  The main statement of the argument appears in the Fifth Meditation. This comes on the heels of an earlier causal argument for God’s existence in the Third Meditation, raising questions about the order and relation between these two distinct proofs. Descartes repeats the ontological argument in a few other central texts including the Principles of Philosophy. He also defends it in the First, Second, and Fifth Replies against scathing objections by some of the leading intellectuals of his day.