Explain and evaluate the ontological argument for the existence of God.

St Anselm's ontological argument defines God as being ‘that than which nothing greater can be conceived’. He bases his argument as being a reply to the fool who says there is no God (‘Fools say in their hearts “there is no God”’ Psalm 14:1). He provides a reduction ad absurdum of the atheist belief and proves that to say 'God does not exist' is logically impossible as the ‘fool’ (atheist) would need to have a concept of God in his mind in order to say He doesn’t exist. However, due to the fact that something that exists in the mind and in reality is better that something that exists in the mind alone, and because God must be the best version of what can be, God exists. Therefore, to say that God does not exist in reality, and still have a notion of Him in the mind, is a contradiction in logic.

Kant’s criticism of using pure reason alone in proving God’s existence is that the ontological theory only proves that if there is such a thing as God then He must exist, but the argument does not prove the existence of such a perfect being. For example, one may know that if there is such a thing as a triangle that it must have three sides and three angles, but the argument does not prove the existence in reality of such a triangle. One can only know if the triangle exists through empiricism by seeing the triangle and experiencing its existence, and this is something the ontological argument cannot provide in terms of proving God’s existence. Many agree with Kant’s criticism as it is thought that the ontological argument can only really claim to prove the qualities of God if He existed, but does not have any proof for God’s existence itself which relies more heavily on empiricism and a posteriori knowledge. Because of this, it could be argued that only a portion of the ontological argument is credit worthy, because when Anselm moves from his third premise to the conclusion that God must therefore exist is incorrect and a leap that is too great to make with any logical argument.