Fundamental progress has to do with the reinterpretation of basic ideas.

A science which hesitates to forget its founders is lost.

The difference between ancients and moderns is that the ancients asked what have we experienced, and moderns asked what can we experience.

We must produce a great age, or see the collapse of the upward striving of our race.

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.

Everything of importance has been said before by somebody who did not discover it.

There is no nature at an instant.