The incomparable Douglas Adams:
"I refuse to prove that I exist," says God, "for proof denies faith, and without faith I am nothing." "But," says Man, "the Babel fish is a dead giveaway isn't it? It could not have evolved by chance. It proves you exist, and so therefore, by your own arguments, you don't. Q.E.D." "Oh dear," says God, "I hadn't thought of that," and promptly vanishes in a puff of logic. "Well, that was easy," says man, who goes on to prove that black = white, and is promptly run over at the next zebra crossing."