We must be careful not to discourage our twelve-year-olds by making them waste the best years of their lives preparing for examinations.

If women are doing a Ph.D., they have a conflict between raising a family or finishing the degree, which is just at the worst time - between the ages of 25 to 30 or whatever it is. It ruins the five years of their lives.

Sometimes we talked about the nature of the human soul and about the Cosmic Unity of souls that I had believed in so firmly when I was 15 years old. My mother did not like the phrase Cosmic Unity. It was too pretentious. She preferred to call it a world soul.

A model is such a fascinating toy that you fall in love with your creation.

[John Wheeler] rejuvenated general relativity; he made it an experimental subject and took it away from the mathematicians

The thing that makes me most optimistic is China and India - both of them doing well. It's amazing how much progress there's been in China, and also India. Those are the places that really matter - they're half of the world's population. They're the places where things are enormously better now than they were 50 years ago. And I don't see anything that's going to stop that.

To me, mathematics is like playing the violin. Some people can do it - others can't. If you don't have it, then there's no point in pretending.