Descartes' version of the ontological argument in the light of Kant's criticism

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God has always been a subject of debate and it will probably always be so. One of the reasons leading to this perpetual debate is that people have never agreed on the concept of God. Some religions (e.g. Hinduism) believe that there are several Gods whilst others (e.g. Christianity, Islam, Judaism) believe that there can only be one. However, all these religions do believe that God exists. That might be obvious for the believers but it is not so for the others. The philosophy of religion has sought to give an answer to that question by developing several arguments who tend to show (or not) the necessity's of God's existence. One of these arguments is the Ontological Argument, primarily developed by Saint Anselm in the 11th century. The argument then faded away because of its weaknesses. It was first in the 17th century that another Ontological Argument was thought of, this time by Descartes.

Extraits

[...] Thus, Descartes' Ontological Argument is unsound because its second premise ‘Existence is a perfection' is false and therefore its conclusion is false. To conclude, Descartes' Ontological Argument is very attracting because it rests on simple example and seems to answer to a very difficult question. For people who doubt God's existence however, it is hard at first to say why this argument should not convince them. Kant's critic point out two valid reasons why one should not. First by showing that a definition is not enough to say that something matches the definition in the real world. [...]

[...] You can reject in thought the concept of God and all the predicates that go with it. Then the supreme being that Descartes tries to show as necessary ‘ceases' to exist. To make that point clear, Kant comes back to the triangle example. To reject only the predicate would lead you to imagine a triangle whose angle sum would not equal 180 degrees, which is contradictory. However, if you reject both the concept of ‘triangle' and its predicates then it is not contradictory that a triangle does not have three angles whose sum is equal to 180 degrees. [...]

[...] These are mathematical examples which truth is necessary, they are, as a matter of fact, conceptual truths[4]. That means that the object, that the concept is pointing at, must by definition have this property. A triangle can only be a triangle if it has three angles whose sum is equal to 180 degrees. So, if you can describe something clearly and with a lot of precision, does it make that something existing in the real world? Take for instance the case of dragons. [...]

[...] A synthetic proposition, on the other hand, is one where the predicate does give you some information that the subject did not contain in itself e.g. ‘Humans are afraid of water'. A way to check if a proposition really is synthetic is to negate the predicate i.e. in the case of the human, saying ‘Human are not afraid in water' to see whether or not a contradiction results. If there is no contradiction, then it is really a synthetic proposition. The free dictionary, entry: synthetic http://www.thefreedictionary.com/synthetic accessed February 1st 2006. [...]

[...] Let us now see how Descartes formulates his (ontological) argument for the existence of God. It his mainly in his Fifth Meditation that Descartes reflects upon the existence of God[3]. In that meditation, he looks at the content of his mind and sees that he can conceive of an infinity of objects to which he can attribute an infinity of properties. Every object has an unchangeable set of qualities. The triangle, for example, always has three corners whose sum equals to 180 degrees. [...]