Books bend space and time. One reason the owners of those aforesaid little rambling, poky secondhand bookshops always seem slightly unearthly is that many of them really are, having strayed into this world after taking a wrong turning in their own bookshops in worlds where it is considered commendable business practice to wear carpet slippers all the time and open your shop only when you feel like it.

The significant owl hoots in the night.

It was nice to hear the voices of little children at play, provided you took care to be far enough away not to hear what they were actually saying.

The jurisdiction of a good man extends to the end of the world.

Wizards don't believe in gods in the same way that most people don't find it necessary to believe in, say, tables. They know they're there, they know they're there for a purpose, they'd probably agree that they have a place in a well-organised universe, but they wouldn't see the point of believing, of going around saying "O great table, without whom we are as naught." Anyway, either the gods are there whether you believe in them or not, or exist only as a function of the belief, so either way you might as well ignore the whole business and, as it were, eat off your knees.

The universe clearly operates for the benefit of humanity. This can be readily seen from the convenient way the sun comes up in the morning, when people are ready to start the day.

A number of religions in Ankh-Morpork still practiced human sacrifice, except that they didn't really need to practice any more because they had got so good at it.