Assistant Professor of Philosophy
Birmingham-Southern College
bmyers@panther.bsc.edu
DESCARTES' PROOF FOR THE EXISTENCE OF GOD THIRD MEDITATION
1) I think, therefore I am.
2) I cannot be mistaken about the ideas that I have. 3) There can never be more objective reality in the effect (i.e., the idea) than there is formal reality in the cause (i.e., object of the idea). 4) I have an idea of perfection or infinite substance. 5) My idea of perfection is the most objectively real idea that I have. 6) The only possible formal cause of that idea is infinite substance. _________________________________________________________________
Therefore, God must exist.
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Explication of premises:
Premises 1 and 2 are incorrigible. That is, they cannot be doubted. Premise number 3 rests upon the principle of sufficient reason. It points out that any cause must have at least as much reality as any effect that it has. If it did not, then the cause would not be sufficient to produce the effect. Another way of saying this is that it is impossible to derive the more perfect from the less perfect. Premise number 4 is Descartes' fourth innate idea. If one denies that one has an idea of perfection, then I can give it to them, though this is misleading. The idea is already there, for it is innate. My pointing it out to someone simply makes the idea discursive. Once perfection is pointed out to someone, then they cannot deny having the idea. Premise number 5 is not quite as easy. The substance doctrine tells us that if there is anything, then that thing has to be either a substance or an attribute of a substance. Attributes are constantly changing and are relative to a perceiver while substances remain numerically one. Given this, my idea of a substance has more objective reality than my idea of an attribute because a substance has more formal reality than an attribute. Likewise, my idea of an infinite substance has more objective reality than my idea of a finite substance, and these are the only possible things that can cause an idea to emerge in my mind. Therefore, my idea of infinite substance must be the most objectively real idea that I have. Premise 6 says that this idea could only have come from God. Since I cannot derive the more perfect from the less perfect, then the idea had to have come from God because everything else in the world is imperfect. So, the idea had to have come from God. If one says that she got the idea from her grandmother, then where did she get if from? We can repeat the question until we find that the ultimate source must be God. Therefore, God exists.
Latest Update by DLH: March 9 , 1999