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

It is part of my thesis that all our knowledge grows only through the correcting of our mistakes.

Reason like science, grows by way of mutual criticism; the only possible way of planning its growth is to develop those institutions that safeguard. the freedom of thought

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

If we are not prepared to defend a tolerant society against the onslaught of the intolerant, then the tolerant will be destroyed, and tolerance with them.

It is not his possession of knowledge, of irrefutable truth, that makes the man of science, but his persistent and recklessly critical quest for truth.

There is an almost universal tendency, perhaps an inborn tendency, to suspect the good faith of a man who holds opinions that differ from our own opinions. It obviously endangers the freedom and the objectivity of our discussion if we attack a person instead of attacking an opinion or, more precisely, a theory.