Anselm’s Argument 1

1. God is that than which nothing greater can be conceived. (Definition)
2. God exists in our thoughts. (Premise)
3. Something that exists in our thoughts either (a) exists only in our thoughts, or (b) exists both in our thoughts and in reality. (Implicit premise)
4. That which exists in thought and reality is greater than that which exists only in thought. (Premise)
5. We can conceive of a being just like God who exists in both thought and reality. (Premise)
6. If God exists only in our thoughts, that being is greater than God. (By 4)
7. If God exists only in our thoughts, we can conceive of a being greater than God. (By 5 and 6)
8. So, it’s false that God exists only in our thoughts. (By 1 and 7)
9. God either exists only in our thoughts or both in our thoughts and in reality. (By 2 and 3)
10. So, God exists in both our thoughts and in reality. (By 8 and 9)

Anselm’s Argument 2

1. God is that than which nothing greater can be conceived. (Definition)
2. Something that cannot be conceived not to exist is greater than something that can be conceived not to exist. (Premise)
3. We can conceive of a being like God who cannot be conceived not to exist.
4. If this being is not God, then we can conceive of something greater than God. (By 2 and 3)
5. We cannot conceive of something greater than God. (By 1)
6. So, this being is God. (By 4 and 5)
7. So, God cannot be conceived not to exist. (By 3 and 6)