There are so many good quotes in Sir Terry's works--and beyond that, a truly astonishing amount of great ones. But there are several that I'll always remember, because they were actually brilliant--quick summations of reality not only pithily and humorously written, but rarely mentioned anywhere else. The overlooked truths, as it were.
“You mean…I could choose certain death?”
“A choice, nevertheless,” said Vetinari. “Or, perhaps, an alternative. You see, I believe in freedom, Mr. Lipwig. Not many people do, although they will, of course, protest otherwise. And no practical definition of freedom would be completely without the freedom to take the consequences. Indeed, it is the freedom upon which all the others are based."
- Going Postal, page somewhere-in-chapter-one (I use epubs)
“Pulling together is the aim of despotism and tyranny. Free men pull in all kinds of directions.”
- The Truth, page somewhere-towards-the-end
“Down there ... are people who will follow any dragon, worship any god, ignore any iniquity. All out of a kind of humdrum, everyday badness. Not the really high, creative loathesomeness of the great sinners, but a sort of mass-produced darkness of the soul. Sin, you might say, without a trace of originality. They accept evil not because they say yes, but because they don't say no."
- Guards! Guards! (pretty close to the end)
I know there's more, but what's the point of trying to do justice to TP's work without quoting an entire book? Looking back, though, I realize these are all quite serious quotes--odd, I guess, for my favorite lines from a humorist author to be the most serious ones there, but maybe not. I think it was his gems of seriousness within the humor that truly took the books to a level higher than almost anything I've ever read.
Edit: (I just have to mention this one, though.)
Samuel Vimes dreamed about Clues.
He had a jaundiced view of Clues. He instinctively distrusted them. They got in the way.
And he distrusted the kind of person who’d take one look at another man and say in a lordly voice to his companion, “Ah, my dear sir, I can tell you nothing except that he is a left-handed stonemason who has spent some years in the merchant navy and has recently fallen on hard times,” and then unroll a lot of supercilious commentary about calluses and stance and the state of a man’s boots, when exactly the same comments could apply to a man who was wearing his old clothes because he’d been doing a spot of home bricklaying for a new barbecue pit, and had been tattooed once when he was drunk and seventeen and in fact got seasick on a wet pavement. What arrogance! What an insult to the rich and chaotic variety of the human experience!
- Feet of Clay