Quote from Wiki...
For other uses, see Babel fish (disambiguation).
"The Babel fish is small, yellow, leech-like, and probably the oddest thing in the universe. It feeds on brain wave energy, absorbing all unconscious frequencies and then excreting telepathically a matrix formed from the conscious frequencies and nerve signals picked up from the speech centres of the brain, the practical upshot of which is that if you stick one in your ear, you can instantly understand anything said to you in any form of language: the speech you hear decodes the brain wave matrix."
It is a universal translator that neatly crosses the language divide between any species. The book points out that the Babel fish could not possibly have developed naturally, and therefore it both proves and disproves the existence of God:
Now it is such a bizarrely improbable coincidence that anything so mindbogglingly useful could evolve purely by chance that some thinkers have chosen to see it as a 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 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 killed on the next zebra crossing.
Most leading theologians claim that this argument is a load of dingo's kidneys. But this did not stop Oolon Colluphid making a small fortune when he used it as the central theme for his best selling book, Well That About Wraps It Up for God. Meanwhile the poor Babel fish, by effectively removing all barriers to communication between different cultures and races, has caused more and bloodier wars than anything else in the history of creation.
Arthur Dent commented only 'Eurgh!' when first inserting the fish into his ear. It enabled him to understand Vogon Poetry - not necessarily a good thing.