Descartes claims to have an idea of God. (This is not yet to claim God exists, since ideas can materially false.)

"By the name God I understand a substance that is infinite [eternal, immutable], independent, all-knowing, all-powerful, and by which I myself and everything else, if anything else does exist, have been created." (IP3 54a)

This leads to a quick argument:

	1.	I have an idea of God.
	2.	I have an idea of God only if God does in fact exist. (By appeal to the causal principle for objective reality)
Therefore,	3.	God does in fact exist. (1,2 MP)