Only one absolute certainty is possible to man, namely that at any given moment the feeling which he has exists.

The question of all questions for humanity, the problem which lies behind all others and is more interesting than any of them, is that of the determination of man's place in nature and his relation to the cosmos.

I would rather be the offspring of two apes than be a man and afraid to face the truth.

There is no absurdity in theology so great that you cannot parallel it by a greater absurdity in Nature.

Follow humbly wherever and to whatever abyss Nature leads, or you shall learn nothing.

Of the few innocent pleasures left to men past middle life, the jamming of common sense down the throats of fools is perhaps the keenest.

Science and literature are not two things, but two sides of one thing.