Replies

Thank you so much for your post!

Asserts, not proves.

I disagree. Descartes is a mathematician and a proof is the process or an instance of establishing the validity of a statement especially by derivation from other statements in accordance with principles of reasoning. As the article said:

Returning to the Dedication, Descartes discusses the importance that the Sorbonne faculty themselves place on rational proofs. He also notes that he intends to follow the method of investigation proposed in his Discourse on the Method. According to Descartes, geometricians rarely show the falsehood of accepted truths and demonstrations. By contrast, philosophers typically show the falsehood of contentions without venturing to explore truth. Descartes closes the dedication pleading with the faculty of the Sorbonne that their support and influence is necessary for the Meditations to be seen as a successful refutation of scepticism. The refutation of scepticism being another instance of the common ground he was trying to emphasise between himself and the Catholic theologians. As an example, here is how the article describes Descartes’ proof of God’s existence:

This, then, is his proof for God's existence: 1. We have an idea of that which has infinite perfection.
2. The idea we have of ourselves entails finitude and imperfection.
3. According to the principle of sufficient reason, there must be as much reality (formally or eminently) in the cause of any idea as (objectively) in the idea itself.
4. Therefore, the idea we have of infinite perfection originated from a being with infinite formal perfection.
5. It follows that the idea could not have originated in ourselves or our ideas of ourselves.
6. The origin of the idea could only be the real existence of the infinite being that we call God.

Descartes addresses three possible criticisms of his argument. Each of these possible criticisms suggests that our idea of infinite perfection need not be caused by God himself. A first possible criticism is based on Descartes' assumption that we initially possess an idea of the infinite, and that our idea of the finite consists of the negation of our idea of the infinite. A critic might argue that the opposite is the case: we have an initial idea of the finite and our idea of the infinite is its negation. (Just as we assumed in the example of the perfect cook above.) In this case, we could be the cause of infinite perfection by (a) taking the idea of finite imperfection from ourselves, and (b) negating this idea. However, both the idea of a cook, and the idea of a perfect cook, are finite ideas (involving only finite complexity, for instance). To arrive at the latter by the negation of the limits of the former is a possible operation for a finite mind. (There is a relation here to Anselm's reply to Guanilo's objection concerning the perfect island, in their debate on the ontological argument.) But the idea of God is not a finite idea in this sense, and cannot be arrived at by a finite mind through negation of finite ideas any more than by way of the positive imagining of ideas. (See also the Fifth Objections and Replies (II, 252).)

A second possible criticism is that the idea of infinite perfection is 'materially false and can therefore be from nothing.' More simply, the suggestion is that the idea of infinite perfection is an incoherent concept, and thus needs no explanation beyond itself. However, Descartes argues that the notion of infinite perfection is clear and distinct in the highest degree, and thus requires an explanation. (Descartes and Arnauld continue the discussion of this problem in the Fourth Objections and Replies.)

A third possible criticism is that perhaps we are potentially infinitely perfect, and thus produced the idea of infinite perfection from our hidden potential. Descartes gives three replies to this third criticism. First, if his potential perfection can be actualized only gradually (through a gradual increase in knowledge), this implies that he is finite. And, if he is a finite being, he could not produce the idea of infinite perfection. Second, he argues that even if his knowledge would increase gradually over an infinite amount of time, at no point would he have infinite knowledge. Third, he argues that the objective being of an idea cannot be produced by a merely potential being.

Another criticism raised in the Fifth Objections (II, 205ff) is that it is impossible for a finite mind to comprehend an infinite idea of God, just as (in Descartes' account) it is impossible for a finite mind to generate an infinite idea. In other words, human beings do not have an idea of God in the sense needed by Descartes' argument. Descartes replies by distinguishing between a fully adequate idea of something (which he claims a finite mind cannot have even of the most simple entity) and an 'understanding suited to the scale' of our finite intellect. In other words, of course our positive idea of God's infinity is not an adequate comprehension of God, but it is sufficient for us to know (a) that the idea could not have originated with us; and (b) that it is the idea of an infinitely perfect being. In the 'Preface' to the Meditations, Descartes discusses a criticism of this argument as it appeared in the Discourses (II, 7). There, he implicitly makes a similar distinction between the finitude of the ideas of our minds, and the possibility of finite ideas representing infinite entities (and thus having non-finite objective reality).

Following a similar line of reasoning, Descartes concludes at the end of Meditation 5 that this idea of God must be innate in him, as 'the mark of the craftsman stamped on his work' (II,35). It is from this unfalsifiable mark, then, that God's existence can be known. Recall our discussion of Descartes' views on the representational nature of mental contents, at the end of the section on Meditation 1 above: the idea of God is the only idea the mere inner characterisitics of which allow us to deduce with certainty the origin of the idea.