> At any rate, I still don't get the proof. It seems like it becomes circular at some point: "How do we know this ultimate being exists outside our imagination?" "Well, if he doesn't, then we can imagine a yet greater being, which requires that he is absolutely real." "And how do we know that this one exists outside our imagination?" "Well, if he doesn't, ..."

Yeah, that's the thing. The ontological argument *is* logically flawed (to begin with, it assumes that having the quality "existence" is a component of greatness; it's a bit of a stretch to take "that which exists is greater than that which does not exist" strictly for granted) - that's why Anselm is not referred to as "The man who proved the existence of God," and that is why the existence of God is still a subject of some debate.

The reason Anselm is still taught is that his argument, while flawed, does bring up several interesting philosophical and theological questions; for one, the afforementioned "existence as a prerequisitve of greatness" concept.