We cannot remember too often that when we observe nature, and especially the ordering of nature, it is always ourselves alone we are observing.

All mathematical laws which we find in Nature are always suspect to me, in spite of their beauty. They give me no pleasure. They are merely auxiliaries. At close range it is all not true.

The most successful tempters and thus the most dangerous are the deluded deluders.

Much reading has brought upon us a learned barbarism.

It is almost impossible to carry the torch of truth through a crowd without singeing somebody's beard.

A clever child brought up with a foolish one can itself become foolish. Man is so perfectible and corruptible he can become a fool through good sense.

The great trick of regarding small departures from the truth as the truth itself - on which is founded the entire integral calculus - is also the basis of our witty speculations, where the whole thing would often collapse if we considered the departures with philosophical rigour.