Man…who lives in three places – in the past, in the present, and in the future – can be unhappy if one of these three is worthless. Religion has even added a fourth – eternity.

Imagine the world so greatly magnified that particles of light look like twenty-four-pound cannon balls.

A good metaphor is something even the police should keep an eye on.

A man has virtues enough if he deserves pardon for his faults on account of them.

One is rarely an impulsive innovator after the age of sixty, but one can still be a very fine orderly and inventive thinker. One rarely procreates children at that age, but one is all the more skilled at educating those who have already been procreated, and education is procreation of another kind.

He was always smoothing and polishing himself, and in the end he became blunt before he was sharp.

I have often noticed that when people come to understand a mathematical proposition in some other way than that of the ordinary demonstration, they promptly say, "Oh, I see. That's how it must be." This is a sign that they explain it to themselves from within their own system.