[Science doesn't deal with facts; indeed] fact is an emotion-loaded word for which there is little place in scientific debate.

All science is full of statements where you put your best face on your ignorance, where you say: ... we know awfully little about this, but more or less irrespective of the stuff we don't know about, we can make certain useful deductions.

If you walk along the street you will encounter a number of scientific problems. Of these, about 80 per cent are insoluble, while 19½ per cent are trivial. There is then perhaps half a per cent where skill, persistence, courage, creativity and originality can make a difference. It is always the task of the academic to swim in that half a per cent, asking the questions through which some progress can be made.

The test of science is not whether you are reasonable—there would not be much of physics if that was the case—the test is whether it works. And the great point about Newton’s theory of gravitation was that it worked, that you could actually say something about the motion of the moon without knowing very much about the constitution of the Earth.

A theory is scientific only if it can be disproved. But the moment you try to cover absolutely everything the chances are that you cover nothing.

... an opportunity to allow the bees in one's bonnet to buzz even more noisily than usual.

An observer situated in a nebula and moving with the nebula will observe the same properties of the universe as any other similarly situated observer at any time.