Scientific greatness is less a matter of intelligence than character; if the scientist refuses to compromise or accept incomplete answers and persists in grappling the most basic and difficult questions.

It is certainly true that principles cannot be more securely founded than on experience and consciously clear thinking.

What good is a reputation not put to good use.

[Asked about a book in which 100 Nazi professors charged him with scientific error.] Were I wrong, one professor would have been quite enough.

You can't solve problems with the same thinking that caused them.

When I think of the most able students I have encountered in my teaching - I mean those who have distinguished themselves not only by skill but by independence of thought - then I must confess that all have had a lively interest in epistemology.

It should be possible to explain the laws of physics to a barmaid.