God-1 = God who exists in reality (the thing whose existence we are trying to prove).
God-2 = a God who exists only as an idea in the mind.
Now we can rephrase the argument:
- Nothing greater than God-1 can be imagined
- God-2 exists.
- God-1 is greater than God-2
- If God-1 does not exist then we can imagine something greater than God-2 (i.e., God-1)
- But we cannot imagine something that is greater than God-1
- Therefore God-1 exists
Point 4 is where it goes wrong. It only
appears to work because Anselm equivocates about the definitions of God-1 and God-2. This is what he is doing. He is trying to make point 4 sound like, If God-1 does not exist then
we can imagine something greater than God-1 (which
would be a contradiction to point 1). But point 4 only makes sense as
we can imagine something greater than
God-2 (i.e., God-1), as in my version. (Otherwise he is actually saying If God-1 does not exist then we can imagine something greater than God-1 (i.e., God-1), which is gibberish.) He hopes you wont notice he changed God-2 to God-1 in point 5, setting up the contradiction to point 1. But he wasnt talking about God-1 in point 4, so there is no contradiction. Consequently, point 6 Therefore God-1 exists, just doesnt follow.