227 Quotes by Karl Popper

I am opposed to looking upon logic as a kind of game. ... One might think that it is a matter of choice or convention which logic one adopts. I disagree with this view.

Nature consists of facts and of regularities, and is in itself neither moral nor immoral. It is we who impose our standards upon nature, and who in this way introduce morals into the natural world, in spite the fact that we are part of this world. We are products of nature, but nature has made us together with our power of altering the world, of foreseeing and of planning for the future, and of making far-reaching decisions for which we are morally responsible. Yet, responsibility, decisions, enter the world of nature only with us

But it is certainly not possible to insist on one hand that the formalism is complete and to insist on the other hand that its application to 'the actual' actually demands a step which cannot be derived from it.

Philosophers should consider the fact that the greatest happiness principle can easily be made an excuse for a benevolent dictatorship. We should replace it by a more modest and more realistic principle - the principle that the fight against avoidable misery should be a recognized aim of public policy, while the increase of happiness should be left, in the main, to private initiative.

I do not overlook the fact that there are irrationalists who love mankind, and that not all forms of irrationalism engender criminality. But I hold that he who teaches that not reason but love should rule opens up the way for those who rule by hate. ( Socrates , I believe, saw something of this when he suggested that mistrust or hatred of argument is related to mistrust or hatred of man).

Evolution is not a fact. Evolution doesn't even qualify as a theory or as a hypothesis. It is a metaphysical research program, and it is not really testable science.

No number of sightings of white swans can prove the theory that all swans are white. The sighting of just one black one may disprove it.

Every solution of a problem raises new unsolved problems.

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.