A Witty Piece of Logic

Here's a witty piece of logic from "The Hitch Hiker's Guide to the Galaxy" (Douglas Adams):

"The Babel fish," said The Hitch Hiker's Guide to the Galaxy quietly, "is small, yellow and leech-like, and probably the oddest thing in the Universe... if you stick a Babel fish in your ear you can instantly understand anything said to you in any form of language...

"Now it is such a bizarrely improbable coincidence that anything so mindboggingly useful could have evolved purely by chance that some thinkers have chosen to see it as the final and clinching proof of the non-existence of God.

"The argument goes something like this: `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. QED.'

"`Oh dear,' says God, `I hadn't thought of that,' and promptly vanished in a puff of logic.

"`Oh, that was easy,' says Man, and for an encore goes on to prove that black is white and gets himself killed on the next zebra crossing.