But I simply can't stand a view limited to this earth, I feel life is so small unless it has windows into other worlds...I like mathematics largely because it is not human.

The Ten Commandments should be headed like an examination paper: No more than six to be attempted.

Science, by itself, cannot supply us with an ethic. It can show us how to achieve a given end, and it may show us that some ends cannot be achieved. But among ends that can be achieved our choice must be decided by other than purely scientific considerations. If a man were to say, "I hate the human race, and I think it would be a good thing if it were exterminated," we could say, "Well, my dear sir, let us begin the process with you." But this is hardly argument, and no amount of science could prove such a man mistaken.

We are all prone to the malady of the introvert who with the manifold spectacle of the world spread out before him, turns away and gazes only upon the emptiness within.

One of the symptoms of approaching nervous breakdown is the belief that one's work is terribly important, and that to take a holiday would bring all kinds of disaster. If I were a medical man, I should prescribe a holiday to any patient who considered his or her work important.

There is in Aristotle an almost complete absence of what may be called benevolence or philanthropy. The sufferings of mankind . . . there is no evidence that they cause him unhappiness except when the sufferers happen to be his friends.

What Galileo and Newton were to the seventeenth century, Darwin was to the nineteenth.