A man's worst difficulties begin when he is able to do as he likes.

. . . I fail to find a trace [in Protestantism] of any desire to set reason free. The most that can be discovered is a proposal to change masters. From being a slave of the papacy, the intellect was to become the serf of the Bible.

The great end of life is not knowledge but action.

The thief and the murderer follow nature just as much as the philanthropist.

There is no sadder sight in the world than to see a beautiful theory killed by a brutal fact.

Nothing great in science has ever been done by men, whatever their powers, in whom the divine afflatus of the truth-seeker was wanting.

The man of science has learned to believe in justification, not by faith, but by verification.