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Descartes 1/17/00 lecture

Keith DeRose


1. Tearing Down and Building Back Up: What’s Become of our Colors?

2. Tearing Down and Building Back Up: The Cartesian Circle*

3. The Real Distinction, God’s Power, and “the Hope of an After-Life”**

*I suspect that I’ll set up the problem of the circle, but won’t have much time for much of a positive attempt to solve it.  For my best shot at this more positive task, see my “Descartes, Epistemic Principles, Epistemic Circularity, and Scientia“.

**See also


(A) I may tell you, between ourselves, that these six Meditations contain all the foundations of my Physics. But please do not tell people, for that would make it harder for supporters of Aristotle to approve them. I hope that readers will gradually get used to my principles, and recognize their truth, before they notice that they destroy the principles of Aristotle. –Letter to Mersenne, 28 January, 1641

(B) That an atheist can know clearly that the three angles of a triangle are equal to two right angles, I do not deny, I merely affirm that, on the other hand, such knowledge on his part cannot constitute true science, because no knowledge that can be rendered doubtful should be called science. Since he is, as supposed, an Atheist, he cannot be sure that he is not deceived in the things that seem most evident to him, as has been sufficiently shown; and though perchance the doubt does not occur to him, nevertheless it may come up, if he examine the matter, or if another suggests it; he can never be safe from it unless he first recognizes the existence of a God. –AT VII, p. 141 = HR, vol. II, p. 39 [Compare the weaker translation in our green book, p.103: Cottingham translates scientia (“science”, in HR) simply as “knowledge”, and has Descartes admitting that the atheist geometer can be “clearly aware” of the fact that HR translates Descartes as admitting that he can “know clearly”; the Latin here is “clare cognoscere.”]

(C) You should not find it strange, either, that I do not prove in my second Meditation that the soul is really distinct from the body, but merely show how to conceive it without the body. This is because I do not yet have, at that point, the premises needed for the conclusion. You find it later on, in the sixth Meditation. –Letter to Mersenne, 24 December, 1640

(D) Geometrical Exposition

Definition X: Two substances are said to be really distinct when each of them can exist apart from the other.

— AT VII, p. 162 = CSM II, p. 114

Proposition IV: There is a real distinction between the mind and the body

Demonstration: God can bring about whatever we clearly and distinctly perceive in a way exactly corresponding to our perception of it (preceding Corollary). But we clearly perceive the mind, that is, a thinking substance, apart from the body, that is, apart from an extended substance (Second Postulate). And conversely we can clearly perceive the body apart from the mind (as everyone readily admits). Therefore, the mind can, at least through the power of God, exist without the body; and similarly the body can exist apart from the mind.

Now, if one substance can exist apart from another the two are really distinct (Def. X). But the mind and the body are substances (Defs. V, VI and VII) which can exist apart from each other (as has just been proved). Therefore, there is a real distinction between the mind and the body.

Notice that I introduce the power of God as a means to separate mind and body not because any extraordinary power is needed to bring about such a separation but because the preceding arguments have dealt solely with God, and hence there was nothing else I could use to make the separation. Our knowledge that two things are really distinct is not affected by the nature of the power that separates them.
— AT VII, pp. 169-170 = CSM II, p. 119

(E) You ask me by what kind of causality God established the eternal truths. I reply: by the same kind of causality as he created all things, that is to say, as their efficient and total cause. For it is certain that he is the author of the essence of created things no less than of their existence; and this essence is nothing other than the eternal truths. I do not conceive them as emanating from God like rays from the sun; but I know that God is the author of everything and that these truths are something and consequently that he is their author….
You ask also what necessitated god to create these truths; and I reply that he was free to make it not true that all the radii of the circle are equal — just as free as he was not to create the world.
— To Mersenne, 27 May 1630, AT I, pp. 151-153 = CSMK 25-26

(F) God did not will the creation of the world in time because he saw that it would be better this way than if he had created from eternity; nor did he will that the three angles of a triangle should be equal to two right angles because he recognized that it could not be otherwise, and so on. On the contrary, it is because he willed to create the world in time that it is better this way than if he had created it from eternity; and it is because he willed that the three angles of a triangle should necessarily equal two right angles that this is true and cannot be otherwise; and so on in other cases.
— Replies Six, AT VII, 431-432 = CSM II, 291-292

(G) I turn to the difficulty of conceiving how God would have been acting freely and indifferently if he had made it false that the three angles of a triangle were equal to two right angles, or in general that contradictories could not be true together. It is easy to dispel this difficulty by considering that the power of God cannot have any limits, and that our mind is finite and so created as to be able to conceive as possible the things which God has wished to be in fact possible, but not to be able to conceive as possible things which God could have made possible, but which he has nevertheless wished to make impossible. The first consideration shows us that God cannot have been determined to make it true that contradictories cannot be true together, and therefore that he could have done the opposite. The second consideration assures us that even if this be true, we should not try to comprehend it, since our nature is incapable of doing so. And even if God has willed that some truths should be necessary, this does not mean that he willed them necessarily; for it is one thing to will that they be necessary, and quite another to will this necessarily, or to be necessitated to will it.
— To Mesland, 2 May 1644, AT IV, 118-119 = CSMK, 235

(H) But I do not think we should ever say of anything that it cannot be brought about by God. For since every basis of truth and goodness depends on his omnipotence, I would not dare to say that God cannot make a mountain without a valley, or bring it about that 1 and 2 are not 3. I merely say that he has given me such a mind that I cannot conceive a mountain without a valley, or a sum of 1 and 2 which is not 3; such things involve a contradiction in my conception. I think the same should be said of a space which is wholly empty, or of an extended piece of nothing, or of a limited universe; because no limit to the world can be imagined without its being understood that there is extension beyond it; and no barrel can be conceived to be so empty as to have inside it no extension, and therefore no body; for wherever extension is, there, of necessity, is body also.
— To Arnauld, 29 July 1648, AT V, 223-224 = CSMK 358-359

(I) You say that you think it is ‘very hard’ to propose that there is anything immutable and eternal apart from God. You would be right to think this if I was talking about existing things, or if I was proposing something as immutable in the sense that its immutability was independent of God. But just as the poets suppose that the Fates were originally established by Jupiter, but that after they were established he bound himself to abide by them, so I do not think that the essences of things, and the mathematical truths which we can know concerning them, are independent of God. Nevertheless I do think that they are immutable and eternal, since the will and decree of God willed and decreed that they should be so. Whether you think this is hard or easy to accept, it is enough for me that it is true.
— Replies Five. AT VII, 380 = CSM II, 261

(J) It will be said that if God had established these truths he could change them as a king changes his laws. To this the answer is: Yes he can, if his will can change. ‘But I understand them to be eternal and unchangeable.’ — I make the same judgement about God. ‘But his will is free.’ — Yes, but his power is beyond our grasp. In general we can assert that God can do everything that is within our grasp but not that he cannot do what is beyond our grasp.
— To Mersenne, 15 April 1630. AT I, 145-146 = CSM III, 23

In interpreting the quoted passage, I follow the usual practice of disallowing any essential role to God’s omnipotence. If we are to take seriously Descartes’ doctrine of God’s free creation of the eternal truths, God can create anything apart from anything, even x apart from x; and this without regard to what we may not find conceivable. Since that doctrine renders irrelevant conceivability considerations which Descartes clearly sees as crucial, and lends itself to conclusions much stronger than he would accept, there is no option but to discount it in the present context. Having done so, the divine power to create x without y essentially converges on the metaphysical possibility of x without y.
— Stephen Yablo, “The Real Distinction Between Mind and Body,” p. 156, n. 6.

We do not want to prove too much…. Of course, if we invoke the doctrine of the creation of eternal truths, we might say that a really omnipotent being could cause the mind and the body to exist apart even if that were not logically possible. But in the Meditations Descartes is careful not to invoke that extravagant conception of omnipotence, and we would do him no service by bringing it in.
— E.M. Curley, Descartes Against the Skeptics, p. 198

The incomprehensibility of the divine power, far from extending contingency to the domain of mathematical truths, where we perceive only necessity, is invoked, on the contrary, to safeguard necessity, where we can only imagine contingency. It is true that our imagination can only represent the work of a free will as contingent….But the Cartesian reminds us that our inability to imagine a will which is free, and nevertheless immutable, and creative of truths truly necessary, does not prove [that there can be no such thing].
— J.-M. Beyssade, La philosophie premiere de Descartes (Paris: Flammarion, 1979), p. 112.

A Few References

Steve Yablo, “The Real Distinction Between Mind and Body,” Canadian Journal of Philosophy, supp. vol. 16 (1990), pp. 149-201.

Steve Yablo, “Is Conceivability a Guide to Possibility?,” Philosophy & Phenomenological Research 53 (1993), pp. 1-42.***

Earl Conee, “The Possibility of Power Beyond Possibility,” Philosophical Perspectives 5 (1991), pp. 447-473.***

***These two papers should available on-line to Yalies on the JSTOR service.  For JSTOR, click here.

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