Descartes' Epistemology

Descartes’ Epistemology• Epistemology: The philosophical

examination of knowledge – its nature and its origin.

• Rationalism: Epistemological school that maintains that the most important truths about reality are obtained by means of the intellect (the mind) alone, without relying at all upon the senses.

Descartes’ World• Descartes lived during the first half of the

Seventeenth Century (1596 – 1649).• A Revolutionary and Uncertain Time

– Copernicus– Galileo– Kepler– Reformation (1520)– Thirty Years War (1619 – 1648)

• Europe’s pop. shrank by 6.5 million during this war.

Descartes’ Motivation• Descartes was a mathematical genius.

Developed the x y graphing grid still used today (the Cartesian point system).

• Given the times in which he lived and his temperament, Descartes wanted to find the same certainty in philosophy that he found in mathematics.

Descartes’ Method of Systematic Doubt

• Descartes resolved to doubt anything that could be doubted.

• He was looking for at least one totally indubitable, absolutely certain truth upon which he could build his entire philosophy.

• He was looking for a philosophical Archimedean point.

– “Archimedes, in order that he might draw the terrestrial globe out of its place, and transport it elsewhere, demanded only that one point should be fixed and immoveable; in the same way, I shall have the right to have high hopes, if I am happy enough to discover one thing only which is certain and indubitable.”Rene Descartes, Meditations on First

Philosophy

• N. B.: Descartes engages in philosophical, NOT genuine, doubt. Despite the hyperbole he sometimes employs, Descartes does not really doubt the things he says he does; rather, he rejects as his philosophical Archimedean point anything that can be doubted.

• What can be doubted?– The reports of the senses.

• Dreams sometimes mistaken for reality.

– “How often has it happened to me that in the night I dreamt that I [was] in this particular place, that I was dressed and seated near the fire, whilst, in reality, I was lying undressed in bed . . . ! [I]n dwelling carefully on this reflection I see so manifestly that there are no certain indications by which we may clearly distinguish wakefulness from sleep . . . .”

Meditations on First Philosophy

• Since in his dreams he’s dreamed that he’s had all sorts of strange, grotesque bodies, Descartes realizes that his belief that he has a body at all could be false; so, he will doubt even that.

– A very powerful, very evil genius (sort of a super Satan) might be continually deceiving Descartes even about his mathematical beliefs, e.g. 2+2=4; so, he will doubt even these.

• What cannot be doubted?– “. . . let him [the evil genius] deceive

me as much as he will, he can never cause me to be nothing so long as I think that I am something. So that, after having reflected well . . . we must come to the definitive conclusion that this proposition, I am, I exist, is necessarily true each time that . . . I mentally conceive it.


– Cogito, ergo, sum. “I think; therefore, I am” from Descartes’ Discourse on Method.

– In order for the evil genius to deceive him, Descartes must exist because something that does not exist cannot be deceived.

– But, what is Descartes, i.e. what type of being is he?

• “I am not more than a thing which thinks, that is to say a mind or a soul, or an understanding, or a reason . . . . I am . . . a real thing and really exist; but what thing? I have answered: A thing which thinks”

Meditations on First Philosophy• Descartes has found his philosophical

Archimedean point – his own existence as a mind.

Clear and Distinct Standard• “[Since] there [is] nothing at all in the

statement ‘I think; therefore, I am’ which assures me of having, thereby, made a true assertion, excepting that I see very clearly that to think is necessarily to be, I came to the general conclusion that I might assume, as a general rule, that the things which we conceive very clearly and distinctly are all true . . . .”


• Descartes will accept as true any idea that he conceives as clearly and distinctly as the idea that he exists as a mind.

The Eidological Proof for God• Descartes has an idea of perfection, i.e. of God• God is “infinite, eternal, immutable,

independent, all knowing, all powerful, and [the Being] by Whom I myself and everything else . . . have been created.”


• Descartes clearly and distinctly conceives that the origin of his idea of God can only be God Himself, i.e. the only thing that can generate within Descartes the idea of a perfect being is a perfect being.

• Since, therefore, Descartes possess an idea of God, God must, and does, exist.

• Anticipating an objection Ludwig Feuerbach would raise 200 years later, Descartes says:– “Nor should I imagine I perceive the infinite . . .

only by the negation of the finite, just as I perceive repose and darkness by the negation of movement and light . . . . For, how would it be possible that I should know . . . that something is lacking [in] me, and that I am not quite perfect, unless I had within me some idea of a Being more perfect than myself, in comparison with which I should recognize [my] deficiencies.”


– Descartes’ idea of God cannot be merely a projection and magnification of his own nature.

– Descartes claims he would not be able to recognize his own imperfections, unless he had a prior idea of perfection by which to judge himself deficient.

– Amadeus

The Deduction of Matter• God has placed in humans the strong

desire to believe in the existence of material objects they clearly and distinctly perceive.

• If God has placed this desire in humans and their clear and distinction perceptions are delusory, then God is a tease and a deceiver.

• Since God is perfectly good, He cannot be a tease and a deceiver.

• Thus, humans’ clear and distinct perceptions are veridical, and the material objects they clearly and distinctly perceive really do exist.

Critique of Descartes• The Cartesian Circle

– Descartes first appeals to the clear and distinct standard to prove God, then he appeals to God to prove the clear and distinct standard.

– Response: There are two clear and distinct standards – one for conceiving and the other for perceiving.

– Descartes uses the intuition of his mind to establish the first standard, and he makes God the guarantor of the second.

• Recognizing imperfection

– Does Descartes really need an idea of perfection to realize he is imperfect?• No.

– Wouldn’t, at most, Descartes only need an idea of the better?• Yes.

– Can’t Descartes conceive of the better by magnifying his own qualities?• Yes.

– If Descartes were to claim that he had an actual experience of perfection, like Salieri’s experience upon encountering Mozart’s music, then, perhaps, he could argue only a perfect being could cause such an experience.

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Descartes' Epistemology