I used to go away for weeks in a state of confusion.

Wisdom is not a product of schooling but of the lifelong attempt to acquire it.

If you want to live a happy life, tie it to a goal, not to people or objects.

Do not grow old, no matter how long you live.

Without the sense of fellowship with men of like mind... life would have seemed to me empty.

I live in that solitude which is painful in youth, but delicious in the years of maturity.

The mere formulation of a problem is far more essential than its solution, which may be merely a matter of mathematical or experimental skills. To raise new questions, new possibilities, to regard old problems from a new angle requires creative imagination and marks real advances in science.