True courage is not the brutal force of vulgar heroes, but the firm resolve of virtue and reason.

The motive of success is not enough.

[In many circumstances,] the most important thing about a proposition is not that it be true, but that it be interesting.

Error itself may be happy chance.

People make the mistake of talking about 'natural laws.' There are no natural laws. There are only temporary habits of nature.

Systems, scientific or philosophic, come and go. Each method of limited understanding is at length exhausted. In its prime each system is a triumphant success: in its decay it is an obstructive nuisance.

Philosophy begins in wonder. And, at the end, when philosophic thought has done its best, the wonder remains.