Quotes from Karl R. Popper

I hold that he who teaches that not reason but love should rule opens up the way for those who rule by hate.

Science must begin with myths, and with the criticism of myths.

And it implies that if we respect truth, we must search for it by persistently searching for our errors: by indefatigable rational criticism, and self-criticism.

Instead of the greatest happiness for the greatest number, one should demand, more modestly, the least amount of avoidable suffering for all; and further, that unavoidable suffering—such as hunger in times of an unavoidable shortage of food—should be distributed as equally as possible.

The more we learn about the world, and the deeper our learning, the more conscious, specific, and articulate will be our knowledge of what we do not know, our knowledge of our ignorance.

The way of science is paved with discarded theories which were once declared self-evident;

Theology, I still think, is due to lack of faith.

Democracy and freedom do not guarantee the millennium. No, we do not choose political freedom because it promises us this or that. We choose it because it makes possible the only dignified form of human coexistence, the only form in which we can be fully responsible for ourselves. Whether we realize its possibilities depends on all kinds of things — and above all on ourselves.

The belief in a political Utopia is especially dangerous. This is possibly connected with the fact that the search for a better world, like the investigation of our environment, is (if I am correct) one of the oldest and most important of all the instincts.

The quest for precision is analogous to the quest for certainty, and both should be abandoned.

What I criticize under the name Utopian engineering recommends the reconstruction of society as a whole, i.e. very sweeping changes whose practical consequences are hard to calculate, owing to our limited experiences. It claims to plan rationally for the whole of society, although we do not possess anything like the factual knowledge which would be necessary to make good such an ambitious claim.

Conjecture or hypothesis must come before observation or perception: we have inborn expectations; we have latent inborn knowledge, in the form of latent expectations, to be activated by a stimuli to which we react as a rule while engaged in active exploration. All learning is a modification (it may be a refutation)of some prior knowledge and thus, in the last analysis, of some inborn knowledge.

I wish to make it clear that 'history' in the sense in which most people speak of it simply does not exist; and this is at least one reason why I say that it has no meaning.

It is not the consciousness of man that determines his existence—rather, it is his social existence that determines his consciousness.

the alleged clash between freedom and security, that is, a security guaranteed by the state, turns out to be a chimera. For there is no freedom if it is not secured by the state; and conversely, only a state which is controlled by free citizens can offer them any reasonable security at all.)

If we extend unlimited tolerance even to those who are intolerant, if we are not prepared to defend a tolerant society against the onslaught of the intolerant, then the tolerant will be destroyed, and tolerance with them.

When the poet or the performer composes or recites he is deeply moved, and indeed possessed (not only by the god but also) by the message; for example, by the scenes he describes. And the work, rather than merely his emotional state, induces similar emotions in his audience.

From this point of view the question of the scientific status of Darwinian theory—in the widest sense, the theory of trial and error-elimination—becomes an interesting one. I have come to the conclusion that Darwinism is not a testable scientific theory, but a metaphysical research programme—a possible framework for testable scientific theories.

The true Enlightenment thinker, the true rationalist, never wants to talk anyone into anything. No, he does not even want to convince; all the time he is aware that he may be wrong. Above all, he values the intellectual independence of others too highly to want to convince them in important matters. He would much rather invite contradiction, preferably in the form of rational and disciplined criticism. He seeks not to convince but to arouse — to challenge others to form free opinions.

The question of the acceptance of theories should, I propose, be demoted to the status of a minor problem. For science may be regarded as a growing system of problems, rather than as a system of beliefs. And for a system of problems, the tentative acceptance of a theory or a conjecture means hardly more than that it is considered worthy of further criticism.

in contrast to the Hegelians of the right-wing, Marx made an honest attempt to apply rational methods to the most urgent problems of social life. The value of this attempt is unimpaired by the fact that it was, as I shall try to show, largely unsuccessful. Science progresses through trial and error. Marx tried, and although he erred in his main doctrines, he did not try in vain. He opened and sharpened our eyes in many ways.

There is no law of progress, and everything will depend on ourselves. But the actual situation is briefly and fairly summed up by Parkes36 in one sentence: 'Low wages, long hours, and child labour have been characteristic of capitalism not, as Marx predicted, in its old age, but in its infancy.

Plato summarizes his reply to equalitarianism in the formula: 'Equal treatment of unequals must beget inequity'20; and this was developed by Aristotle into the formula 'Equality for equals, inequality for unequals'. This formula indicates what may be termed the standard objection to equalitarianism; the objection that equality would be excellent if only men were equal, but that it is manifestly impossible since they are not equal, and since they cannot be made equal.

For Aristotle's essentialist definitions are the principles from which all our knowledge is derived; they thus contain all our knowledge; and they serve to substitute a long formula for a short one. As opposed to this, the scientific or nominalist definitions do not contain any knowledge whatever, not even any 'opinion'; they do nothing but introduce new arbitrary shorthand labels; they cut a long story short.