Psychologism is, I believe, correct only in so far as it insists upon what may be called 'methodological individualism' as opposed to 'methodological collectivism'; it rightly insists that the 'behaviour' and the 'actions' of collectives, such as states or social groups, must be reduced to the behaviour and to the actions of human individuals. But the belief that the choice of such an individualist method implies the choice of a psychological method is mistaken.

A theory which is not refutable by any conceivable event is non-scientific. Irrefutability is not a virtue of a theory (as people often think) but a vice.

I have come to the conclusion that Darwinism is not a testable scientific theory, but a metaphysical research programme.

The quest for precision is analogous to the quest for certainty and both - precision and certainty are impossible to attain.

Why do I think that we, the intellectuals, are able to help? Simply because we, the intellectuals, have done the most terrible harm for thousands of years. Mass murder in the name of an idea, a doctrine, a theory, a religion - that is all "our" doing, "our" invention: the invention of the intellectuals. If only we would stop setting man against man - often with the best intentions - much would be gained. Nobody can say that it is impossible for us to stop doing this.

Piecemeal social engineering resembles physical engineering in regarding the ends as beyond the province of technology.

The history of science is everywhere speculative. It is a marvelous hiatory. It makes you proud to be a human being.