Theistic Arguments: Descartes' God-claim

Descartes was a rationalist philosopher. The rationalists wanted to prove everything by reason alone, because they thought that 'the senses' were unreliable. The difference between analytic statements or synthetic statements was not yet clear at that moment. We think that "God exists" can only be proven by using both senses and reason, but Descartes' 'proved' the existence of god with reason alone. Let us look at his argument.

Descartes thought about things that he could know for sure, and as he discarded the information given to him by his senses as untrustworthy, he found that he knew nothing. He doubted about all his knowledge. However, he suddenly realised that because he doubted, he could be at least sure that there existed a being that doubted. He could be sure that he himself existed. This is in fact what he expressed in his famous saying: 'Cogito, ergo sum.', 'I think, therefore I am.'

Descartes examined himself further, and he found that he had in his mind the notion of a 'perfect being'. From this, he concluded that god must exist, in the following way:

1. I exist (Axiom)
2. I have in my mind the notion of a perfect being (Axiom, partly based on 1)
3. An imperfect being, like myself, cannot think up the notion of a perfect being (Axiom)
4. Therefore the notion of a perfect being must have originated from the perfect being himself (from 2 & 3)
5. A perfect being would not be perfect if it did not exist (Axiom)
6. Therefore a perfect being must exist (from 4 & 5)

But is this valid reasoning? Should this argument convince us that there is a god? I will now point out the weak spots in his reasoning.

I think we can all agree that point 1 is a valid axiom. We can all be sure that we at least exist. No problem there.

The second axiom however is not so obviously true. Maybe Descartes had an idea of the perfect entity in his mind, but I certainly don't have such an idea. What am I to believe? That God failed to put that idea into my mind, or that Descartes' idea of this perfect being was not as innate as he thought? It is obvious that not all of us have this idea. In fact, many Christians have told me that mankind cannot conceive God. This is in direct contradiction with Descartes' belief that everybody has this idea of a perfect being from birth on.

The third axiom is weaker still. Descartes postulates that an imperfect being can never think up the notion of a perfect being. But can we accept this as truth? Why would this be impossible? The imperfect being does not have to understand or contain the perfect being, it only has to think up the notion 'perfect being'. If an imperfect being can have an idea of a perfect being, why couldn't he think it up? And if we say that an imperfect being can not think up the notion of a perfect being, can we be sure that an imperfect being could recognize the notion of a perfect being? Maybe the notion Descartes had was in fact of an imperfect being, but seemed perfect to the imperfect mind of the imperfect Descartes.

Not only that, but who or what can define the notion 'perfect'? Many philosophers have argued that good and evil do not exist objectively, but are in the mind of the beholder; since a perfect being must be ultimately good, the definition of a perfect being is also in the mind of the beholder. If the imagined God differs from person to person, must we then say that there are as many Gods as there are people? A counter-argument could be that the notions of Him God has placed on us are not perfect, and thus we can differ in opinion about evil, good and God. But in this case, we wouldn't have the idea of a perfect being, but of an almost perfect being, and Descartes entire argument breaks down.

The fourth point seems to be a valid line of reasoning; however as it is based on two very dubious axioms, 2 & 3, it's conclusion cannot be accepted.

The fifth point will be discussed at some length in Anselm's Ontologi cal Argument, but cannot be accepted either. 'Existence' is not an attribute one can use in a defenition.

We thus see that the sixth point, the conclusion, is based on the axioms 2 & 3, which are extremely dubious, and axiom 5, which cannot be accepted either. I conclude that Descartes' argument fails. To rehabilitate it one would have to prove the following points:

  • There exists an imperfect being with the notion of a perfect being in his mind. This being is truly perfect.
  • An imperfect being cannot think up the notion of a perfect being.
  • Perfect and imperfect are objectively definable notions.
  • 'Existence' is a necessary attribute of a perfect being.
  • The second and third point have never yet be proved. I doubt if it is possible at all. The first point is even more difficult, for I think an imperfect being could never find out the difference between a 'perfect' and an 'almost perfect' being, due to his imperfectness. I think that proving the first point is impossible for us non-perfect humans. Thus Descartes' claim is not based on a solid foundation, and ought to be rejected.

    Victor Gijsbers