The optimist thinks that this is the best of all possible worlds; the pessimist knows it.

The foolish man seeks happiness in the distance; The wise grows it under his feet.

In some sort of crude sense, which no vulgarity, no humor, no overstatement can quite extinguish, the physicists have known sin; and this is a knowledge which they cannot lose.

As long as men are free to ask what they must, free to say what they think, free to think what they will, freedom can never be lost and science can never regress.

When you see something that is technically sweet, you go ahead and do it and you argue about what to do about it only after you have had your technical success. That is the way it was with the atomic bomb.

A man whose errors take ten years to correct is quite a man.