Intellectual liberty is the air of the soul, the sunshine of the mind, and without it, the world is a prison, the universe is a dungeon.

Grant others the same rights as you claim for yourself.

Intellect, without heart, is infinitely cruel. . . . So that, after all, the real aristocracy must be that of goodness where the intellect is directed by the heart.

Belief is not a matter of choice, but of conviction.

Only a few years ago there was no person too ignorant to successfully answer Charles Darwin; and the more ignorant he was the more cheerfully he undertook the task.

If I had my way I'd make health catching instead of disease.

Years should not be devoted to the acquisition of dead languages or to the study of history which, for the most part, is a detailed account of things that never occurred. It is useless to fill the individual with dates of great battles, with the births and deaths of kings. They should be taught the philosophy of history, the growth of nations, of philosophies, theories, and, above all, of the sciences.