The Wisdom of Terry Pratchett.

Build a man a fire, and he'll be warm for a day. Set a man on fire, and he'll be warm for the rest of his life.

Five exclamation marks, the sure sign of an insane mind.

People who are rather more than six feet tall and nearly as broad across the shoulders often have uneventful journeys. People jump out at them from behind rocks then say things like, "Oh. Sorry. I thought you were someone else."

The universe, they said, depended for its operation on the balance of four forces which they identified as charm, persuasion, uncertainty and bloody-mindedness.

You can't trample infidels when you're a tortoise. I mean, all you could do is give them a meaningful look.

In ancient times cats were worshipped as gods; they have not forgotten this.

In the beginning there was nothing, which exploded.

Genius is always allowed some leeway, once the hammer has been pried from its hands and the blood has been cleaned up.

It's not worth doing something, unless you were doing something that someone somewere, would much rather you weren't doing.

Everything starts somewhere, although many physicists disagree.

Your affected air of cowardice does not fool me.

Ridcully assumed that anything people had time to write down couldn't be that important.

Susan stopped. Of course someone would be that stupid. Some humans would do anything to see if it was possible to do it. If you put a large switch in some cave somewhere, with a sign on it saying 'End-of-the-World Switch. PLEASE DO NOT TOUCH', the paint wouldn't even have time to dry.

'Sometimes I really think people ought to have to pass a proper exam before they're allowed to be parents. Not just the practical, I mean.'

But still, one of the most basic rules for survival on any planet is never to upset someone wearing black leather.[*]
[*]This is why protesters against the wearing of animal skins by humans unaccountably fail to throw their paint over Hell's Angels.

His movements could be called cat-like, except that he did not stop to spray urine up against things.

The truth is that even big collections of ordinary books distort space, as can readily be proved by anyone who has been around a really old-fashioned secondhand bookshop, one of those that look as though they were designed by M. Escher on a bad day and has more staircases than storeys and those rows of shelves which end in little doors that are surely too small for a full-sized human to enter. The relevant equation is: Knowledge = power = energy = matter = mass; a good bookshop is just a genteel Black Hole that knows how to read.

The three rules of the Librarians of Time and Space are: 1) Silence; 2) Books must be returned no later than the date last shown; and 3) Do not interfere with the nature of causality.

The only things known to go faster than ordinary light is monarchy, according to the philosopher Ly Tin Weedle. He reasoned like this: you can't have more than one king, and tradition demands that there is no gap between kings, so when a king dies the succession must therefore pass to the heir *instantaneously*. Presumably, he said, there must be some elementary particles -- kingons, or possibly queons -- that do this job, but of course succession sometimes fails if, in mid-flight, they strike an anti-particle, or republicon. His ambitious plans to use his discovery to send messages, involving the careful torturing of a small king in order to modulate the signal, were never fully expanded because, at that point, the bar closed.

"Sodomy non sapiens," said Albert under his breath.
"What does that mean?"
"Means I'm buggered if I know."

Sheep are stupid, and have to be driven. But goats are intelligent, and need to be led.

"Did I hear things, or can that little dog speak?" said Dibbler.
"He says he can't," said Victor.
Dibbler hesitated. "Well," he said, "I suppose he should know."

Never build a dungeon you wouldn't be happy to spend the night in yourself. The world would be a happier place if more people remembered that.

Nanny Ogg had a pragmatic attitude to the truth; she told it if it was convenient and she couldn't be bothered to make up something more interesting.