What is wanted is not the will to believe, but the will to find out, which is the exact opposite.

Self-respect will keep a man from being abject when he is in the power of enemies, and will enable him to feel that he may be in the right when the world is against him.

Philosophy, from the earliest times, has made greater claims, and achieved fewer results, than any other branch of learning.

Science has made unrestricted national sovereignty incompatible with human survival. The only possibilities are now world government or death.

The three main extra-rational activities in modern life are religion, war, and love. all these are extra-rational, but love is not anti-rational, that is to say, a reasonable man may reasonably rejoice in its existence

The more things a man is interested in, the more opportunities of happiness he has and the less he is at the mercy of fate, since if he loses one thing he can fall back upon another.

But as the work proceeded I was continually reminded of the fable about the elephant and the tortoise. Having constructed an elephant upon which the mathematical world could rest, I found the elephant tottering, and proceeded to construct a tortoise to keep the elephant from falling. But the tortoise was not more secure than the elephant, and after some twenty years of very arduous toil, I came to the conclusion that there was nothing more that I could do in the way of making mathematical knowledge indubitable.