The argument developed by Descartes differs from Anselm’s in a number of respects. He avoids the term ‘great’ (and notes the fact in the course of his argument). Instead he uses the concept ‘perfect’, so that God is described as the ‘supremely perfect Being’. He also uses variations on the phrase ‘clearly and distinctly’ in connection with his apprehension of the idea of God. [i]
If just because I can draw the idea of something from my thought, it follows that all which I know clearly and distinctly as pertaining to this object does really belong to it, may I not derive from this an argument demonstrating the existence of God? It is certain that I no less find the idea of God, that is to say, the idea of a supremely perfect Being, in me, than that of any figure or number whatever it is; and I do not know any less clearly and distinctly that an actual and eternal existence pertains to this nature than I know that all that which I am able to demonstrate of some figure or number truly pertains to the nature of this figure or number, and therefore, although all that I concluded in the preceding Meditations were found to be false, the existence of God would pass with me as at least as certain as I have ever held the truths of mathematics to be.
To paraphrase: ‘If it follows that an idea in thought can be expressed, and all I know clearly and distinctly about it, is the case, then may I not use this as the basis of an argument to prove the reality of God?’ He finds the idea of a ‘supremely perfect Being’ as real within himself as ideas of geometric figures, and numbers. He does not know any less clearly and distinctly that actual and eternal existence is a property of the supreme perfect Being, than he knows all which he can demonstrate in relation to geometrical figures or a number truly comprises the properties of these. And were everything else in the preceding Meditations to be found false, the reality of God would be as real for Descartes as he ever held the truths of mathematics to be.
However clear and distinct is Descartes idea of a ‘supremely perfect Being’, and that this idea can be expressed, it does not follow that it can be used as the basis of an argument to prove the reality of God. To follow his analogy, his knowledge of the properties of geometrical figures and numbers, may be extensive and even comprehensive, but it does not follow that his knowledge of these properties is complete. The properties of which he knows are just that. It is obvious that it is easier to circumscribe the properties and characteristics of geometrical figures and numbers than to have a clear and distinct idea of the properties and nature of a ‘supremely perfect Being’. What Descartes can have in his mind is a ‘notion’ of the properties and nature of such a perfect Being. He might think that the reality of God, the existence of God is at least as real as the truths of mathematics; this is a notion only, rather than something which can be established.
This indeed is not at first manifest, since it would seem to present some appearance of being a sophism. For being accustomed in all other things to make a distinction between existence and essence, I easily persuade myself that the existence can be separated from the essence of God, and that we can thus conceive God as not actually existing. But, nevertheless, when I think of it with more attention, I clearly see that existence can no more be separated from the essence of God than can its having its three angles equal to two right angles be separated from the essence of a rectilinear triangle, or the idea of a mountain from the idea of a valley; and so there is not any less repugnance to our conceiving a God (that is, a Being supremely perfect) to whom existence is lacking (that is to say, to whom a certain perfection is lacking), than to conceive of a mountain which has no valley.
Descartes defends himself against the possible charge that his argument is sophistry. He can ordinarily distinguish between the existence and the essence of something. And so he can easily persuade himself that the property ‘existence’ can be separated from the ‘essence’ of God. And thus that we can conceive of God as not possessing the property of something which exists. This however he says is the result of inattentive thinking, and more attention to the question allows him to clearly see that the existence of God cannot be separated from the essence of God any more than the properties of a right-angled triangle can be separated from the essence of it. Or any more than that the idea of a mountain can be separated from the idea of a valley. So the repugnance of the idea of conceiving a supremely perfect Being without the property of existence is no less than to conceive of a mountain without a valley.
The problem here is the conception of existence as a form or mode of perfection. In antiquity this equation would not have been made – rather the nature and properties of divinity would have been drawn in contrast with those of existence. There are many ways to express this difference – the secular world has existence, the world of coming-to-be and passing-away has existence, man has existence, the world of things and of representation has existence. The Divine and the eternal did not have existence in the same way in the ancient world. The world of reality was understood to be separate in essence from the secular world; this separate reality was the realm of the divine, and so existence would not be a property of the divine, even if the divine was (as it generally was) considered to be completely real. This is not to say that the divine could not manifest or act in the world of existence; but that existence is a species of imperfection, with which the divine could be (and was) contrasted. Descartes cannot mean that God is real in the sense of having a presence in the material world. And it is curious that later he treated God as if he was walled up in his own sphere. This was necessary to promote the idea that one could do mathematics without reference to God, and without concern that God would interfere with the purely mathematical workings of the world.
But although I cannot really conceive of a God without existence any more than a mountain without a valley, still from the fact that I conceive of a mountain with a valley, it does not follow that there is such a mountain in the world; similarly although I conceive of God as possessing existence, it would seem that it does not follow that there is a God which exists; for my thought does not impose any necessity upon things, and just as I may imagine a winged horse, although no horse with wings exists, so I could perhaps attribute existence to God, although no God existed.
Here, Descartes concedes that though he can conceive of the supreme perfect Being as possessing existence, it does not necessarily follow that there is a God which exists, since his thought ‘does not impose any necessity upon things’. What he means by this is that the reality or otherwise or god is not dependent on his understanding of the nature of God.’ So Descartes might be attributing the property of existence to God, even if no God existed.
[End of extract]