[Do not] put too much confidence in experimental results until they have been confirmed by theory.

Asked in 1919 whether it was true that only three people in the world understood the theory of general relativity, [Eddington] allegedly replied: 'Who's the third?

We used to think that if we knew one, we knew two, because one and one are two. We are finding that we must learn a great deal more about 'and'.

The mathematics is not there till we put it there.

Proof is the idol before whom the pure mathematician tortures himself.

Science is one thing, wisdom is another. Science is an edged tool, with which men play like children, and cut their own fingers.