We must plan for freedom, and not only for security, if for no other reason than only freedom can make security more secure.

We all remember how many religious wars were fought for a religion of love and gentleness; how many bodies were burned alive with the genuinely kind intention of saving souls from the eternal fire of hell.

Contrary to the outstanding work of art, outstanding theory is susceptible to improvements.

The difference between the amoeba and Einstein is that, although both make use of the method of trial and error elimination, the amoeba dislikes erring while Einstein is intrigued by it.

There will be well-testable theories, hardly testable theories, and non-testable theories. Those which are non-testable are of no interest to empirical scientists. They may be described as metaphysical.

The history of science, like the history of all human ideas, is a history of irresponsible dreams, of obstinacy, and of error.

Science must begin with myths, and with the criticism of myths.