While thinking about the independence of these ideas of external objects, Descartes realizes that he is just as certain about God as he is about these mathematical ideas. He asserts that this is natural as the ideas of God are the only ideas that imply God's existence. He uses the example of a mountain and a valley. While one cannot picture a mountain without a valley, it's possible that these do not exist. However, the fact that one cannot conceive of God without existence inherently rules out the possibility of God's non-existence. Simply put, the argument is framed as follows: