[context added]
Rats had featured largely in the history of Ankh-Morpork. Shortly before the Patrician came to power there was a terrible plague of rats. The city council countered it by offering twenty pence for every rat tail. This did, for a week or two, reduce the number of rats--and then people were suddenly queing up with tails, the city treasury was being drained, and no one seemed to be doing much work. And there still seemed to be a lot of rats around.
Lord Vetinari had listened carefully while the problem was explained, and had solved the thing with one memorable phrase which said a lot about him, about the folly of bounty offers, and about the natural instinct of Ankh-Morporkians in any situation involving money: "Tax the rat farms."
-- Soul Music, by Terry Pratchett
Needs more context.
This is our monthly thread for collecting these little gems and pearls of wisdom, rationality-related quotes you've seen recently, or had stored in your quotesfile for ages, and which might be handy to link to in one of our discussions.