What is a babel fish?

[technobabel]

The Babel fish is a fictional species of fish in The Hitchhiker's Guide to the Galaxy by Douglas Adams.

http://disney.wretch.cc/mvdata/data/Hit ... Galaxy.htm

A Babel fish is a highly improbable biological universal translator. It appears as a "small, yellow and leechlike" fish. When a Babel fish is inserted into the ear canal it allows the wearer to "instantly understand anything said... in any form of language." This was both a useful plot device for Adams, who wrote on the subject that he always found the ability of all aliens to speak English very strange; and also the starting point for a joke about the existence of God.

According to the Hitchhiker's Guide, the Babel fish was put forth as a fideist example for the non-existence of God:

"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 that 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.
"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.

from: http://en.wikipedia.org/wiki/Babel_fish