The feeling of health can only be gained by sickness.

All mathematical laws which we find in Nature are always suspect to me, in spite of their beauty. They give me no pleasure. They are merely auxiliaries. At close range it is all not true.

The proof that man is the noblest of all creatures is that no other creature has ever denied it.

The writer who cannot sometimes throw away a thought about which another man would have written dissertations, without worry whether or not the reader will find it, will never become a great writer.

It not seldom happens that in the purposeless rovings and wanderings of the imagination we hunt down such game as can be put to use by our purposeful philosophy in its well-ordered household.

Do not say hypothesis, and even less theory: say way of thinking.

It is a question whether, when we break a murderer on the wheel, we do not fall into the error a child makes when it hits the chair it has bumped into.