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

Understanding a theory has, indeed, much in common with understanding a human personality. We may know or understand a man's system of dispositions pretty well; that is to say, we may be able to predict how he would act in a number of different situations. But since there are infinitely many possible situations, of infinite variety, a full understanding of a man's dispositions does not seem to be possible.

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

A theory that explains everything, explains nothing

A rationalist, as I use the word, is a man who attempts to reach decisions by argument and perhaps, in certain cases, by compromise, rather than by violence. He is a man who would rather be unsuccessful in convincing another man by argument than successful in crushing him by force, by intimidation and threats, or even by persuasive propaganda.

It is complete nihilism to propose laying down arms in a world where atom bombs are around. It is very simple: there is no way of achieving peace other than with weapons.

Every solution of a problem raises new unsolved problems.