This is my most favorite quote. It's an excellent definition of atheism. And it explains why anyone who is not an atheist is insane.

Atheism is the world of reality, it is reason, it is freedom, Atheism is human concern, and intellectual honesty to a degree that the religious mind cannot begin to understand. And yet it is more than this. Atheism is not an old religion, it is not a new and coming religion, in fact it is not, and never has been, a religion at all. The definition of Atheism is magnificent in its simplicity: Atheism is merely the bed-rock of sanity in a world of madness.

-- Emmett F. Fields