You: Let me see if this fits in with your thinking: if God is perfect then he has perfect imagination. If he has perfect imagination, then he can imagine a god greater than himself. Because that god would necessarily exist (or not be perfect) then there is a god greater than God.

Aaron: There is no way for a god to be greater than God.

You: If God cannot imagine a god greater than him, then there is something that he cannot do and, therefore, he is not perfect.

Aaron: You do not understand the nature of God's infinite power.

You: And I will not discuss it before you prove to me that he exists.

*Exodus 34:14 For thou shalt worship no other god: for the LORD, whose name is Jealous, is a jealous God.