The survival value of intelligence is that it allows us to extinct a bad idea, before the idea extincts us.

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

I see now more clearly than ever before that even our greatest troubles spring from something that is [as] admirable and sound as it is dangerous – from our impatience to better the lot of our fellows.

A system such as classical mechanics may be 'scientific' to any degree you like; but those who uphold it dogmatically - believing, perhaps, that it is their business to defend such a successful system against criticism as long as it is not conclusively disproved - are adopting the very reverse of that critical attitude which in my view is the proper one for the scientist.

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

My thesis is that what we call 'science' is differentiated from the older myths not by being something distinct from a myth, but by being accompanied by a second-order tradition-that of critically discussing the myth. ... In a certain sense, science is myth-making just as religion is.

Every genuine test of a theory is an attempt to falsify it, or to refute it.