The best of a book is not the thought which it contains, but the thought which it suggests; just as the charm of music dwells not in the tones but in the echoes of our hearts.

In my opinion, economists and sociologists are the people to whom we ought to turn more than we do for instruction in the grounds and foundations of all rational decisions.

Who does not feel that Nansen's account of his search for the Pole rather loses than gains in ideal satisfaction by the pretense of a few trifling acquisitions for science?

We should be eternally vigilant against attempts to check the expression of opinions that we loathe.

The greatest act of faith is when a man understands he is not God.

Every idea is an incitement. It offers itself for belief, and if believed it is acted on unless some other belief outweighs it or some failure of energy stifles the movement at its birth. The only difference between the expression of an opinion and an incitement is the speaker's enthusiasm for the result.

To be master of any branch of knowledge, you must master those which lie next to it, and thus to know anything you must know all.