Explain Descartes’ Ontological Argument.
The Ontological Argument is one of the only few a prior arguments for the existence of God. The most famous ontological argument is proposed by St Anselm of Canterbury; however Descartes’ version is also very well known. Essentially the two versions of ontological argument are compatible with each other.
Descartes starts his ontological argument with the premise that God is a supremely perfect being and because existence is a perfection, God must exist. This is not very different from the version proposed by St Anselm in his Proslogion 2. It is worth noting that Descartes’ ontological argument is based on Descartes’ theory of innate idea and his doctrine of clear and distinct ideas. The former supports the notion that God is a supremely perfect being while the latter supports the validity of the argument. To Descartes, God’s existence is a de dicto necessity, that is, existence is part of the definition of God. God’s existence is like the three sides of a triangle; and so Descartes claims that it is clear and distinct that the idea of existence cannot be separated from the idea of God.