100 Quotes by Karl Popper
Karl Popper, a preeminent philosopher of science, illuminated the path of scientific inquiry with his groundbreaking philosophy of falsifiability. Born in Austria, he emphasized the critical importance of subjecting hypotheses and theories to rigorous empirical testing that could potentially prove them wrong. In his work, "The Logic of Scientific Discovery," Popper argued that the distinguishing factor between science and pseudoscience is the potential for falsification, paving the way for a more robust and accountable scientific methodology. His ideas didn't merely shape the scientific process; they extended to political and social realms, encouraging the value of open debate, tolerance for differing opinions, and the continuous refinement of knowledge through the relentless pursuit of truth.
Karl Popper Quotes
Unlimited tolerance must lead to the disappearance of tolerance. If we extend unlimited tolerance even to those who are intolerant, if we are not prepared to defend a tolerant society, then the tolerant will be destroyed, and tolerance with them. We should therefore claim, in the name of tolerance, the right not to tolerate the intolerant.
True ignorance is not the absence of knowledge, but the refusal to acquire it.
I remained a socialist for several years, even after my rejection of Marxism; and if there could be such a thing as socialism combined with individual liberty, I would be a socialist still. For nothing could be better than living a modest, simple, and free life in an egalitarian society.
Whenever a theory appears to you as the only possible one, take this as a sign that you have neither understood the theory nor the problem which it was intended to solve.
The growth of knowledge depends entirely upon disagreement. (Meaning)
No rational argument will have a rational effect on a man who does not want to adopt a rational attitude.
The question is not how to get good people to rule; THE QUESTION IS: HOW TO STOP THE POWERFUL from doing as much damage as they can to us.
In so far as a scientific statement speaks about reality, it must be falsifiable; and in so far as it is not falsifiable, it does not speak about reality.
If you can't say it simply and clearly, keep quiet, and keep working on it till you can.
The best thing that can happen to a human being us to find a problem, to fall in love with that problem, and to live trying to solve that problem, unless another problem even more lovable appears.
Ignorance is not a simple lack of knowledge but an active aversion to knowledge, the refusal to know, issuing from cowardice, pride, or laziness of mind.
The war of ideas is a Greek invention. It is one of the most important inventions ever made. Indeed, the possibility of fighting with with words and ideas instead of fighting with swords is the very basis of our civilization, and especially of all its legal and parliamentary institutions.
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.
When we enter a new situation in life and are confronted by a new person, we bring with us the prejudices of the past and our previous experiences of people. These prejudices we project upon the new person. Indeed, getting to know a person is largely a matter of withdrawing projections; of dispelling the smoke screen of what we imagine he is like and replacing it with the reality of what he is actually like.
I may be wrong and you may be right, and by an effort, we may get nearer to the truth
The attempt to make heaven on earth invariably produces hell.
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.
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.
Those who promise us paradise on earth never produced anything but a hell.
We all remember how many religious wars were fought for a religion of love and gentleness; how many bodies were burned alive with the genuinely kind intention of saving souls from the eternal fire of hell.
Our aim as scientists is objective truth; more truth, more interesting truth, more intelligible truth. We cannot reasonably aim at certainty. Once we realize that human knowledge is fallible, we realize also that we can never be completely certain that we have not made a mistake.
The only way to test a hypothesis is to look for all the information that disagrees with it.
The game of science is, in principle, without end. He who decides one day that scientific statements do not call for any further test, and that they can be regarded as finally verified, retires from the game.
Astrologers were greatly impressed, and misled, by what they believed to be confirming evidence-so much so that they were quite unimpressed by any unfavorable evidence. Moreover, by making their interpretations and prophecies sufficiently vague they were able to explain away anything that might have been a refutation of the theory had the theory and the prophecies been more precise. In order to escape falsification they destroyed the testability of their theory. It is a typical soothsayer's trick to predict things so vaguely that the predictions can hardly fail: that they become irrefutable.
We have the right not to tolerate the intolerant. We should tolerate even them whenever we can do so without running a great risk; but the risk may become so great that we cannot allow ourselves the luxury.
For myself, I am interested in science and in philosophy only because I want to learn something about the riddle of the world in which we live, and the riddle of man's knowledge of that world. And I believe that only a revival of interest in these riddles can save the sciences and philosophy from an obscurantist faith in the expert's special skill and in his personal knowledge and authority.
Optimism is a duty. The future is open. It is not predetermined. No one can predict it, except by chance. We all contribute to determining it by what we do. We are all equally responsible for its success.
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.
We should therefore claim, in the name of tolerance, the right not to tolerate the intolerant.
In my view, aiming at simplicity and lucidity is a moral duty of all intellectuals: lack of clarity is a sin, and pretentiousness is a crime.
Bold ideas, unjustified anticipations, and speculative thought, are our only means for interpreting nature: our only organon, our only instrument, for grasping her. And we must hazard them to win our prize. Those among us who are unwilling to expose their ideas to the hazard of refutation do not take part in the scientific game.
It is not his possession of knowledge, of irrefutable truth, that makes the man of science, but his persistent and recklessly critical quest for truth.
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.
no matter how many instances of white swans we may have observed, this does not justify the conclusion that all swans are white.
Science does not rest upon solid bedrock. The bold structure of its theories rises, as it were, above a swamp. It is like a building erected on piles. The piles are driven down from above into the swamp, but not down to any natural or 'given' base; and if we stop driving the piles deeper, it is not because we have reached firm ground. We simply stop when we are satisfied that the piles are firm enough to carry the structure, at least for the time being.
It is not possible to write clearly enough to avoid being misrepresented by people who are sufficiently determined to do so.
Philosophy is a necessary activity because we, all of us, take a great number of things for granted, and many of these assumptions are of a philosophical character; we act on them in private life, in politics, in our work, and in every other sphere of our lives -- but while some of these assumptions are no doubt true, it is likely, that more are false and some are harmful. So the critical examination of our presuppositions -- which is a philosophical activity -- is morally as well as intellectually important.
The difference between the amoeba and Einstein is that, although both make use of the method of trial and error elimination, the amoeba dislikes erring while Einstein is intrigued by it.
It is impossible to speak in such a way that you cannot be misunderstood.
We do not know. We can only guess.
A rationalist is simply someone for whom it is more important to learn than to be proved right; someone who is willing to learn from others - not by simply taking over another's opinions, but by gladly allowing others to criticize his ideas and by gladly criticizing the ideas of others
Whenever we propose a solution to a problem, we ought to try as hard as we can to overthrow our solution, rather than defend it.
If you know that things are bound to happen whatever you do, then you may feel free to give up the fight against them.
Appealing to his [Einstein's] way of expressing himself in theological terms, I said: If God had wanted to put everything into the universe from the beginning, He would have created a universe without change, without organisms and evolution, and without man and man's experience of change. But he seems to have thought that a live universe with events unexpected even by Himself would be more interesting than a dead one.
Every solution of a problem raises new unsolved problems. (Meaning)
Do not allow your dreams of a beautiful world to lure you away from the claims of men who suffer here and now. Our fellow men have a claim to our help; no generation must be sacrificed for the sake of future generations.
If we are uncritical we shall always find what we want: we shall look for, and find, confirmations, and we shall look away from, and not see, whatever might be dangerous to our pet theories. In this way it is only too easy to obtain what appears to be overwhelming evidence in favor of a theory which, if approached critically, would have been refuted.
The genuine rationalist does not think that he or anyone else is in possession of the truth; nor does he think that mere criticism as such helps us achieve new ideas. But he does think that, in the sphere of ideas, only critical discussion can help us sort the wheat from the chaff.
If we wish our civilization to survive we must break with the habit of deference to great men.
There is an almost universal tendency, perhaps an inborn tendency, to suspect the good faith of a man who holds opinions that differ from our own opinions. It obviously endangers the freedom and the objectivity of our discussion if we attack a person instead of attacking an opinion or, more precisely, a theory.
It can't happen here is always wrong: a dictatorship can happen anywhere.
In point of fact, no conclusive disproof of a theory can ever be produced; for it is always possible to say that the experimental results are not reliable or that the discrepancies which are asserted to exist between the experimental results and the theory are only apparent and that they will disappear with the advance of our understanding. If you insist on strict proof (or strict disproof) in the empirical sciences, you will never benefit from experience, and never learn from it how wrong you are.
Science is perhaps the only human activity in which errors are systematically criticized and, in time, corrected.
The metaphysical doctrine of determinism simply asserts that all events in this world are fixed, or unalterable, or predetermined. It does not assert that they are known to anybody, or predictable by scientific means. But it asserts that the future is as little changeable as is the past. Everybody knows what we mean when we say that the past cannot be changed. It is in precisely the same sense that the future cannot be changed, according to metaphysical determinism.
There is no pure, disinterested, theory-free observation.
We are social creatures to the inmost centre of our being. The notion that one can begin anything at all from scratch, free from the past, or unindebted to others, could not conceivably be more wrong.
Aestheticism and radicalism must lead us to jettison reason, and to replace it by a desperate hope for political miracles. This irrational attitude which springs from intoxication with dreams of a beautiful world is what I call Romanticism. It may seek its heavenly city in the past or in the future; it may preach 'back to nature' or 'forward to a world of love and beauty'; but its appeal is always to our emotions rather than to reason. Even with the best intentions of making heaven on earth it only succeeds in making it a hell - that hell which man alone prepares for his fellow-men.
I personally call the type of government which can be removed without violence 'democracy,' and the other, 'tyranny.'.
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 survival value of intelligence is that it allows us to extinct a bad idea, before the idea extincts us.
It is wrong to ask who will rule. The ability to vote a bad government out of office is enough. That is democracy.
Our aim must be to make our successive mistakes as quickly as possible. To speed up evolution.
Rationalism is an attitude of readiness to listen to contrary arguments and to learn from experience... of admitting that "I may be wrong and you may be right and, by an effort, we may get nearer the truth."
It is wrong to think that belief in freedom always leads to victory; we must always be prepared for it to lead to defeat. If we choose freedom, then we must be prepared to perish along with it.
While differing widely in the various little bits we know, in our infinite ignorance we are all equal.
The open society is one in which men have learned to be to some extent critical of taboos, and to base decisions on the authority of their own intelligence.
I have come to the conclusion that Darwinism is not a testable scientific theory, but a metaphysical research programme.
We know a great deal, but our ignorance is sobering and boundless. With each step forward, with each problem which we solve, we not only discover new and unsolved problems, but we also discover that where we believed that we were standing on firm and safe ground, all things are, in truth, insecure and in a state of flux.
Instead of encouraging the student to devote himself to his studies for the sake of studying, instead of encouraging in him a real love for his subject and for inquiry, he is encouraged to study for the sake of his personal career; he is led to acquire only such knowledge as is serviceable in getting him over the hurdles which he must clear for the sake of his advancement.
[Great scientists] are men of bold ideas, but highly critical of their own ideas: they try to find whether their ideas are right by trying first to find whether they are not perhaps wrong. They work with bold conjectures and severe attempts at refuting their own conjectures.
All life is problem solving (Meaning)
There is no history, only histories.
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.
Science must begin with myths, and with the criticism of myths.
A theory that explains everything, explains nothing (Meaning)
We have become makers of our fate when we have ceased to pose as its prophets.
Science may be described as the art of systematic over-simplification.
We do not know anything - this is the first. Therefore, we should be very modest - this is the second. Not to claim that we do know when we do not - this is the third. That's the kind of attitude I'd like to popularize. There is little hope for success.
Our knowledge can only be finite, while our ignorance must necessarily be infinite.
We never know what we are talking about.
You cannot have a rational discussion with a man who prefers shooting you to being convinced by you.
We must plan for freedom, and not only for security, if for no other reason than only freedom can make security more secure.
It is complete nihilism to propose laying down arms in a world where atom bombs are around. It is very simple: there is no way of achieving peace other than with weapons.
A theory is just a mathematical model to describe the observations.
All we can do is search for the falsity content in our best theory.
The quest for precision is analogous to the quest for certainty and both - precision and certainty are impossible to attain.
I see now more clearly than ever before that even our greatest troubles spring from something that is [as] admirable and sound as it is dangerous – from our impatience to better the lot of our fellows.
Understanding a theory has, indeed, much in common with understanding a human personality. We may know or understand a man's system of dispositions pretty well; that is to say, we may be able to predict how he would act in a number of different situations. But since there are infinitely many possible situations, of infinite variety, a full understanding of a man's dispositions does not seem to be possible.
The defence of democracy must consist in making anti-democratic experiences too costly for those who try them; much more costly than a democratic compromise
All things living are in search of a better world. (Meaning)
We should realize that, if [Socrates] demanded that the wisest men should rule, he clearly stressed that he did not mean the learned men; in fact, he was skeptical of all professional learnedness, whether it was that of the philosophers or of the learned men of his own generation, the Sophists. The wisdom he meant was of a different kind. It was simply the realization: how little do I know! Those who did not know this, he taught, knew nothing at all. This is the true scientific spirit.
The use of violence is justified only under a tyranny which makes reforms without violence impossible, and should have only one aim, that is, to bring about a state of affairs which makes reforms without violence possible.
The conspiracy theory of society... comes from abandoning god and then asking: "Who is in his place"
A rationalist, as I use the word, is a man who attempts to reach decisions by argument and perhaps, in certain cases, by compromise, rather than by violence. He is a man who would rather be unsuccessful in convincing another man by argument than successful in crushing him by force, by intimidation and threats, or even by persuasive propaganda.
I have learned more from Hayek than from any other living thinker, except perhaps Alfred Tarski - but not even excepting Russell.
I have spoken to Einstein and he admitted to me that his theory was in fact no different from the one of Parmenides.
The growth of our knowledge is the result of a process closely resembling what Darwin called 'natural selection'; that is, the natural selection of hypotheses: our knowledge consists, at every moment, of those hypotheses which have shown their (comparative) fitness by surviving so far in their struggle for existence, a competitive struggle which eliminates those hypotheses which are unfit.
My thesis is that what we call 'science' is differentiated from the older myths not by being something distinct from a myth, but by being accompanied by a second-order tradition-that of critically discussing the myth. ... In a certain sense, science is myth-making just as religion is.
Some scientists find, or so it seems, that they get their best ideas when smoking; others by drinking coffee or whisky. Thus there is no reason why I should not admit that some may get their ideas by observing, or by repeating observations.
The fundamental thing about human languages is that they can and should be used to describe something; and this something is, somehow, the world. To be constantly and almost exclusively interested in the medium - in spectacle-cleaning - is a result of a philosophical mistake.
The moral decisions of others should be treated with respect, as long as such decisions do not conflict with the principle of tolerance.
Plato felt that a complete reconstruction of society's political program was needed.
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.
It is part of my thesis that all our knowledge grows only through the correcting of our mistakes.
We hate the very idea that our own ideas may be mistaken, so we cling dogmatically to our conjectures.
The future is always present, as a promise, a lure and a temptation.
A system is empirical or scientific only if it is capable of being tested by experience. These considerations suggest that not the verifiability but the falsifiability of a system is to be taken as a criterion of demarcation... It must be possible for an empirical or scientific system to be refuted by experience.
There is no history of mankind, there are only many histories of all kinds of aspects of human life. And one of these is the history of political power. This is elevated into the history of the world.
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 genuine test of a theory is an attempt to falsify it, or to refute it.
Simple statements are to be prized more highly than less simple ones because they tell us more; because their empirical content is greater; and because they are better testable.
It is a myth that the success of science in our time is mainly due to the huge amounts of money that have been spent on big machines. What really makes science grow is new ideas, including false ideas.
Better our hypotheses die for our errors than ourselves.
Man, some modern philosophers tell us, is alienated from his world: he is a stranger and afraid in a world he never made. Perhaps he is; yet so are animals, and even plants. They too were born, long ago, into a physico-chemical world, a world they never made.
Thus science must begin with myths, and with the criticism of myths; neither with the collection of observations, nor with the invention of experiments, but with the critical discussion of myths, and of magical techniques and practices.
Good tests kill flawed theories; we remain alive to guess again.
The old scientific ideal of episteme - of absolutely certain, demonstrable knowledge - has proved to be an idol. The demand for scientific objectivity makes it inevitable that every scientific statement must remain tentative for ever.
Science is the century-old endeavour to bring together by means of systematic thought the perceptible phenomena of this world into as thorough-going an association as possible. To put it boldly, it is the attempt at a posterior reconstruction of existence by the process of conceptualization. Science can only ascertain what is, but not what should be, and outside of its domain value judgements of all kinds remain necessary.
The initial stage, the act of conceiving or inventing a theory, seems to me neither to call for logical analysis nor to be susceptible of it.
I have insisted that we must be tolerant. But I also believe that this tolerance has its limits. We must not trust those anti-humanitarian religions which not only preach destruction but act accordingly. For if we tolerate them, then we become ourselves responsible for for their deeds.
What really makes science grow is new ideas, including false ideas.
It is wrong and dangerous to extol freedom by telling people that they will certainly be all right once they are free. The most we can say of democracy or freedom is that they give our personal abilities a little more influence on our well-being.
Every discovery contains an irrational element or a creative intuition.
Contrary to the outstanding work of art, outstanding theory is susceptible to improvements.
There is no history of mankind, there is only an indefinite number of histories of all kinds of aspects of human life.
There can be no ultimate statements science: there can be no statements in science which can not be tested, and therefore none which cannot in principle be refuted, by falsifying some of the conclusions which can be deduced from them.
Is the world ruled by strict laws or not? This question I regard as metaphysical. The laws we find are always hypotheses; which means that they may always be superseded, and that they may possibly be deduced from probability estimates. Yet denying causality would be the same as attempting to persuade the theorist to give up his search; and that such an attempt cannot be backed by anything like a proof.
There will be well-testable theories, hardly testable theories, and non-testable theories. Those which are non-testable are of no interest to empirical scientists. They may be described as metaphysical.
Reason like science, grows by way of mutual criticism; the only possible way of planning its growth is to develop those institutions that safeguard. the freedom of thought
Historically speaking all - or very nearly all - scientific theories originate from myths.
Propose theories which can be criticized. Think about possible decisive falsifying experiments-crucial experiments. But do not give up your theories too easily-not, at any rate, before you have critically examined your criticism.
Genuine philosophical problems are always rooted outside philosophy and they die if these roots decay.
Our belief in any particular natural law cannot have a safer basis than our unsuccessful critical attempts to refute it.
No particular theory may ever be regarded as absolutely certain. No scientific theory is sacrosanct.
To interpret Parmenides as a Kant before Kant, this is exactly what we must do.
Serious rational criticism is so rare that it should be encouraged. Being too ready to defend oneself is more dangerous than being too ready to admit a mistake.
― Karl Popper Quotes
Chief Editor
Tal Gur is an author, founder, and impact-driven entrepreneur at heart. After trading his daily grind for a life of his own daring design, he spent a decade pursuing 100 major life goals around the globe. His journey and most recent book, The Art of Fully Living, has led him to found Elevate Society.
