No man is rich who is unsatisfied, but who wants nothing possess his heart's desire.

When a scientist doesn't know the answer to a problem, he is ignorant. When he has a hunch as to what the result is, he is uncertain. And when he is pretty darn sure of what the result is going to be, he is in some doubt.

I find that teaching and the students keep life going, and I would never accept any position in which somebody has invented a happy situation for me where I don't have to teach. Never.

If you have any talent, or any occupation that delights you, do it, and do it to the hilt. Don't ask why, or what difficulties you may get into.

To test whether you have learned an idea or a definition, rephrase what you just learned without using the new word.

You see, one thing is, I can live with doubt and uncertainty and not knowing. I have approximate answers and possible beliefs and different degrees of certainty about different things... It doesn't frighten me.

We have this terrible struggle to try to explain things to people who have no reason to want to know.