Quotes from Karl Popper

Criticism, I said, is an attempt to find the weak spots in a theory, and these, as a rule, can be found only in the more remote logical consequences which can be derived from it. It is here that purely logical reasoning plays an important part in science.

For nothing could be better than living a modest, simple, and free life in an egalitarian society. It took some time before I recognized this as no more than a beautiful dream; that freedom is more important than equality; that the attempt to realize equality endangers freedom; and that, if freedom is lost, there will not even be equality among the unfree.

This is why the conflict between rationalism and irrationalism has become the most important intellectual, and perhaps even moral, issue of our time.

Science is most significant as one of the greatest spiritual adventures that man has yet known.

there is no reason to believe that a definition necessarily determines the ontological status of the term defined.)

in philosophy methods are unimportant; any method is legitimate if it leads to results capable of being rationally discussed. What matters is not methods or techniques but a sensitivity to problems, and a consuming passion for them; or, as the Greeks said, the gift of wonder.

We can all participate in the heritage of man. We all can help to preserve it. And we can all make our own modest contribution to it. We must not as for more.

Every genuine test of a theory is an attempt to falsify it, or to refute it. Testability is falsifiability; but there are degrees of testabilty: some theories are more testable, more exposed to refutation, than others; they take, as it were, greater risks.

What we call nowadays totalitarianism belongs to a tradition which is just as old or just as young as our civilization itself

The simple truth is that truth is hard to come by, and that once found may easily be lost again.

The essential feature of dualist-interactionism is that the mind and brain are independent entities...and that they interact by quantum physics.

The point is that, whenever we propose a solution to a problem, we ought to try as hard as we can to overthrow out solution, rather than defend it. Few of us, unfortunately, praise this precept; but other people, fortunately, will supply the criticism for us if we fail to supply it ourselves. Yet criticism will be fruitful only if we state our problem as clearly as we can and put our solution in a sufficiently definite form - a form in which it can be critically discussed.

Theories are nets cast to catch what we call 'the world': to rationalize, to explain, and to master it. We endeavor to make the mesh ever finer and finer.

Again, we cannot search the whole world in order to make sure that nothing exists which the law forbids. Nevertheless, both kinds of strict statements, strictly existential and strictly universal, are in principle empirically decidable, each, however, in one way only: they are unilaterally decidable. Whenever it is found that something exists here or there, a strictly existential statement may thereby be verified, or a universal one falsified.

Marxism is only an episode—one of the many mistakes we have made in the perennial and dangerous struggle for building a better and freer world.

An argument which appeals to the fact that we possess knowledge or that we can learn from experience, and which concludes from this fact that knowledge or learning from experience must be possible, and further, that every theory which entails the impossibility of knowledge, or of learning from experience, must be false, may be called a 'transcendental argument'.

Is it within the power of any social science to make sweeping historical prophecies? Can we expect to get more than the irresponsible reply of the soothsayer if we ask a man what the future has in store for mankind?

Science can be viewed from various standpoints, not only from that of epistemology; for example, we can look at it as a biological or as a sociological phenomenon. As such it might be described as a tool, or an instrument, comparable perhaps to some of our industrial machinery. Science may be described as a means of production - as the last word in 'roundabout production.

Denying realism amounts to megalomania.

A tapasztalatok motiválhatnak egy döntést, és így egy állítás elfogadását vagy elvetését is, de velük épp úgy nem lehet egy alapállítást igazolni, mint azzal, hogy ököllel rácsapunk az asztalra.

Every 'good' scientific theory is a prohibition: it forbids certain things to happen. The more a theory forbids, the better it is.

The attempt to make heaven on earth invariably produces hell.

Adev?rata ignoran?? nu este absen?a cunoa?terii, ci refuzul de a o dobândi.

Most of us, it seems, have a strong inclination to accept the peculiarities of our social environment as if they were "natural".... that we live in a charmed circle of unchanging taboos, of laws and customs which are felt to be as inevitable as the rising of the sun.