I am a thinking thing. Do I not therefore also know what is required for my being certain about anything?” (AT 7:35). What are the phenomenal marks of this impressive perception — what is it like to have perception that good? Descartes’ answer: “In this first item of knowledge [cognitione] there is simply a clear and distinct perception of what I am asserting” (ibid.).

The third and fourth paragraphs help clarify (among other things) what Descartes takes to be epistemically impressive about clear and distinct perception, though absent from external sense perception. The third paragraph has the meditator observing:

Yet I previously accepted as wholly certain and evident many things which I afterwards realized were doubtful. What were these? The earth, sky, stars, and everything else that I apprehended with the senses. But what was it about them that I perceived clearly? Just that the ideas, or thoughts, of such things appeared before my mind. Yet even now I am not denying that these ideas occur within me. But there was something else which I used to assert, and which through habitual belief I thought I perceived clearly, although I did not in fact do so. This was that there were things outside me which were the sources of my ideas and which resembled them in all respects. Here was my mistake; or at any rate, if my judgement was true, it was not thanks to the strength of my perception. (Med. 3, AT 7:35)

The very next paragraph (the fourth) draws an epistemically important contrast with external sense perception (as just characterized). External sense perception does not admit of any great “strength of perception,” quite unlike clear and distinct perception. As earlier noted (Section 1.1), the certainty of interest to Descartes is psychological in character, though not merely psychological. Not only does occurrent clear and distinct perception resist doubt, it provides a kind of cognitive illumination. Both of these epistemic virtues — its doubt-resistance, and its luminance — are noted in the fourth paragraph:

[Regarding] those matters which I think I see utterly clearly with my mind’s eye … when I turn to the things themselves which I think I perceive very clearly, I am so convinced by them that I spontaneously declare: let whoever can do so deceive me, he will never bring it about that I am nothing, so long as I continue to think I am something; or make it true at some future time that I have never existed, since it is now true that I exist; or bring it about that two and three added together are more or less than five, or anything of this kind in which I see a manifest contradiction. (Med. 3, AT 7:36)

The contrast drawn in the third and fourth paragraphs gets at a theme that Descartes thinks crucial to his broader project: namely, that there is “a big difference” — an introspectible difference — between external sense perception, and perception that is genuinely clear and distinct. The external senses result in, at best, “a spontaneous impulse” to believe something, an impulse we’re able to resist. In contrast, occurrent clear and distinct perception is utterly irresistible: “Whatever is revealed to me by the natural light — for example that from the fact that I am doubting it follows that I exist, and so on — cannot in any way be open to doubt.” (Med. 3, AT 7:38) As Descartes repeatedly conveys: “my nature is such that so long as I perceive something very clearly and distinctly I cannot but believe it to be true” (Med. 5, AT 7:69; cf. 3:64, 7:36, 7:65, 8a:9).

Because of the epistemic impressiveness of clear and distinct perception (notably, as exhibited in the cogito), the meditator concludes that such perception will issue as the mark of truth, if anything will. He tentatively formulates the following candidate for a criterion of truth: “I now seem [videor] to be able to lay it down as a general rule that whatever I perceive very clearly and distinctly is true” (Med. 3, AT 7:35). I shall call this general principle the ‘C&D Rule’. The announcement of the candidate criterion is carefully tinged with caution (videor), as the C&D Rule has yet to be subjected to hyperbolic doubt. Should it turn out that clarity and distinctness — as an epistemic ground — is shakable, then, there would remain some doubt about the general veracity of clear and distinct perception. In that case, when reflecting back on having perceived something clearly and distinctly, it would not seem so impressive, after all — it “would not be enough to make me certain of the truth of the matter” (ibid.). This cautionary note anticipates the sobering realization of the fourth paragraph, that, for all its impressiveness, even clear and distinct perception is in some sense defeasible.

In what sense defeasible? Recall that the Evil Genius Doubt is, fundamentally, a doubt about our cognitive natures. Maybe my mind was made flawed, such that I go wrong even when my perception is clear and distinct. As the meditator conveys in the fourth paragraph, my creator might have “given me a nature such that I was deceived even in matters which seemed most evident,” with the consequence that “I go wrong even in those matters which I think I see utterly clearly with my mind’s eye” (AT 7:36). The result is a kind of epistemic schizophrenia:

Moments of epistemic optimism: While I am directly attending to a proposition — perceiving it clearly and distinctly — I enjoy an irresistible cognitive luminance and my assent is compelled.

Moments of epistemic pessimism: When no longer directly attending — no longer perceiving the proposition clearly and distinctly — I can entertain the sceptical hypothesis that such feelings of cognitive luminance are epistemically worthless, arising from a defective cognitive nature.

The doubt is thus indirect, in the sense that these moments of epistemic pessimism arise when I am no longer directly attending to the propositions in question. This indirect operation of hyperbolic doubt is conveyed not only in the fourth paragraph, but in numerous other texts, including the following:

Admittedly my nature is such that so long as I perceive something very clearly and distinctly I cannot but believe it to be true. But my nature is also such that I cannot fix my mental vision continually on the same thing, so as to keep perceiving it clearly; and often the memory of a previously made judgement may come back, when I am no longer attending to the arguments which led me to make it. And so other arguments can now occur to me which might easily undermine my opinion, if I were unaware of [the true] God; and I should thus never have true and certain knowledge about anything, but only shifting and changeable opinions. For example, when I consider the nature of a triangle, it appears most evident to me, steeped as I am in the principles of geometry, that its three angles are equal to two right angles; and so long as I attend to the proof, I cannot but believe this to be true. But as soon as I turn my mind’s eye away from the proof, then in spite of still remembering that I perceived it very clearly, I can easily fall into doubt about its truth, if I am unaware of God. For I can convince myself that I have a natural disposition to go wrong from time to time in matters which I think I perceive as evidently as can be. (Med.5, AT 7:69–70; cf. AT 3:64–65; AT 8a:9–10).

Granted, this indirect doubt is exceedingly hyperbolic. Even so, it means that we lack fully indefeasible Knowledge. Descartes thus closes the fourth paragraph as follows:

And since I have no cause to think that there is a deceiving God, and I do not yet even know for sure whether there is a God at all, any reason for doubt which depends simply on this supposition is a very slight and, so to speak, metaphysical one. But in order to remove even this slight reason for doubt, as soon as the opportunity arises I must examine whether there is a God, and, if there is, whether he can be a deceiver. For if I do not know this, it seems that I can never be quite certain about anything else. (Med. 3, AT 7:36)

The leading role played by the cogito in this four paragraph passage is easily overlooked. Not only is it (in paragraph two) the exemplar of judging clearly and distinctly, it is listed (paragraph four) among the propositions that are compellingly certain while attended to, though undermined when we no longer thus attend.

What next? How does Descartes think we’re to make epistemic progress if even our epistemic best is subject to hyperbolic doubt? This juncture of the Third Meditation (the end of the fourth paragraph) marks the beginning point of Descartes’ notorious efforts to refute the Evil Genius Doubt. His efforts involve an attempt to establish that we are the creatures not of an evil genius, but an all-perfect creator who would not allow us to be deceived about what we clearly and distinctly perceive. Before turning our attention (in Section 6) to these efforts, let’s digress somewhat to consider a Cartesian doctrine that has received much attention in its subsequent history.
5.2 The Epistemic Privilege of Judgments About the Mind

Descartes holds that our judgments about our own minds are epistemically better-off than our judgments about bodies. In our natural, pre-reflective condition, however, we’re apt to confuse the sensory images of bodies with the external things themselves, a confusion leading us to think our judgments about bodies are epistemically impressive. The confusion is clearly expressed (Descartes would say) in G. E. Moore’s famous claim to knowledge — “Here is a hand” — along with his more general defense of common sense:

I begin, then, with my list of truisms, every one of which (in my own opinion) I know, with certainty, to be true. … There exists at present a living human body, which is my body. This body was born at a certain time in the past, and has existed continuously ever since … But the earth had existed also for many years before my body was born … (1962, 32–33)

In contrast, Descartes writes:

[I]f I judge that the earth exists from the fact that I touch it or see it, this very fact undoubtedly gives even greater support for the judgement that my mind exists. For it may perhaps be the case that I judge that I am touching the earth even though the earth does not exist at all; but it cannot be that, when I make this judgement, my mind which is making the judgement does not exist. (Prin. 1:11, AT 8a:8–9)

Methodical doubt is intended to help us appreciate the folly of the commonsensical position — helping us to recognize that the perception of our own minds is “not simply prior to and more certain … but also more evident” than that of our own bodies (Prin. 1:11, AT 8a:8). “Disagreement on this point,” writes Descartes, comes from “those who have not done their philosophizing in an orderly way”; from those who, while properly acknowledging the “certainty of their own existence,” mistakenly “take ‘themselves’ to mean only their bodies” — failing to “realize that they should have taken ‘themselves’ in this context to mean their minds alone” (Prin. 1:12, AT 8a:9).

In epistemological contexts, Descartes underwrites the mind-better-known-than-body doctrine with methodic doubt. For example, while reflecting on his epistemic position in regards both to himself, and to the wax, the Second Meditation meditator says:

Surely my awareness of my own self is not merely much truer and more certain than my awareness of the wax, but also much more distinct and evident. For if I judge that the wax exists from the fact that I see it, clearly this same fact entails much more evidently that I myself also exist. It is possible that what I see is not really the wax; it is possible that I do not even have eyes with which to see anything. But when I see, or think I see (I am not here distinguishing the two), it is simply not possible that I who am now thinking am not something. (Med. 2, AT 7:33)

Other reasons motivate Descartes as well. The doctrine is closely allied with his commitment to a representational theory of sense perception. On his view of sense perception, our sense organs and nerves serve as literal mediating links in the perceptual chain: they stand between (both spatially and causally) external things themselves, and the brain events that occasion our perceptual awareness (cf. Prin. 4:196). In veridical sensation, the immediate objects of sensory awareness are not external bodies themselves, nor are we immediately aware of states of our sense organs or nerves. Rather, the immediate objects of awareness — whether in veridical sensation, or dreams — are the mind’s ideas. Descartes thinks that the fact of physiological mediation helps explain delusional ideas, because roughly the same kinds of physiological processes that produce waking ideas are employed in producing delusional ideas:

[I]t is the soul which sees, and not the eye; and it does not see directly, but only by means of the brain. That is why madmen and those who are asleep often see, or think they see, various objects which are nevertheless not before their eyes: namely, certain vapours disturb their brain and arrange those of its parts normally engaged in vision exactly as they would be if these objects were present. (Optics, AT 6:141; cf. Med. 6, AT 7:85ff; Passions 26)

Various passages of the Meditations lay important groundwork for this theory of perception. For instance, one of the messages of the wax passage is that sensory awareness does not reach to external things themselves:

We say that we see the wax itself, if it is there before us, not that we judge it to be there from its colour or shape; and this might lead me to conclude without more ado that knowledge of the wax comes from what the eye sees, and not from the scrutiny of the mind alone. But then if I look out of the window and see men crossing the square, as I just happen to have done, I normally say that I see the men themselves, just as I say that I see the wax. Yet do I see any more than hats and coats which could conceal automatons? I judge that they are men. (Med. 2, AT 7:32)

Descartes thinks we’re apt to be “tricked by ordinary ways of talking” (ibid.). In ordinary contexts we don’t say that it seems there are men outside the window; we say we see them. Nor, in such contexts, are our beliefs about those men apt to result from conscious, inferentially complex judgments, say, like this one: “Well, I appear to be awake, and the window pane looks clean, and there’s plenty of light outside, and so on, and I thus conclude that I am seeing men outside the window.” Even so, our ordinary ways of speaking and thinking often mislead. Descartes’ view is that the mind’s immediate perception does not, strictly speaking, extend beyond itself, to external bodies. This is an important basis of the mind-better-known-than-body doctrine. In the concluding paragraph of the Second Meditation, Descartes writes:

I see that without any effort I have now finally got back to where I wanted. I now know that even bodies are not strictly [proprie] perceived by the senses or the faculty of imagination but by the intellect alone, and that this perception derives not from their being touched or seen but from their being understood; and in view of this I know plainly that I can achieve an easier and more evident perception of my own mind than of anything else. (Med. 2, AT 7:34)

Related is a Third Meditation remark. Discussing sense perception and our ideas of external things, Descartes writes that the mind’s sensation extends strictly and immediately only to the ideas: “the ideas were, strictly speaking, the only immediate objects of my sensory awareness [solas proprie et immediate sentiebam]” (Med. 3, AT 7:75). The theme that ideas are the only immediate objects of awareness repeats itself elsewhere in Descartes’ writings. As he tells Hobbes: “I make it quite clear in several places … that I am taking the word ‘idea’ to refer to whatever is immediately perceived by the mind” (Replies 3, AT 7:181).

Complicating an understanding of such passages is that Descartes scholarship is divided on whether to attribute to him some version of an indirect theory of perception, or instead some version of a direct theory. According to indirect perception accounts, in normal sensation the mind’s perception of bodies is mediated by an awareness of its ideas of those bodies. By contrast, direct perception interpretations allow that in normal sensation the mind’s ideas play a mediating role, though this role doesn’t have ideas functioning as items of awareness; rather, the objects of direct awareness are the external things, themselves. On both accounts, ideas mediate our perception of external objects. On direct theory accounts, the mediating role is only a process role. By analogy, various brain processes mediate our perception of external objects, but in the normal course of perception we are not consciously aware of those processes; and likewise for the mind’s ideas, according to direct perception accounts. I hold an indirect perception interpretation. On the version of the interpretation I favor — and elsewhere defend (2009) — sensory ideas mediate our perception of the external bodies they’re of, in much the same way that pictures (or other representational imagery) mediate our perception of what they portray. More generally, Descartes seems to view all ideas as mental pictures, of a sort. As he writes: “the term ‘idea’ is strictly appropriate” only for thoughts that “are as it were the images of things” (Med. 3, AT 7:37); he adds that “the ideas in me are like {pictures, or} images” (Med. 3, AT 7:42).

Indirect perception interpretations have figured prominently in the history of Descartes scholarship. A number of recent commentators, however, have challenged this traditional view. For example, John Carriero’s recent book on Descartes defends a direct perception interpretation: “I don’t read Descartes as holding that I am (immediately) aware only of my sensory ideas and only subsequently (and perhaps indirectly) aware of bodies or their qualities” (2009, 25). Thus on Carriero’s reading, Descartes’ broader argument rebutting our doubts about the external world is not to be understood as an effort to get on the other side (as it were) of our ideas:

The argument (as I understand it) is not intended to get us from a realm of inner mental objects (“sensory ideas”) to some other realm of outer, physical objects (“bodies”); rather, it is to confirm our instinctive feeling that we have been receiving information (“directly”) from outer objects, bodies, all along. (2009, 26)

Returning to Descartes’ views of epistemic privilege, it is generally overlooked that his mind-better-known-than-body doctrine is intended as a comparative rather than a superlative thesis. For Descartes, the only superlative perceptual state is that of clarity and distinctness: only it is correctly characterized as our epistemic best. All manner of judgments are susceptible to error except when based on clear and distinct perception.

This understanding of Descartes deviates from a “Cartesian” view widely attributed to him, namely: that we simply cannot be mistaken about the present contents of consciousness; that such judgments about the mind are, by their very nature, as good as it gets. (People widely attribute to Descartes a variety of related doctrines. Compare the doctrines of the infallibility of the mental — roughly, the doctrine that sincere introspective judgments are always true; the indubitability of the mental — roughly, that sincere introspective judgments are indefeasible; and omniscience with respect to the mental — roughly, that one has Knowledge of every true proposition about one’s own present contents of consciousness. There is some variation in the way these doctrines are formulated in the literature.) Am I really denying that this is Descartes’ view? How could we be mistaken about the present contents of consciousness? And how do I explain the passages in which Descartes explicitly embraces the thesis?

Descartes’ view is that introspective judgments are indeed privileged, but he regards them as nonetheless subject to error. Even introspective perception — e.g., our awareness of occurrent pains and other sensations — must be rendered clear and distinct to be counted among our epistemic best. Such matters may be clearly and distinctly perceived, writes Descartes,

…provided we take great care in our judgements concerning them to include no more than what is strictly contained in our perception — no more than that of which we have inner awareness. But this is a very difficult rule to observe, at least with regard to sensations. (Prin. 1:66, AT 8a:32; cf. Prin. 1:68)

Elsewhere, Descartes writes that we do “frequently make mistakes, even in our judgements concerning pain” (Prin. 1:67). These mistakes arise because “people commonly confuse this perception [of pain] with an obscure judgement they make concerning the nature of something which they think exists in the painful spot and which they suppose to resemble the sensation of pain” (Prin.1:46, AT 8a:22).

But how could I be mistaken in judging, say, that I seem to see a speckled hen with two speckles? Descartes holds that we can be mistaken quite simply, by thinking obscurely or confusedly. On his view, the key to infallibility is not merely that the mind’s attention is on its ideas, but that it renders its ideas clear and distinct. To help appreciate his view, notice that judgments about seeming to see hens with two speckles are the same, in kind, as those about seeming to see hens with two hundred forty-seven speckles. Quite obviously, I might be confused in this latter case. (Indeed, it is plausible to hold that only in confusion could I seem to be seeing exactly that many speckles.) Yet there is no relevant difference that would explain why the one judgment is infallible (not merely correct), while the other is fallible. For Descartes, both are fallible; the relevant consideration distinguishing their susceptibility to error is that the two-speckled case is so much easier to render clear and distinct. But though simpler ideas are generally easier to make clear and distinct, simplicity is not a requirement: “A concept is not any more distinct because we include less in it; its distinctness simply depends on our carefully distinguishing what we do include in it from everything else” (Prin. 1:63, AT 8a:31; cf. Prin. 1:45).

What about the texts wherein Descartes seems explicitly to embrace the infallibility of introspective judgments? Consider two key texts often cited in this connection:

I certainly seem to see, to hear, and to be warmed. This cannot be false; what is called “having a sensory perception” is strictly just this, and in this restricted sense of the term it is simply thinking. (Med. 2, AT 7:29)

Now as far as ideas are concerned, provided they are considered solely in themselves and I do not refer them to anything else, they cannot strictly speaking be false; for whether it is a goat or a chimera that I am imagining, it is just as true that I imagine the former as the latter. As for the will and the emotions, here too one need not worry about falsity; for even if the things which I may desire are wicked or even non-existent, that does not make it any less true that I desire them. Thus the only remaining thoughts where I must be on my guard against making a mistake are judgements. (Med. 3, AT 7:37)

On close inspection, these texts make no claim about the possibility of introspective judgment error, because these texts — barring the final sentence of the second passage — are not about fully formed judgments. Rather, Descartes is isolating the components of judgment. His two-faculty theory of judgment requires an interaction between the perceptions of the intellect and the will’s assent (a theory elaborated in the Fourth Meditation). A sine qua non of judgment error is that there be an act of judgment, but acts of judgment require both a perception and a volition. Descartes’ claim that mere seemings “cannot strictly speaking be false” is therefore innocuous: for in isolating the mere seeming, he isolates the perceptual from the volitional. My merely seeming to see a speckled hen with two speckles could not, per se, involve judgment error, because it is not in itself a judgment.

Further reading: On discussions of truth criteria in the 16th and 17th centuries, see Popkin (1979). On Descartes’ theory of ideas, see Carriero (2009), Chappell (1986), Hoffman (1996), Jolley (1990), Nadler (2006), Nelson (1997), and Newman (2009). On the defeasibility of clear and distinct perception (including the cogito), see Carriero (2009, 339ff), Newman and Nelson (1999). On contemporary treatments of infallibility, indubitability, and omniscience, see Alston (1989) and Audi (1993).
6. Cartesian Circle

At the end of Section 5.1 we left off with the fourth paragraph of the Third Meditation. That passage clarifies that the Evil Genius Doubt undermines even clear and distinct perception: upon turning my attention away from matters thus perceived, I can then wonder whether I have a defective cognitive nature that makes me go wrong even in such cases. In his Principles treatment of the same issues, Descartes summarizes the broader problem as follows:

The mind, then, knowing itself, but still in doubt about all other things, looks around in all directions in order to extend its knowledge [cognitionem] further. … Next, it finds certain common notions from which it constructs various proofs; and, for as long as it attends to them, it is completely convinced of their truth. … But it cannot attend to them all the time; and subsequently, when it happens that it remembers a conclusion without attending to the sequence which enables it to be demonstrated, recalling that it is still ignorant as to whether it may have been created with the kind of nature that makes it go wrong even in matters which appear most evident, the mind sees that it has just cause to doubt such conclusions, and that the possession of certain knowledge [scientiam] will not be possible until it has come to know the author of its being. (Prin. 1.13, AT 8a:9–10)

How can we overcome this lingering hyperbolic doubt? At the close of the fourth paragraph of the Third Meditation, Descartes lays out an ambitious plan: “in order to remove even this slight reason for doubt, as soon as the opportunity arises I must examine whether there is a God, and, if there is, whether he can be a deceiver” (Med. 3, AT 7:36).

The broader argument that unfolds has seemed to many readers to be viciously circular — the so-called Cartesian Circle. Descartes first argues from clearly and distinctly perceived premises to the conclusion that a non-deceiving God exists; he then argues from the premise that a non-deceiving God exists to the conclusion that what is clearly and distinctly perceived is true. The worry is that he presupposes the C&D Rule in the effort to prove the C&D Rule. In what follows, I first clarify the key steps in the broader argument for the divine guarantee of the C&D Rule. I then turn to the Cartesian Circle.
6.1 Establishing the Divine Guarantee of the C&D Rule

Descartes’ broader argument unfolds in two main steps. The first main step has him making arguments in the Third Meditation for the existence of an all-perfect God. From these arguments Descartes concludes:

I recognize that it would be impossible for me to exist with the kind of nature I have — that is, having within me the idea of God — were it not the case that God really existed. By ‘God’ I mean the very being the idea of whom is within me, that is, the possessor of all the perfections which I cannot grasp, but can somehow reach in my thought, who is subject to no defects whatsoever. It is clear enough from this that he cannot be a deceiver, since it is manifest by the natural light that all fraud and deception depend on some defect. (Med. 3, AT 7:51f)

There is much of interest to say about Descartes’ arguments for an all-perfect God. (The Fifth Meditation advances a further such argument.) In the interests of space, and of focusing on epistemological concerns, however, these arguments will not be considered here. (For an overview of Descartes’ proofs, see Nolan and Nelson (2006).)

Descartes’ second main step is to argue from the premise (now established) that an all-perfect God exists, to the general veracity of the C&D Rule — whereby, whatever is clearly and distinctly perceived is true. As Descartes tells us: “In the Fourth Meditation it is proved that everything that we clearly and distinctly perceive is true” (Synopsis, AT 7:15). It is this second main step of the broader argument that I want to develop here.

It is tempting to suppose that this second main step is unneeded. That is, one might have thought that the C&D Rule is a straightforward consequence of the existence of a God who is no deceiver. But this is is too fast. Why should only the C&D Rule be a straightforward consequence, but not also a more general infallibility of all our judgments? Essentially this point is made in the First Meditation, at the introduction of the Evil Genius Doubt. The meditator observes that what seems to follow from the standard view — whereby God “is said to be supremely good,” rather than a deceiver — is that God would not allow us ever to be mistaken in our judgments:

But if it were inconsistent with his goodness to have created me such that I am deceived all the time, it would seem equally foreign to his goodness to allow me to be deceived even occasionally; yet this last assertion cannot be made. (Med. 1, AT 7:21)

In short, the “rule for truth” that would seem to be the most straightforward consequence of an all-perfect creator is this perfectly general rule: If I form a judgment, then it is true. Yet quite clearly, this rule for truth doesn’t hold. But then, this fact — the very existence of error — calls into question whether there is an all-perfect creator. In this First Meditation passage Descartes is raising the traditional problem of evil, but here applied to the case of judgment error. As the passage reasons:

1. There is judgment error.
2. Judgment error is incompatible with the hypothesis that I am the creature of a non-deceiving God.
3. Therefore, I am not the creature of a non-deceiving God.

These First Meditation remarks set the stage for the discussion that will come in the Fourth Meditation. Descartes will need a theodicy for error. (A theodicy is an effort to explain how God is compatible with evil.) The theodicy needs to show that the existence of God is compatible with some forms of judgment error, but not others. The Fourth Meditation thus begins by revisiting the problem of error. But in context, the meditator has just proven the existence of an all-perfect God — a scenario generating cognitive dissonance:

To begin with, I recognize that it is impossible that God should ever deceive me. … I know by experience that there is in me a faculty of judgement which, like everything else which is in me, I certainly received from God. And since God does not wish to deceive me, he surely did not give me the kind of faculty which would ever enable me to go wrong while using it correctly.

There would be no further doubt on this issue were it not that what I have just said appears to imply that I am incapable of ever going wrong. For if everything that is in me comes from God, and he did not endow me with a faculty for making mistakes, it appears that I can never go wrong. (Med. 4, AT 7:53–54)

In an effort to resolve the problem, the meditator begins an investigation into the causes of error. In the course of the discussion, Descartes puts forward his theory of judgment. Judgment arises from the cooperation of the intellect and the will. The investigation concludes that the cause of error is an improper use of the will: error arises when the will gives assent to propositions of which the intellect lacks a clear and distinct understanding. It is therefore within our power to avoid judgment error. Error is our fault:

[If] I simply refrain from making a judgement in cases where I do not perceive the truth with sufficient clarity and distinctness, then it is clear that I am behaving correctly and avoiding error. But if in such cases I either affirm or deny, then I am not using my free will correctly. (Med. 4, AT 7:59–60)

The theodicy that emerges is a version of the freewill defense. Accordingly, we should thank God for giving us freewill, but the cost of having freewill is the possibility of misusing it. Since error is the result of misusing our freewill, we should not blame God.

Not only is the theodicy used to explain the kinds of error God can allow, it serves to clarify the kinds of error God cannot allow. From the latter arises a proof of the C&D Rule. God can allow errors that are my fault, though not errors that would be God’s fault. When my perception is clear and distinct, giving assent is not a voluntary option — thus not explainable by the freewill defense. In such cases, assent is a necessary consequence of my cognitive nature — a point made in many passages: “our mind is of such a nature that it cannot help assenting to what it clearly understands” (AT 3:64); “the nature of my mind is such that I cannot but assent to these things, at least so long as I clearly perceive them” (Med. 5, AT 7:65). Since, on occasions of clarity and distinctness, my assent arises from the cognitive nature that God gave me, God would be blamable if those judgments resulted in error. Therefore, they are not in error; indeed they could not be. That an evil genius might have created me casts doubt on my clear and distinct judgments. That, instead, an all-perfect God created me guarantees that these judgments are true. A clever strategy of argument thus unfolds — effectively inverting the usual reasoning in the problem of evil:

1. There is a non-deceiving God.
2. A non-deceiving God is incompatible with the hypothesis that I am in error about what I clearly and distinctly perceive.
3. Therefore, I am not in error about what I clearly and distinctly perceive.

The first premise was argued in the Third Meditation. The second premise arises out of the discussion of the Fourth Meditation. The result is a divine guarantee of the C&D Rule.

By the end of the Fourth Meditation, important pieces of Descartes’ broader argument are in place. Whether further important pieces arise in the Fifth Meditation is a matter of interpretive dispute. In any case, the Fifth Meditation comes to a close with Descartes asserting that indefeasible Knowledge has finally been achieved:

I have perceived that God exists, and at the same time I have understood that everything else depends on him, and that he is no deceiver; and I have drawn the conclusion that everything which I clearly and distinctly perceive is of necessity true. … what objections can now be raised? That the way I am made makes me prone to frequent error? But I now know that I am incapable of error in those cases where my understanding is transparently clear. … And now it is possible for me to achieve full and certain knowledge of countless matters, both concerning God himself and other things whose nature is intellectual, and also concerning the whole of that corporeal nature which is the subject-matter of pure mathematics. (Med. 5, AT 7:70-71)

6.2 Circularity and the Broader Argument

Students of philosophy can expect to be taught a longstanding interpretation according to which Descartes’ broader argument is viciously circular. Despite its prima facie plausibility, Descartes commentators generally resist the vicious circularity interpretation.

Consider first what every plausible interpretation must concede: that the two main steps of the broader argument unfold in a manner suggestive of a circle — I’ll indeed refer to them as ‘arcs’. The Third Meditation arguments for God define one arc:

Arc 1: The conclusion that a non-deceiving God exists is derived from premises that are clearly and distinctly perceived.

The Fourth Meditation argument defines a second arc:

Arc 2: The general veracity of propositions that are clearly and distinctly perceived (i.e., the C&D Rule) is derived from the conclusion that a non-deceiving God exists.

That the broader argument unfolds in accord with these two steps is uncontroversial. The question of interest concerns whether, strictly speaking, these arcs form a circle. The statement of Arc 1 admits of considerable ambiguity. How one resolves this ambiguity determines whether vicious circularity is the result. Let’s begin by clarifying what Arc 1 would have to mean to generate vicious circularity. We’ll then consider the main alternative interpretations of that arc by which commentators avoid a vicious circle.

Vicious Circularity interpretation:

Arc 1: The conclusion that a non-deceiving God exists is derived from premises that are clearly and distinctly perceived — i.e., premises that are accepted because of first accepting the general veracity of propositions that are clearly and distinctly perceived.

Arc 2: The general veracity of propositions that are clearly and distinctly perceived is derived from the conclusion that a non-deceiving God exists.

Thus rendered, Descartes’ broader argument is viciously circular. The italicized segment of Arc 1 marks an addition to the original statement of it, thereby clarifying the circularity reading. Interpreted in this way, Descartes begins his Third Meditation proofs of God by presupposing the general veracity of clear and distinct perception. That is, he starts by assuming the C&D Rule and then uses the rule in the course of demonstrating it. Evidently, this way of reading Descartes’ argument has pedagogical appeal, for it is ubiquitously taught (outside of Descartes scholarship) despite the absence of any textual merit. If there is one point of general agreement in the secondary literature, it is that the texts do not sustain this interpretation.

How then should Arc 1 be understood? There are countless interpretations that avoid vicious circularity, along with numerous schemes for cataloguing them. For present purposes, I’ll catalogue the various accounts according to two main kinds of non-circular strategies that commentators attribute to Descartes. (The secondary literature offers multiple variations of each these main kinds of interpretations, though I won’t here explore the variations.)

Unbounded Doubt interpretations:

Arc 1: The conclusion that a non-deceiving God exists is derived from premises that are clearly and distinctly perceived — i.e., premises that are accepted, despite being defeasible, because our cognitive nature compels us to assent to clearly and distinctly perceived propositions.

Arc 2: The general veracity of propositions that are clearly and distinctly perceived is derived from the conclusion that a non-deceiving God exists.

Again, the italicized segment marks an addition to the original statement of Arc 1. I call this an ‘Unbounded Doubt’ interpretation, because this kind of interpretation construes hyperbolic doubt as unbounded. More precisely, the Evil Genius Doubt is (on this reading) unbounded in the sense that it undermines all manner of judgments — even the cogito, even the premises of the Third Meditation proofs of God. It is the unboundedness of hyperbolic doubt that underwrites the No Atheistic Knowledge Thesis.

Importantly, if doubt is thus unbounded then there is no circularity. For, on this reading of it, Arc 1 does not presuppose the general veracity of the C&D Rule. Hyperbolic doubt is in play throughout Arc 1.

A question immediately arises for such unbounded doubt interpretations. Given that hyperbolic doubt is unbounded, why then are the Arc 1 arguments for God accepted? Why does the meditator assent to the premises of those arguments, if indeed hyperbolic doubt undermines them? The answer lies in our earlier discussion of the indirect manner in which hyperbolic doubt operates (Section 5.1). Recall that while I am clearly and distinctly attending to a proposition, it compels my assent: “my nature is such that so long as I perceive something very clearly and distinctly I cannot but believe it to be true” (Med. 5, AT 7:69; cf. 3:64, 7:36, 7:65, 8a:9). Descartes holds that while we are attending to the steps of the Third Meditation arguments for God, we have no choice but to accept those arguments. Of course, from the fact that those arguments compel our assent while attending to them, it does not (yet) follow that we have Knowledge of their conclusions. At present, our focus is on the issue of circularity, not the issue of how hyperbolic doubt is finally overcome.

The other main kind of interpretation avoids circularity in a different manner. Let’s consider that alternative.

Bounded Doubt interpretations:

Arc 1: The conclusion that a non-deceiving God exists is derived from premises that are clearly and distinctly perceived — indeed, premises belonging to a special class of truths immune to doubt.

Arc 2: The general veracity of propositions that are clearly and distinctly perceived is derived from the conclusion that a non-deceiving God exists.

Once again, the italicized segment marks an addition to the original statement of Arc 1. I call this a ‘Bounded Doubt’ interpretation, because this kind of interpretation construes hyperbolic doubt as bounded. More precisely, the Evil Genius Doubt is (on this reading) bounded in the sense that its sceptical potency does not extend to all judgments: a special class of truths is outside the bounds of doubt. Exemplary of this special class are the cogito and, importantly, the premises of the Third Meditation proofs of God. Propositions in this special class can be indefeasibly Known even by atheists. Since the truths in this special class are Knowable independently of a divine guarantee of the C&D Rule, there is no vicious circularity in the broader argument. Throughout the arguments of Arcs 1 and 2, the premises employed count as indefeasibly Known prior to the Knowledge of the C&D Rule they help establish.

Proponents of this interpretation are apt to cite Third Meditation texts referring to truths said to be revealed by the natural light. The interpretation has it that these natural light propositions are in no way subject to doubt, unlike ordinary clearly and distinctly perceivable truths. In order to extend indefeasible Knowledge to all such truths, it is necessary to establish the general veracity of the C&D Rule. Thus, the need (on this interpretation) for Arc 2 in the broader project.

Though bounded and unbounded doubt interpretations both avoid vicious circularity, each confronts further difficulties, both textual and philosophical. Avoiding the charge of vicious circularity marks the beginning of the interpreter’s work, not the end. Bounded doubt interpreters must explain why, in the first place, the Evil Genius Doubt’s potency does not extend to propositions in the special class. Unbounded doubt interpreters must explain why, in the final analysis, the Evil Genius Doubt eventually loses it undermining potency. Let’s consider each of these further problems.

Granting a bounded doubt interpretation, why — in the first place — does the Evil Genius Doubt’s potency not extend to propositions in the special class? How is it that the doubt does undermine the proposition “that two and three added together make five,” but not the proposition “that there must be at least as much [reality] in the efficient and total cause as in the effect of that cause”? The first proposition is included in the list of examples that are undermined by the Evil Genius Doubt (see fourth paragraph of Med. 3). The second proposition is a premise in a Third Meditation argument for God — a proposition immune to doubt, according to bounded doubt interpretations. What is supposed to be the relevant difference between these propositions? Given the indirect manner in which hyperbolic doubt operates, there seems no clear explanation of why the doubt succeeds in undermining the first proposition but is somehow resisted by the second. Even more awkward for this interpretation is that the cogito is included in the list of examples that that same fourth paragraph passage implies is vulnerable to doubt.

Granting an unbounded doubt interpretation, why — in the final analysis — does the Evil Genius Doubt eventually lose its undermining potency? Putting the point ironically: Why doesn’t the Evil Genius Doubt undermine the very arguments intended to refute the Evil Genius Doubt, as soon as the mind is no longer attending to those premises? Consider Descartes’ own explanation of how hyperbolic doubt undermines the conclusions of arguments once their premises are no longer in the mind’s view:

There are other truths which are perceived very clearly by our intellect so long as we attend to the arguments on which our knowledge of them depends; and we are therefore incapable of doubting them during this time. But we may forget the arguments in question and later remember simply the conclusions which were deduced from them. The question will now arise as to whether we possess the same firm and immutable conviction concerning these conclusions, when we simply recollect that they were previously deduced from quite evident principles (our ability to call them ‘conclusions’ presupposes such a recollection). (Replies 2, AT 7:146)

So, when we’re no longer clearly and distinctly perceiving the steps of an argument, we do not “possess the same firm and immutable conviction” of its conclusion. But precisely such moments are when hyperbolic doubt does its undermining work. This means that upon diverting attention from the premises of Arcs 1 and 2, it is then possible to run the Evil Genius Doubt on their conclusions. It would thus seem that unbounded doubt interpretations leave us in a Sisyphus-like predicament. According to the myth, each time Sisyphus pushes his boulder near to the top of the hill, the boulder somehow slips away, rolling to the very bottom, and the whole process must start all over. By carefully constructing the arguments of Arcs 1 and 2, the meditator gains anti-sceptical momentum, pushing his project near to the goal of Knowledge. But each time, upon diverting his attention from the premises, he finds himself back at the bottom of the hill, wondering about the credibility of those proofs that seemed so evident: “perhaps some God could have given me a nature such that I was deceived even in matters which seemed most evident” (Med. 3, AT 7:36).

Again, the hard question for this interpretation: Why, in the final analysis, does the Evil Genius Doubt eventually lose it undermining potency? Because I hold an unbounded doubt interpretation, this is the hard problem I must confront. Elsewhere (1999), Alan Nelson and I have proposed a solution. Though space doesn’t permit a full recounting of our proposal, I’ll try to summarize the account.

Various themes about innate truths are introduced in the Fifth Meditation. Among them concerns the effects of repeated meditation: truths initially noticed only by means of inference might come to be apprehended self-evidently. In the build-up to the passage claiming that the Evil Genius Doubt is finally and fully overcome, Descartes has his meditator say:

But as regards God, if I were not overwhelmed by preconceived opinions, and if the images of things perceived by the senses did not besiege my thought on every side, I would certainly acknowledge him sooner and more easily than anything else. For what is more self-evident [ex se est apertius] than the fact that the supreme being exists, or that God, to whose essence alone existence belongs, exists?

Although it needed close attention for me to perceive this, I am now just as certain of it as I am of everything else which appears most certain. And what is more, I see that the certainty of all other things depends on this, so that without it nothing can ever be perfectly known. (Med. 5, AT 7:69)

Descartes reiterates this same theme in the Second Replies:

I ask my readers to spend a great deal of time and effort on contemplating the nature of the supremely perfect being. Above all they should reflect on the fact that the ideas of all other natures contain possible existence, whereas the idea of God contains not only possible but wholly necessary existence. This alone, without a formal argument, will make them realize that God exists; and this will eventually be just as self-evident [per se notum] to them as the fact that the number two is even or that three is odd, and so on. For there are certain truths which some people find self-evident, while others come to understand them only by means of a formal argument. (Replies 2, AT 7:163 64)

Let’s build on these texts. Let’s assume that Descartes holds that the needed conclusion comes to be self-evident — namely, the conclusion that a non-deceiving God exists who guarantees the C&D Rule. Indeed, let’s assume that this truth comes to have a kind of cogito-like status, in the following sense: whenever I try to doubt whether God exists, or is a deceiver, or the like, the effort at doubt ends up being self-stultifying. When I try to doubt my own existence, I immediately apprehend that I must exist in order to be attempting the doubt. Similarly (on this interpretation), when I try to doubt God’s existence, or benevolence, or the like, I immediately apprehend, as Descartes writes, that any such sceptical conception of God “implies a conceptual contradiction — that is, it cannot be conceived” (May 1643 letter, AT 8b:60). In that case, the hard problem for an unbounded doubt interpretation has dissolved. I can no longer doubt the Arc 1 conclusions about God, or the Arc 2 conclusions about the divine guarantee, because those conclusions have become self-evident. The mechanism for doubting inferential truths — that of attending to a conclusion without also attending to the premises on which it rests — is now impotent. No longer resting on premises, those truths are recognized as true whenever I attend to them. This interpretation explains why Descartes holds, in the final analysis, that the Evil Genius Doubt eventually loses it undermining potency.

Further reading: For Descartes’ response to the charges of circularity: see the Fourth Replies. For texts concerning his final solution to hyperbolic doubt: see Fifth Meditation; Second Replies; letter to Regius (24 May 1640). For a treatment of the Fourth Meditation proof of the C&D Rule, see Newman (1999). For examples of unbounded doubt interpretations, see Carriero (2009), Curley (1978 and 1993), DeRose (1992), Loeb (1992), Newman and Nelson (1999), Sosa (1997a and 1997b), and Van Cleve (1979). For examples of bounded doubt interpretations, see Broughton (2002), Doney (1955), Della Rocca (2005), Kenny (1968), Morris (1973), Rickless (2005), and Wilson (1978). For an anthology devoted largely to the Cartesian Circle, see Doney (1987).
7. Proving the Existence of the External Material World

The opening line of the Sixth Meditation makes clear its principal objective: “It remains for me to examine whether material things exist” (AT 7:71). At this juncture, the meditator Knows of his own existence and of God’s. It follows that there’s an external world with at least one object, God. The existence of an external material world remains in doubt. Establishing the existence of bodies is not a straightforward matter of perceiving them, because, as we have seen, “bodies are not strictly perceived by the senses” (see Section 5.2 above).

Descartes’ strategy for proving an external material world has two main parts: first, he argues for the externality of the causes of sensation; second, he argues for the materiality of these external causes. (I will refer to these putative sensations as sensations, though, strictly speaking, we cannot yet be using the term in a way that presupposes being caused by external sense organs.) From these two steps it follows that there exists an external material world. Let’s consider each phase of the argument.
7.1 The Case for the Externality of the Causes of Sensation

Descartes builds on a familiar argument in the history of philosophy, an argument that appeals to the involuntariness of sensations. The familiar argument is first articulated in the Third Meditation. Speaking of his apparently adventitious ideas (sensations), the meditator remarks:

I know by experience that these ideas do not depend on my will, and hence that they do not depend simply on me. Frequently I notice them even when I do not want to: now, for example, I feel the heat whether I want to or not, and this is why I think that this sensation or idea of heat comes to me from something other than myself, namely the heat of the fire by which I am sitting. (Med. 3, AT 7:38)

The familiar involuntariness argument amounts to the following — and recall that the me is a thinking thing, a mind:

1. Sensations come to me involuntarily (I’m unaware of causing them with my will).
2. Therefore, sensations are caused by something external to me.
3. Therefore, there exists something external to me — an external world.

(Note: in context, when this argument is first considered by the meditator, he hasn’t yet argued for the existence of God; he has yet to establish any manner of an external world.)

Though some such involuntariness argument has convinced many philosophers, the inference from 1 to 2 does not hold up to methodic doubt, as the meditator explains:

Then again, although these [apparently adventitious] ideas do not depend on my will, it does not follow that they must come from things located outside me. Just as the impulses which I was speaking of a moment ago seem opposed to my will even though they are within me, so there may be some other faculty [of my mind] not yet fully known to me, which produces these ideas without any assistance from external things; this is, after all, just how I have always thought ideas are produced in me when I am dreaming. (Med. 3, AT 7:39)

We first looked at this passage in connection with the Always Dreaming Doubt. Methodic doubt raises the problem of the existence of external things. For all I Know, my “waking” experiences are produced not by external things, but by processes similar to those producing my dreams. This sceptical hypothesis explains why the familiar involuntariness argument fails: the inference from 1 to 2 presupposes exactly what is at issue — namely, that involuntarily sensory ideas are produced by external things, rather than by a subconscious faculty of my mind.

Many philosophers have assumed that we lack the epistemic resources to solve this sceptical problem. For example, Hume writes:

By what argument can it be proved, that the perceptions of the mind must be caused by external objects … and could not arise either from the energy of the mind itself … or from some other cause still more unknown to us? It is acknowledged, that, in fact, many of these perceptions arise not from anything external, as in dreams, madness, and other diseases. … It is a question of fact, whether the perceptions of the senses be produced by external objects … But here experience is, and must be entirely silent. (Enquiry Sec. 12)

Interestingly, Descartes would agree that experiential resources cannot solve the problem. By the Sixth Meditation, however, Descartes purports to have the innate resources he needs to solve it — notably, innate ideas of mind and body. Among the metaphysical theses he develops is that mind and body have wholly distinct essences: the essence of thinking substance is pure thought; the essence of body is pure extension. In a remarkable maneuver, Descartes invokes this distinction to refute the sceptical worry that sensations are produced by a subconscious faculty of the mind: “nothing can be in me, that is to say, in my mind, of which I am not aware,” and this “follows from the fact that the soul is distinct from the body and that its essence is to think” (1640 letter, AT 3:273). This result allows Descartes to supplement the involuntariness argument, thereby strengthening the inference from line 1 to line 2. For from the additional premise that nothing can be in my mind of which I am unaware, it follows that if sensations were being produced by some activity in my mind, then I’d be aware of that activity on the occasion of its operation. Since I’m not thus aware, it follows that the sensation I’m having is produced by a cause external to my mind. As Descartes writes, this cause

cannot be in me, since clearly it presupposes no intellectual act [of awareness] on my part, and the ideas in question are produced without my cooperation and often even against my will. So the only alternative is that it is in another substance distinct from me … (Med. 6, AT 7:79)

It follows that my sensations are caused by external world objects. It remains to be shown that these external causes are material objects.
7.2. The Case for the Materiality of the Causes of Sensation

On Descartes’ analysis, there are three possible options for the kind of external thing causing sensations:

1. God
2. material/corporeal substance
3. some other created substance

That is, the cause is either infinite substance (God), or finite substance; and if finite, then either corporeal, or something else. Descartes eliminates options (a) and (c) by appeal to God being no deceiver:

But since God is not a deceiver, it is quite clear that he does not transmit the ideas to me either directly from himself, or indirectly, via some creature [other than corporeal substance] … For God has given me no faculty at all for recognizing any such source for these ideas; on the contrary, he has given me a great propensity to believe that they are produced by corporeal things. It follows that corporeal things exist. (Med. 6, AT 7:79–80, italics added)

This is a highly problematic passage. The “great propensity” here referred to is not the irresistible compulsion of clear and distinct perception. (If it were, the conclusion that sensation is caused by material objects would follow straightaway from this clear and distinct perception, via the C&D Rule.) But unless each step of the argument is clearly and distinctly perceived, Descartes should not be making the argument. Adding to the difficulties of the passage, he expressly cites the conclusion as following from the fact that “God is not a deceiver,” implying that he thinks this inference is supported by a divine guarantee. What is going on in this passage?

On one kind of interpretation, Descartes relaxes his epistemic standards in the Sixth Meditation. He no longer insists on indefeasible Knowledge, now settling for probabilistic arguments. Though there are no decisive texts indicating that this is Descartes’ intent, the interpretation does find some support. For instance, in the Synopsis Descartes writes of his Sixth Meditation arguments:

The great benefit of these arguments is not, in my view, that they prove what they establish … The point is that in considering these arguments we come to realize that they are not as solid or as transparent as the arguments which lead us to knowledge of our own minds and of God … (AT 7:15–16)

The remark can be read as a concession that the Sixth Meditation arguments are weaker than the earlier arguments about minds and God — that these later arguments do not “prove what they establish.” Of course, one need not read the remark this way. And other texts are unfavorable to this interpretation. For example, in the opening paragraphs of the Sixth Meditation Descartes considers a probabilistic argument for the existence of external bodies. Though he accepts the proposed account as offering the best explanation, he nonetheless dismisses it for the express reason that it grounds “only a probability” — it does not provide the “basis for a necessary inference that some body exists” (Med. 6, AT 7:73). This is a puzzling dismissal, assuming Descartes has relaxed his standards to probable inference.

The relaxed standards interpretation falls short for another reason. It provides no explanation of why Descartes cites a divine guarantee for the conclusion that sensations are caused by material objects.

On another kind of interpretation, the troubling passage appealing to a “great propensity” does not mark a relaxing of epistemic standards. Instead, Descartes is extending the implications of his discussion of theodicy in the Fourth Meditation. I earlier argued (Section 6.1) that Descartes thinks he demonstrates the divine guarantee of the C&D Rule by showing that an all-perfect God cannot allow us to be in error about what we clearly and distinctly perceive. What if Descartes holds that there are other perceptual circumstances under which an all-perfect God could not allow us to be in error? And suppose these other circumstances are cases like those occurring in the highly problematic passage. Under these assumptions, the resulting rule for truth would look something like the following:

I am not in error in cases in which (i) I have a great propensity to believe, and (ii) God provided me no faculty by which to correct a false such belief.

This rule is more expansive than the C&D Rule, in that it licenses more kinds of judgments. (Elsewhere (1999), I have called this the ‘Inclination Without Correction Rule’.) Clauses (i) and (ii) are tailored to the problematic passage wherein, as we’ve seen, Descartes invokes two conditions: “God has given me no faculty at all for recognizing any such source for these ideas; on the contrary, he has given me a great propensity to believe that they are produced by corporeal things.” If indeed we’re on the right interpretive track, then Descartes needs some way to prove this rule. Assuming a proof similar in structure to the proof of the C&D Rule, it would run as follows:

1. There is a non-deceiving God.
2. A non-deceiving God cannot allow me to be in error in cases in which (i) I have a great propensity to believe, and (ii) God provided me no faculty by which to correct a false such belief.
3. Therefore, I am not in error in cases in which (i) I have a great propensity to believe, and (ii) God provided me no faculty by which to correct a false such belief.

Assuming Descartes could establish premise 2, he would be entitled to this more powerful rule, and without having relaxed his standards of indefeasibility.

Elsewhere (1999), I argue that premise 2 follows from Descartes’s Fourth Meditation discussion. Prima facie, this may seem ad hoc. But even without detailing the argument, a number of texts make clear that he holds some version of premise 2. In the relevant Sixth Meditation passage, Descartes adds that from “the very fact that God is not a deceiver” there is a “consequent impossibility of there being any falsity in my opinions which cannot be corrected by some other faculty supplied by God” (Med. 6, AT 7:80). In another passage he writes that we would be “doing God an injustice” if we implied “that God had endowed us with such an imperfect nature that even the proper use of our powers of reasoning allowed us to go wrong” (Prin. 4:43, AT 8a:99). In the Second Replies he addresses the case of judgments that “could not be corrected by any clearer judgements or by means of any other natural faculty,” adding: “in such cases I simply assert that it is impossible for us to be deceived” (Replies 2, AT 7:143f). These passages strongly suggest that Descartes thinks that God’s benevolent nature entails a more expansive rule of truth than the C&D Rule. Assuming this interpretation is correct, the inferential moves in the problematic passage are not ad hoc. And as will emerge, Descartes looks again to call on this same more expansive rule in his effort to prove that he is not dreaming.

A final observation. It is often unnoticed that the conclusion of Descartes’ argument for the existence of an external material world leaves significant scepticism in place. Granting the success of the argument, my sensations are caused by an external material world. But for all the argument shows — for all the broader argument of the Meditations shows, up to this point — my mind might be joined to a brain in a vat, rather than a full human body. This isn’t an oversight on Descartes’ part. It’s all he thinks the argument can prove. For even at this late stage of the Meditations, the meditator does not yet Know himself to be awake.

Further reading: For a variation of the Sixth Meditation argument for the existence of the external material world, see Descartes’ Prin. 2.1. See also Friedman (1997), Garber (1992), and Newman (1994). On the respects in which the Sixth Meditation inference draws on Fourth Meditation work, see Newman (1999). For an interpretation of the Sixth Meditation argument that’s consistent with a direct realist interpretation, see Carriero (2009, 146ff).
8. Proving that One is Not Dreaming

By design, the constructive arguments of the Meditations unfold though the meditator remains in doubt about being awake. This of course reinforces the ongoing theme that Knowledge does not properly include judgments of external sense. In the closing paragraph of the Sixth Meditation, Descartes revisits the issue of dreaming. He claims to show how, in principle — even if not easily in practice — it is possible to achieve Knowledge that one is awake.

A casual reading of that final paragraph might suggest that Descartes offers a naturalistic solution to the problem (viz., a non-theistic solution), in the form of a continuity test: since continuity with past experiences holds only of waking but not dreaming, checking for the requisite continuity is the test for ascertaining that one is awake. The following remarks can be read in this way:

I now notice that there is a vast difference between the two [“being asleep and being awake”], in that dreams are never linked by memory with all the other actions of life as waking experiences are. … But when I distinctly see where things come from and where and when they come to me, and when I can connect my perceptions of them with the whole of the rest of my life without a break, then I am quite certain that when I encounter these things I am not asleep but awake. (Med. 6, AT 7:89–90)

This naturalistic “solution” prompts two obvious criticisms, both raised by Hobbes in the Third Objections. First, the solution runs contrary to Descartes’ No Atheistic Knowledge Thesis: since the continuity test (on the naturalistic reading of it) does not invoke God, it thus appears, as Hobbes notes, “that someone can know he is awake without knowledge of the true God” (AT 7:196). Second, as Hobbes adds, it seems one could dream the requisite continuity: one could “dream that his dream fits in with his ideas of a long series of past events,” thus undermining the credibility of the continuity test (AT 7:195).

Mirroring our discussion in Section 7.2, one kind of interpretation has Descartes relaxing his epistemic standards. He’s aware that the naturalistic solution does not stand up to methodic doubt, but he’s not attempting to overcome the Now Dream Doubt with indefeasible Knowledge. A problem for this interpretation is that it doesn’t square with the reply Descartes makes to Hobbes’ first objection: “an atheist can infer that he is awake on the basis of memory of his past life” (via the continuity test); but “he cannot know that this criterion is sufficient to give him the certainty that he is not mistaken, if he does not know that he was created by a non-deceiving God” (Replies 3, AT 7:196). Evidently, Descartes’ solution is not supposed to be available to the atheist. Taken at face value, this reply rules out a relaxed standards reading; it indeed rules out any interpretation involving a naturalistic solution to the problem of dreaming.

On closer inspection, the Sixth Meditation passage puts forward not a naturalistic solution, but a theistic one. The meditator finally concludes that he’s awake because, as the passage explicitly reads, “God is not a deceiver” (AT 7:90).

How does his argument go? Recall, in the proof of the external material world (Section 7.2), that Descartes mysteriously invokes the following (divinely guaranteed) truth rule:

I am not in error in cases in which (i) I have a great propensity to believe, and (ii) God provided me no faculty by which to correct a false such belief.

I suggest that in the dreaming passage Descartes is again invoking this rule. The passage opens with the meditator observing the following:

I can almost always make use of more than one sense to investigate the same thing; and in addition, I can use both my memory, which connects present experiences with preceding ones, and my intellect, which has by now examined all the causes of error. Accordingly, I should not have any further fears about the falsity of what my senses tell me every day; on the contrary, the exaggerated doubts of the last few days should be dismissed as laughable. This applies especially to … my inability to distinguish between being asleep and being awake. (Med. 6, AT 7:89)

Referring to the worry that he’s dreaming as exaggerated suggests that condition (i) is met — i.e., suggests that the present circumstance includes a “great propensity” to believe he’s awake. As such, he needs only to establish condition (ii), and he’ll have a divine guarantee of being awake. Notice that an important theme of the above passage concerns the meditator’s faculties for correcting sensory error — suggesting condition (ii). I propose that, in context, Descartes’ appeal to the continuity test is best understood in conjunction with condition (ii). As the meditator says (speaking of his apparently waking experience):

[W]hen I distinctly see where things come from and where and when they come to me, and when I can connect my perceptions of them with the whole of the rest of my life without a break, then I am quite certain that when I encounter these things I am not asleep but awake. And I ought not to have even the slightest doubt of their reality if, after calling upon all the senses as well as my memory and my intellect in order to check them, I receive no conflicting reports from any of these sources. For from the fact that God is not a deceiver it follows that in cases like these I am completely free from error. (Med. 6, AT 7:90; italics added)

Central to the inference is the meditator’s effort to check the correctness of his belief, by means of his various faculties. The cases like these to which Descartes refers look to be those where conditions (i) and (ii) are both satisfied. Recall what Descartes writes in conjunction with the proof of the external material world: from “the very fact that God is not a deceiver” there is a “consequent impossibility of there being any falsity in my opinions which cannot be corrected by some other faculty supplied by God” (Med. 6, AT 7:80). On the reading that I am proposing, Descartes’ theistic solution to the Now Dreaming Doubt employs the same rule that he employs in his proof for the external material world.

What about Hobbes’ second objection — in effect, that one could dream both (i) and (ii)? Descartes’ response: “A dreamer cannot really connect his dreams with the ideas of past events, though he may dream that he does. For everyone admits that a man may be deceived in his sleep.” (AT 7:196) Perhaps Descartes thinks the situation parallels that of waking life. Those who are sufficiently tired, or otherwise perceptually inattentive, “cannot really” perceive truths clearly and distinctly, though it may seem to them that they do. Whether in waking or dreaming, the Fourth Meditation theodicy has God allowing us to make judgment errors, provided that they are correctable. Relevant, therefore, is that Descartes seems to hold that the mistake of dreaming that we’re awake is correctable: “to be aware that we are dreaming we need only the intellect” (Replies 5, AT 7:359).

Importantly, Descartes does not say we can easily correct the mistake of dreaming that we’re awake. To the contrary, the Sixth Meditation treatment of the Now Dreaming Doubt closes with a concession that his solution is more theoretical than practical:

But since the pressure of things to be done does not always allow us to stop and make such a meticulous check, it must be admitted that in this human life we are often liable to make mistakes about particular things, and we must acknowledge the weakness of our nature. (Med. 6, AT 7:90)

Thus the importance of Descartes’ First Meditation remark that “no danger or error will result” from the program of methodic doubt, “because the task now in hand does not involve action” (Med. 1, AT 7:22). Methodic doubt should not be applied to practical matters. Prudence dictates that when making practical decisions I should assume I’m awake, even if I don’t Know that I’m awake. Judgment errors made while mistakenly assuming I’m awake won’t have any actual practical consequences, but those made while mistakenly assuming I’m dreaming might.

Further reading: See Newman (1999), Williams (1978), and Wilson (1978).
Bibliography
Primary Sources

Abbreviations Used:
Rules = Rules for the Direction of our Native Intelligence
Discourse = Discourse on Method
Synopsis = Synopsis of the Meditations
Meditations = Meditations on First Philosophy
Med. = any one of the six Meditations
Objs./Replies = any of the seven sets of objections/replies that Descartes published along with the Meditations
Prin. = Principles of Philosophy
Passions = The Passions of the Soul
Search = The Search for Truth
AT = Oeuvres de Descartes, Adam, Charles, and Paul Tannery, (eds.) 1904. Paris: J. Vrin. (References are to volume number and page.)
CSM = The Philosophical Writings of Descartes, Cottingham, John, and Robert Stoothoff, and Dugald Murdoch. (eds.) 1984. Cambridge: Cambridge University Press.

Dates in parentheses indicate a reference to Descartes’ correspondance. All quoted texts are from CSM. For full bibliographic information on Descartes’ writings, see the entry on Descartes.
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Other Internet Resources

* Latin text of the Meditations (original version, 1641)
* French translation of the Meditations (by Duc de Luynes, 1647)
* English translation of the Meditations (by John Veitch, 1901)
* English translation of the Discourse on Method (by John Veitch, 1901)

Related Entries

a priori justification and knowledge | certainty | Descartes, René | Descartes, René: modal metaphysics | Descartes, René: theory of ideas | Gassendi, Pierre | idealism | idealism: British | ideas | innateness: historical controversies | justification, epistemic: foundationalist theories of | knowledge: analysis of | moral particularism | original position | perception: epistemological problems of | primary and secondary qualities | rationalism vs. empiricism | realism | reasoning: defeasible | sense-data | skepticism | truth
Acknowledgments

Thanks to Robert Audi, Alan Nelson, Ram Neta, and Shaun Nichols, for helpful discussions about the ideas in this essay.
Copyright © 2010 by
Lex Newman

Published in: on February 14, 2011 at 8:53 am  Leave a Comment  

Descartes( en inglés )

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descartes
René Descartes
First published Wed Dec 3, 2008

René Descartes (1596–1650) was a creative mathematician of the first order, an important scientific thinker, and an original metaphysician. During the course of his life, he was a mathematician first, a natural scientist or “natural philosopher” second, and a metaphysician third. In mathematics, he developed the techniques that made possible algebraic (or “analytic”) geometry. In natural philosophy, he can be credited with several specific achievements: co-framer of the sine law of refraction, developer of an important empirical account of the rainbow, and proposer of a naturalistic account of the formation of the earth and planets (a precursor to the nebular hypothesis). More importantly, he offered a new vision of the natural world that continues to shape our thought today: a world of matter possessing a few fundamental properties and interacting according to a few universal laws. This natural world included an immaterial mind that, in human beings, was directly related to the brain; in this way, Descartes formulated the modern version of the mind–body problem. In metaphysics, he provided arguments for the existence of God, to show that the essence of matter is extension, and that the essence of mind is thought. Descartes claimed early on to possess a special method, which was variously exhibited in mathematics, natural philosophy, and metaphysics, and which, in the latter part of his life, included, or was supplemented by, a method of doubt.

Descartes presented his results in major works published during his lifetime: the Discourse on the Method (in French, 1637), with its essays, the Dioptrics, Meteorology, and Geometry; the Meditations on First Philosophy (i.e., on metaphysics), with its Objections and Replies (in Latin, 1641); the Principles of Philosophy, covering his metaphysics and much of his natural philosophy (in Latin, 1644); and the Passions of the Soul, on the emotions (in French, 1649). Important works published posthumously included his Letters (in Latin and French, 1657–67); World, or Treatise on Light, containing the core of his natural philosophy (in French, 1664); Treatise on Man (in French, 1664), containing his physiology and mechanistic psychology; and the Rules for the Direction of the Mind (in Latin, 1704), an early, unfinished work attempting to set out his method.

Descartes was known among the learned in his day as the best of the French mathematicians, as the developer of a new physics, and as the proposer of a new metaphysics. In the years following his death, his natural philosophy was widely taught and discussed. In the eighteenth century aspects of his science remained influential, especially his physiology, and he was remembered for his failed metaphysics and his method of doubt. In the nineteenth century he was revered for his mechanistic physiology and theory that animal bodies are machines (that is, are constituted by material mechanisms, governed by the laws of matter alone). The twentieth century variously celebrated his famous “cogito” starting point, reviled the sense data that some alleged to be the legacy of his skeptical starting point, and looked to him as a model of the culturally engaged philosopher. He has been seen, at various times, as a hero and as a villain; as a brilliant theorist who set new directions in thought, and as the harbinger of a cold, rationalistic, and calculative conception of human beings.

* 1. Intellectual Biography
o 1.1 Early life and education
o 1.2 First results, a new mission, and method
o 1.3 Metaphysical turn, comprehensive physics, Discourse
o 1.4 The metaphysics and comprehensive physics revealed
o 1.5 Theological controversy, Passions, and death
* 2. Philosophical Development
* 3. A New Metaphysics
o 3.1 How do our minds know?
o 3.2 The mark of truth
o 3.3 The nature of reality
o 3.4 Mind–body relation
o 3.5 God and error
* 4. The New Science
* 5. Theory of Sense Perception
* 6. Legacy
* Bibliography
o References
o English translations
o Other readings
* Other Internet Resources
* Related Entries

1. Intellectual Biography
1.1 Early life and education

Descartes was born on 31 March 1596 in his maternal grandmother’s house in La Haye, in the Touraine region of France. His father Joachim, a lawyer who lived in Châtteleraut (22 kilometers southwest of La Haye, across the Creuse River in the Poitou region), was away at the Parliament of Brittany in Rennes. The town of La Haye, which lies 47 kilometers south of Tours, has subsequently been renamed Descartes.

When Descartes was thirteen and one-half months old, his mother, Jeanne Brochard, died in childbirth. The young René spent his first years with his grandmother, Jeanne Sain Brochard, in La Haye, together with his older brother Pierre and older sister Jeanne. It is likely that he then moved to the house of his great uncle, Michel Ferrand, who, like many of René’s male relatives, was a lawyer, and who was Counselor to the King in Châtteleraut. When Descartes met Isaac Beeckman in 1618, Descartes introduced himself as “Poitevin,” or from Poitou (10:46, 51–4; Rodis-Lewis 1998, 26; see also 2:642). At this time (and now and again later on), he signed letters as “du Perron” and called himself “sieur du Perron” (Lord of Perron), after a small farm in Poitou he had inherited from his mother’s family (Watson 2007, 81, 230). But he did not neglect his birth place in La Haye: in a letter of 1649, he described himself as “a man who was born in the gardens of Touraine” (5:349).

In 1606 or 1607, Descartes entered the newly founded Jesuit College of La Fleche, where he remained until 1614 or 1615. He followed the usual course of studies, which included five or six years of grammar school, including Latin and Greek grammar, classical poets, and Cicero, followed by three years of philosophy curriculum. By rule, the Jesuit curriculum was based on the philosophy of Aristotle, and divided into the then-standard topics of logic, morals, physics, and metaphysics. The Jesuits also included mathematics in the final three years of study.

Aristotle’s philosophy was approached through textbooks and commentaries. Even within this framework, and taking into account the reading of Cicero, Descartes would have been exposed to the doctrines of the ancient atomists, Plato, and the Stoics, and he would have heard of the skeptics. Further, important intellectual events were known at La Fleche, including the discovery of the moons of Jupiter by Galileo in 1610.

Famously, Descartes wrote in the autobiographical portion of the Discourse that, when he left school, “I found myself beset by so many doubts and errors that I came to think I had gained nothing from my attempts to become educated but increasing recognition of my ignorance” (6:4). And yet in the next paragraph he allowed that he did not “cease to value the exercises done in the schools” (6:5), for languages, fables, oratory, poetry, mathematics, morals, theology, and philosophy all had their value, as did jurisprudence, medicine, and the other sciences (including engineering), which serve as professions and which one might study after attending a school such as La Fleche. He went on to note the contradiction and disagreement that beset philosophy and so infected the higher sciences (including medicine) “insofar as they borrow their principles from philosophy” (6:8). A year later, in 1638, he advised a correspondent on the virtues of sending the correspondent’s son to La Fleche (even if he wanted his son subsequently to transcend the learning of the schools), while also suggesting that the son might study at Utrecht with Henry le Roy, a disciple of Descartes (2:378–9). Descartes was, in the Discourse, suggesting that it was no accident that the philosophy he learned at La Fleche was uncertain: previous philosophy was bound to be uncertain, since he (Descartes) was now offering a first glimpse of the one true philosophy that he had only recently discovered. Until it could be promulgated, La Fleche, or another good school, would be the best on offer.

His family wanted Descartes to be a lawyer, like his father and many other relatives. To this end, he went to Poitiers to study law, and obtained a degree in 1616. But he never practiced law or entered into the governmental service such practice would make possible. Instead, he became a gentleman soldier, moving in 1618 to Breda, to support the Protestant Prince Maurice against the Catholic parts of the Netherlands (later, Belgium), which were controlled by Spain—a Catholic land, like France, but at this point an enemy.
1.2 First results, a new mission, and method

While in Breda, Descartes met Isaac Beeckman, a Dutch mathematician and natural philosopher. Beeckman set various problems for Descartes, including questions about falling bodies, hydrostatics, and mathematical problems. Descartes and Beeckman engaged in what they called “physico-mathematica,” or mathematical physics (10:52). Since antiquity, mathematics had been applied to various physical subject matters, in optics, astronomy, mechanics (focusing on the lever), and hydrostatics. Beeckman and Descartes brought to this work a commitment to atoms as the basic constituents of matter; as had ancient atomists, they attributed not only size, shape, and motion but also weight to those atoms (10:68). Descartes opened a section in his notebook entitled “Democritica” (10:8), in honor of the ancient atomist Democritus.

At this time, Descartes discovered and conveyed to Beeckman the fundamental insight that makes analytic geometry possible: the technique for describing lines of all sorts by using mathematical equations involving ratios between lengths. Descartes himself did not foresee replacing geometrical constructions with algebraic formulas; rather, he viewed geometry as the basic mathematical science and he considered his algebraic techniques to provide a powerful alternative to actual compass-and-ruler constructions when the latter became too intricate. When, in the nineteenth century, algebra and analysis took precedence over geometry, the rectilinear coordinate system of algebraic geometry came to be called “Cartesian coordinates” in honor of Descartes’ discovery.

Descartes left Breda in 1619 to join the Catholic army of Maximilian I (Duke of Bavaria and ally of France). The war concerned the authority of Ferdinand V, a Catholic, who had been crowned emperor of the Holy Roman Empire in September. Descartes attended the coronation and was returning to the army when winter caught him in the small town of Ulm (or perhaps Neuburg), not far from Munich. On the night of November 10, 1619, Descartes had three dreams that seemed to provide him with a mission in life. The dreams themselves are interesting and complex (see Sebba 1987). Descartes took from them the message that he should set out to reform all knowledge. He decided to begin with philosophy, since the principles of the other sciences must be derived from it (6:21–2).

Descartes’ activities over the next nine years are not well documented. He lived part of the time in Paris, visited Poitou to sell some inherited properties, and also traveled to Italy. During this time he worked on some mathematical problems, and he derived the sine law of refraction (later published in the Dioptrics). His major effort was on a work to convey his new method, the Rules.

In the Rules, he sought to generalize the methods of mathematics so as to provide a route to clear knowledge of everything that human beings can know. His methodological advice included a suggestion that is familiar to every student of elementary geometry: break your work up into small steps that you can understand completely and about which you have utter certainty, and check your work often. But he also had advice for the ambitious seeker of truth, concerning where to start and how to work up to greater things. Thus, Rule 10 reads: “In order to acquire discernment we should exercise our intelligence by investigating what others have already discovered, and methodically survey even the most insignificant products of human skill, especially those which display order” (10:403). As examples of “simple” arts “in which order prevails,” he offered carpet-making and embroidery, and also number-games and arithmetic games. He went on to discuss the roles of the “cognitive faculties” in acquiring knowledge, which include the intellect, imagination, sense perception, and memory. These faculties allow the seeker of knowledge to combine simple truths in order to solve more complex problems, such as the solution to problems in optics (10:394), or the discovery of how a magnet works (10:427).

By the end of 1628 Descartes had abandoned work on the Rules, having completed about half of the projected treatise. In that year he moved to the Dutch Netherlands, and after that he returned to France infrequently, prior to moving to Sweden in 1649. While in the Netherlands, he endeavored to keep his address a secret and he changed locations frequently, in accordance with his motto, “to live well, live secretly.”
1.3 Metaphysical turn, comprehensive physics, Discourse

Upon arriving in the Netherlands, Descartes undertook work on two sorts of topics. In Summer, 1629, an impressive set of parhelia, or false suns, were observed near Rome. When Descartes heard of them, he set out to find an explanation. (He ultimately hypothesized that a large, solid ice-ring in the sky acts as a lens to form multiple images of the sun [6:355].) This work interrupted his investigations on another topic, which had engaged him for his first nine months in the Netherlands (1:44)—the topic of metaphysics, that is, the theory of the first principles of everything that there is. The metaphysical objects of investigation included the existence and nature of God and the soul (1:144, 182). However, these metaphysical investigations were not entirely divorced from problems such as the parhelia, for he claimed that through his investigations into God and the human self, he had been able “to discover the foundation of physics” (1:144). Subsequently, Descartes mentioned a little metaphysical treatise in Latin—presumably an early version of the Meditations—that he wrote upon first coming to the Netherlands (1:184, 350). And we know that Descartes later confided to Mersenne that the Meditations contained “all the principles of my physics” (3:233).

While working on the parhelia, Descartes conceived the idea for a very ambitious treatise. He wrote to Mersenne that he had decided not to explain “just one phenomenon” (the parhelia), but rather to compose a treatise in which he explained “all the phenomena of nature, that is to say, the whole of physics” (1:70). This work eventually became The World, which was to have had three parts: on light (a general treatise on visible, or material, nature), on man (a treatise of physiology), and on the soul. Only the first two survive (and perhaps only they were ever written), as the Treatise on Light and Treatise on Man. In these works, which Descartes decided to suppress upon learning of the condemnation of Galileo (1:270, 305), he offered a comprehensive vision of the universe as constituted from a bare form of matter having only length, breadth, and depth (three-dimensional volume) and carved up into particles with size and shape, which may be in motion or at rest, and which interact through laws of motion enforced by God (11:33–4). These works contained a description of the visible universe as a single physical system in which all its operations, from the formation of planets and the transmission of light from the sun, to the physiological processes of human and nonhuman animal bodies, can be explained through the mechanism of moving matter arranged into shapes and structures and moving according to three laws of motion.

After suppressing his World, Descartes decided to put forward, anonymously, a limited sample of his new philosophy, in the Discourse with its attached essays. The Discourse recounted Descartes’ own life journey, explaining how he had come to the position of doubting his previous knowledge and seeking to begin afresh. It offered some initial results of his metaphysical investigations, including mind–body dualism. It did not, however, engage in the deep skepticism of the later Meditations, nor did it claim to establish, metaphysically, that the essence of matter is extension. This last conclusion was presented merely as a hypothesis whose fruitfulness could be tested and proven by way of its results, as contained in the attached essays on Dioptrics and Meteorology. The latter subject area comprised “atmospheric” phenomena. In his Meteorology, Descartes described his general hypothesis about the nature of matter, before continuing on to provide accounts of vapors, salt, winds, clouds, snow, rain, hail, lightning, the rainbow, coronas, and parhelia.

Near the beginning of the Meteorology, Descartes wrote that he was working from the following “supposition” or hypothesis: “that the water, earth, air, and all other such bodies that surround us are composed of many small parts of various shapes and sizes, which are never so properly disposed nor so exactly joined together that there do not remain many intervals around them; and that these intervals are not empty but are filled with that extremely subtle matter through the mediation of which, I have said above, the action of light is communicated” (6:233). He presented a corpuscularian basis for his physics, which denied the atoms-and-void theory of ancient atomism and affirmed that all bodies are composed from one type of matter, which is infinitely divisible (6:239). In the World, he had presented his non-atomistic corpuscularism, but without denying void space outright and without affirming infinite divisibility (11:12–20).

In the Meteorology, he also proclaimed that his natural philosophy had no need for the “substantial forms” and “real qualities” that other philosophers “imagine to be in bodies” (6:239). He had taken the same position in the World, where he said that in conceiving his new “world” (i.e., his conception of the universe), “I do not use the qualities called heat, cold, moistness, and dryness, as the Philosophers do” (11:25). Indeed, Descartes claimed that he could explain these qualities themselves through matter in motion (11:26), a claim that he repeated in the Meteorology (6:235–6). In effect, he was denying the then-dominant scholastic Aristotelian ontology, which explained all natural bodies as comprised of a “prime matter” informed by a “substantial form,” and which explained qualities such as hot and cold as really inhering in bodies in a way that is “similar” to the qualities of hot and cold as we experience them tactually.

Unlike Descartes’ purely extended matter, which can exist on its own having only size and shape, scholastic Aristotelians held that prime matter cannot exist on its own. To form a substance, or something that can exist by itself, prime matter must be “informed” by a substantial form (a form that renders something into a substance). The four Aristotelian elements, earth, air, fire, and water, had substantial forms that combined the basic qualities of hot, cold, wet, and dry: earth is cold and dry; air is hot and wet; fire is hot and dry; and water is cold and wet. These elements can themselves then serve as “matter” to higher substantial forms, such as the form of a mineral, or a magnet, or a living thing. Whether in the case of earth or of a living rabbit, the “form” of a thing directs its characteristic activity. For earth, that activity is to approach the center to the universe; water has the same tendency, but not as strongly. For this reason, Aristotelians explained, the planet earth has formed at the center, with water on its surface. A new rabbit is formed when a male rabbit contributes, through its sperm, the “form” of rabbithood to the seed-matter of the female rabbit. This form then organizes that matter into a the shape of a rabbit, including organizing and directing the activity of its various organs and physiological processes. The newborn rabbit’s behavior is then guided by its rabbit-specific “sensitive soul,” which is the name for the substantial form of the rabbit. Other properties of the rabbit, such as the whiteness of its fur, are explained by the “real quality” of white inhering in each strand of hair.

Although in the World and Meteorology Descartes avoided outright denial of substantial forms and real qualities, it is clear that he intended to deny them (1:324; 2:200; 3:420, 500, 648). Two considerations help explain his tentative language: first, when he wrote these works, he was not yet prepared to release his metaphysics, which would support his hypothesis about matter and so rule out substantial forms (1:563); and, second, he was sensitive to the prudential value of not directly attacking the scholastic Aristotelian position (3:298), since it was the accepted position in university education (3:577) and was strongly supported by orthodox theologians, both Catholic and Protestant (1:85–6; 3:349).

After publication of the Discourse in 1637, Descartes received in his correspondence queries and challenges to various of the doctrines, including his account of the sequence of phenomena during heart-beat and the circulation of the blood; his avoidance of substantial forms and real qualities; his argument for a distinction between mind and body; and his view that natural philosophical hypotheses could be “proven” through the effects that they explain (6:76). Descartes’ correspondence from the second half of the 1630s repays close study, among other things for his discussions of hypothesis-confirmation in science, his replies to objections concerning his metaphysics, and his explanation that he had left the most radical skeptical arguments out of this work, since it was written in French for a wide audience (1:350, 561).

In 1635, Descartes fathered a daughter named Francine. Her mother was Descartes’ housekeeper, Helena Jans. They lived with Descartes in the latter 1630s, until Francine’s untimely death in September 1640. Descartes subsequently contributed a dowry for Helena’s marriage in 1644 (Watson 2007, 188).
1.4 The metaphysics and comprehensive physics revealed

In a letter of 13 November 1639, Descartes wrote to Mersenne that he was “working on a discourse in which I try to clarify what I have hitherto written” on metaphysics (2:622). This was the Meditations, and presumably he was revising or recasting the Latin treatise from 1629. He announced to Mersenne a plan to put the work before “the twenty or thirty most learned theologians” before it was published. In the end, he and Mersenne collected seven sets of objections to the Meditations, which Descartes published with the work, along with his replies. Some objections were from theologians, one set was from the Jesuit philosopher Pierre Bourdin, and others were from Mersenne himself, the philosophers Pierre Gassendi and Thomas Hobbes, and the philosopher-theologian Antoine Arnauld.

As previously mentioned, Descartes considered the Meditations to contain the principles of his physics. But there is no Meditation labeled “principles of physics.” The principles in question, which are spread through the work, concern the nature of matter (that its essence is extension), the activity of God in creating and preserving the world, the nature of mind (that it is unextended, thinking substance), mind–body union and interaction, and the ontology of sensory qualities.

Once Descartes had presented his metaphysics, he felt free to proceed with the publication of his entire physics. However, he needed first to teach it to speak Latin (3:523), the lingua franca of the seventeenth century. He hatched a scheme to publish a Latin version of his physics (the Principles) together with a scholastic Aristotelian work on physics, so that the comparative advantages would be manifest. For this purpose, he chose the Summa philosophiae of Eustace of St. Paul. That part of his plan never came to fruition. His intent remained the same: he wished to produce a book that could be adopted into the schools, even Jesuit schools such as La Fleche (3:233, 523). Ultimately, he had some success in having his physics taught in the Netherlands and England; but for the Catholic lands, teaching of his philosophy was dampened when his works were placed on the Index of Prohibited Books in 1663.

The Principles appeared in Latin in 1644, with a French translation following in 1647. Descartes added to the French translation an “Author’s Letter” to serve as a preface. In the letter he explained important elements of his attitude toward philosophy, including the view that in matters philosophical one must reason through the arguments and evaluate them for one’s self (9B:3). He also presented an image of the relations among the various parts of philosophy, in the form of a tree:

Thus the whole of philosophy is like a tree. The roots are metaphysics, the trunk is physics, and the branches emerging from the trunk are all the other sciences, which may be reduced to three principal ones, namely medicine, mechanics and morals. By “morals” I understand the highest and most perfect moral system, which presupposes a complete knowledge of the other sciences and is the ultimate level of wisdom. (9B:14)

The extant Principles offer metaphysics in Part I; the general principles of physics, in the form of his matter theory and laws of motion, are presented in Part II, as following from the metaphysics; Part III concerns astronomical phenomena; and Part IV covers the formation of the earth and seeks to explain the properties of minerals, metals, magnets, fire, and the like, to which are appended discussions of how the senses operate and a final discussion of methodological issues in natural philosophy. His intent had been also to explain the origins of plants and animals, human physiology, mind–body union and interaction, and the function of the senses. In the end, he had to abandon the discussion of plants and animals (Princ. IV.188), but he included some discussion of mind–body union in his account of the senses.
1.5 Theological controversy, Passions, and death

From early in his correspondence with Mersenne, Descartes showed a concern to avoid becoming embroiled in theological controversy or earning the enmity of church authorities (1:85–6, 150, 271). In the end, he was drawn into theological controversy with Calvinist theologians in the Netherlands. In the latter 1630s, Henry le Roy, or Regius, a professor of medicine in Utrecht, taught Descartes’ system of natural philosophy. Already by 1640, Gisbert Voetius, a theologian at Utrecht, expressed his displeasure over this to Mersenne (3:230). Controversy brewed, at first between Regius and Voetius, with Descartes advising the latter. Voetius, who was rector of the University, convinced the faculty senate to condemn Descartes’ philosophy in 1642. He and his colleagues published two works (in 1642 and 1643) attacking Descartes’ philosophy, to which Descartes himself responded by publishing a Letter to Voetius (1643). The controversy simmered through the mid 1640s. Descartes eventually had a falling out with Regius, who published a broadsheet or manifesto, in which Regius departed from Descartes’ theory of the human mind. Descartes replied with his Comments on a Certain Broadsheet (1648).

In the mid 1640s, Descartes continued work on his physiological system, which he had pursued throughout the 1630s. He had his Treatise on Man recopied, and he began a new work, Description of the Human Body. During this period he corresponded with Princess Elisabeth, at first on topics in metaphysics stemming from her reading of the Meditations, and then on the passions and emotions. Eventually, he wrote the Passions of the Soul, which gave the most extensive account of his behavioral physiology to be published in his lifetime, and which contained a comprehensive and original theory of the passions and emotions. Portions of this work constitute what we have of Descartes’ moral theory.

In 1649, Descartes accepted the invitation of Queen Christina of Sweden to join her court. At the Queen’s request, he composed the Statutes of the Swedish Royal Academy. On the day he delivered them to her, he became ill. He never recovered. He died on 11 February 1650.
2. Philosophical Development

In general, it is rare for a philosopher’s positions and arguments to remain the same across an entire life. This means that, in reading philosophers’ works and reconstructing their arguments, one must pay attention to the place of each work in the philosophical development of the author in question. Readers of the philosophical works of Immanuel Kant are aware of the basic distinction between his critical and precritical periods. Readers of the works of G. W. Leibniz are also aware of his philosophical development, although in his case there is less agreement on how to place his writings into a developmental scheme.

Scholars have proposed various schemes for dividing Descartes’ life into periods. I favor a relatively simple division between the era when mathematics provided the model for his method, and the period after the “metaphysical turn” of 1629, when his conception of the role of the intellect in acquiring knowledge changed, and when he came to conceive the truth of his special or particular hypotheses in natural philosophy as less than certain, and so as subject to the scheme of confirmation through consequences mentioned above. In effect, he adopted a hypothetico-deductive scheme of confirmation, but with this difference: the range of hypotheses was limited by his metaphysical conclusions concerning the essence of mind and matter, their union, and the role of God in creating the preserving the universe. Consequently, some hypotheses, such as the “substantial forms” of scholastics, were ruled out. I explain argumentative differences among the World, Discourse, and Meditations and Principles as stemming from the fact that in the 1630s Descartes was arguing without yet having presented his metaphysics, and so he adopted an empirical mode of justification, whereas after 1641 he could appeal to his published metaphysics in seeking to secure the general framework of his physics.

Other scholars see things differently. John Schuster (1980) finds that the epistemology of the Rules lasted into the 1630s, and was superseded (unhappily, in his view) only by the metaphysical quest for certainty of the Meditations. Daniel Garber (1992, 48) also holds that Descartes abandoned his early method after the Discourse. Machamer and McGuire (2006) believe that Descartes expected natural philosophy to meet the standard of absolute certainty through the time of the Meditations, and that he in effect admitted defeat on that score in the final articles of the Principles, adopting a lower standard of certainty for his particular hypotheses (such as the explanation of magnetism by cork-screw shaped particles). They see the Principles as marking Descartes’ “epistemic turn” away from the methodological stance of realism found in the Rules, Discourse, and Meditations.

These contrasting views of Descartes’ intellectual development suggest different relations between his metaphysics and physics. Schuster (1980) treats Descartes’ metaphysical arguments as a kind of afterthought. Machamer and McGuire (2006) see Descartes’ alleged “epistemic turn” and his retreat from realism as a response to philosophical criticism in 1641; they find more continuity between Descartes’ Rules and his writings up to 1641 than do Garber or I. In the version I have presented, Descartes was working on physical problems first, but his metaphysical insights of 1628–9 allowed him to achieve a general conception of matter as having only “geometrical” properties, viz., size, shape, and motion.

There are also differences among interpreters concerning the relative priority in Descartes’ philosophical endeavors of epistemology or the theory of knowledge as opposed to metaphysics or first philosophy. In the account of Descartes’ development that I have given, he was interested in epistemological and methodological questions first, and these interests came to a head in the Rules. Thereafter, his aim was to establish a new natural philosophy based on a new metaphysics. In the extant works from the 1630s, the World and Discourse plus essays, he argued for the general principles of his physics, including his conception of matter, on empirical grounds. He argued from explanatory scope and theoretical parsimony. As regards parsimony or simplicity, he pointed out that his reconceived matter had only a few basic properties (especially size, shape, and motion), from which he would construct his explanations. He claimed great explanatory scope by contending that his explanations could extend to all natural phenomena, celestial and terrestrial, inorganic and organic. But throughout the 1630s, Descartes claimed that he also was in possession of a metaphysics that could justify the first principles of his physics. His arguments to establish that metaphysics are found in the Meditations and Principles.

Some scholars emphasize the epistemological aspects of Descartes’ work, starting with the Rules and continuing through to the Principles. Accordingly, the main change in Descartes’ intellectual development is the introduction of skeptical arguments in the Discourse and Meditations. Many interpreters, represented prominently in the latter twentieth century by Richard Popkin (1979), believe that Descartes took the skeptical threat to knowledge quite seriously and sought to overcome it in the Meditations. By contrast, in the main interpretive thread that I follow here, skeptical arguments were a cognitive tool that Descartes used in order to guide the reader of the Meditations into the right cognitive frame of mind for grasping the first truths of metaphysics.

The reader who is curious about these issues should read the relevant works of Descartes, together with his correspondence from the latter half of the 1630s and early 1640s.
3. A New Metaphysics

Descartes first presented his metaphysics in the Meditations, and then reformulated it in textbook-format in the Principles. His metaphysics sought to answer these philosophical questions: How does the human mind acquire knowledge? What is the mark of truth? What is the actual nature of reality? How are our experiences related to our bodies and brains? Is there a benevolent God, and if so, how can we reconcile his existence with the facts of illness, error, and immoral actions?
3.1 How do our minds know?

Descartes had no doubt that human beings know some things and are capable of discovering others, including (at least since his metaphysical insights of 1629) fundamental truths about the basic structure of reality. Yet he also believed that the philosophical methods taught in the schools of his time and used by most of his contemporaries were deeply flawed. He believed that the doctrines of scholastic Aristotelian philosophy contained a basic error about the manner in which fundamental truths, such as the truths of metaphysics, are to be gained. He expressed this mistaken view in the First Meditation, by saying (not in his own voice, but in a voice for the reader): “Whatever I have up till now accepted as most true I have acquired either from the senses or through the senses” (7:18). He then went on to challenge the veridicality of the senses with the skeptical arguments of First Meditation, including arguments from previous errors, the dream argument, and the evil-deceiver argument.

In the Aristotelian scheme against which Descartes is moving, all knowledge arises from the senses, in accordance with the slogan “There is nothing in the intellect that was not previously in the senses” (7:75, 267). Similarly, orthodox scholastic Aristotelians agreed that there is “no thought without a phantasm,” or an image. Descartes explained these convictions as the results of childhood prejudice (7:2, 17, 69, 107; Princ. I.71–3). As children, we are naturally led by our senses in seeking benefits and avoiding bodily harms. As a result, when we grow into adults we are “immersed” in the body and the senses, and so we accept the philosophical view that the senses are the basis for learning about the nature of the reality (7:38, 75, 82–3).

Descartes denied that the senses reveal the natures of substances. He held that in fact the human intellect is able to perceive the nature of reality through a purely intellectual perception. This means that in order to procure the fundamental truths of metaphysics, we must “withdraw the mind from the senses” (7:4, 12, 14) and turn toward our innate ideas of the essences of things, including the essences of mind, matter, and an infinite being (God). Descartes constructed the Meditations so as to secure this process of withdrawal from the senses in Meditation I. Meditation II brings the discovery of an initial truth, in the cogito (7:25), which is elsewhere summarized as the argument “cogito, ergo sum,” or “I think, therefore I am” (7:140). Descartes then observes that the cogito result is known only from the fact that it is “clearly and distinctly” perceived by the intellect (7:35). Hence, he sets up clear and distinct intellectual perception, independent of the senses, as the mark of truth (7:35, 62, 73).

Descartes then unfolds the results of clear and distinct perception in Meditations III–VI, and he repeats and extends these results in Principles I–II. We consider these results in Secs. 3.3–5. For now, let us examine what Descartes thought about the senses as a source of knowledge that was different from the pure intellect.

Descartes famously calls the senses into doubt in the First Meditation, and he affirms in Meditation Six that the senses are not meant to provide knowledge of the “essential nature” of external objects (7:83). In that way, his position in the Meditations differs from that in the Rules, for in that work he allowed that some “simple natures” pertaining to corporeal things can and should be considered through the images of the senses (10:383, 417). In the Meditations, he held that the essence of matter could be apprehended by innate ideas, independently of any sensory image (7:64–5, 72–3). To that extent, his later position agrees with the Platonic tradition in philosophy, which denigrated sensory knowledge and held that the things known by the intellect have a higher reality than the objects of the senses. Descartes, however, was no Platonist, a point to which we will return. His attitude toward the senses in his mature period was not one of total disparagement.

Descartes assigned two roles to the senses in the acquisition of human knowledge. First, he acknowledged that the senses are usually adequate for detecting benefits and harms for the body. Indeed, he considered their natural function to be “to inform the mind of what is beneficial or harmful for the composite of which the mind is a part” (7:83), that is, for the composite of mind and body. In this connection, he was agreeing with the conception of the function of the senses that was widely shared in the traditional literature in natural philosophy, including the Aristotelian literature, as well as in the medical literature on the natural functions of the senses.

Second, he recognized that the senses have an essential role to play in natural philosophy. The older literature on Descartes sometimes had him claiming that he could derive all natural philosophical or scientific knowledge from the pure intellect, independent of the senses. But Descartes knew full well that he could not do that. He distinguished between the general principles of his physics and the more particular mechanisms that he posited to explain natural phenomena, such as magnetism or the properties of oil and water. He claimed to derive the general principles “from certain seeds of truth” that are innate in the mind (6:64). These include the fundamental doctrine that the essence of matter is extension (Princ. II.3–4, IV.203). As to particular phenomena, in general he had to rely on observations to determine their properties (such as the properties of the magnet), and he acknowledged that multiple hypotheses about subvisible mechanisms could be constructed to account for those phenomena. The natural philosopher must, therefore, test the various hypotheses by their consequences, and consider empirical virtues such as simplicity and scope (Disc. VI; Princ. IV.201–6). Further, Descartes knew that some problems rely on measurements that can only be made with the senses, including determining the size of the sun (7:80) or the refractive indexes of various materials (Met. VIII).

In considering Descartes’ answer to how we know, we can distinguish classes of knowledge. Metaphysical first principles are known by the intellect acting alone. Such knowledge should attain absolute certainty. Practical knowledge concerning immediate benefits and harms is known by the senses. Such knowledge is usually good enough. Objects of natural science are known by a combination of pure intellect and sensory observation: the pure intellect tells us what properties bodies can have, and we use the senses to determine which particular instances of those properties bodies do have. For submicroscopic particles, we must reason from observed effects to potential cause. In these latter cases, our measurements and our inferences may be subject to error, but we may also hope to arrive at the truth.
3.2 The mark of truth

At the beginning of the Third Meditation, Descartes declares “I now seem to be able to lay it down as a general rule that whatever I perceive very clearly and distinctly is true” (7:35). Clarity and distinctness of intellectual perception is the mark of truth.

In the fifth set of Objections to the Meditations, Gassendi suggestions that there is difficulty concerning

what possible skill or method will permit us to discover that our understanding is so clear and distinct as to be true and to make it impossible that we should be mistaken. As I objected at the beginning, we are often deceived even though we think we know something as clearly and distinctly as anything can possibly be known. (7:318)

Gassendi has in effect asked how it is that we should recognize clear and distinct perceptions. If clarity and distinctness is the mark of truth, what is the method for recognizing clarity and distinctness?

In reply, Descartes claims that he has already supplied such a method. What could he have in mind? It cannot be the simple belief that one has attained clarity and distinctness, for Descartes himself acknowledges that individuals can be wrong in that belief (7:35, 361). Nonetheless, he does offer a criterion. We have a clear and distinct perception of something if, when we consider it, we cannot doubt it (7:145). That is, in the face of genuine clear and distinct perception, our affirmation of it is so firm that it cannot be shaken.

Descartes held that any act of judgment, such the affirmation “I think, therefore I am,” involves both the intellect and will. The intellect perceives or represents the content of the judgment; the will affirms or denies that content. In the face of genuine clarity and distinctness, “a great light in the intellect” is followed by “a great inclination of the will” (7:59). The inclination of the will is so strong that it amounts to compulsion; we cannot help but so affirm. Descartes thus makes unshakable conviction the criterion. But can’t someone be unshakable in their conviction merely because they are stubborn? Assuredly so. But Descartes is talking about the conviction that remains unshakable in face of serious and well-thought out challenges (7:22). To be immune from doubt does mean simply that you do not doubt a proposition, or even that it resists a momentary attempt to doubt; the real criterion for truth is that the content of a proposition is so clearly perceived that the will is drawn to it in such a way that the will’s affirmation cannot be shaken even by the systematic and sustained doubts of the Meditations. Perhaps because the process for achieving knowledge of fundamental truths requires sustained, systematic doubt, Descartes indicates that such doubt should be undertaken only once in the course of a life (7:18; 3:695).

Having extracted clarity and distinctness as the criterion of truth at the beginning of the Third Meditation, Descartes immediately calls it into question. He re-introduces an element of the radical doubt from the First Meditation: that a powerful God might have created him with “a nature such that I was deceived even in matters which seemed most evident” (7:36). Descartes therefore launches an investigation of “whether there is a God, and, if there is, whether he can be a deceiver” (7:36).

In the course of the Third Meditation, Descartes constructs an argument for the existence of God that starts from the fact that he has an idea of an infinite being. The argument is intricate. It invokes the metaphysical principle that “there must be at least as much reality in the efficient and total cause as in the effect of that cause” (7:40). This principle is put forward as something that is “manifest by the natural light” (7:40), which itself is described as a cognitive power whose results are indubitable (7:38), like clear and distinct perception (7:144). Descartes then applies that principle not to the mere existence of the idea of God as a state of mind, but to the content of that idea. Descartes characterizes that content as infinite, and he then argues that a content that represents infinity requires an infinite being as its cause. He concludes, therefore, that an infinite being, or God, must exist. He then equates an infinite being with a perfect being, and asks whether a perfect being could be a deceiver. He concludes: “It is clear enough from this that he cannot be a deceiver, since it is manifest by the natural light that all fraud and deception depend on some defect” (7:52).

The second and fourth sets of objections drew attention to a problematic characteristic of this argument. In the words of Arnauld:

I have one further worry, namely how the author avoids reasoning in a circle when he says that we are sure that what we clearly and distinctly perceive is true only because God exists. But we can be sure that God exists only because we clearly and distinctly perceive this. Hence, before we can be sure that God exists, we ought to be able to be sure that whatever we perceive clearly and evidently is true. (7:214).

Arnauld here raises the well-known problem of the Cartesian circle, which has been much discussed by commentators in recent years.

In reply to Arnauld, Descartes claims that he avoided this problem by distinguishing between present clear and distinct perceptions and those that are merely remembered (7:246). He is not here raising a question the reliability of memory (Frankfurt 1962). Rather, his strategy is to suggest that the hypothesis of a deceiving God can only present itself when we are not clearly and distinctly perceiving the infinity and perfection of God, because when we are doing that we cannot help but believe that God is no deceiver. It is as if this very evident perception is then to be balanced with the uncertain opinion that God might be a deceiver (7:144). The evident perception wins out, and the doubt is removed.

Descartes explicitly responds to the charge of circularity in the manner just described. Over the years, scholars have debated whether this response is adequate. Some scholars have constructed other responses on Descartes’ behalf, or have found such responses embedded in his text at various locations. One type of response appeals to a distinction between the natural light and clear and distinct perception, and seeks to vindicate the natural light without appeal to God (Jacquette 1996). Another response suggests that, in the end, Descartes was not aiming at metaphysical certainty concerning a mind-independent world, but was merely seeking an internally coherent set of beliefs (Frankfurt 1965). A related response suggests that Descartes was after mere psychological certainty (Loeb 1992). The interested reader can follow up this question by turning to the literature here cited (including Carriero 2008, Doney 1987, and Hatfield 2005).

Building on his claim that clear and distinct perceptions are true, Descartes claims to establish various results concerning the nature of reality, including the existence and fraudlessnes of God, and the natures of mind and matter, to which we turn in the next subsection. Here we must ask: What is the human mind that it can perceive the nature of reality? Descartes has a specific answer to this question: the human mind comes supplied with innate ideas that allow it to perceive the main properties of God (infinity and perfection), the essence of matter, and the essence of mind. For readers in Descartes’ day, this claim would naturally raise a further question: assuming that these innate ideas concern “eternal truths” about God, matter, and mind, do these truths hold independent of God, or do they instead reflect the contents of God’s own intellect?

Descartes had an interesting answer to this question. He rejected, with many of his contemporaries, the notion that there are eternal truths that obtain independently of the existence of God. Some Neoplatonist philosophers held that the eternal truths in the human mind are copies, or ectypes, of the archetypes in the mind of God. Some Aristotelian philosophers just prior to Descartes, including Francisco Suarez, held that the eternal truths reflect God’s own understanding of his creative power; God’s power includes that, if he creates a rabbit, it must be an animal. Eternal truths are latent in God’s creative power, and he understands this, so that if human beings understand the eternal truths as eternal, they do so by understanding the creative power of God.

Descartes had a different account. He held that the eternal are the free creations of God (1:145, 149, 151; 7:380, 432). God decides what the essence of circle is, or to make 2 + 3 = 5. He might have created other essences, although we are unable to conceive what they might have been. Our conceptual capacity is limited to the innate ideas that God has implanted in us, and these reflect that actual truths that he created. God creates the eternal truths (concerning logic, mathematics, the nature of the good, the essences of mind and matter), and he creates the human mind and provisions it with innate ideas that correspond to those truths.
3.3 The nature of reality

Descartes reveals his ontology implicitly in the Meditations, more formally in the Replies, and in textbook fashion in the Principles. The main metaphysical results that describe the nature of reality assert the existence of three substances, each characterized by an essence. The first and primary substance is God, whose essence is perfection. In fact, God is the only true substance, that is, the only being that is capable of existing on its own. The other two substances, mind and matter, are created by God and can only exist through his ongoing act of preservation or conservation, called God’s “concurrence” (Princ. I.51).

Descartes’ arguments to establish the essences of these substances appeal directly to his clear and distinct perception of those essences. The essence of matter is extension in length, breadth, and depth. One might speak here of “spatial extension,” but with this proviso: that Descartes denied the existence of space separate from matter. Cartesian matter does not fill a distinct spatial container; rather, spatial extension is constituted by extended matter (there is no void, or unfilled space). This extended substance possesses the further “modes” of size, shape, position, and motion. Modes are properties that exist only as modifications of the essential (principal) and the general attributes of a substance. In addition to its essence, extension, matter also has the general attributes of existence and duration. The individual parts of matter have durations as particular modes. All the modes, of matter, including size, shape, position, and motion, can exist only as modifications of extended substance.

The essence of mind is thought. Besides existence and duration, minds have two chief powers or faculties: intellect and will. The intellectual (or perceiving) power is further divided into the modes of pure intellect, imagination, and sense perception. Pure intellect operates independent of the brain or body; imagination and sense perception depend upon the body for their operation. The will is also divided into various modes, including desire, aversion, assertion, denial, and doubt. These always require some intellectual content (whether pure, imagined, or sensory) upon which to operate. Perhaps for that reason, Descartes describes the mind as an “intellectual substance” (7:78; also, 7:12). It seems he held that the mind essentially has a will, but that the intellectual (or perceptive, or representational) power is more basic, because the will depends upon it in its operation.

What role does consciousness play in Descartes’ theory of mind? Many scholars believe that, for Descartes, consciousness is the defining property of mind. There is some support for this position in the Second Replies. There Descartes defines mind as “the substance in which thought immediately resides” (7:161). He says of the term “thought” that it extends to “everything that is within us in such a way that we are immediately aware of it” (7:160). If mind is thinking substance and thoughts are essentially conscious, perhaps consciousness is the essence of thought?

Descartes in fact did hold that all thoughts are, in some way, conscious (7:226). He did not mean by this that we have reflective awareness of, and can remember, every thought that we have (5:220). In the Second Meditation, he describes himself as a thinking thing by enumerating all the modes of thoughts of which he is conscious: understanding (or intellection), willing, imagining, and (at this point, at least seeming to have) sense perceptions (7:28). He thus sets up consciousness as a mark of thought. But is it the essence? There is another possibility. If perception (intellection, representation) is the essence of thought, then all thoughts might be conscious in a basic way because the character of the intellectual substance is to represent, and any representation present in an intellectual substance is thereby conscious. Similarly, any act of will present in an intellectual substance also is available to consciousness, because it is of the essence of such a substance to perceive its own states (11:343). Accordingly, perception or representation is the essence of mind, and consciousness follows as a result of the mind’s being a representing substance.
3.4 Mind–body relation

In the Discourse, Descartes presented the following argument to establish that mind and body are distinct substances:

Next I examined attentively what I was. I saw that while I could pretend that I had no body and that there was no world and no place for me to be in, I could not for all that pretend that I did not exist. I saw on the contrary that from the mere fact that I thought of doubting the truth of other things, it followed quite evidently and certainly that I existed; whereas if I had merely ceased thinking, even if everything else I had ever imagined had been true, I should have had no reason to believe that I existed. From this I knew I was a substance whose whole essence or nature is simply to think, and which does not require any place, or depend on any material thing, in order to exist. (6:32–3)

This argument moves from the fact that he can doubt the existence of the material world, but cannot doubt the existence of himself as a thinking thing, to the conclusion that his thoughts belong to a nonspatial substance that is distinct from matter.

The problem with this argument is that it is fallacious. It relies on conceivability based in ignorance. For Descartes has not included anything in the argument to ward off the possibility that he, as a thinking thing, is not in fact a complex material system. He has merely relied on the fact that he can doubt the existence of matter to conclude that matter is distinct from mind. But this argument is clearly inconclusive. From the fact that the Joker cannot, at a certain moment, doubt the existence of Batman (because he is with him), but he can doubt the existence of Bruce Wayne (who might, for all the Joker knows, have been killed by the Joker’s henchmen), it does not follow that Bruce Wayne is not Batman. In fact, he is Batman. The Joker is merely ignorant of that fact.

In the Meditations, Descartes changed the structure of the argument. In the Second Meditation, he established that he could not doubt the existence of himself as a thinking thing, but that he could doubt the existence of matter. However, he explicitly refused to use this situation to conclude that his mind was distinct from body, on the grounds that he was still ignorant of his nature (7:27). Then, in the Sixth Meditation, having established, to his satisfaction, the mark of truth, he used the mark to frame a positive argument to the effect that the essence of mind is thought, and that a thinking thing is unextended; and that the essence of matter is extension, and that extended things cannot think (7:78). He based this argument on clear and distinct intellectual perceptions of the essences of mind and matter, not on the fact that he could doubt the existence of one or the other.

The conclusion of the Sixth Meditation constitutes the well-known substance dualism of Descartes. That dualism leads to problems. As Princess Elisabeth, among others, asked Descartes: if mind is unextended and matter is extended, how do they interact? This problem vexed not only Descartes, who admitted to Elisabeth that he didn’t have a good answer (3:694), but it also vexed Descartes’ followers and other metaphysicians. It seems that, somehow, the states of mind and body must be brought into relation, because when we decide to pick up a pencil our arm actually moves, and when light hits our eyes we experience the visible world. But how do mind and body interact? Some of Descartes’ followers adopted an occasionalist position, according to which God mediates the causal relations between mind and body; mind does not affect body, and body does not affect mind, but God gives the mind appropriate sensations at the right moment, and he makes the body move by putting it into the correct brain states at a moment that corresponds to the volition to pick up the pencil. Other philosophers adopted yet other solutions, including the monism of Spinoza and the pre-established harmony of Leibniz.

In the Meditations and Principles, Descartes did not focus on the metaphysical question of how mind and body interact. Rather, he discussed the functional role of mind–body union in the economy of life. As it happens, our sensations serve us well in avoiding harms and pursuing benefits. Pain-sensations warn us of bodily damage. Pleasure leads us to approach things that (usually) are good for us. Our sense perceptions are reliable enough that we can distinguish objects that need distinguishing, and we can navigate as we move about. As Descartes saw it, “God or nature” set up these relations for our benefit. They are not perfect. Sometimes we feel pain because a nerve has been damaged, and yet there is no tissue damage at the place in which the pain is felt. Descartes observed that amputees may feel pain in their fingers when they have no fingers (Princ. IV.196). Sometimes we experience sensory illusions. All the same, he regarded the union of mind and body to have been instituted by God in the best manner possible for finite beings such as ourselves (7:88). Further, we can use our intellects to interpret illusions or other false sensations (7:438).
3.5 God and error

In discussing the mark of truth, Descartes suggested that the human intellect is as reliable as it is because it was created by God. In discussing the functioning of the senses to preserve or maintain the body, he explained that God has arranged the rules of mind–body interaction in a manner that is conducive to the good of the body. Nonetheless, in each case, errors occur, just as, more broadly, human beings make poor moral choices, even though God has given them a will that is intrinsically drawn to the good (1:366, 5:159, Princ. I.42).

Descartes responded these problems differently. He explained cognitive and moral errors as resulting from human freedom. God provides human beings with a will, and wills are intrinsically free. In this way, there is no difference in degree in freedom between God and man. But human beings have finite intellects. And because they are free, they can choose to judge in cognitive or moral situations for which they do not have clear and distinct perceptions of the true or the good. If human beings restricted their acts of will to cases of clear and distinct perception, they would never err. But the vicissitudes of life may require judgments in less than optical circumstances, or we may decide to judge even though we lack a clear perception. In either case, we may go wrong.

Matters are different for the errors of the senses. The senses depend on media and sense organs, and on nerves that must run from the exterior of the body into the brain. God sets up the mind–body relation so that our sensations are good guides for most circumstances. But the media may be poor (the light may not be good), circumstances may be unusual (as with the partially submerged stick that appears as if bent), or the nerves may be damaged (as with the amputee). In these cases, the reports of the senses are suboptimal. Since God has set up the system of mind–body union, shouldn’t God be held accountable for the fact that the senses can mislead? Here Descartes does not appeal to our freedom not to attend to the senses, for in fact we must often use the senses in suboptimal cognitive circumstances when navigating through life. Rather, he points out that God was working with the finite mechanisms of the human mind and body, and he suggests that God did the best he could (7:88).
4. The New Science

When Descartes was at La Fleche, there already were signs that the conception of the universe was changing. Recall that Galileo’s discovery of four moons of the planet Jupiter was celebrated at La Fleche in 1610. More generally, Copernicus had, in the previous century, offered a forceful argument for believing that the sun, not the earth, is at the center of the solar system. Early in the seventeenth century, Johannes Kepler announced new results in optics, concerning the formation of images, the theory of lenses, and the fact that the retinal image plays a central role in vision. By the early 1630s, Descartes was aware (1:263) of William Harvey’s claim that the blood circulates in the body.

Descartes himself contributed some specific new results to the mathematical description of nature, as co-discoverer of the sine law of refraction, and as developer of an accurate model of the rainbow. Nonetheless, as significant as these results are, his primary contribution to the “new science” lay in the way in which he described a general vision of a mechanistic approach to nature and sketched in the details of that vision to provide a comprehensive alternative to the dominant Aristotelian physics.

In the textbooks of Aristotelian physics of Descartes’ day, it was common to divide physics into “general” and “special.” General physics pertained to the basic Aristotelian principles for analyzing natural substances: form, matter, privation, cause, place, time, motion. Special physics concerned actually existing natural entities, divided into inanimate and animate. Inanimate physics further divided into celestial and terrestrial, in accordance with the Aristotelian belief that the earth was at the center of the universe, and that the earth was of a different nature than the heavens (including the moon, and everything beyond it). Inanimate terrestrial physics first covered the four elements (earth, air, fire, and water), then the “mixed” bodies composed from them, including the various mineral kinds. Animate terrestrial physics concerned the various powers that Aristotelians ascribed to the ensouled beings, where the soul is considered as a principle of life (possessing vital as well as mental or cognitive powers). In the simplest textbooks, the powers of the soul were divided into three groups: vegetative (including nutrition, growth, and reproduction), which pertained to both plants and animals; sensitive (including external senses, internal senses, appetite, and motion), which pertain to animals alone; and rational powers, pertaining to human beings alone. All the bodies in both inanimate and animate terrestrial physics were governed by a “form” or active principle, as described in Section 1.3.

Descartes’ ambition was to provide replacements for all the main parts of Aristotelian physics. In his physics, there is only one matter and it has no active forms. Thus, he dissolved the boundary that had made the celestial and the terrestrial differ in kind. His one matter had only the properties of size, shape, position, and motion. The matter is infinitely divisible and it constitutes space; there is no void, hence no spatial container distinct from matter. The motions of matter are governed by three laws of motion, including a precursor to Newton’s law of inertia (but without the notion of vector forces), and a law of impact. Descartes’ matter possessed no “force” or active agency; the laws of motion were decreed by God and were sustained by his activity. Earth, air, fire, and water were simply four among many natural kinds, all distinguished simply by the characteristic sizes, shapes, positions, and motions of their parts.

Although Descartes nominally subscribed to the Biblical story of creation, in his natural philosophy he presented the hypothesis that the universe began as a chaotic soup of particles in motion and that everything else was subsequently formed as a result of patterns that developed within this moving matter. Thus, he conceived that many suns formed, around which planets coalesced. On these planets, mountains and seas formed, as did metals, magnets, and atmospheric phenomena such as clouds and rain. The planets themselves are carried around the sun in their orbits by a fluid medium that rotates like a whirlpool or vortex. Objects fall to earth not because of any intrinsic “form” that directs them to the center of the universe, and also not because of a force of attraction or other downward-tending force. Rather, they are driven down by the whirling particles of the surrounding ether. Descartes insisted that all cases of apparent action at a distance, including magnetism, must be explained through the contact of particle on particle. He explained magnetism as the result of cork-screw shaped particles that spew forth from the poles of the earth and flow from north to south, causing magnetized needles to align with their flow.

Descartes also wanted to provide an account of the formation of plants and animals by mechanical causes, but he did not succeed during his lifetime in framing an account that he was willing to publish. He did, however, develop an extensive physiological description of animal bodies, in which he explained the functions of life in purely mechanical manner, without appeal to a soul or vital principle.

In mechanizing the concept of living thing, Descartes did not deny the distinction between animate and inanimate, but he redrew the line between ensouled and unensouled beings. In his view, among earthly beings only humans have souls. He thus equated soul with mind: souls account for intellection and volition, including conscious sensory experiences, conscious experience of images, and consciously experienced memories. Descartes regarded nonhuman animals as machines, devoid of mind and consciousness. This meant that he was required to explain all of the powers that Aristotelians had ascribed to the vegetative and sensitive soul by means of purely material and mechanistic processes (11:202). These mechanistic explanations extended, then, not merely to nutrition, growth, and reproduction (which he wrote about but never achieved results that were published during his lifetime), but also to the functions of the external and internal senses, including the ability of nonhuman animals to respond via their sense organs in a situationally appropriate manner: to approach things that are beneficial to their body (including food), and to avoid danger (as the sheep avoids the wolf).

In the Treatise on Man and Passions, Descartes described purely mechanical processes in the sense organs, brain, and muscles, that were to account for the functions of the sensitive soul. These processes involved “animal spirits,” or subtle matter, as distilled out of the blood at the base of the brain and distributed down the nerves to cause muscle motions in accordance with brain structures and current sensory stimulation. The brain structures that mediate behavior may be innate or acquired. Descartes ascribed some things that animals can do to instinct; other aspects of their behavior he explained through a kind of mechanistic associative memory. He held that human physiology is similar to nonhuman animal physiology, as regards both vegetative and (some) sensitive functions—those sensitive functions that do not involve consciousness or intelligence:

Now a very large number of the motions occurring inside us do not depend in any way on the mind. These include heartbeat, digestion, nutrition, respiration when we are asleep, and also such waking actions as walking, singing, and the like, when these occur without the mind attending to them. When people take a fall, and stick out their hands so as to protect their head, it is not reason that instructs them to do this; it is simply that the sight of the impending fall reaches the brain and sends the animal spirits into the nerves in the manner necessary to produce this movement even without any mental volition, just as it would be produced in a machine. (7:229–30)

Many of the behaviors of human beings are actually carried out without intervention from the mind.

The fact that Descartes offered mechanistic explanations for many features of nature does not mean that his explanations were successful. Indeed, his followers and detractors debated the success of his various proposals for nearly a century after his death. His accounts of magnetism and gravity were challenged. Leibniz challenged the coherence of Descartes’ laws of motion and impact. Newton offered his own laws of motion and an inverse square law of gravitational attraction. His account of orbital planetary motions replaced Descartes’ vortexes. Others struggled to make Descartes’ physiology work. There were also deeper challenges. Some wondered whether Descartes could actually explain how his infinitely divisible matter could coalesce into solid bodies. Why shouldn’t collections of particles act like whiffs of smoke, that separate upon contact with large particles? Indeed, how do particles themselves cohere?

Such problems were real, and Descartes’ physics was abandoned over the course of the eighteenth century. Nonetheless, it provided a conception for a comprehensive replacement of Aristotelian physics that persisted in the Newtonian vision of a unified physics of the celestial and terrestrial realms, and that continued in the mechanistic vision of life that was revived in the latter part of the nineteenth century.
5. Theory of Sense Perception

As the new “mechanical philosophy” of Descartes and others replaced the Aristotelian physics, the theory of sensory qualities had to undergo substantial change. This was especially true for what came to be known as the secondary qualities (in the terminology of Robert Boyle and John Locke). The secondary qualities include colors, sounds, odors, tastes, and tactile qualities such as hot and cold. The Aristotelians maintained that these qualities exist in objects as “real qualities” that are like instances or samples of the quality as experienced. A red thing possesses the quality red in just the same way it possesses a shape: it simply is red, and we experience that very redness when we see a red object.

Descartes sought to replace “real qualities” with a mechanistic account of qualities in objects. He rendered light as a property of particles and their motions: it is a “tendency to move” as found in a continuous medium and radiating out from a luminous body. When light strikes an object, the particles that constitute light alter their rotation about their axis. “Spin” is what makes light have one color rather than another. When particles with one or another degree of spin interact with the nerves of the retina, they cause those nerves to jiggle in a certain way. This jiggling is conveyed to the brain where it affects the animal spirits, which in turn affect the mind, causing the mind to experience one or another color, depending on the degree of spin and how it affects the brain. Color in objects is thus that property of their surface that causes light particles to spin in one way or another, and hence to cause one sort of sensation or another. There is nothing else in the surface of an object, as regards color, than a certain surface-shape that induces one or another spin in particles of light.

Descartes introduced this new theory of sensory qualities in the first six chapters of the World. There, he defended it on the grounds of that his explanation of qualities in bodies in terms of size, shape, and motion are clearly understood, by comparison with the Aristotelian qualities (11:33). Subsequently, in the Meditations and Principles, he defended this account by appeal to the metaphysical result that body possesses only geometrical modes of extension. Real qualities are ruled out because they are not themselves instances of size, shape, or motion (even if patches of color have a size and a shape, and can be moved about).

In addition to a new theory of sensory qualities, Descartes offered theories of the way in which the spatial properties—size, shape, distance, and position—are perceived in vision. Optics had been an area of inquiry since antiquity. Euclid and Ptolemy had each written on optical problems. During the Middle Ages, the Arabic natural philosopher Ibn al-Haytham produced an important new theoretical work in which he offered an extensive account of the perception of spatial properties.

The theoretical terrain in optics changed with Kepler’s doctrine that vision is mediated by the retinal image and that the retina is the sensitive body in the eye. Previous theorists generally believed that the “crystalline humor,” now known as the lens, was the sensitive body. Descartes accepted Kepler’s result and framed a new theory of spatial perception. Some of his theorizing simply adapted Ibn al-Haytham’s theories to the newly discovered retinal image. Thus, Ibn al-Haytham held that size is perceived by combining the visual angle that a body subtends with perception of its distance, to arrive at a perception of the true size of the object. In al-Haytham’s scheme, visual angle is registered at the surface of the crystalline humor. Descartes held that size is perceived by combining visual angle with perceived distance, but now he treated visual angle as the extent of an object’s projection onto the retina.

In Ibn al-Haytham’s account, distance may be inferred if the size of an object is known; then, its visual angle is an inversely proportional to its distance. Descartes recognized this traditional account, depending as it does on past experience of an object’s size and on an inference or rapid judgment that combines perceived visual angle with known or remembered size. Ibn al-Haytham also explained that distance can be perceived by an observer’s being sensitive to the number of equal portions of ground space that lie between the observer and a distant object. Descartes did not adopt this explanation. However, Descartes used his mechanistic physiology to frame a new account of how distance might be perceived, a theory different from anything that could have been found in Ibn al-Haytham.

In Kepler’s new theory of how the eye works, an image is formed on the retina as a result of refraction by the cornea and lens. For objects at different distances, the focal properties of the system must be changed, just as the focal length of a camera is changed. There were several theories of how this might occur, but Descartes accepted the view that the lens changes shape or “accommodates” for near and far vision. He then theorized that this change in the shape of the lens must be controlled by muscles, which themselves are controlled by nerve processes in the brain. He realized that the central nervous state that controls accommodation would vary directly in proportion to the distance of objects. However, unlike the case of inferring distance from known size and visual angle, Descartes did not suppose that the mind is aware of the apparatus for controlling the accommodation of the eye. Rather, he supposed that, by an innate mechanism, the central brain state that varies with distance directly causes an idea of distance in the mind (6:137; 11:183). This physiologically produced idea of distance could then be combined with perceived visual angle in order to perceive an object’s size, as in al-Haytham’s theory of size perception.
6. Legacy

The things that readers find valuable in Descartes’ work have changed over the centuries. We have seen that his natural philosophy had an immediate impact that lasted into the eighteenth century. His theory of vision was part of that heritage, as were his results in mathematics. We have also seen that his mechanistic account of the psychology of the sensitive soul and his view that animals are like machines were revived in the nineteenth century.

The fortune of the metaphysical and epistemological aspects of Descartes’ philosophy is complex. In his own time, he inspired a raft of followers, who sought to develop his metaphysics, epistemology, natural philosophy, and even to add a worked-out ethics. These authors included Geraud de Cordemoy, Arnold Geulincx, Antoine Le Grand, Nicolas Malebranche, Pierre Regis, and Jacques Rohault. The British philosopher Henry More at first followed Descartes but subsequently turned against him. Other major philosophers, including Benedict de Spinoza and G. W. Leibniz, were influenced by Descartes’ thought but developed their own, distinct systems.

Philosophers in subsequent ages have stressed various aspects of Descartes’ philosophy, in some cases without undertaking close study of his writings. In the eighteenth century, Hume and Kant (each in his own way) rejected the metaphysical aspirations of Descartes, to know the nature of reality as it is in itself. They did not merely deny his particular metaphysical theories; they rejected his sort of metaphysical project altogether.

During the twentieth century, two aspects of his philosophy became widely invoked and perhaps just as widely misinterpreted. The first is Descartes’ skepticism. In the early twentieth century, one response to the threat of skepticism was to retreat to the position that we can only know our own sense data, where “sense data” are equated with the supposed contents of immediate sensory experience: for vision, color patches having a shape. Some authors then treated Descartes’ project in the Meditations as that of reducing human knowledge to immediate sense data, from which knowledge of the external world was then to be constructed.

As a reading of Descartes, this position has little to offer. As we have seen, in the Second and Third Meditations Descartes argues from the indubitability of the cogito reasoning to the trustworthiness of intellectual perception to the existence of a perfect being (God). In the latter argument, he does indeed seek to infer the reality of a being external to himself. But the inference has nothing to do with sensory experience. The inference proceeds from a nonsensory and innate idea of God to the existence of that God. Whatever one may think of the quality of the argument, it has nothing to do with sense data. Descartes used skeptical arguments as a tool to disengage the reader from the sensory world in order to undertake metaphysical investigations. There did result, in the Sixth Meditation, a re-evaluation of the senses in relation to metaphysics. But again, sense data were not in the mix.

Another prominent line of twentieth-century interpretation also focuses on the isolation of the subject in the Second Meditation. In the course of that Meditation, Descartes accepts that he knows the contents of his mind, including putative sensory experiences, even though he doubts the existence of his body. Some philosophers have concluded from this that Descartes believed that human beings actually can, in their natural state, have sensory experiences even if they lack a body. But Descartes in fact denied that possibility. In his metaphysics, sense perception and imagination depend for their existence on mind–body union. There can be intellectual perceptions that do not depend on the brain. But acts of imagination and sense perception depend on the brain for their occurrence (Pass. I.19–20, 43). Thus, Descartes did not in fact hold that we might have all of our sense experiences even if we had no brain. Rather, he allowed that he could conceive his sensory experiences independent of the brain, and that, if God were not supremely good, God could produce those experiences in us independent of the brain. But conceivability does not in all cases—and especially not in cases of mere ignorance, as in the Second Meditation—yield metaphysical possibility (as we have seen in the Discourse argument for the mind–body distinction).

In Descartes’ view, it is impossible that a deceiving God would cause our sensory experiences (since God is essentially perfect and so supremely good). Descartes denied that human beings can clearly conceive that God is a deceiver (7:144), and he also maintained that it is “self-contradictory that men [human beings] should be deceived by God” (7:428). But, as he argued in the Sixth Meditation, if our sensory perceptions were not in fact caused by bodies, God would be a deceiver (7:80). Since we can neither clearly conceive of him as a deceiver nor allow the possibility that he is a deceiver, we cannot take seriously the possibility that he produces our sensory experiences in the absence of the existence of material things and, more specifically, in the absence of the relevant brain states.

In the end, Descartes’ legacy in part consists of problems he raised, or brought into prominence, but did not solve. The mind–body problem is a case in point. Descartes himself argued from his ability clearly and distinctly to conceive mind and body as distinct beings to the conclusion that they really are separate substances. Most philosophers today accept neither the methodological basis for his claim nor the claim itself. Indeed, since the time of Kant, few philosophers have believed that the clear and distinct thoughts of the human mind are a guide to the absolute reality of things. Hence, the notion that even clear conceivability discerns metaphysical possibility is not accepted. Moreover, few philosophers today are substance dualists.

All the same, the mind–body problem persists. In distinguishing the domain of the mental from that of the physical, Descartes struck a chord. Many philosophers accept the conceptual distinction, but remain uncertain of the underlying metaphysics: whether mind is identical with brain; or the mental emerges from complex processes in the brain; or constitutes a property that is different from any purely physical property, even while being instantiated by the brain. In this case, a problem that Descartes made prominent has lived far beyond his proposed solution.
Bibliography

NOTE: In referring to Descartes’ works, I have used the pagination of the Adam and Tannery volumes (AT), Oeuvres de Descartes, 11 vols. The citations give volume and page numbers only (dropping the abbreviation “AT”). Whenever possible, I have used the Cottingham, Stoothoff, Murdoch, and Kenny translation, The Philosophical Writings Of Descartes, 3 vols., which shows the AT pagination in the margins. The AT volume numbers provide a guide to which work is being cited in translation: vols. 1–5, correspondence; vol. 6, Discourse; vol. 7, Meditations; vol. 10, Rules; vol. 11:1–118, World, or Treatise on Light; vol. 11:119–222, Treatise on Man; vol. 11:301–488, Passions. Where there is no accessible translation for a citation from AT, I show the citation in italics. I also cite works that are broken into articles by abbreviated title, part, and article: Princ. for the Principles, and Pass. for the Passions.
References

* Carriero, John. 2008. “Cartesian Circle and the Foundations of Knowledge,” in Companion to Descartes, ed. Janet Broughton and John Carriero. Malden, Mass.: Blackwell.
* Descartes, René 1964–76. Oeuvres de Descartes, 11 vols., ed. Charles Adam and Paul Tannery. Paris: Vrin/CNRS. Cited by volume and page number.
* Doney, Willis, ed., 1987. Eternal Truth and the Cartesian Circle. New York: Garland Publishing.
* Frankfurt, Harry G. 1962. “Memory and the Cartesian Circle,” Philosophical Review, 71: 504–11.
* Frankfurt, Harry G. 1965. “Descartes’ Validation of Reason,” American Philosophical Quarterly, 2: 149–56.
* Garber, Daniel. 1992. Descartes’ Metaphysical Physics. Chicago: University of Chicago Press.
* Hatfield, Gary. 2005. “Cartesian Circle,” in Blackwell Guide to Descartes’ Meditations, ed. S. Gaukroger. Oxford: Blackwell, 122–41.
* Jacquette, Dale. 1996. “Descartes’ Lumen Naturale and the Cartesian Circle,” Philosophy and Theology: Marquette University Quarterly, 9: 273–320.
* Loeb, Louis. 1992. “Cartesian Circle,” in Cambridge Companion to Descartes, ed. J. Cottingham. Cambridge: Cambridge University Press, 200–35.
* Machamer, Peter, and J. E. McGuire. 2006. “Descartes’s Changing Mind,” Studies In History and Philosophy of Science, 37: 398–419.
* Popkin, Richard H. 1979. History of Scepticism from Erasmus to Spinoza. Berkeley: University of California Press.
* Schuster, John. 1980. “Descartes’ Mathesis Universalis, 1619–28,” in Descartes: Philosophy, Mathematics and Physics, ed. S. Gaukroger. New Jersey: Barnes and Noble, 41–96.
* Sebba, Gregor. 1987. Dream of Descartes. Carbondale, Ill.: Southern Illinois University Press.
* Watson, Richard. 2007. Cogito, Ergo Sum, rev. edn. Boston: Godine.

English translations

* Descartes, René. 1965. Discourse on Method, Optics, Geometry, and Meteorology, trans. Paul J. Olscamp. Indianapolis: Bobbs-Merrill. Originally published in French in 1637.
* –––. 1983. Principles of Philosophy, trans. V. R. Miller and R.P. Miller. Dordrecht: Reidel. Originally published in Latin in 1644.
* –––. Philosophical Writings of Descartes, 3 vols., trans. John Cottingham, Robert Stoothoff, Dugald Murdoch, and Anthony Kenny (Cambridge: Cambridge University Press, 1984–91).
* –––. 1989. Passions of the Soul, trans. Stephen H. Voss Indianapolis: Hackett. Originally published in French in 1649.
* –––. 1998. World and Other Writings, trans. Stephen Gaukroger. Cambridge: Cambridge University Press.

Other readings

* Broughton, Janet, and John Carriero, eds. 2008. Companion to Descartes. Malden, Mass.: Blackwell.
* Clarke, Desmond M. 1982. Descartes’ Philosophy of Science. University Park: Pennsylvania State University Press.
* Cottingham, John, ed. 1992. Cambridge Companion to Descartes. Cambridge: Cambridge University Press.
* –––, ed. 1994. Reason, Will and Sensation: Studies in Descartes’s Metaphysics. Oxford: Clarendon Press.
* –––, ed. 1998. Descartes. Oxford: Oxford University Press.
* Curley, Edwin. 1978. Descartes against the Skeptics. Cambridge, Mass.: Harvard University Press.
* Dicker, Georges. 1993. Descartes: An Analytical and Historical Introduction. New York: Oxford University Press.
* Frankfurt, Harry. 1970. Demons, Dreamers, and Madmen. Indianapolis: Bobbs-Merrill.
* Gaukroger, Stephen. 1995. Descartes: An Intellectual Biography. Oxford: Oxford University Press.
* –––. 2002. Descartes’ System of Natural Philosophy. Cambridge: Cambridge University Press.
* Gaukroger, Stephen, John Schuster, and John Sutton, eds. 2000. Descartes’ Natural Philosophy. London: Routledge.
* Guèroult, Martial. 1984–85. Descartes’ Philosophy Interpreted According to the Order of Reasons, trans. R. Ariew, 2 vols. Minneapolis: University of Minnesota Press.
* Hatfield, Gary. 2003. Descartes and the Meditations. London: Routledge.
* Nelson, Alan, ed. 2005. Blackwell Companion to Rationalism. Oxford: Blackwell.
* Rodis-Lewis, Geneviève. 1998. Descartes: His Life and Thought, trans. J. M. Todd. Ithaca: Cornell University Press.
* Rorty, Amélie, ed. 1986. Essays on Descartes’ Meditations. Berkeley: University of California Press.
* Shea, William R. 1991. Magic of Numbers and Motion. Canton, Mass.: Science History Publications.
* Smith, Norman Kemp. 1953. New studies in the Philosophy of Descartes: Descartes as Pioneer. London: Macmillan.
* Voss, Stephen, ed. 1993. Essays on the Philosophy and Science of René Descartes. New York: Oxford University Press.
* Williams, Bernard. 1978. Descartes, The Project of Pure Inquiry. London: Penguin.
* Wilson, Catherine. 2003. Descartes’s Meditations: An Introduction. Cambridge: Cambridge University Press.
* Wilson, Margaret D. 1978. Descartes. London: Routledge & Kegan Paul.

Other Internet Resources

* Descartes, resources from PhilWeb

Related Entries

Arnauld, Antoine | Cordemoy, Geraud de | Descartes, René: and the pineal gland | Descartes, René: epistemology | Descartes, René: ethics | Descartes, René: life and works | Descartes, René: modal metaphysics | Descartes, René: ontological argument | Descartes, René: physics | Descartes, René: theory of ideas | emotion: 17th and 18th century theories of | Gassendi, Pierre | Le Grand, Antoine | More, Henry | Regius, Henricus
Acknowledgments

The editors would like to thank Gintautas Miliauskas (Vilnius University) for notifying us of a variety of typographical errors in this entry.
Copyright © 2008 by
Gary Hatfield

Published in: on February 14, 2011 at 8:51 am  Leave a Comment  

teoría de las ideas de Descartes

FUENTE http://plato.stanford.edu/entries/descartes-ideas/
Descartes’ Theory of Ideas
First published Wed Mar 14, 2007

“Idea,” in its various linguistic forms, has been used in many ways by many philosophers, ancient, medieval, and early modern. Unfortunately for our current purposes, it was also used in many ways by Descartes himself. Exegesis of his views is, as a result, both a challenging and inescapably contentious affair. Amongst the many problems a complete exegesis would make sense of are these:

1. Descartes’ uses of the term “idea” diverge from perhaps the original or primary scholastic use;
2. He provides multiple non-equivalent definitions of the term, uses it to refer to as many as six distinct kinds of entities, and divides ideas inconsistently into various genetic categories;
3. He makes a trio of apparently inconsistent distinctions concerning ideas, invoking other opaquely employed scholastic concepts;
4. It’s not clear that his “ideas” are consistent with his own ontology in general;
5. What he says about ideas suggests a “veil of perception” account of cognition,[1] on which the cognizing mind is not directly “aware” of the external object itself, but only of some representative proxy; yet at the same time his texts sometimes indicate some form of direct cognition of the object itself;
6. Ideas’ most important epistemic property — that of being clear and distinct — is ill-defined and poorly explicated, to the point that debates arise about whether and which ideas have this property;[2]
7. To this day there are divergent interpretations of Descartes’ account of sensory processes and ideas, concerning where and how he distinguishes between them and intellectual processes and ideas, whether sensory ideas have representational content, what Descartes means by the “material falsity” of some (or all?) sensory ideas, what the ontological status of “secondary” qualities is, etc.

These issues may be divided, roughly, into the metaphysical and the epistemological, reflecting the central role ideas play in both domains for Descartes. Since Descartes’ conception of “clarity and distinctness” is discussed elsewhere in SEP,[3] and since an adequate account of his views on sensation and its relationship to the intellectual would require a whole article in its own right, this entry will focus on (1)–(5) above, and thus primarily on the metaphysical issues and on intellectual ideas. Since many of the difficulties in Cartesian “ideas” arise from his simultaneously both reflecting and attempting to reject the relevant scholastic philosophy, we must begin there.

* 1. The Scholastic Background
* 2. The What and the Whence of Cartesian Ideas
* 3. Formal, Material, Objective
* 4. Cartesian Ontology, and Ideas
* 5. Ideas and Direct Cognition
* Conclusion
* Bibliography
o Primary Sources
o Secondary Sources
* Other Internet Resources
* Related Entries

1. The Scholastic Background[4]

I used the word ‘idea’ because it was the standard philosophical term used to refer to the forms of perception belonging to the divine mind … (3rd Replies, II.127, AT VII.181)[5]

For Christian philosophers from Augustine onwards, “ideas” were commonly conceived to be the “forms of divine perception”: roughly, Platonic forms transported into the divine mind, where they served as archetypes according to which God created the particulars of the created world.[6] But this general formulation invited much scholastic debate over their precise nature: Are they eternal and necessary — and so perhaps uncreated — beings ontologically independent of God? Or are they in some way dependent on God or God’s intellect? If the latter, would that mean that actual being somehow comes in degrees, since the “being” of “being-known” seems “less real” than that of mind-independent beings? Are they actual universal beings — since many created particulars can instantiate the same form — or are they too as particular as the created beings “modeled” on them? Or are they best construed as merely possible beings, i.e. as essences which are possibly (but not always actually) instantiated in the created world? But then what are those? Nor was it straightforward simply to identify them with God Himself, for ideas and essences are all limited in a way that God is not. Aquinas suggested that they be identified with the various finite ways in which God’s infinite being may be imitated, but that just buries the problem deeper: What are these “possible modes of imitation,” exactly, and how are they to be grounded in a purely actual being?

At the same there was equally much debate about the nature of human cognition. Through an enormous thicket of jargon — forms, essences, intentions, species, notions, concepts, phantasms, images, agent and patient intellect, etc — roughly the following general picture emerged. The cognitive process — the activity of coming to know the world — begins in the world, works through the senses, and culminates in the intellect. The form of some sensible quality — such as (say) the color red — “informs” some matter or object, and is then transmitted through the relevant medium (such as the air) to the relevant sensory organ (the eye), and ultimately to the intellect. The object instantiates or “realizes” the form “formally,” such that the object becomes actually red; but the air and the eye realize the form only “intentionally,” as a species, which means that they carry the red “information” without themselves actually becoming red. The form realized in the eye results in an act of sensation “directed towards” or “attentive of” that quality. The immaterial intellect may then in turn, by a complex process, extract or abstract the form in order to contemplate it, as it were, at which point the original object or quality is fully cognized or perceived or understood.

A few key points:

1. The account reflects the Aristotelian doctrine that in cognizing, the cognizer becomes identical to or “like” the thing cognized (De Anima 5, 7 (430a20, 431a1)): the thing and the sense organ and the intellect all realize the very same form, albeit in different manners or modes.
2. Intentional species were generally held to causally mediate cognition without themselves being objects of cognition, i.e. “what” is cognized.[7] The relevant form insofar as it informs the medium, sense organs and/or perhaps even the intellect, in other words, directs the latter not to the transmitting media nor to the states of the sense organ themselves, nor to its own states, but to the original quality or object initiating the sequence. Consequently the scholastic account is generally interpreted as one of “direct cognition.”[8]
3. Species are said to “represent” the external quality or object, which means, at the least, that they make the thing knowable or known. But they perform this function by virtue of the fact that they “resemble” or are “similar” to the thing they represent. Due to this resemblance they are sometimes referred to as “images” of things, which gives rise to the picture — later ridiculed by Descartes (Optics I, I.153-4, AT VI.85) — that objects continuously slough off little images of themselves in order to allow our cognition of them. But Descartes’ ridicule here was not perfectly fair. The scholastics were well aware that something which does not formally instantiate a sensible quality does not literally resemble the thing which does. All they meant by invoking terms such as “image” and “resemblance” was that species carry information (in-“form”-ation) about — i.e. the form of — the quality despite themselves not (formally) instantiating the quality: species are images of and resemble the object only insofar as the same form is (differently) realized in each.[9] In any case, as we’ll see shortly, Descartes himself sometimes uses the notions of “image” and “resemblance” in just the same way.

How, then, are ideas qua archetypes in the divine mind connected to this account of human cognition? The very short answer might start with this text from Aquinas:

…[T]he human soul knows all things in the eternal types, since by participation of these types we know all things. For the intellectual light itself which is in us, is nothing else than a participated likeness of the uncreated light, in which are contained the eternal types …. But since besides the intellectual light which is in us, intelligible species, which are derived from things, are required in order for us to have knowledge of material things; therefore this same knowledge is not due merely to a participation of the eternal types, as the Platonists held … (ST 1.84.a5, 427)

Universal forms are present in the divine intellect. On the basis of these God creates the world, bringing these forms to be realized, formally, in the world, particularized through matter. Through the processes of human cognition these same forms come to be in the human intellect. Aquinas’s (and scholasticism’s) empiricist bent is reflected in the requirement that we proceed via deriving the forms, ultimately, “from things,” as sketched above — at the same time as it is recognized that our intellect’s ability to extract or abstract forms also involves an ultimately divine “light.”

Descartes, of course, rejects many of the particulars of the doctrines above, since his ontology leaves no room for the sorts of “forms” (such as those of colors) being discussed. Nevertheless, as we’ll see, he appears to adopt the account in its broader strokes, mutatis mutandis. Indeed, the very fact that he co-opts the term “idea” from its original use with respect to divine perception and applies it to human cognition is some evidence for this suggestion.

Once the link is made between the forms in the divine and human intellects, now, many of the problems mentioned above arise again in the new context. In particular, there’s much scholastic debate over the precise nature of and relationships between forms, objects, acts of cognition, and the cognizers themselves. Already in Aquinas we read the following, as part of his argument that species mediate cognition without being objects thereof:

Hence that by which the sight sees is the likeness of the visible thing; and the likeness of the thing understood, that is, the intelligible species, is the form by which the intellect understands. But since the intellect reflects upon itself, by such reflection it understands both its own act of intelligence, and the species by which it understands. Thus the intelligible species is that which is understood secondarily; but that which is primarily understood is the object, of which the species is the likeness …[I]t follows that the soul knows external things by means of its intelligible species. (ST 1.85.a2, 434)

As we noted, when the relevant form is “in” a state or act of thinking (say), the mind (or that state) is (somehow) “directed towards” the object (or the form qua present in the object). Consequently an act or state of thinking may be considered in at least two ways: as a state or property intrinsic to a thinker, and as a mechanism by which the thinker is related to the external object, O, thought about. Similarly, the act or state of thinking may perhaps be considered as a “way” in which O exists in the intellect, as “O-in-thought”: after all, both actually being a particular object O and being a thought of O involve the “same” form being realized (if in different media or ways).[10] Although a strong distinction was made between an actually existing external O and the act of thinking about O, much debate occurred over precisely what sorts of distinctions to make (if any) between the external O and O-in-thought, and between O-in-thought and the act of thinking, especially in cases where O does not actually exist in external reality. The core questions were these: Must O-in-thought be granted its own mode of (actual) being somehow distinct from the act of thought itself? If so, what is that kind of being — the being of “being-known” — exactly? Must O-in-thought stand as a “third thing,” a tertium quid, between the cognizing mind and the external O (if there is one), thus introducing the “veil of perception”? Or could O-in-thought possibly be identified either with the act of the thought or O itself, thus eliminating it as a distinct ontological category?

By the time of Suárez, these debates had crystallized around what he calls the “common distinction” (vulgaris distinctio) between a formal and an objective concept. He writes:

When we conceive of a man, the act which we perform in our minds … is called the ‘formal concept,’ while the man known and represented by that act is called the ‘objective concept.’ [The latter] is doubtless called a ‘concept’ by an extrinsic denomination from the formal concept through which, as it is said, the ‘object’ is conceived — and so it is properly [also] called ‘objective,’ because it is not conceived as a form intrinsically terminating the conception, but as an object and subject-matter with which the formal concept is concerned and towards which the mind’s gaze is immediately directed. (DM 2.1.1, transl. Ayers 1998 (1099))

The formal concept is called a “concept,” (conceptus) from the verb to conceive (concipere), because it is, Suárez notes, “as if an offspring of the mind” (veluti prolis mentis) (DM 2.1.1:25, 64-65); the thinking-of-O involves O being taken into or generated in the mind just as biologically conceiving of O involves O being taken into or generated in a womb. As Wells 1990 notes, “it is designated as ‘formal’ because it is the ‘final form of the mind’ (ultima forma mentis), or because it ‘formally represents’ (formaliter repraesentat) to the mind the thing known, or because it is ‘the intrinsic formal terminus of the act of mental conception’ (intrinsecus et formalis terminus conceptionis mentalis)” (40).[11] The formal concept, then, just is the act of a mind, and as such realizes (formally) some relevant mental form, to make it that very mental act; but at the same time it realizes (intentionally) the form of some object or quality O, which makes the act to be “of” O.

This latter leads to the “objective concept,” i.e. to the thing which is “known and represented” by the mental act.[12] Note that the objective concept does not do the representing; it is, rather, the thing represented by the formal concept, which does. It is called a “concept” only “by extrinsic denomination,” insofar as (in being thought) it is related to the act of mind which in the strictest sense is a concept. It is called an “object” insofar as the mental act is not directed (merely) towards either itself, nor towards the form intentionally realized in the act, but towards the object itself (formally) realizing that form. While the formal concept, as an actual act or state of a mind, is always a “true positive thing inhering as a quality in the mind” (DM 2.1.1, 25, 65) and is thus always a singular or particular, the same is not always the case for the objective concept: we can conceive of mere “beings of reason” (such as privations), and of universals (such as “man”), and of mere possibilities, or “possible essences.” One can say of such things that, though not actually existing in the world, they have, qua objective concepts, “objective being.”

As a result, however, Suárez’s “common distinction” does not itself solve any of the problems mentioned above, but merely provides a terminology for expressing them. For it is tempting to identify the objective concept with some externally existing object until we recognize that, in many cases, there is no such object available. This point is particularly pressing with respect to possible essences, commonly invoked to provide a ground for the eternal truths involved in essential predication. When we think of a perfect triangle, or a chiliagon, or even of some possible animal not actually existent, the object of our thought, the objective concept, is a possible essence. But what sort of being, precisely, does that thing enjoy, particularly insofar as it doesn’t actually exist in the world? Well, the being of “being-thought.” But what is that, and how is related to the act of thinking, etc.?

There is much scholarly debate over how precisely to interpret Suárez’s views on these questions. Readers familiar with the secondary literature on Descartes will recognize that precisely analogous debate occurs over interpreting Descartes’ views on the very same questions. Roughly, the logical geography of the competing interpretations of both philosophers mirrors that of all the possible theories relating the relevant entities. Even restricting ourselves to the paradigm case of an act of thought T about some actually existing external object O, we have at least the following options:

1. Admit only T and O into our ontology. Here talk of “objective concepts” (or the “objective being” of O) has no ontological commitment distinct from that of the being of T or O.
2. Admit T and O, plus some tertium quid Q, which enjoys an “objective being” distinct from the being of T and O.

But now both (a) and (b) come in two versions. On (a1), T is related in some intrinsic way to O, while on (a2) T is related only extrinsically to O. Thus on (a1) we might say something like “T is O-itself-existing-in-thought,” while on (a2) we might merely say that T terminates at O, or represents O. Similarly, on (b1) the tertium quid Q is related to O in some intrinsic way, while on (b2) it is not. Thus on (b1) we might think of Q as O-existing-in-thought, while on (b2) we wouldn’t, and instead think of Q as (say) some mental thing representing O.

But now, unfortunately, (a1), (a2), (b1), and (b2) themselves each come in two versions. Suffice to say that the dividing factor is whether T or Q are taken to be objects of cognition, i.e. “what” we cognize, or merely causal intermediaries in the cognitive process. The former is prone to generate a “veil of perception,” while the latter is not.

These are a lot of options from which to choose. It’s no surprise that the scholastics spent centuries debating which is the best theory, nor that contemporary scholars spend years debating interpretations both of the various scholastics and of Descartes. Roughly, contemporary debate about Descartes’ theory of ideas — and so his theory of cognition — amounts to an attempt to locate him in the logical space above, and the various points we’ll explore below constitute some of the arguments supporting different locations. For now, our main conclusion is merely this modest one: despite Descartes’ 1st-Meditation-fueled reputation as developing his philosophy from scratch, his conception of and doctrines concerning ideas not only do not come out of an intellectual vacuum, but in fact are extracted from something more resembling a plenum.

Sources/Further Reading: Cronin 1966, Wells 1967, O’Neill 1974, Doyle 1984, Yolton 1984, Normore 1986, M. Adams 1987, Hoffman 1990, Wells 1990, Grene 1991, Wells 1993, Ariew & Grene 1995, Pasnau 1997, Ayers 1998, Hatfield 1998, Hoffman 2002, King 2005, Lagerlund 2005, and mental representation in medieval philosophy.
2. The What and the Whence of Cartesian Ideas

So what are “ideas,” according to Descartes? Here are just some of his definitions or relevant texts:

1. I use the word ‘idea’ to mean everything which can be in our thought… (To Mersenne 16 June 1641, III.183-4)
2. …[A]n idea is the thing which is thought of in so far as it has objective being in the intellect. (1st Replies, II.74, AT VII.102)
3. Idea. I understand this term to mean the form of any given thought, immediate perception of which makes me aware of the thought. (2nd Replies, II.113, AT VII.160-1; cf. 3rd Replies, II.132, AT VII.188)
4. …I am taking the word ‘idea’ to refer to whatever is immediately perceived by the mind. For example, when I want something … I simultaneously perceive that I want … and this is why I count volition … among my ideas. (3rd Replies, II.127, AT VII.181)
5. Some of my thoughts are as it were the images of things, and it is only in these cases that the term ‘idea’ is strictly appropriate — for example, when I think of a man, or a chimera, or the sky, or an angel, or God. (3rd Med., II.25, AT VII.37)

The difficulties are immediately apparent. In (5) ideas are equated with our thoughts, or acts of thinking, some of which are “as it were images.” But it’s clear that Descartes doesn’t mean “image” literally here, as a kind of visual picture, since his examples include the idea of “God,” of whom we can form no such image. In (1) “idea” is applied not to our thoughts but to that which can be “in” our thoughts, which would seem to include all sorts of non-mental things, “in” our thoughts at least in the sense that these are what we can think of. But (2), invoking a scholastic term, suggests there’s a special way of “being” in our thought, viz. objective being, which raises the question of how or whether these objective (perhaps mental) beings are identifiable with (or otherwise related to) the non-mental things external to mind. In (3) “idea” is applied specifically to the “form” of the thought — another scholastic term — “immediate perception of which” makes us aware of the thought itself. (4) may imply that what is “immediately perceived” is not a form but the act of thinking itself (but then again may not). We see within these definitions all the elements generating our logical geography above: the act of thinking, the object-in-thought (which may or may not be a mind-dependent being), the external object, and the “immediate” object of cognition. As unhelpfully as perhaps possible, Descartes uses the term “idea” rather indiscriminately for all of them.

Even worse, in his earlier works Descartes was inclined also to refer to various images in the brain as ideas.[13] And though he abandons this use in his later work, that’s not so much a change of view as a clarification. Continuing definition (3) above, he writes:

… [I]t is not only the images depicted in the imagination which I call ‘ideas.’ Indeed, in so far as these images are in the corporeal imagination, that is, are depicted in some part of the brain, I do not call them ‘ideas’ at all; I call them ‘ideas’ only in so far as they give form to [informant] the mind itself, when it is directed towards that part of the brain. (2nd Replies, II.113, AT VII.160-1)

Corporeal images merited the term “idea,” in other words, insofar as they were related in some way to thought; just as, perhaps, external objects may merit the term “idea” insofar as they, as objects thought of or as objects-in-thought, are related to thought. This allows us, at least, to grasp the unifying theme of all these applications of “idea”: it is Descartes’ generalized term for perhaps all the elements relevant to a theory of human cognition.

There is possibly one more important use. When discussing innate ideas Descartes is prone to speak of dispositions: roughly, to have an innate idea is to have a disposition towards forming certain thoughts on certain occasions. What is less than perfectly clear is whether the disposition is meant to be identified with the idea itself or merely with the manner in which the idea is stored in the mind. If the former, then we have a new use of “idea,” to refer to certain mental dispositions; but if the latter, then “idea” may be restricted to its previously discussed uses.[14]

What, then, are Cartesian ideas? Depending on context (and interpretation) the term may refer to: some (or all) of our acts of thinking, the external objects we think of (qua thought-of), objective (perhaps mental) beings, the forms of our acts of thinking, images in the brain, or certain kinds of mental dispositions we have with respect to all the preceding. What all these share, as noted, is their relevance to the theory of human cognition. To work out Descartes’ “theory of ideas,” then, is to determine the nature of each of these elements and exactly how they’re all related to each other. If the word “idea” itself is not used with perfect consistency — by him, or subsequently by us — then so be it.

As to the whence of Cartesian ideas:

Among my ideas, some appear to be innate, some to be adventitious, and others to have been invented by me. My understanding of what a thing is, what truth is, and what thought is, seems to derive simply from my own nature. But my hearing a noise, as I do now, or seeing the sun, or feeling the fire, comes from things which are located outside me, or so I have hitherto judged. Lastly, sirens, hippogriffs and the like are my own invention. (3rd Med., II.26, AT VII.37-38)

This passage appears to explain where his ideas at least seem to come from: his own nature (innate), from outside (adventitious), or from his invention. But immediately there’s a small problem: the third category might reduce to the prior two, for his “invention” of ideas may involve only a recombination of ideas he already has, presumably from the first two sources. And then there’s a slightly larger problem: in a later work Descartes offers an account of the origin of ideas inconsistent with the preceding.

…[I]n no case are the ideas of things presented to us by the senses just as we form them in our thinking. So much so that there is nothing in our ideas which is not innate to the mind or the faculty of thinking …. Nothing reaches our mind from external objects through the sense organs except certain corporeal motions … But neither the motions themselves nor the figures arising from them are conceived by us exactly as they occur in the sense organs … Hence it follows that the very ideas of the motions themselves and of the figures are innate in us. The ideas of pain, colours, sounds, and the like must be all the more innate … for there is no similarity between these ideas and the corporeal motions [which cause their production]. (Comments, I.304, AT VIIIB.358-9)

According to this text, it would seem, all ideas are innate, including the very sensory ideas which were paradigms of adventitious ideas in the earlier text.

But fortunately this problem is easily resolved: Descartes merely appears to be using “innate” in different senses between the two texts. In the later text an idea is innate insofar as it may be grounded in our very faculty or power of thinking; and since the Cartesian mind is created with the ability, roughly speaking, to think of or experience everything it will in fact think of or experience, then every such thought or experience (i.e. idea) will count as innate:

Consequently these ideas, along with that faculty [of thinking], are innate in us, i.e. they always exist within us potentially, for to exist in some faculty is not to exist actually, but merely potentially … (Comments I.305, AT VIIIA.360)

In the earlier text, to the contrary, the genetic distinction appears to concern the immediate causal origin of the ideas: adventitious ideas are those (perhaps typically) triggered externally, invented ideas are those whose construction entirely depends on our own relatively unconstrained will, and innate ideas are those we form (or actualize) not merely on the basis of our will but by reasoning or self-reflection.[15] So construed, ideas which are not innate in the earlier sense may count as innate in the later sense.[16]

Sources/Further Reading: McRae 1965, Kenny 1968, McRae 1972, R. Adams 1975, Costa 1983, Chappell 1986, Jolley 1990, Schmaltz 1997, Gorham 2002, and Nadler 2006.
3. Formal, Material, Objective

In so far as the ideas are simply modes of thought, there is no recognizable inequality among them … But in so far as different ideas represent different things, it is clear that they differ widely. (3rd Med., II.27-28, AT VII.40; cf. Principles I.17, I.198-9, AT VIIIA.11)

In this text Descartes famously introduces the distinction between

(a) “formal reality” and “objective reality.”

The formal reality of ideas corresponds to what they are, “intrinsically,” or “actually,” viz. states or acts or modes of thinking. All ideas are, formally, on a par, sharing the same “degree” or kind of formal reality. But at the same time it is the nature of such states to “contain” or represent external objects,[17] and insofar as ideas vary here they are not all on a par:

Undoubtedly, the ideas which represent substances to me … contain within themselves more objective reality than the ideas which merely represent modes or accidents. (3rd Med., II.28, AT VII.40)

Our concern won’t be with the ontological “hierarchy” here, but with the notion that ideas have or contain an “objective reality” corresponding to the object they represent, or at least “may be considered” as such.

Note, to start, that distinction (a) is similar to another distinction concerning not ideas directly but the “modes of existence” of objects: the sun (say) exists “formally” in the sky but may also exist “objectively,” “in” a mind or intellect, insofar as someone is thinking of it. Since Descartes is explicit that the former is “really” distinct from the latter,[18] we’ll speak, for convenience, of the “formal sun” and the “objective sun.” The obvious temptation now would be to equate or identify the objective sun with the objective reality of the idea of the sun, but that would be too quick. Since Descartes also suggests that the objective and formal realities of an idea in fact are two aspects of some single thing, two ways an idea “may be considered,” these are not “really” but merely “conceptually” distinct[19] — but then the objective sun would be really identical not merely to the objective reality of the idea of the sun but also to the formal reality of that idea, since these are really identical. In short, the objective sun would be identified with the idea simpliciter:

… [T]he idea of the sun is the sun itself existing in the intellect — not of course formally existing, as it does in the heavens, but objectively existing, i.e. in the way in which objects normally are in the intellect. (1st Replies, II.75, AT VII.102-03)

This result naturally opens a large can of (fortunately, objective) worms. The core problem is that the objective sun here seems to enjoy some kind of identity both with the act of thought (as just described) and with the formal sun, since the objective sun is in some sense the “sun itself” — and yet the act of thought is really distinct from the formal sun. But of course this problem is familiar by now: we have here the usual suspects — the act of thought, the object-in-thought, and the external object —described in the roughly Suárezian vocabulary from Section 1 above, so we ought to expect the usual problems in working out their precise natures and relations. Teasing it all apart will take some work. But first Descartes complicates the picture by introducing two other, apparently inconsistent distinctions.

In another famous passage, Descartes writes:

When M. Arnauld says ‘if cold is merely an absence, there cannot be an idea of cold which represents it as a positive thing,’ it is clear that he is dealing solely with an idea taken in the formal sense. Since ideas are forms of a kind, and are not composed of any matter, when we think of them as representing something we are taking them not materially but formally. If, however, we were considering them not as representing this or that, but simply as operations of the intellect, then it could be said that we were taking them materially, but in that case they would have no reference to the truth or falsity of their objects. (4th Replies, II.162-3, AT VII.232)

Here we have what appears to be the same distinction as in (a): an idea may be considered or “taken” (sumpta) in terms of what it is actually, intrinsically, in itself, i.e. an operation or act of thought, or it may be taken in terms of the external thing it contains or represents. But the terminology changes, as the distinction is now said to be between

(b) an idea taken “materially” v. taken “formally,”

where in distinction (a) the “formal” reality of the idea seems equivalent to the idea taken in the “material” sense here! As if that weren’t confusing enough, Descartes elsewhere also writes:

…[T]here is an ambiguity here in the word ‘idea.’ ‘Idea’ can be taken materially, as an operation of the intellect, in which case it cannot be said to be more perfect than me. Alternatively, it can be taken objectively, as the thing represented by that operation; and this thing, even if it is not regarded as existing outside the intellect, can still, in virtue of its essence, be more perfect than myself. (Preface to Med., II.7, AT VII.8)

Again, apparently we have the same distinction, here said to be between

(c) an idea taken “materially” v. taken “objectively,”

where the “material” sense corresponds to the “material” sense of (b); only now, he uses “objective” where he used “formal” in (b), but just as he’d used it in (a). Overall, then, the word “material” seems to be used with the same meaning in (b) and (c), but is absent from (a); the word “objective” seems to be used with the same meaning in (a) and (c), but is absent from (b); and the word “formal” seems to switch dramatically in meaning between (a) and (b), but is absent from (c).

The problems here are more than merely terminological, unfortunately; for while it does appear to be the same underlying distinction in play in (a)-(c) — and indeed all three are invoked in and around the Meditations — even that underlying distinction seems susceptible to differing interpretations with different metaphysical implications. On the one hand, the distinction may be roughly a semantic one: the word “idea” can be used to refer to two distinct entities, viz. an act of thought and the object of that thought — where, pending resolution of Descartes’ ontology, the object may be either a mental object in some way distinct from the thinking mind, or some actual external or abstract object itself. On the other hand, the distinction might be meant as a metaphysical one: ideas just are entities with a two-fold nature, or with two distinguishable aspects, viz. they are modes-of-thought-‘containing’-objects, i.e. modes-of-thought-with-representational-content. When Descartes invokes (a) and (b) he sounds as if he may, possibly, have the latter in mind; when he speaks of the “ambiguity” of the word “idea,” in invoking (c), he sounds as if he may, possibly, have the former in mind. Either way, once again we have the usual suspects in play, and thus all the familiar problems.

The central question, of course, is the nature of the objective reality of ideas, or, alternatively, of the objective mode of existing of objects. We noted above that Descartes seems to want to identify the objective sun (for example) both with the act of thought and the formal sun, while noting these latter two are really distinct. But in addition to some of the texts we’ve seen, various aspects of Cartesian metaphysics in general themselves seem to pull in opposing directions here, thus sharply deepening this difficulty.

1. On the one hand, Descartes notes that the formal reality of his idea does not have the same causal requirements as its objective reality, which may imply that the objective sun is really distinct from the act of thought:

The nature of an idea is such that of itself it requires no formal reality except what it derives from my thought, of which it is a mode. But in order for a given idea to contain such and such objective reality, it must surely derive it from some cause which contains at least as much formal reality as there is objective reality in the idea. (3rd Med., II.28-29, AT VII.41)

Indeed, his very application of his causal principle — “…that there must be at least as much in the efficient and total cause as in the effect of that cause” (3rd Med., II.28, AT VII.40) — to the objective reality of ideas itself strongly suggests that the objective sun might somehow be identified with the formal sun, the sun itself, since each requires a cause of equivalent reality or stature.
2.

On the other hand, his general dualist substance-mode ontology would seem to rule out any mental objects distinct from a mind, and so reinforce the identity between the objective sun and the act of thought. Nor would it do here to identify the objective sun with a physical object, the formal sun, as (1) does, since the objective sun has something to do with the objective reality of an idea, and an idea, Descartes insists, “is never outside the intellect” (2nd Replies, II.74, AT VII.102) — which the formal sun most certainly is.
3.

On a third hand, Descartes stresses the mind-independence of the objectively existing essences providing the objective reality of at least some of his ideas (5th Med., II.44-45, AT VII.64). Though there’s debate over just what the mind-independence amounts to,[20] it too at least suggests strengthening the distinction between the objective sun and the act of thought, as in (1). But at the same time, contra (1), Descartes also admits objective beings which may not even have any actually existing formal counterparts at all (5th Med., II.44-45, AT VII.64) — in which case there’s no external formal thing with which they may be identified.

Ayers 1998 offers a particularly succinct way of stating the problem, to which the preceding three points have been supplying arguments for the opposed responses:

The question could be put as follows. Which is the mere [conceptual distinction], and which the real distinction: (1) the distinction between the idea as mode of thought and the idea as intentional object of thought [i.e. the objective being] or (2) the distinction between the latter … and the real object (the thing as it exists in reality)? It seems clear that, at least on ordinary realist assumptions, there cannot be one thing, the idea, which is really identical both to the mode of thought and to the real object. (Ayers 1998, 1067)

Ayers notes that much rides on the answer: If (2) is the conceptual distinction, for example — so there is no real distinction between the objective and formal suns — then we have support for a “direct cognition” interpretation of Descartes: that ideas are the “immediate” objects of thought wouldn’t preclude a sense in which external objects are as well. The problems here of course include those just noted: the objective and formal object couldn’t be really identical since the former is “in” the intellect in a way the latter isn’t, and the account must explain the cases where no relevant formal object exists extra-mentally. If, on the other hand, (1) is the conceptual distinction, it’s not apparent how thought ever makes contact with the external world, since the object of thought turns out to be really identical just to the act of thinking itself. Further, there are the problems just noted, including that the real distinction between the objective and formal sun leaves unexplained Descartes’ insistence that the objective sun just is the sun itself.

Ayers himself asserts that Descartes takes (1) to be the conceptual distinction. But Ayers makes no effort to accommodate the conflicting tensions both in the Cartesian texts and in his metaphysics, as expressed in points (1) and (3) above. Nor does he accommodate the apparent hint of direct cognition in Descartes’ suggestion that the mind grasps the sun itself.

We can do better.

Sources/Further Reading: Kenny 1970, Chappell 1986, Jolley 1990; Bennett 1994, Chappell 1997, Nolan 1997, Ayers 1998, Hoffman 2002, Clemenson 2005, Nadler 2006, and Rozemond (forthcoming).
4. Cartesian Ontology, and Ideas

Let us remind ourselves of four of the basic elements of Descartes’ ontology.

1. All created entities are either substances or properties of substances (Principles I.48, I.208, AT VIIIA.22).
2. Created substances are either mental or physical in nature, i.e., either minds or bodies (Principles I.48, I.208, AT VIIIA.23). Each kind has a principal attribute — thought and extension respectively — and each has corresponding properties, which are construed as modifications or “modes” of that principal attribute (Principles I.53, I.210, AT VIIIA.25).
3. Descartes generally rejects scholastic hylomorphism, aspects of which were sketched in Section 1 above.[21] In brief, this was the theory that created things are composed of matter and form. The matter here is not physical matter, but rather a kind of indeterminate potentiality which becomes actualized when in-formed by a form. Forms were generally understood as kinds of universals or essences but, unlike those of the Platonic variety, were not conceived to have any independent ontological status but rather only to exist when particularized “in things,” either formally or intentionally.[22] Forms divide into “substantial forms,” which make something into the kind of thing it is and thus bestow its essential properties and characteristic behaviors on it, and “accidental forms” which bestow its non-essential or contingent properties on it. That Descartes rejects hylomorphism is supported by (i) his generally negative remarks about it, (ii) the fact that he dispenses with it in his physical science, and (iii) items (1) and (2) in his ontology above: his substances are capable of existing independently in a way that substantial forms (requiring “matter”) ordinarily are not, and properties qua “modifications” seem attached to a substance more intimately than accidental forms would be.[23]
4. Descartes has at least an inclination towards nominalism, i.e. the view that everything that exists is a particular:[24]

…[N]umber, when it is considered simply in the abstract or in general, and not in any created things, is merely a mode of thinking; and the same applies to all the other universals, as we call them … These universals arise solely from the fact that we make use of one and the same idea for thinking of all individual items which resemble each other: we apply one and the same term [nomen] to all the things which are represented by the idea in question, and this is the universal term. (Principles I.58-59, I.212, AT VIIIA.27)

This sounds like a traditional nominalist position: there are no genuinely universal beings, we merely apply the same term [nomen] or idea to particular things which resemble each other. Indeed Descartes goes so far as to claim that universals are merely “modes of thinking,” suggesting they have no mind-independent reality at all.

Overall, then, Descartes subscribes to a substance-mode, dualist, anti-hylomorphist, and nominalist-inclining ontology. Yet much in our discussion of Cartesian ideas, so far, was possibly in tension with this ontology. There were suggestions that objective beings might be mental objects which are not minds, or that mental states somehow “contain” (otherwise) mind-independent, non-mental objects such as bodies, or even abstract or universal beings. We’ve also seen Descartes invoke the hylomorphic “matter-form” terminology in his various distinctions. Any coherent exegesis of Cartesian ideas must make sense of these conflicting tendencies.

It must also make sense of his conflicting terminologies. We saw, in Section 3, that Descartes had three distinctions in play with respect to ideas, invoking these terms:

1. formal v. objective,
2. material v. formal,
3. material v. objective.

Since these seemed to be three ways of stating the same (if ambiguous) distinction, two questions arise: Why introduce all these terms? And why does “formal” seem to shift so dramatically in meaning between (a) and (b)? With these questions in mind, let’s now see what we can learn by revisiting Descartes’ also conflicting definitions of “idea” from Section 2.

The word “form” in definition (3) naturally calls hylomorphism to mind. Again, as Aquinas writes:

Now Plato held … that the forms of things subsist of themselves apart from matter … by participation of which he said that our intellect knows all things: so that just as corporeal matter by participating the [form] of a stone becomes a stone, so our intellect, by participating the same [form], has knowledge of a stone. But since it seems contrary to faith that forms of things should subsist of themselves, outside the things themselves and apart from matter … Augustine … substituted the types of all creatures existing in the Divine mind, according to which types all things are made in themselves, and are known to the human soul. (ST 1.84.a5, 427)

The form of a stone in matter makes the matter (formally) a stone; the same form “in intellect” does not make the intellect formally into a stone, but only intentionally, by “forming it” into the thought of a stone. Augustine, placing these forms into the divine mind, called them “ideas.” And we can now appreciate, I think, just how deliberately Descartes chooses the term “idea” for the elements of human cognition: for his account of human cognition, ultimately, invokes entities playing precisely the same role that forms played for the scholastics.

We see this in definition (3), to be sure: an idea is the form of a thought. That suggests that mind is playing a role much like that of hylomorphic matter: in itself it is, in a sense, indeterminate, a potential or capacity for thought or thinking, but when in-formed it becomes a determinate thought, i.e. one with a determinate object or content.[25] In light of this, Descartes’ distinction (b) makes perfect sense: a thought (or mind) considered “in itself” or intrinsically is like matter, and only insofar as it is in-formed, or considered with respect to a form, and thus to an object, is it taken “formally.” In our current example the form in question would be the form of the stone.

But forms, of course, also make something what it actually (formally) is. If the form of the stone makes matter into a formal stone, then the Cartesian dualist might also entertain forms for the mind, mental forms which make a mind (and particular mental states) formally into minds and mental states respectively. And indeed Descartes observes that some of his thoughts, in addition to representing objects (thus counting as “ideas”), “have various additional forms: thus when I will, or am afraid, or affirm … my thought includes something more than the likeness of [its object]” (3rd Med., II.25-26, AT VII.37; cf. 3rd Replies, II.128, AT VII.182-82). But of course there’s an important difference here between the case of the physical stone and that of mental entities. The stone can ultimately be described, for Descartes, as a modification of extension, in precise, quantifiable terms, as some sort of mathematical essence. The mental forms here determining the category of representational state — viz. willing, fearing, etc. — enjoy nothing more precise than that vocabulary itself. More importantly, no account is given here of what mental form turns the state into one with that particular representational content. As Malebranche would later critique Descartes, we might say here that we lack a perfectly “clear idea” of the mind:[26] we do not conceive of mind in a way allowing us to understand its modes or states, or at least none comparable to the way our conception of mathematics affords us a grasp of the nature of extended matter and its modifications.

Still, we have enough now to also make sense of Descartes’ distinction (a). The notion of “form” in play there is not that (say) of the stone, but that indescribable one which makes the mind what it actually or intrinsically is; in the common scholastic idiom we saw in Suárez in Section 1, this “formal” will contrast with “objective,” which invokes the object represented or its form. And this partly answers one of our questions: the apparently dramatic shift in meaning of “formal” between (a) and (b) is not so dramatic, as “formal” refers to forms in both. In our thinking of a stone, we can now see, there appear to be two forms in play: the form of the stone, and the relevant (if indescribable) form of the mind or mental state. When invoking (a), Descartes’ focus is on the latter; when invoking (b), on the former.

What, then, about distinction (c)? We saw earlier that Descartes appears to take all three distinctions to be equivalent, and we can now see how this may be so: (c) merely combines the hylomorphic “material” with the common scholastic idiom of “objective.” This in turn partially answers our other question: Descartes uses this shifting vocabulary because all of it means what he wants it to mean, and would be familiar to his readers as so meaning. Its messiness, in other words, derives from his predecessors’ own terminological profligacy.

But now reading Descartes as adopting, in broad strokes, this scholastic account of cognition, has the additional virtue of making sense of his varying definitions of “idea” from Section 2. Definition (1) reflects the fact that objects can be “in” our thought, i.e. insofar as their forms in-form our minds. Definition (5) asserts that ideas are thoughts which are “as it were images,” where “image” invokes the notion of some sort of (non-literal, non-pictorial) likeness or resemblance between the thought and its object. As we saw in Section 1, forms were frequently referred to as “images” precisely when they were intentionally realized either in species or in the mind, and we can now see Descartes to be following suit: Our thought of a stone is an “image” of the stone insofar as the form of the stone (intentionally) in-forms our mind. Definition (2) reflects a similar point: a thing has objective being in the intellect insofar as its form intentionally in-forms the mind. And of course definition (3): If the mind is like “matter,” it only becomes determined into a particular mode or thought, with an object, once in-formed. The “idea”-ness of a thought, its having an object, is thus traced to its form. Similarly for definition (4): it’s precisely by their “forms” (as we saw) that mental states become the type they are, thus volition etc. count as ideas by virtue of their forms.

But (3) and (4) also introduce something new: the notion of “immediate perception.” In (3) the idea is the form of a thought “immediate perception of which makes me aware of the thought”; in (4) the mind “immediately perceives” that it’s willing, etc., which (again) is traced to the forms of its states. To simplify we’ll ignore the mental forms responsible for generating the categories of representational states, and thus focus on (3) and the problem of representational content. The idea in (3) is the “immediately perceived form,” but as we’ve seen, there are apparently two in play: the form of the object of the thought (the stone), and the mental form of the thought itself qua representational state. So which one is relevant here?

To read Descartes in broadly scholastic terms is to recognize that they both are — and they both are because they are one and the same. As with the scholastics, when the form is realized in matter you get a formal, actual, particular stone; when that very same form is realized in a Cartesian mind, now, you get a particular thought of a stone.

A scholastic reading of Descartes appears to have a number of advantages:

(1) It’s economical. With respect to substance dualism, the one form does both sorts of work: (formally) modifies matter, and (intentionally) modifies mind. Or with respect to the mind alone, the one form does both sorts of work: modifies the mind, and provides it with its representational content.

(2) Descartes appears to hold that all thought is representational, i.e. that it’s the very nature of mind to represent (3rd Med., II.25, AT VII.36-37; II.29, AT VII.42).[27] But it also seems that our only epistemic access to the nature of our mind is via the contents of our thoughts. What we know in knowing our thoughts, in other words, are their objects. Thus definition (3): our immediate perception of the form of a given thought makes us aware of the thought. Which form is that? The form of the stone. It is both that which gives the thought its object AND that which makes the thought what it actually is, viz. a thought of a stone. Descartes has no need to specify “which” form is in play here, because there is only one.

Or to put this point more metaphysically: given the mind’s nature to represent, thoughts are partly individuated by their contents.[28] If so, then that form which bestows content on the state is also that which determines what state it is. If some other form were required for the latter, then we’d need an entire theory relating the modes of the mind, individuated by nameless forms, to their representational contents, a theory conspicuously lacking in Descartes. Or even more succinctly: Cartesian minds are, primitively, “thought-makers,” which on receiving the forms of objects become thoughts of those objects. No distinct mental forms are necessary for representational content, just as the scholastic reading suggests.

(3) We saw a moment ago that Descartes’ shift in meaning of the term “formal” between distinctions (a) and (b) was not actually that dramatic. In light of definition (3) we can now see that it may in fact be no shift at all — if the same form provides the “formal” in both (a) and (b)!

(4) A fourth advantage of the scholastic reading is that it affords a general, coherent account of the various conflicting metaphysical tendencies raised in Section 3.

We saw there, for example, that the objective sun seemed to enjoy some kind of identity both with the act of thought (since the formal and objective reality of an idea seemed to be two aspects of some single thing) and with the formal sun (since the objective sun is in some sense the “sun itself”) — and yet the act of thought is really distinct from the formal sun. But this tension is now easily satisfied: the act of thought is really identical to the objective sun, since both are constituted by the mind-informed-by-the-sun-form; the objective sun is the sun itself, since the very same form constitutes both the objective and formal suns (if in different media); and the act of thought remains really distinct from the formal sun.[29]

Similarly, we saw both that the objective being and the formal being of an object require causes of equal stature while the objective and formal realities of an idea differ in causal requirements; further, that Descartes sometimes stresses the mind-independence of objectively existing essences. These points supported distinguishing the objective sun from the act of thought and perhaps even identifying it with the formal sun. Yet at the same time Descartes also restricted objective beings to the mind: they’re never “outside the intellect,” and sometimes no formal being exists to correspond to them.

But these tensions are now also satisfiable. Objective and formal beings require equal causes due to their sharing the same form. Yet that the objective and formal realities of an idea differ in causal requirements need not require that they be really distinct, for a conceptual distinction may support diverse causal explanations: The informed mind is a mind-thinking-of-O; when we “consider” it “intrinsically,” we need only invoke causes sufficient to create the finite mind, while when we “consider” it as “of-O” we need to invoke a cause sufficient to make it that particular state, of-O, which involves the form of O.[30] Meanwhile objective beings are naturally restricted to the mind, since objective beings are forms-realized-in-mind. If a given form is realized in mind and not in matter, we’ll have an objective being that does not correspond to a formal one, but there’s nothing particularly metaphysically problematic about that. But even if there does exist a corresponding formal being, nothing here requires a real identity between the objective and formal beings; they will share a form, but be really distinct instantiations or particularizations of that form. Finally objective essences may be mind-independent in the sense that the contents (or possible states) of our thoughts are not “up to us”: an objectively existing triangle may reasonably be said to contain all the essential properties of a triangle whether I notice it or like it or will it or not.[31] But whatever the final account of that fact, it doesn’t entail that the objectively existing triangle itself exists “outside” the mind.

Lastly, Ayers’ Descartes placed the real distinction between the objective and formal suns, as the scholastic Descartes does, thus identifying the objective sun with the act of thought. But Ayers made no effort to accommodate the conflicting tensions in the Cartesian texts above, and indeed, left as a major problem the hint of direct cognition in Descartes’ suggestion that the mind grasps the sun itself: if the objective sun is identified with the act of thought, and so in thinking of the sun the mind is only aware of its own state, how does the mind make cognitive contact with the external world? The scholastic reading, to the contrary, supplies what Ayers’ thesis lacked: the conflicting tensions are resolved as above, and the direct cognition is accommodated, as we’ll see further in Section 5, by the fact that the very same form constituting external objects also in-forms the mind.

(5) The scholastic reading’s fifth and final advantage is that it provides a coherent account of Descartes’ overall ontology, as sketched at the start of this section. Three points in particular need attention: (i) Descartes rejects scholastic hylomorphism, yet often invokes the hylomorphic vocabulary; (ii) his objective beings sometimes seem to be mental objects which are not minds, or kinds of mental states which somehow “contain” non-mental objects, both of which seem inconsistent with his dualist, substance-mode ontology; and (iii) the mind-independent essences sometimes constituting his objective beings often seem to be abstract or universal beings, despite his inclination towards nominalism.

(i) Descartes’ bark about hylomorphism is in general far worse than his bite: he does not so much reject it as refurbish it in accord with the mechanical philosophy.[32] Gone are the vast array of particular scholastic forms conjoined with hylomorphic matter in the physical world (such as those constituting “secondary” qualities and perhaps the genera-species of scholastic essences), but in their place are roughly analogous mechanical, and ultimately mathematical, essences (Principles IV.198, I.285, AT VIIIA.321-23; To Regius, January 1642, III.206-209, AT III.499-509). Gone are the sensible and intelligible species which convey the scholastic forms ultimately to the cognizing intellect, but in their place is matter in motion conveying “in-form-ation” about the surface textures of objects to the sensory organs, then onwards to the pineal gland, which in turn leads the cognizing mind to sense or understand, such that the object of cognition “itself” is now “present to the mind” (Optics 4-6, I.165ff., AT VI.112ff.; 6th Replies, II.295, AT VII.437; Principles IV.197-8, I.284-5, AT VIIIA.320-23; cf. O’Neil 1974). Nothing in this refurbishing precludes Descartes’ accepting the basic scholastic notion that the same “form” — i.e. mathematical essence — may enjoy two kinds of realization, corresponding to his two kinds of substances. That Descartes expresses his account of cognition in thoroughly scholastic terms, and (again) that he chose the word “idea” in the first place, is perhaps the strongest evidence that he embraces the account in its broad outline, while differing in the important particulars above.

(ii) Texts suggestive of “mental objects” are understandable: the mind’s awareness of its state of thinking, which is individuated by its form, is at the same time awareness of the object of the state which formally is (or would be) constituted by that form. Equally understandable is talk of these objects as “in the mind”: there’s a real identity, after all, between the objective being and the act of thought. And so too we can understand the sense in which non-mental objects are “contained” in thought: the same form which, by in-forming matter, constitutes the object, by in-forming the mind constitutes a thought of that object. But nothing here violates Descartes’ dualist, substance-mode ontology — at least on the obviously crucial assumption that his forms — which we’ll now speak of interchangeably with his (ultimately mathematical) “essences” — do not.

(iii) Unfortunately, the ontological status of Cartesian essences is a matter of much dispute, as is, consequently, the question whether they truly fit within his overall ontology. A proper account of this issue would require its own article, so here I must be overly brief.

The major positions on Cartesian essences are roughly these:

1. Essences are mind-independent, universal, abstract entities, like Platonic forms (Kenny 1968, 1970);
2. Essences are grounded in the human cognitive structure, i.e. our capacities for thinking. That there “is” a triangle essence containing the essential properties of triangles, then, means merely that our minds are so structured that we cannot conceive of triangles without, ultimately, ascribing them their essential properties (Bennett 1994, Chappell 1997, Nolan 1997);[33]
3. Essences just are the objects which have those essences (Cunning 2003);
4. Essences are to be identified either with divine decrees or with the contents thereof (Schmaltz 1991, Rozemond (forthcoming)).

Each position finds some textual support. 5th Med., for example, displays a strong hint of (A) in its insistence on the eternal, immutable, (human) mind-independent status of essences. We saw in Principles, to the contrary, the nominalist inclination which may support (B). That Descartes denies a real distinction between (say) a substance and its attributes is some evidence for (C) (To ***, 1645 or 1646, III.280-1, AT IV.349-51). And in Descartes’ mysterious doctrine of the divine creation of eternal truths — and thus of essences, with which the eternal truths are identified (To [Mersenne], 5/27/30, III.25, AT I.152) — we may find indications of (D). Yet another Cartesian conundrum — but one which perhaps, too, may be made intelligible by a scholastic reading.

When an essence in-forms a mind, the result is an act of thought whose content is determined by the essence. But we saw just above that that content may be mind-independent in the sense that it is not up to us, in particular to our wills, what must be included in the content. If that’s not up to us, then what it is up to — the Cartesian God’s eternal, immutable will — is free to confer that eternality and immutability on the content (To Mersenne, 4/15/30, III.23, AT I.145-46; To [Mesland], III.235, AT IV.118-19). But that fact does not require that essences ever exist except when realized or particularized in matter or minds. Thus we may make sense of the Platonic-sounding texts without reaching the Platonist conclusion. So much for (A).

(B) is more of a contender. For the scholastic Descartes, mental states are individuated by the essences realized in them, which may support identifying essences and our cognitive structure and so make sense of the texts supporting (B). Yet (B) may not do full justice to Descartes’ references to “eternal” essences, since our minds are not eternal. Further, these “same” essences may be realized in matter as well. These points suggest that the essences are in some sense “prior” to our cognitive structures.

(C), similarly, has something right about it, insofar as essences do in-form matter; but it, too, may not do full justice to their eternality, and in particular, may struggle with the cases where essences exist “in thought” without any formally existing external object with which to identify them.

What about (D)? For our purposes we need not distinguish between its two versions: given the Cartesian God’s simplicity, there can be no real distinction between God’s “decrees” and their contents, just as we saw there to be none between the objective and formal realities of human ideas. And though we cannot engage here with the complex mysteries of Descartes’ creation doctrine, we can observe at least an element of truth in (D): ultimately all Cartesian things must find their source in the Cartesian God, including essences. As such (D) gets closest to accommodating the eternality and mind-independence of essences supporting (A) while avoiding the demerits of (B) and (C).

Still we must note that (D) need not exactly rule out (B) and (C):

First, briefly, divine simplicity entails that the distinctions we make in God — between His perfections, faculties, decrees, etc. — are merely conceptual ones. Following a long scholastic tradition, Descartes will hold that anything we say about God involves our applying our very limited concepts to something with respect to which they are not fully adequate. But then our very characterization of the divine essence — as omnipotent, omniscient, infinite, etc. — will be determined by our own cognitive structure. And since it’s that characterization which ultimately grounds Descartes’ affirmation of (D) — and since it is our cognitive structure which determines how/what essences we can grasp in the first place — we have a sense, distinct from the earlier one, in which our cognitive structure might in fact be “prior” to the essences.

Second, more generally, Descartes’ God’s perfection precludes His systematically deceiving us (4th Med., II.37, AT VII.53). He has thus created us with a cognitive structure which accurately maps the general structure of reality, i.e. the complete set of what’s possible; but this structure in turn maps neatly onto the structure of God’s will, to the degree to which it’s intelligible, since He is the causal source of all possibilities. While the order of explanation certainly starts with God, it may be a matter of taste to decide whether to identify the essences with the divine decrees or their content or with the minds and matter which are their causal consequences, or even all of the above. After all, it’s the “same” essence present in all domains.

Similarly, lastly, perhaps the biggest problem for (D) arises from the fact that Descartes holds not only that God is the efficient cause of essences but that God is not the efficient cause of Himself (4th Replies, II.164-6, AT VII.235-7). Since, by divine simplicity, there can be no real distinction between God and His decrees (or their contents), it would seem that essences cannot be identified with divine decrees without entailing, contra Descartes, that God is the efficient cause of Himself. But the availability of (B) and (C) mitigate this problem: the very same essences present in the divine decrees are also present in creatures, as realized either in minds or in matter. Since creatures are uncontroversially the products of God’s efficient causation, we can make sense of Descartes’ claim that God is the efficient cause of essences without giving up (D).[34]

It may not matter, then, whether we ultimately go with (B) or (C) or (D), or all three (more or less). None raises an immediate problem for Descartes’ ontology, which indisputably accepts minds with their cognitive structure, bodies with mechanical essences, and God with His decrees and their contents. Nevertheless a deeper problem is brewing. The Cartesian essences, even if “originating” with God, are realized not merely “in” God’s decrees but also (consequently) in finite minds and matter. But does that mean we must say that essences are universal beings, and thus inconsistent with Descartes’ nominalist leanings?

Let us briefly return to the Principles text above:

…[N]umber, when it is considered simply in the abstract or in general, and not in any created things, is merely a mode of thinking; and the same applies to all the other universals, as we call them … These universals arise solely from the fact that we make use of one and the same idea for thinking of all individual items which resemble each other: we apply one and the same term to all the things which are represented by the idea in question, and this is the universal term. (Principles I.58-59, I.212, AT VIIIA.27)

There are several important points here:

First, nothing in this text in fact is inconsistent with the scholastic Descartes. Descartes insists that universals — essences — “considered simply in the abstract or in general,” are merely “modes of thinking,” but that is consistent with allowing that universals, considered “in created things,” in fact also are realized in those things. He speaks of items resembling each other, but nothing precludes that resemblance’s being a matter of their sharing the “same” essence. His account whereby material particulars are subsumed under an idea is both one of explaining the origin of an idea as well as its ability to represent a multiplicity; but when he says that universals are “modes of thinking,” he is merely saying that, when they are not realized in matter, they are realized only in mind. What he is keen to deny is just that essences exist in that mind-independent, Platonic way, which we may falsely think when we think about them “in the abstract or in general.”

Indeed Descartes quite explicitly refers to the idea as a “universal.” In the quoted text he calls it a “universal term” [quod nomen est universale], and in other parts of the text he makes several references to the “universal idea” [quae ideò est universalis]. There can be no doubt that he considers our individual acts of thought to be particulars, but insofar as these have the same “content,” they become, as he says in the text, “one and the same idea” (my italics): what we have is a “universal essence” realized in diverse acts of thought. In light of the considerations in the preceding paragraph, there is no reason to resist allowing a universal essence to be realized in diverse material particulars as well.

Finally, Descartes is quite clear that there is no real distinction between a thing’s existence and its essence (To ***, 1645 or 1646, III.280-1, AT IV.349-351). What he does allow is a real distinction between the objective object and the formal object, but in the former we have an essence realized in mind, and in the latter, an essence realized in matter. The realizations of this essence, in mind and in matter, are really distinct, or “token-distinct”; but he simply lacks the resources (and on the scholastic account the motive) to treat the “essence” in this case itself as token-distinct across the instances. But if one and the same essence is realized in two media, we do indeed have a universal essence.

The conclusion, then? For Descartes, every existing thing is indeed a particular, and that will satisfy his nominalist inclinations. But that is consistent with allowing universal aspects or natures, i.e. essences, as long as these only “exist” insofar as they are realized in particulars.[35] Now realism about universals comes in many varieties, as does nominalism, and the position we’ve ascribed to Descartes may lean more towards the realist end of the spectrum than towards the nominalist. What’s important to note, however, is that Descartes is concerned to reject a Platonic realism. Whether the resulting position still merits the label “realism” — perhaps “Aristotelian-scholastic realism” — is a merely terminological issue.

The broadly scholastic account of Cartesian ideas, then, nicely ties together the disparate elements of his ontology.

Sources/Further Reading: Kenny 1968, Kenny 1970, Brown 1980, Schmaltz 1991, Bennett 1994, Garber 1994, Chappell 1997, Nolan 1997, Bolton 1998, Rozemond 1998, Cunning 2003, Pessin 2003, Rozemond (forthcoming), Aristotle’s psychology, medieval theories of universals, and properties.
5. Ideas and Direct Cognition[36]

The Cartesian texts often suggest, as we’ve seen, that (i) ideas are the “immediate” objects of our thoughts, (ii) they are never “outside the intellect,” (iii) they’re distinct from the act of thought, but (iv) they can’t be identified with any formal, external object, etc. Put these together and you’ve got strong hints at a doctrine in which ideas “veil” us off cognitively from the world: “what” we are aware of “directly,” in cognition, are only ideas, and not external objects themselves. Similarly we saw, in Section 3, Ayers’ observation that the conceptual distinction between the act of thought and the objective being seemed to preclude our having cognitive contact with anything other than our own acts of thought, and thus also to support a “veil.” Yet at the same time, there are also hints of direct cognition in Descartes, in, for example, his insistence that the objective sun is the “sun itself,” and more generally in his account of “simple natures” which are both manifest in the physical world and directly graspable by the mind (Rules 12, I.39ff., AT X.411ff.; cf. O’Neil 1974). Fortunately the scholastic reading of Descartes can make sense of this final Cartesian conundrum as well.

What Ayers has failed to consider, on the scholastic Descartes, is the significance of the sameness of form across realizations in matter and in mind. There is a real distinction between the act of thought (objective being) and the formal being, but their sameness in form supports what we might call an identity in reason between them. Thus the act of thought is made determinate by a form, so constituting the objective being, while one and the same form is particularized in matter. This allows Descartes to say both, as we’ve seen, that our “immediate perception” of the form of a thought makes us aware of the act of thought itself, and that the objective sun — the object of our thought — is the sun itself. This is how the mind makes “cognitive contact” with the world, pace Ayers’ concerns: the same form realized out there is also realized in here, and awareness of one is therefore awareness of the other. There is no tertium quid serving as an object of cognition.

So yes, ideas are “only in the intellect,” and may be the “immediate objects of awareness”; we can thus make sense of many of the texts supporting the “veil.” Nevertheless the identity in reason — the sameness of form — between the in-formed mind and in-formed matter ensures that the in-formed mind constitutes a thought “directed towards” the object, and the Cartesian intellect may be said to be (directly) aware of (say) “the sun itself.” Consequently, but unsurprisingly, the scholastic Descartes may be seen as subscribing to “direct cognition,” exactly (as we saw in Section 1) as his scholastic predecessors are generally taken to do.[37]

This doesn’t solve every problem for the exegesis of Cartesian ideas, naturally. Most importantly, we’ve been focusing on “intellectual” ideas, the paradigm examples of which are the mathematical essences which can be realized in the physical world; we’ve not addressed the problem of “sensory” ideas, of which we certainly seem directly aware yet which do not and cannot in fact be manifest in the physical world of Descartes’ mechanical philosophy. But that is a problem for another day.[38]

Sources/Further Reading: Lennon 1974, O’Neil 1974, Yolton 1975, Yolton 1984, Cook 1987, Nadler 1989, Wilson 1990, Tipton 1992, Wilson 1994, Simmons 1999, Hoffman 2002, Clemenson 2005, and Pessin 2007.
Conclusion

Let us close by situating this account in the logical geography sketched at the end of Section 1, focusing on the paradigm case of an act of thought T about some actually existing external object O. While Descartes appears to speak of a kind of tertium quid, Q, viz. an objective being, the mere conceptual distinction between Q and the act of thought T indicates that he grants Q no distinct being from that of T, thus putting us into option (a). Given the “sameness of form” doctrine, T is “intrinsically related” to O, putting us into (a1). Finally, in light of the real identity between T and the objective being, and the identity in reason between the latter and O, then T may indeed count as an object of cognition — but not in a way which in fact, after all, generates a “veil of perception.”[39]
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* –––. 1970. “The Cartesian Circle and the Eternal Truths.” Journal of Philosophy, 67, 692-700.
* King, Peter. 2005. “Rethinking Representation in the Middle Ages.” In Lagerlund 2005, 83-102..
* Lagerlund, Henrik, ed. Representation and Objects of Thought in Medieval Philosophy. Aldershot: Ashgate.
* Lennon, Thomas. 1974. “The Inherence Pattern and Descartes’ Ideas.” Journal of the History of Philosophy, 12, 43-52.
* McRae, Robert. 1965. “’Idea’ as a Philosophical Term in the Seventeenth Century.” Journal of the History of Ideas, 26, 175-190.
* –––. 1972. “Descartes’ Definition of Thought.” In Butler, ed., 1972, 55-70.
* Nadler, Steven. 1989. Arnauld and the Cartesian Philosophy of Ideas. Princeton: Princeton University Press.
* –––. 2006. “The Doctrine of Ideas.” In Gaukroger 2006, 86-103.
* Nolan, Larry. 1997. “The Ontological Status of Cartesian Natures.” Pacific Philosophical Quarterly, 78, 169-94.
* Normore, Calvin. 1986. “Meaning and Objective Being: Descartes and His Sources.” In Rorty 1986, 223-41.
* O’Neil, Brian. 1974. Epistemological Direct Realism in Descartes’ Philosophy. Albuquerque: University of New Mexico Press.
* Pasnau, Robert. 1997. Theories of Cognition in the later Middle Ages. Cambridge: Cambridge University Press.
* Pessin, Andrew. 2003. “Descartes’ Nomic Concurrentism: Finite Causation and Divine Concurrence.” Journal of the History of Philosophy, 41, 1, 25-49.
* –––. 2007. “Mental Transparency, Direct Sensation, and the Unity of the Cartesian Mind.” In ed. J. Miller, Topics in Early Modern Philosophy of Mind (Dordrecht: Kluwer).
* Rorty, Amelie, ed. 1986. Essays on Descartes’ Meditations. Berkeley: University of California Press.
* Rozemond, Marleen. 1998. Descartes’ Dualism. Cambridge, MA: Harvard University Press.
* –––. (Forthcoming.) “Descartes’ Ontology of the Eternal Truths.”
* Schmaltz, Tad. 1991. “Platonism and Descartes’ View of Immutable Essences.” Archiv fur Geschichte der Philosophie, 73, 2, 129-170.
* –––. 1996. Malebranche’s Theory of the Soul. New York: Oxford University Press.
* –––. 1997. “Descartes on Innate Ideas, Sensation, and Scholasticism: The Reponse to Regius.” In Stewart 1997, 33-74.
* Simmons, Alison. 1999. “Are Cartesian Sensations Representational?” Nous, 33, 3, 347-69.
* Stewart, M. A. 1997. Studies in Seventeenth-Century European Philosophy. Oxford: Clarendon Press.
* Stich, Stephen, ed. 1975. Innate Ideas. Berkeley, CA: University of California Press.
* Tipton, Ian. 1992. “’Ideas’ and ‘Objects’: Locke on Perceiving ‘Things’.” In Cummins & Zoeller, eds., 1992, 97-110.
* Wells, Norman. 1967. “Objective Being: Descartes and His Sources.” The Modern Schoolman, XLV, 49-61.
* –––. 1990. “Objective Reality of Ideas in Descartes, Caterus, and Suárez.” Journal of the History of Philosophy, 28, 1, 33-61.
* –––. 1993. “Descartes’ Idea and its Sources.” American Catholic Philosophical Quarterly, LXVII, 4, 513-36.
* Wilson, Margaret. 1990. “Descartes on the Representationality of Sensation.” Reprinted in Wilson 1999, Ch. 5, 69-83.
* –––. 1994. “Descartes on Sense and ‘Resemblance’.” Reprinted in Wilson 1999, Ch. 2, 10-25.
* –––. 1999. Ideas and Mechanism: Essays on Early Modern Philosophy. Princeton: Princeton University Press.
* Yolton, John. 1975. “On Being Present to the Mind: A Sketch for the History of an Idea.” Dialogue 14, 373-88.
* –––. 1984. Perceptual Acquaintance from Descartes to Reid. Minneapolis: University of Minnesota Press.

Other Internet Resources

Published in: on February 14, 2011 at 8:37 am  Leave a Comment  

material para Historia de la Filosofía (inglés)

http://www.class.uidaho.edu/mickelsen/ToC/Weber%20ToC.htm
HISTORY OF PHILOSOPHY

BY

ALFRED WEBER
PROFESSOR IN THE UNIVERSITY OF STRASBURG

AUTHORIZED TRANSLATION
BY
FRANK THILLY, A.M., Ph.D.
PROFESSOR OF PHILOSOPHY IN THE UNIVERSITY OF MISSOURI

FROM THE SIXTH FRENCH EDITION

NEW YORK
CHARLES SCRIBNER’S SONS
1908

CONTENTS

INTRODUCTION
(§§ 1 – 3)

I. GREEK PHILOSOPHY
(§§ 4 – 26)

II. PHILOSOPHY OF THE MIDDLE AGES
(§§ 27 – 48)

III. MODERN PHILOSOPHY
(§§ 49 – 71)

FIRST PERIOD
THE AGE OF INDEPENDENT METAPHYSICS
(From Bruno to Locke and Kant)

§ 49. Giordano Bruno
§ 50. Tommaso Campanella
§ 51. Francis Bacon
§ 52. Thomas Hobbes
§ 53. Descartes
§ 54. The Cartesian School
§ 55. Spinoza
I. Definitions
II. Deductions
(1) Theory of Substance
(2) Theory of Attributes
(3) Theory of Modes
§ 56. Leibniz

SECOND PERIOD
THE AGE OF CRITICISM

§ 57. John Locke
§ 58. Berkeley
§ 59. Condillac
§ 60. The Progress of Materialism
§ 61. David Hume
§ 62. Immanuel Kant
I. Critique of Pure Reason
II. Critique of Practical Reason
III. Critique of Judgment
§ 63. Kant and German Idealism
§ 64. Fichte
§ 65. Schelling
§ 66. Hegel
I. Logic, or Genealogy of Pure Concepts
II. Philosophy of Nature
III. Philosophy of Mind

The creation of this e-text of History of Philosophy by Alfred Weber utilized resources of the University of Idaho, Department of Philosophy.

Permission is granted for electronic copying, distribution in print form for educational purposes and personal use. If you duplicate the document, please indicate the original source. No permission is granted for commercial use of this material.

J. Carl Mickelsen

Published in: on February 13, 2011 at 11:21 pm  Leave a Comment  

artículo sobre Descartes con una reseña de la edición de Vidal Peña de Meditaciones, de Descartes


FUENTE http://unizarfilosofia.wordpress.com/2010/02/16/descartes/
Descartes.

Posted by forseti4y9 en 16 febrero 2010

1. Introducción.

En las Meditaciones metafísicas Descartes trata de asentar el conocimiento sobre bases ciertas. Para ello, Descartes utilizará la Razón, aplicando el método al que él mismo da nombre (el método luego llamado cartesiano).

De hecho, no debemos olvidar que es Descartes quien da comienzo a la filosofía moderna, al racionalismo, movimiento en el que además del autor de las Meditaciones metafísicas podemos incluir a Leibniz, Spinoza o Malebranche.

En este sentido, son varios los autores que han remarcado la importancia de Descartes. Es famoso el juicio al respecto de Hegel en las Lecciones sobre la historia de la filosofía, en donde señala que “Descartes es en realidad el verdadero fundador de la filosofía moderna en tanto que toma el pensamiento por el principio […]. La acción de este hombre sobre su siglo y sobre los tiempos modernos no podría exagerarse. Es un héroe, que ha retomado de una vez la cuestión desde el principio, que ha constituido desde cero el terreno, terreno ya únicamente filosófico, sobre el cual, entonces sólo, después de un abandono milenario, la filosofía ha sido reemplazada” .

La obra de Descartes ha de ser analizada por tanto desde esta perspectiva. En las propias Meditaciones, al comienzo, ya señala que debe demoler todas las opiniones previas. Además, hemos de tener en cuenta, que todo el pensamiento filosófico de Descartes se encuentra muy imbricado en sus ideas fundamentales en todas sus obras. Según señala Fernández Prat, en las Meditaciones, publicadas cuatro años después del Discurso del método, “se dramatiza y expone sistemáticamente, según el orden de un descubrimiento, el núcleo del análisis que realizó en el Discurso, entre otras cosas para mostrar su método y los resultados que ya había alcanzado en él” .

Según escribe el propio Descartes a Mersenne en carta fechada el 28 de enero de 1641, sus Meditaciones tratan de la naturaleza y el conocimiento de la mente, la posibilidad de que esta exista sin el cuerpo, la existencia de Dios y la esencia y existencia de la materia .

A modo introductorio, puede ser útil recordar algunos rasgos acerca del contenido filosófico de la obra El Discurso del método, tal como han sido comentados por Fataud :
a) La doble hostilidad de Descartes hacia el escepticismo y la escolástica.
b) Un ideal de conocimiento inspirado en las matemáticas.
c) Una metafísica donde se unen idealismo y realismo.
d) La unión entre mecanicismo y espiritualismo.
e) Un voluntarismo eudemonista en moral.

La filosofía es entendida como ese tronco del que Descartes hablaba en Los Principios de Filosofía, cuyas raíces son la metafísica, el tronco es la física, y las ramas que salen de este tronco son todas las demás ciencias, que se reducen a tres principales: la medicina, la mecánica y la moral.

El método que Descartes propugna para llegar a entender así la filosofía se puede resumir en cuatro principales reglas:
a) La regla de la evidencia: se trata del acto intuitivo que se autojustifica por su claridad y distinción.
b) El método analítico: dividir todo problema, pues para la intuición es necesaria la simplicidad.
c) La síntesis: hay que conducir con orden los pensamientos, partir de elementos absolutos hacia otros relativos o dependientes, creando una cadena de argumentos y razonamiento.
d) El control de los pasos individuales y la corrección de la síntesis.

Como señala Reale, de este modo “lo universal y la abstracción, que son dos momentos fundamentales de la filosofía aristotélico-escolástica, son substituidos por las naturalezas simples y por la intuición” .

Pero esa relación entre el método cartesiano y su metafísica no es tan clara, como advierte Vidal Peña : “la célebre claridad cartesiana no queda muy bien parada cuando esta problemática es encarada en serio”.

Se podría resumir el pensamiento metódico cartesiano, siguiendo en esto a Vidal Peña, en que la satisfacción de la conciencia se alcanza conociendo con arreglo a la evidencia clara y distinta, que no se obtiene en el dominio de la experiencia, presidido por los falaces sentidos, sino en el de la especulación gobernada por el principio de identidad, intuitivamente captado en una pluralidad de esquemas inanalizables: la matemática es el dominio material donde ese principio lógico queda realizado con absoluta excelencia .

2. Exégesis del recorrido de Descartes en las Meditaciones.

Una vez hemos visto a modo de introducción algunas de las líneas argumentales del pensamiento cartesiano, podemos ya pasar a analizar en concreto el recorrido de Descartes en la obra concreta que es el centro principal de nuestro ensayo.

El punto de partida de su argumentación es la duda de todas las cosas . También llamada duda metódica, por la importancia que esta tiene para su método. Y advierte Descartes que no es necesario probar que todas las opiniones son falsas, sino que basta con que demostremos que alguna aserción no es verdadera para que podamos dudar de nuestra experiencia sensible, sobre la que se ha asentado buena parte del saber tradicional.

Y como Descartes comprueba que nuestros sentidos a veces nos engañan, supone que ninguna cosa es tal como la representan nuestros sentidos.

Llega al punto de establecer la hipótesis del genio maligno, que tiene especial fuerza argumentativa. Así, en la meditación primera, señala :

“Así pues, supondré que hay, no un verdadero Dios –que es fuente de suprema verdad-, sino cierto genio maligno, no menos artero y engañador que poderoso, el cual ha usado de toda su industria para engañarme”.

Ya no se trata sólo de que pueda haber fallos en la percepción, que mis sentidos me engañen, ni siquiera le basta a Descartes con darse cuenta de que es difícil distinguir la realidad y el sueño, sino que pasa a un tercer nivel de duda más profundo, el del genio maligno.

Con esta hipótesis, como dice Reale, la duda es hiperbólica , nada resiste a la fuerza corrosiva de la duda. Pero no por ello dejar de ser metódica, pues su objetivo no es el escepticismo sino la verdad, el encuentro con la verdad.

Por esquematizar los niveles de la duda cartesiana:
a) Desconfianza ante la información de los sentidos.
b) Imposibilidad de distinguir cuando soñamos o estamos despiertos. El llamado argumento del sueño (que deja intactas las verdades matemáticas).
c) Hipótesis de un genio maligno que nos confunde.

La hipótesis del genio maligno necesitará para ser destruida de la demostración de la existencia de Dios, como veremos más adelante. Se trata del problema de cómo fundamentar la racionalidad o cognoscibilidad de lo real.

Esto es, la conexión que Descartes establece en la primera meditación entre el genio maligno y Dios lo es en el sentido de que este debe ser entendido como un ser perfecto y que no cabe que un ser perfecto pueda engañarnos. Como dice Fernández Prat, “la existencia de un Dios perfecto es el requisito fundamental para progresar hacia un sistema de conocimiento cierto” .

2.1 Anclaje de su argumentación: la verdad primera es el “yo pienso” (cogito ergo sum).

Para el encuentro de esa verdad el punto en el que se apoya Descartes es que soy, que existo. Se puede ver en la meditación segunda, por ejemplo:

“¿Qué soy, entonces?, una cosa que piensa. Y ¿qué es una cosa que piensa? Es una cosa que duda, que entiende, que afirma, que niega, que quiere, que no quiere, que imagina también, y que siente” .

También en su anterior obra del Discurso o en los posteriores Principios de la Filosofía.

Incluso bajo la hipótesis del genio maligno, si este me engaña, no hay ninguna duda de que existo. El cogito ergo sum no es un razonamiento, pese a lo que su expresión pueda indicar, sino una pura intuición, clara y distinta.

Tal como señala Reale: “Soy una res cogitans, una realidad pensante, en la que no hay ninguna ruptura entre pensamiento y ser” .

Esto es, la característica de la verdad es que es una percepción clara y distinta. La del pensamiento es que es una idea innata.

La verdad necesita de la claridad y la distinción, según el método cartesiano antes expuesto. Mi existencia es verdadera, soy cogito. Las demás verdades se descubrirán a partir del método, si tienen claridad y distinción, inmediata (intuición) o derivada (deducción).

Así por tanto vemos que Descartes lo que en último término está utilizando es la Razón, una razón que para Descartes pertenece a todos los hombres. De ahí que inaugure el racionalismo y la filosofía moderna, dejando de lado la teología y la escolástica. Hay que empezar definiendo el hombre. Con Descartes, la filosofía moderna entra en su fase idealista y racionalista.

Como dice Reale: “el banco de pruebas del nuevo saber filosófico y científico es el sujeto humano, la conciencia racional” .

La verdad no depende del pensamiento, sino del ser. Detrás de la verdad está el hombre, el método, la ciencia, no Dios.

Añadir quizá que según Vidal Peña el “yo” que concluye Descartes no es un “yo” personal, sino que se desubjetiviza: “siempre que se recorra este camino, se obtendrá la misma evidencia; si algo piensa, existirá” .

2.2 Estación de llegada de la argumentación.

2.2.1 La existencia de Dios.

Así, la conclusión a la que llega Descartes es la de la existencia de Dios, en la tercera y en la quinta meditación. Parecería paradójico, en función de lo que acabamos de señalar. Veamos su explicación. En la meditación tercera :

“Pues ¿cómo podría yo saber que dudo y de que deseo, es decir, que algo me falta y que no soy perfecto, si no hubiese en mí la idea de un ser más perfecto, por comparación con el cual advierto la imperfección de mi naturaleza?”.

En todo caso, según pone de manifiesto Vidal Peña, ya lo hemos visto en parte, las Meditaciones admiten una traducción no teológica de la idea de Dios y su relación con el hombre . Incluso señala este autor que del Dios despersonalizado de Descartes, identificado con el orden racional, al Dios sive natura spinoziano sólo hay un paso .

Las ideas para Descartes se pueden clasificar en innatas, las que nacen en mi conciencia, adventicias, que me llegan desde fuera referidas a cosas distintas de mí, y las artificiales, construidas por mí mismo.

Pues bien, la perfección, la sustancia infinita, eterna, inmutable, omnisciente, Dios, es una idea innata de mi pensamiento. La idea de perfección, que está en mí pero no procede de mí, sólo puede tener como causa adecuada un ser infinito, es decir, Dios. No la puedo producir yo mismo esa idea, pues yo soy imperfecto. Como dice Vidal Peña, en nota a pie de página de la meditación tercera , se trata de que la idea de un ser perfecto debe tener tanta realidad como su causa (es la prueba de la existencia de Dios por los efectos).

Es más, ontológicamente, la existencia es parte integrante de la esencia , como dice Reale. Se trata en último término de la llamada prueba ontológica de Dios.

Esquemáticamente: hay tres pruebas de la existencia de Dios, las dos primeras (o una misma, realidad, según expone Fernández Prat ) en la tercera meditación, y la última en la quinta meditación.

La más importante es la del argumento ontológico, la de la quinta meditación (igual que no puede concebirse una montaña sin un valle): si la idea como realidad objetiva exige una causa real adecuada, la idea de un ser infinito exige una causa infinita, por lo que Dios, el ser infinito, existe. Es decir: la existencia es una perfección, y Dios tiene todas las perfecciones, luego Dios tiene existencia.

Como dice Vidal Peña: “la idea de un ser perfectísimo no puede haber brotado de mí, que soy finito y limitado; debe haber sido puesta desde fuera” .

En realidad, según Vidal Peña, en la propia respuesta de Descartes a las primeras objeciones podemos ver que la prueba de Dios como causa de mi ser y la prueba de Dios como causa de que yo tenga la idea de Dios, en el fondo, son la misma .

Pero tal como señala Reale, la existencia de Dios no hace sino reforzar la capacidad natural del hombre para conocer la verdad, no lleva a defender la primacía de la Escritura sobre la Razón. Así, según Reale, “se ve derrotada de forma radical la idea del genio maligno” .

Según Reale, Dios lo que hace es garantizar el carácter objetivo de las facultades cognoscitivas que pertenecen al cogito.

En este planteamiento, el error procede de mi actividad, no de mi ser. La confianza de Descartes en el hombre, por tanto, es total.

Descartes configura así una metafísica grandiosa, donde se unen idealismo y realismo, que ha generado dudas interpretativas y tiene flancos no del todo satisfactorios.

Como explica Fataud , El Dios no engañador es el que nos garantiza la fiabilidad de nuestras ideas, si son claras y distintas, y de nuestros sentidos, que atestiguan la existencia del mundo exterior. El mundo exterior no es como nos lo presentan nuestros sentidos: su testimonio no tiene valor de verdad, sino que pertenece a la física matemática darnos a conocer la realidad. Pero eso no significa que los testimonios que nos dan los sentidos no sean útiles: al contrario, son algo precioso para nosotros, en tanto que somos seres vivos que debemos adaptarnos al mundo. Conclusión: verdad de las relaciones inteligibles y utilidad de las representaciones sensible (una metafísica que conjuga por tanto idealismo y realismo).

2.2.2 La independencia de alma y cuerpo.

Otro de los puntos destacados en la filosofía de Descartes que no queremos dejar de mencionar en el marco de este ensayo, sin querer por ello agotar ni mucho menos la mención de todos los temas clave de su filosofía (tales como el mecanicismo, por ejemplo), es el de la independencia de alma y cuerpo, consecuencia en cierto modo de su planteamiento anterior del cogito.

Para Descartes, en el hombre conviven dos sustancias radicalmente distintas entre sí, la res cogitans y la res extensa. El alma es pensamiento, mientras que el cuerpo es extenso.

Desde este planteamiento, Descartes plantea que es en la glándula pineal del cerebro donde se encuentra el alma, desde donde imprime el movimiento a la res extensa. El problema que plantea aceptar el pensamiento cartesiano a este respecto no es, según Popper , tanto el de la distinción entre dos mundos (el físico y el de la conciencia) cuanto que el de cómo el Descartes de la causalidad mecánica puede explicar que el alma inextensa actúe en el cuerpo extenso.

Para explicar este dualismo Descartes escribirá una obra posterior, El tratado de Las pasiones del alma, donde distingue entre pasiones fisiológicas, psicológicas y morales. Y propone que el hombre se guíe por la Razón, no por los sentimientos. Y en este sentido propone diferentes reglas de moral (obedecer las leyes y costumbres de mi país, incluida la religión; perseverar en mis acciones; vencerme a mí mismo, cambiar mis deseos más que el mundo; y emplear toda mi vida en el cultivo de mi razón).

Como concluye Reale: “Así, el eje de la reflexión y de la acción se desplaza desde el ser hasta el pensamiento, desde Dios y desde el mundo hasta el hombre, desde la revelación hasta la razón, que es el nuevo fundamento de la filosofía y el permanente ideal regulador de la acción” .

En relación con esta distinción entre alma y cuerpo, resulta curioso que Descartes rehuyera tratar de la inmortalidad del alma , como le objetaba Arnauld, el cual infería de dicha distinción real entre alma y cuerpo que el alma era inmortal.

3. Conclusión: el círculo cartesiano entre objetividad/subjetividad.

El problema de la verdad en Descartes se encuentra resuelto, como hemos visto, por la apelación a Dios como garantía de que las representaciones de la res extensa son verdaderas. Por tanto, hay un argumento circular. Si partíamos de las ideas claras y distintas para asentar nuestro conocimiento metódico, resulta que al final esa ideas claras y distintas se asientan en Dios, con lo que la garantía no parece ser tan metódica como pretendíamos, pues en último término estamos apelando a algo que no deja de estar presente ya en nuestro argumento desde el principio.

Como acaba exclamando Vidal Peña : decir que existe Dios es decir que existe en realidad lo que mi conciencia lógica me representa como claro y distinto… ¡Precisamente aquellos rasgos que la hipótesis del genio maligno ponía en tela de juicio!. Dicho más claramente: ¿Hay, acaso, tan sólo un enorme círculo, algo así como decir: “mi creencia en la evidencia matemática está garantizada porque existe realmente Dios, es decir, un orden matemático objetivo, en el cual creo porque, si no lo hubiera, mis evidencias no estarían garantizadas”?. Según Vidal Peña, la doctrina cartesiana no anda muy lejos de afirmar esto, y no deja de ser un valioso exponente histórico de razonamiento trascendental . Luego, su filosofía-ontología acabaría moralizándose, para acallar la terrible hipótesis del genio maligno.

El círculo cartesiano también podría ser explicado así: para saber de Dios ha partido de un cogito donde Dios no estaba; más tarde, para fundar la posibilidad del cogito, lo asienta en Dios .

Según Vidal Peña, la modernidad de Descartes es tal que afirma dos cosas a la vez respecto de Dios, hay un doble concepto de Dios : que garantiza que mis evidencias son legítimas tal y como las tengo; y que podría hacer que el mundo fuera enteramente otro. Garante de la inteligibilidad del mundo, y de otro lado, el límite de nuestras posibilidades racionales .

En todo caso, el juicio de Vidal Peña acerca de Descartes no es desfavorable. El voluntarismo de Descartes no es contradictorio con su proyecto racionalista , pues todo racionalismo crítico comporta a la vez las limitaciones y las garantías de la Razón. Podemos estar seguros de que lo que conocemos lo conocemos bien, pero no podemos estar seguros de conocer todo. Dios no nos engaña, nos limita. En realidad, esto se acomoda bastante bien al vocabulario cristiano.

En un sentido más general, podemos recordar qué se entiende por razonamiento circular: “presumir la verdad de la conclusión para dar apoyo a una premisa desbarata este propósito debido a que el grado inicial de confianza en la premisa no puede exceder el grado de confianza inicial en la conclusión” .

Efectivamente, el grado de confianza que necesito en la existencia de Dios no difiere del que necesito para creer en las ideas claras y distintas iniciales, que son las que han hecho que llegue a la verdad del cogito.

En este mismo sentido, es de resaltar que ya es terreno común el denunciar el problema del círculo cartesiano. Podemos leer en el Diccionario Akal de Filosofía, cuando resume a Descartes, que: “Lo que sí es cierto, no obstante, es que los elementos fundamentales de la ciencia cartesiana son las ideas innatas (principalmente las de las matemáticas), cuya fiabilidad toma Descartes como algo garantizado por el hecho de haber sido implantadas en nuestra mente por Dios. Esto, sin embargo, da lugar a uno de los mayores problemas des sistema cartesiano, que fue primeramente descrito por alguno de los contemporáneos del propio Descartes (principalmente Mersenne y Arnauld), y que ha llegado a ser posteriormente conocido bajo el nombre de círculo cartesiano. Si sucede que da fiabilidad de las ideas claras y distintas del intelecto depende del conocimiento de Dios, ¿cómo puede llegarse a establecer ese conocimiento en primer lugar?. Si la respuesta consiste en afirmar que probamos la existencia de Dios a partir de premisas que percibimos de forma clara y distinta, entonces el razonamiento parece circular; porque ¿cómo estamos autorizados en esta etapa a asumir que nuestras percepciones claras y distintas son realmente fiables?” .

En este mismo sentido, puede verse el comentario de Fernández Prat , que incluso se refiere expresamente a las Objeciones de Arnauld. Dicho en breves palabras, el círculo vicioso es el que sigue: Descartes apela a Dios para certificar que las ideas claras y distintas que ayudan a probar la existencia de este Ser Supremo no son engañosas.

La estrategia defensiva al respecto de Descartes apela a la luz natural (a la que ya hace referencia en la meditación tercera ) en sus respuestas a Mersenne y a Arnauld; a la crítica de argumento cartesiano se sumó Hume poniendo en cuestión que un ser perfecto no pueda ser engañador como algo que sepamos por luz natural.

Esa estrategia defensiva no parece, como dice Fernández Prat , que tenga un soporte muy firme.

Incluso el propio Descartes en su meditación tercera cuando afirma que resulta evidente que el Ser Supremo no puede ser engañador, reconoce que no podemos “comprender” las propiedades del Ser Supremo, sino sólo tener una “ligera idea” de las mismas.

En este punto nos podríamos plantear si Dios no es en realidad el mismo genio maligno de la hipótesis, con lo que todo el edificio cartesiano, construido para garantizar la racionalidad y cognnoscibilidad de la realidad y la verdad, se vería seriamente dañado.

Es más, esa es la interpretación de Vidal Peña, que señala que cuando Descartes resume esto en sus Principios de filosofía, se “olvida” del genio, refiriéndose lisa y llanamente a Dios. Y dice expresamente Vidal Peña : “y nos parece que de Dios tiene que tratarse, pues la condición para que el genio maligno pueda hacer que yo me engañe al creer que dos más tres son cinco es que sea absolutamente omnipotente, y eso sólo puede serlo Dios”.

Así, si entendemos que la hipótesis del genio maligno es consustancial al pensamiento cartesiano, el problema es real y efectivo, y su significación filosófica profunda, como dice Vidal Peña. Se pone en tela de juicio la conciencia racional misma, y no como mero artificio retórico.

Así, se nos aparece un Descartes muy moderno, nada medieval, en el que la hipótesis del genio maligno arroja dudas sobre el conjunto de la realidad: sobre el entero carácter racional de esta .

4. Corolario final.

Descartes ha caído ante el empuje del pensamiento filosófico posterior. Como señala García Morente en su introducción al Discurso del Método, ya Kant arruinó la metafísica cartesiana al distinguir esencia y existencia: la esencia puede conocerse intelectualmente, pero la existencia sólo puede ser objeto de conocimiento sensible. Así, el cogito y la prueba ontológica de la prueba de Dios pueden instituir ideas, pero no cosas existentes.

En este mismo sentido, Fernández Prat , al señalar que la existencia no es una propiedad o característica que tengan unas cosas y otras no tengan, pues “existir” no es un predicado.

No obstante, la importancia de Descartes sigue siendo mucha. Todo el pensamiento acrítico de la gente tiene mucho de cartesiano. Es más, según confirma Péguy, en la trascripción que nos ofrece Fataud, la importancia de Descartes, más allá de los problemas de su filosofía, es imperecedera, precisamente por plantearlos y por hacerlo de una determinada manera. Señala : “Una gran filosofía no es la que pronuncia juicios definitivos, instalando una verdad definitiva. Es la que introduce una inquietud, la que causa una conmoción […]. Una gran filosofía no es la que es invencible o la que una vez venció; es la que una vez combatió. Una gran filosofía no es una filosofía sin reproche, es una filosofía sin miedo”.

La deuda eterna de la filosofía con el pensamiento cartesiano es clara para Vidal Peña : lo que empezó como buceo en la subjetividad acaba en reconocimiento de la objetividad, pero un reconocimiento ya crítico. El reconocimiento ingenuo de una “realidad exterior a la conciencia” es algo que, desde Descartes (no digamos ya desde Kant), no podrá pretenderse sin infantilismo.

Y es que conviene subrayar la importancia de la hipótesis del genio maligno. Como dice en otro momento Vidal Peña : ya no es el mismo “Dios” el que se recupera cuando la hipótesis del genio maligno queda destruida; ya no es la misma confianza en la racionalidad que antes.

Como concluye Vidal Peña , y nosotros con él, el círculo cartesiano sería el reconocimiento de que no hay claridad, de que la evidencia que se trata de fundamentar viene, a la postre, a fundamentar ella misma el fundamento.

Es la de Descartes, bien entendida, una filosofía algo paradójica. Reconoce que la razón necesita de cierta fe, de cierto trascendente, de buenas obras, de voluntad, de moral. Siempre habrá que postular algo para escapar del genio maligno; fantasma que, por otra parte, nunca puede ser conjurado del todo.

Este es el trabajo, salvo que ahora no hay notas al pie, que presenté a Teoría del Conocimiento.

Bibliografía:
• AUDI, R. (ed.), Diccionario Akal de Filosofía. Ediciones Akal. 2004. Madrid.

• DESCARTES, R., Meditaciones metafísicas, Edición de Vidal Peña, KRK Ediciones, Oviedo, 2005.

• DESCARTES, R., Discurso del método y Meditaciones metafísicas, Edición de Olga Fernández Prat, Traducción de Manuel García Morente, TECNOS, 2002, Madrid.

• FATAUD, J.M. Discours de la méthode : Avec des aperçus sur le mouvement des idées avant Descartes, une biographie chronologique, une introd. à l’œuvre, une analyse méthodique du Discours, des notes, des questions et des documents, Bordas, Paris, 1972.

• REALE, G. y ANTISERI, D., Historia del Pensamiento filosófico y científico. Tomo II. Del humanismo a Kant. Herder, Barceona, 1988.
RESEÑA
http://www.fgbueno.es/bas/pdf/bas10311.pdf

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Racionalismo y empirismo (en inglés)


Contiene un curso sobre estas dos corrientes filosóficas, de utilidad ( aunque está en idioma inglés)
http://www.earlham.edu/~peters/courses/re/rehome.htm

GUIA DE LA CADENA DEL SER TAL COMO EL PROFESOR PETER SUBER LO PRESENTA EN SU CURSO SOBRE RACIONALISMO Y EMPIRISMO
http://www.earlham.edu/~peters/courses/re/chain.htm
The Great Chain of Being
Peter Suber, Philosophy Department, Earlham College
Here is a brief restatement of the vision of the great chain of being. I’ve put the various claims comprising the vision into logical order to show that they form a single, large argument.

I include references to Descartes, Spinoza, and Leibniz in order to lead you to texts which clarify and amplify these propositions. I have indented these references out of the way to allow you read the main propositions without distraction.

The top of the chain represents perfection in the highest degree. Most believers in the chain call this God.

The chain in its entirety represents all degrees of perfection from the highest and fullest to the lowest and least; it is complete.
Spinoza, Ethics, all possibilities are actualities: 43.7 (I.16 cor.1), 56.2 (I.33 sch.2), 56.8 (I.35), 62.5 (App. to Part I), 66.9 (II.7 cor)
Leibniz, Discourse §3.

Hence the universe would not be complete if the chain did not extend all the way to the bottom or if it had gaps in it.

The universe is more perfect (in the sense that it is more complete) if all degrees of perfection are represented in it than if only the highest is represented.

This explains why a perfect God would create an imperfect world. It was not a mistake or an imperfection; on the contrary.
The most perfect (complete) universe must contain every kind of imperfect thing. Hence imperfect things are not evidence of the imperfection of creation.
Descartes, Meditations 111.8, 117.3.

The bottom of the chain represents the least possible perfection, which is nothingness (as opposed to evil).
Descartes, Meditations 110.4.
Spinoza, Ethics 37-38 (I.11.3d proof), 38.7 (I.11 sch)

Hence, every point on the chain above the very bottom has some degree of perfection.

Hence, any idea, insofar as it exists at all, has its share of truth.
Descartes, Discourse 30.6; Meditations 94.3, 116.4, 117-18, 120.3.
Spinoza, Ethics 85.8 (II.32), 86.3 (II.34); Treatise 250.8

Hence, error is not something positive; truth is. Error is the lack of truth; error is privation.
Descartes, Discourse 26.2, 29.6; Meditations 110.7, 115.7, 116.6, 120.4.
Spinoza, Ethics 63.6 (II def.4), 86.1 (II.33), 86.5 (II.35), 92.4 (II.43 sch); Treatise 246.n, 250.8, 261.6
Leibniz, Monadology § 49.

Similarly, evil is not something positive; good is. Evil is the lack of good; evil is privation.
Descartes, Meditations 114.5, 116.5.
Leibniz, Discourse §§ 4, 30.

In general, being or existence is a perfection; to be is more perfect than not to be. What has positive existence is good and was created by God; what is privation lacks being and goodness, and was not created at all.
Descartes, Meditations 97.5, 110.4, 121.5.
Spinoza, Ethics 38.3 (I.11 sch), 38.6 (I.11 sch), 63.8 (II def.6), 98.4 (II.49 sch)
Leibniz, Monadology §§ 40-41, 45.

It follows (from principle 11) that the idea of the being with all perfections is the idea of an existing being. This is the ontological argument for the existence of God.
Descartes, Discourse 27.8; Meditations 107.3, 121.5.
Spinoza, Ethics 31 (I defs 1, 3, 6), 37.2 (I.11), 46.9 (I.20)
Leibniz, Discourse § 23; Monadology §§ 40, 44.

It follows (from principle 9) that for propositions, truth is the default; and (from principle 11) that for entities, existence is the default. If a proposition’s truth is possible, we may assume that it is actually true, and if an entity’s existence is possible, we may assume that it actually exists, unless there are special reasons to think not. Proofs of truth and existence tend to follow from possibility alone; the burden of proof is on the denial of truth or existence.
Spinoza, Ethics 37.5 (I.11.2d proof), 37-38 (I.11.3d proof), 99.7 (II.49 sch).
Leibniz, Monadology § 45.

Dependence is an imperfection.
Descartes, Discourse 27.3.
Leibniz, Monadology § 50.

Hence, the things in the middle of the chain are dependent or contingent. (The nothingness at the bottom is dependent in the sense that nothingness depends on the contrast with somethingness.)

The being at the top of the chain is utterly independent or self-sufficient or absolute.
Descartes, Meditations 104.3, 106.3.
Spinoza, Ethics 31 (I defs 1, 3, 6), 44.2 (I.17), 56.5 (I.33 sch.2).
Leibniz, Monadology § 40.

If A causes B, then B depends on A. Hence (by principle 14 above) B is less perfect than A. Therefore a cause must be more perfect than its effect.
Descartes, Discourse 26.3; Meditations 96-97.
Leibniz, Monadology § 50.

Dependent beings, therefore, depend on more perfect causes than themselves, which in turn depend on more perfect causes themselves, and so on, until the series comes to an end with the most perfect, uncaused (or self-caused), independent being, which is at the top of the chain.
Descartes, Meditations 106.3.
Leibniz, Monadology §§ 36, 40, 45.

It follows that, if there are any dependent beings (for example, ourselves), then there must be an independent, hence perfect or absolute being (God). This is the cosmological argument for the existence of God.
Descartes, Discourse 26.6; Meditations 106.3.
Spinoza, Ethics 38.2 (I.11 3d proof).
Leibniz, Monadology §§ 36, 40, 44.

God, then, is either self-caused or uncaused.
Descartes, Meditations 106.2.
Spinoza, Ethics 56.7 (I.34 proof).
Leibniz, Monadology § 36.

References

Descartes, René. Philosophical Essays. Trans. Laurence Lafleur, Bobbs-Merrill, 1964.

Spinoza, Baruch. Ethics, Treatise on the Emendation of the Intellect, and Selected Letters. Trans. Samuel Shirley and Seymour Feldman, Hackett, 1992. In addition to page numbers from this edition, I cite Spinoza’s propositions in the Ethics by number.

Leibniz, Gottfried Wilhelm. Discourse on Metaphysics and Other Essays. Trans. Daniel Garber and Roger Ariew, Hackett, 1991. I cite Leibniz only by section numbers, not page numbers.