I mean by intellectual integrity the habit of deciding vexed questions in accordance with the evidence, or of leaving them undecided where the evidence is inconclusive. This virtue, though it is underestimated by almost all adherents of any system of dogma, is to my mind of the very greatest social importance and far more likely to benefit the world than Christianity or any other system of organized beliefs.

The scientific attitude of mind involves a sweeping away of all other desires in the interest of the desire to know.

Collective wisdom, alas, is no adequate substitute for the intelligence of individuals. Individuals who opposed received opinions have been the source of all progress, both moral and intellectual. They have been unpopular, as was natural.

I do not think that the real reason why people accept religion has anything to do with argumentation. They accept religion on emotional grounds.

Man is a rational animal – so at least I have been told. Throughout a long life, I have looked diligently for evidence in favour of this statement, but so far I have not had the good fortune to come across it, though I have searched in many countries spread over three continents.

Berkeley retains the merit of having shown that the existence of matter is capable of being denied without absurdity.

Change is one thing, progress is another.