Do not imagine that you have to know everything before you can do anything. My own best work was done when I was most ignorant.

For me, science is just a bunch of tools - it's like playing the violin. I just enjoy calculating, and it's an instrument I know how to play. It's almost an athletic performance, in a way. I was just watching the Olympics, and that's how I feel when proving a theorem.

It's better to get mugged than to live a life of fear.

Most of the papers which are submitted to the Physical Review are rejected, not because it is impossible to understand them, but because it is possible. Those which are impossible to understand are usually published.

If you want to have a program for moving out into the universe, you have to think in centuries not in decades.

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.

It has become part of the accepted wisdom to say that the twentieth century was the century of physics and the twenty-first century will be the century of biology.