Well logic and rationality actually makes me an atheist.
1. we do not understand everything. But so far every time we managed to understand something, it had a rational, logical and natural explanation. I don't see why that should change, and thus it's a safe bet to say the supernatural is not part of this universe.
2. as I said, if I must admit that God might exists because I can't prove he does not, then I must admit the Flying Spaghetti monster exists because I can't prove he does not, and I must admit that ghosts exists because I can't prove they do not, and so on and so forth... the rational and logical choice would be to say things you can not prove do not exist, do not exist.
Why is that rational, science cannot prove that something does not exist, in fact it's a fundemental law of science that it cannot, it can only prove that something has evidence ergo, no evidence no proof that it exists or doesn't.