The Ontological Argument

The ontological argument is the most audacious proof of God's existence, because it claims to establish that God exists purely by analyzing the concept of God, with no appeal to observation. If it works, God's existence is as certain as a truth of mathematics. If it fails, understanding why it fails teaches deep lessons about existence, necessity, and the limits of definition. For nearly a thousand years philosophers have been unable to agree on which is the case.

Anselm's argument

Saint Anselm of Canterbury formulated the argument in his Proslogion. He defines God as "that than which nothing greater can be conceived." Even the fool of the Psalms who says "there is no God" understands this phrase, so God exists at least in the understanding. But, Anselm reasons, it is greater to exist in r