There are savages without God in any proper sense of the word, but none without ghosts.

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

Any one who has studied the history of science knows that almost every great step therein has been made by the "anticipation of Nature," that is, by the invention of hypotheses, which, though verifiable, often had very little foundation to start with; and, not unfrequently, in spite of a long career of usefulness, turned out to be wholly erroneous in the long run.

The more rapidly truth is spread among mankind the better it will be for them. Only let us be sure that it is the truth.

Proclaim human equality as loudly as you like, Witless will serve his brother.

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.

Extinguished theologians lie about the cradle of every science, as strangled snakes beside that of Hercules