“Either dragons should exist completely or fail to exist at all, he felt. A dragon only half-existing was worse than the extremes.”

“...either the gods are there whether you believe or not, or exist only as a function of the belief, so either way you might as well ignore the whole business...”

“But all them things exist," said Nanny Ogg. "That's no call to go around believing in them. It only encourages 'em.”

“You can't map a sense of humor. Anyway, what is a fantasy map but a space beyond which There Be Dragons? On the Discworld we know that There Be Dragons Everywhere. They might not all have scales and forked tongues, but they Be Here all right, grinning and jostling and trying to sell you souvenirs. ”

“There’s no point in believing in things that exist.”

“What is a fantasy map but a space beyond which There Be Dragons?”

“...no-one is finally dead until the ripples they cause in the world die away... The span of someone's life, they say, is only the core of their actual existence.”