Descartes' Proof for the Existence of God
Many readers follow Descartes with fascination and pleasure as he descends into the pit of skepticism in the first two Meditations, defeats the skeptics by finding the a version of the cogito, his nature, and that of bodies, only to find them selves baffled and repulsed when they come to his proof for the existence of God in Meditation III. In large measure this change of attitude results from a number of factors. One is that the proof is complicated in ways which the earlier discourse is not. Second is that the complications include the use of scholastic machinery for which the reader is generally quite unprepared -- including such doctrines as a Cartesian version of the Great Chain of Being, the Heirloom theory of causaltiy, and confusi ng terms such as "eminent," "objective" and "formal reality" used in technical ways which require explanation. Third, we live in an age which is largely skeptical of the whole enterprise of giving proofs for the existence of God. A puzzled student once remaked, "If it were possible to prove that God exists, what would one need faith for?" So, even those inclined to grant the truth of the conclusion of Descartes' proof are often skeptical about the process of reaching it.
Philosophers are inclined to evaluate arguments carefully. This page is aimed to help students analyze the complex elements of Descartes' proof into simpler parts and to provide some explanation of how those work, so that the student may grasp the nat ure of the proof and thus be in a much better position to give a reasoned evaluation of it. Such an exercise is both interesting and useful in itself, and also helps the student understand philosophical machinery which Descartes puts to other important u ses later in the Meditations.
LEADING UP TO THE PROOF
At the beginning of Meditation III, Descartes has made some progress towards defeating skepticism. Using his methods of Doubt and Analysis he has systematically examined all his beliefs and set aside those which he could call into doubt until he reach ed one belief which he could not doubt -- that the evil genius seeking to deceive him could not deceive him into thinking that he did not exist when in fact he did exist. Having determined for certain that he exists, by a second application of the method s of Doubt and Analysis he has also determined that his essence is to be a thinking thing. And by yet a third application of these methods, he has also determined that the essence of matter (which can only be known by the mind) is to be flexible, changea ble and extended (if there is any such thing as matter). This is where things stand at the end of Meditation II.
At the beginning of Meditation III, Descartes makes yet more progress, he comes up with a criterion of certainty. By examining the truths which he discovered in the course of his second meditation, he decides that all of them have in common the proper ties of being clear and distinct....