There are no whole truths: all truths are half-truths. It is trying to treat them as whole truths that plays to the devil.

Without adventure civilization is in full decay. ... The great fact [is] that in their day the great achievements of the past were the adventures of the past.

Whenever a text-book is written of real educational worth, you may be quite certain that some reviewer will say that it will be difficult to teach from it. Of course it will be difficult to teach from it. It it were easy, the book ought to be burned.

Learning is often spoken of as if we are watching the open pages of all the books which we have ever read, and then, when occasion arises, we select the right page to read aloud to the universe.

The preternatural solemnity of a good many of the professionally religious is to me a point against them.

The importance of an individual thinker owes something to chance. For it depends upon the fate of his ideas in the minds of his successors.

Nature gets credit which should in truth be reserved for ourselves: the rose for its scent, the nightingale for its song; and the sun for its radiance. The poets are entirely mistaken. They should address their lyrics to themselves and should turn them into odes of self congratulation on the excellence of the human mind.