1. By definition, God is a being than which none greater can be imagined. 2. A being that necessarily exists in reality is greater than a being that does not necessarily exist. 3. Thus, by definition, if God exists as an idea in the mind but does not necessarily exist in reality, then we can imagine something that is greater than God. 4. But we cannot imagine something that is greater than God. 5. Thus, if God exists in the mind as an idea, then God necessarily exists in reality. 6. God exists in the mind as an idea. 7. Therefore, God necessarily exists in reality