Karl Popper Quotes

It is easy to obtain confirmations, or verifications, for nearly every theory-if we look for confirmations. Confirmations should count only if they are the result of risky predictions ... 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. Every genuine test of a theory is an attempt to falsify it, or refute it.

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.

The point is that, 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. Few of us, unfortunately, practice this precept; but other people, fortunately, will supply the criticism for us if we fail to supply it ourselves.

We do not know. We can only guess.

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.

It is often asserted that discussion is only possible between people who have a common language and accept common basic assumptions. I think that this is a mistake. All that is needed is a readiness to learn from one's partner in the discussion, which includes a genuine wish to understand what he intends to say. If this readiness is there, the discussion will be the more fruitful the more the partner's backgrounds differ.

Every solution of a problem raises new unsolved problems.

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).

Perhaps the most powerful cause of the breakdown of the closed society was the development of sea-communications and commerce. Close contact with other tribes is liable to undermine the feeling of necessity with which tribal institutions are viewed; and trade, commercial initiative, appears to be one of the few forms in which individual initiative and independence can assert itself, even in a society in which tribalism still prevails. These two, seafaring and commerce, became the main characteristics of Athenian imperialism, as it developed in the fifth century B.C. And indeed they were recognized as the most dangerous developments by the oligarchs, the members of the privileged, or of the formerly privileged, classes of Athens.

There is no history, only histories.

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.

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.

Plato felt that a complete reconstruction of society's political program was needed.

With the idol of certainty (including that of degrees of imperfect certainty or probability) there falls one of the defences of obscurantism which bar the way of scientific advance. For the worship of this idol hampers not only the boldness of our questions, but also the rigour and the integrity of our tests. The wrong view of science betrays itself in the craving to be right; for 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.

I don't know whether God exists or not ... Some forms of atheism are arrogant and ignorant and should be rejected, but agnosticism - to admit that we don't know and to search - is all right ... When I look at what I call the gift of life, I feel a gratitude which is in tune with some religious ideas of God. However, the moment I even speak of it, I am embarrassed that I may do something wrong to God in talking about God.

Every time we proceed to explain some conjectural law or theory by a new conjectural theory of a higher degree of universality, we are discovering more about the world, trying to penetrate deeper into its secrets. And every time we succeed in falsifying a theory of this kind, we make an important new discovery. For these falsifications are most important. They teach us the unexpected; and they reassure us that, although our theories are made by ourselves, although they are our own inventions, they are none the less genuine assertions about the world; for they can clash with something we never made.

But the secret of intellectual excellence is the spirit of criticism ; it is intellectual independence. And this leads to difficulties which must prove insurmountable for any kind of authoritarianism. The authoritarian will in general select those who obey, who believe, who respond to his influence. But in doing so, he is bound to select mediocrities. For he excludes those who revolt, who doubt, who dare to resist his influence. Never can an authority admit that the intellectually courageous, i.e. those who dare to defy his authority, may be the most valuable type. Of course, the authorities will always remain convinced of their ability to detect initiative. But what they mean by this is only a quick grasp of their intentions, and they will remain for ever incapable of seeing the difference.

We must plan for freedom, and not only for security, if for no other reason than only freedom can make security more secure.

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

I may be wrong and you may be right, and by an effort, we may get nearer to the truth

It is not possible to write clearly enough to avoid being misrepresented by people who are sufficiently determined to do so.

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.

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.

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.

The discovery of instances which confirm a theory means very little if we have not tried, and failed, to discover refutations. For if we are uncritical we shall always find what we want: we shall look for, and find, confirmation, 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 favour of a theory which, if approached critically, would have been refuted.

Now this principle of induction cannot be a purely logical truth like a tautology or an analytic statement ...

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

It is interesting that for Plato, and for most Platonists, an altruistic individualism cannot exist. According to Plato, the only alternative to collectivism is egoism; he simply identifies all altruism with collectivism, and all individualism with egoism. This is not a matter of terminology, of mere words, for instead of four possibilities, Plato recognized only two. This has created considerable confusion in speculation on ehtical matters, even down to our own day.

Plato's identification of individualism with egoism furnishes him with a powerful weapon for his defence of collectivism as well as for his attack upon individualism. In defending collectivism, he can appeal to our humanitarian feeling of unselfishness; in his attack, he can brand all individualists as selfish, as incapable of devotion to anything but themselves. This attack, although aimed by Plato against individualism in our sense, i.e. against the rights of human individuals, reaches of course only a very different target, egoism. But this difference is constantly ignored by Plato and by most Platonists...

Individualism was part of the old intuitive idea of justice. That justice is not, as Plato would have it, the health and harmony of the state, but rather a certain way of treating individuals, is emphasized by Aristotle, when he says, 'justice is something that pertains to persons.

It is the rule which says that the other rules of scientific procedure must be designed in such a way that they do not protect any statement in science against falsification.

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.

Learning to read, and to a lesser degree, to write, are of course the major events in one's intellectual development. There is nothing to compare with it, since very few people (Helen Keller is the great exception) can remember what it meant for them to learn to speak.

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.

If you can't say it simply and clearly, keep quiet, and keep working on it till you can.

Knowledge consists in the search for truth - the search for objectively true, explanatory theories. It is not the search for certainty. To err is human. All human knowledge is fallible and therefore uncertain. It follows that we must distinguish sharply between truth and certainty. That to err is human means not only that we must constantly struggle against error, but also that, even when we have taken the greatest care, we cannot be completely certain that we have not made a mistake… To combat the mistake, the error, means therefore to search for objective truth and to do everything possible to discover and eliminate falsehoods. This is the task of scientific activity. Hence we can say: our aim as scientists is objective truth; more truth, more interesting truth, more intelligible truth. We cannot reasonably aim at certainty.... Since we can never know anything for sure, it is simply not worth searching for certainty; but it is well worth searching for truth; and we do this chiefly by searching for mistakes, so that we can correct them.

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.

I have spoken to Einstein and he admitted to me that his theory was in fact no different from the one of Parmenides.

While differing widely in the various little bits we know, in our infinite ignorance we are all equal.

The only way to test a hypothesis is to look for all the information that disagrees with it.

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."

[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.

Science may be described as the art of systematic oversimplification.

At least some of them, I suspect, have turned to probability theory in the hope that it would give them what they had originally expected from a subjectivist or epistemological theory of the attainment of truth through verification; that is, a theory of rational and justifiable belief, based upon observed instances.

The method of science depends on our attempts to describe the world with simple theories: theories that are complex may become untestable, even if they happen to be true. Science may be described as the art of systematic over-simplification-the art of discerning what we may with advantage omit.

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.

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.

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.

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.

One cannot do justice to Marx without recognizing his sincerity. His open-mindedness, his sense of facts, his distrust of verbiage, and especially of moralizing verbiage, made him one of the world's most influential fighters against hypocrisy and pharisaism. He had a burning desire to help the oppressed, and was fully conscious of the need for proving himself in deeds, and not only in words. His main talents being theoretical, he devoted immense labour to forging what he believed to be scientific weapons for the fight to improve the lot of the vast majority of men. His sincerity in his search for truth and his intellectual honesty distinguish him, I believe, from many of his followers (although unfortunately he did not altogether escape the corrupting influence of an upbringing in the atmosphere of Hegelian dialectics, described by Schopenhauer as 'destructive of all intelligence'). Marx's interest in social science and social philosophy was fundamentally a practical interest. He saw in knowledge a means of promoting the progress of man.

It is part of my thesis that all our knowledge grows only through the correcting of our mistakes.

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.

To give a causal explanation of an event means to deduce a statement which describes it, using as premises of the deduction one or more universal laws, together with certain singular statements, the initial conditions ... We have thus two different kinds of statement, both of which are necessary ingredients of a complete causal explanation.

A theory is just a mathematical model to describe the observations.

The belief that science proceeds from observation to theory is still so widely and so firmly held that my denial of it is often met with incredulity. I have even been suspected of being insincere- of denying what nobody in his senses would doubt.
But in fact the belief that we can start with pure observation alone, without anything in the nature of a theory is absurd; as may be illustrated by the story of the man who dedicated his life to natural science, wrote down everything he could observe, and bequeathed his priceless collection of observations to the Royal Society to be used as evidence. This story should show us that though beetles may profitably be collected, observations may not.
Twenty-five years ago I tried to bring home the same point to a group of physics students in Vienna by beginning a lecture with the following instructions : 'Take pencil and paper; carefully observe, and write down what you have observed!' They asked, of course, what I wanted them to observe. Clearly the instruction, 'Observe!' is absurd. (It is not even idiomatic, unless the object of the transitive verb can be taken as understood.) Observation is always selective. It needs a chosen object, a definite task, an interest, a point of view, a problem. And its description presupposes a descriptive language, with property words; it presupposes similarity and classification, which in their turn presuppose interests, points of view, and problems.

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.

[ ... ] while I felt that the Marxist attitude towards their theory was not at all admirable but was typically dogmatic and had all these properties which the Marxists usually said were characteristic of the churches. So I realized fairly early that Marxism was more of a church than of a science.

Always remember that it is impossible to speak in such a way that you cannot be misunderstood: there will always be some who misunderstand you.

It is impossible to speak in such a way that you cannot be misunderstood.

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.

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.

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 when we cease our attempts to drive our piles into a deeper layer, it is not because we have reached firm ground. We simply stop when we are satisfied that they are firm enough to carry the structure, at least for the time being.

No book can ever be finished. While working on it we learn just enough to find it immature the moment we turn away from it

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.

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.

Almost everyone ... seems to be quite sure that the differences between the methodologies of history and of the natural sciences are vast. For, we are assured, it is well known that in the natural sciences we start from observation and proceed by induction to theory. And is it not obvious that in history we proceed very differently? Yes, I agree that we proceed very differently. But we do so in the natural sciences as well.

We all have an unscientific weakness for being always in the right, and this weakness seems to be particularly common among professional and amateur politicians. But the only way to apply something like scientific method in politics is to proceed on the assumption that there can be no political move which has no drawbacks, no undesirable consequences. To look out for these mistakes, to find them, to bring them into the open, to analyse them, and to learn from them, this is what a scientific politician as well as a political scientist must do. Scientific method in politics means that the great art of convincing ourselves that we have not made any mistakes, of ignoring them, of hiding them, and of blaming others from them, is replaced by the greater art of accepting the responsibility for them, of trying to learn from them, and of applying this knowledge so that we may avoid them in future.

True ignorance is not the absence of knowledge, but the refusal to acquire it.

Science is not a system of certain, or -established, statements; nor is it a system which steadily advances towards a state of finality ... And our guesses are guided by the unscientific, the metaphysical (though biologically explicable) faith in laws, in regularities which we can uncover-discover. Like Bacon, we might describe our own contemporary science-'the method of reasoning which men now ordinarily apply to nature'-as consisting of 'anticipations, rash and premature' and as 'prejudices'.

What we should do, I suggest, is to give up the idea of ultimate sources of knowledge, and admit that all knowledge is human; that it is mixed with our errors, our prejudices, our dreams, and our hopes; that all we can do is to grope for truth even though it be beyond our reach. We may admit that our groping is often inspired, but we must be on our guard against the belief, however deeply felt, that our inspiration carries any authority, divine or otherwise. If we thus admit that there is no authority beyond the reach of criticism to be found within the whole province of our knowledge, however far it may have penetrated into the unknown, then we can retain, without danger, the idea that truth is beyond human authority. And we must retain it. For without this idea there can be no objective standards of inquiry; no criticism of our conjectures; no groping for the unknown; no quest for knowledge.

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.

It has always been asked in the spirit of: 'What are the best sources of our knowledge – the most reliable ones, those which will not lead us into error, and those to which we can and must turn, in case of doubt, as the last court of appeal?' I propose to assume, instead, that no such ideal sources exist – no more than ideal rulers – and that all 'sources' are liable to lead us into errors at times. And I propose to replace, therefore, the question of the sources of our knowledge by the entirely different question: 'How can we hope to detect and eliminate error?' The question of the sources of our knowledge, like so many authoritarian questions, is a genetic one. It asks for the origin of our knowledge, in the belief that knowledge may legitimize itself by its pedigree. The nobility of the racially pure knowledge, the untainted knowledge, the knowledge which derives from the highest authority, if possible from God: these are the (often unconscious) metaphysical ideas behind the question. My modified question, 'How can we hope to detect error?' may be said to derive from the view that such pure, untainted and certain sources do not exist, and that questions of origin or of purity should not be confounded with questions of validity, or of truth. …. The proper answer to my question 'How can we hope to detect and eliminate error?' is I believe, 'By criticizing the theories or guesses of others and – if we can train ourselves to do so – by criticizing our own theories or guesses.'

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

It must be possible for an empirical system to be refuted by experience.

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.

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

Our knowledge can only be finite, while our ignorance must necessarily be infinite.

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.

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

Science is perhaps the only human activity in which errors are systematically criticized and, in time, corrected.

A theory that explains everything, explains nothing

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 think that there is only one way to science - or to philosophy, for that matter: to meet a problem, to see its beauty and fall in love with it; to get married to it and to live with it happily, till death do ye part - unless you should meet another and even more fascinating problem or unless, indeed, you should obtain a solution. But even if you do obtain a solution, you may then discover, to your delight, the existence of a whole family of enchanting, though perhaps difficult, problem children, for whose welfare you may work, with a purpose, to the end of your days.

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.

If we wish our civilization to survive we must break with the habit of deference to great men.

Historically, all ethics undoubtedly begin with religion; but I do not now deal with historical questions. I do not ask who was the first lawgiver. I only maintain that it is we, and we alone, who are responsible for adopting or rejecting some suggested moral laws; it is we who must distinguish between the true prophets and the false prophets. All kinds of norms have been claimed to be God-given. If you accept 'Christian' ethics of equality and toleration and freedom of conscience only because of its claim to rest upon divine authority, then you build on a weak basis; for it has been only too often claimed that inequality is willed by God, and that we must not be tolerant with unbelievers. If, however, you accept the Christian ethics not because you are commanded to do so but because of your conviction that it is the right decision to take, then it is you who have decided.

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.

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.

Democracy provides the institutional framework for the reform of political institutions (other than this framework). It makes possible the reform of institutions without using violence, and thereby the use of reason in the designing of new institutions and the adjusting of old ones. It cannot provide reason. The question of the intellectual and moral standard of its citizens is to a large degree a personal problem. (The idea that this problem can be tackled, in turn, by an institutional eugenic and educational control is, I believe, mistaken ; some reasons for my belief will be given below.) It is quite wrong to blame democracy for the political shortcomings of a democratic state. We should rather blame ourselves. In a non-democratic state, the only way to achieve reasonable reforms is by the violent overthrow of the government, and the introduction of a democratic framework. Those who criticize democracy on any ' moral ' grounds fail to distinguish between personal and institutional problems. It rests with us to improve matters. The democratic institutions cannot improve themselves. The problem of improving them is always a problem of persons rather than of institutions.

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. 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.

I think that we shall have to get accustomed to the idea that we must not look upon science as a 'body of knowledge,' but rather as a system of hypotheses; that is to say, as a system of guesses or anticipations which in principle cannot be justified, but with which we work as long as they stand up to tests, and of which we are never justified in saying that we know they are 'true' or 'more or less certain' or even 'probable.'

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 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.

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

The moral decisions of others should be treated with respect, as long as such decisions do not conflict with the principle of tolerance.

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.

I found that those of my friends who were admirers of Marx, Freud, and Adler, were impressed by a number of points common to these theories, and especially by their apparent explanatory power. These theories appeared to be able to explain practically everything that happened within the fields to which they referred. The study of any of them seemed to have the effect of an intellectual conversion or revelation, opening your eyes to a new truth hidden from those not yet initiated. Once your eyes were thus opened you saw confirming instances everywhere: the world was full of verifications of the theory. Whatever happened always confirmed it. Thus its truth appeared manifest; and unbelievers were clearly people who did not want to see the manifest truth; who refused to see it, either because it was against their class interest, or because of their repressions which were still 'un-analysed' and crying aloud for treatment.
The most characteristic element in this situation seemed to me the incessant stream of confirmations, of observations which 'verified' the theories in question; and this point was constantly emphasized by their adherents. A Marxist could not open a newspaper without finding on every page confirming evidence for his interpretation of history; not only in the news, but also in its presentation--which revealed the class bias of the paper--and especially of course in what the paper did not say. The Freudian analysts emphasized that their theories were constantl

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.

Every intellectual has a very special responsibility. He has the privilege and the opportunity of studying. In return, he owes it to his fellow men (or 'to society') to represent the results of his study as simply, clearly and modestly as he can. The worst thing that intellectuals can do – the cardinal sin – is to try to set themselves up as great prophets vis-à-vis their fellow men and to impress them with puzzling philosophies. Anyone who cannot speak simply and clearly should say nothing and continue to work until he can do so.

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.

It is often asserted that, in view of the situation in quantum theory, object and subject can no longer be sharply separated. 1 To use Heitler's words, the 'separation of the world into an "objective outside reality", and "us", the self-conscious onlookers, can no longer be maintained. Object and subject become inseparable from each other'. 2 This, according to Bohr, is due to 'the impossibility of any sharp separation between the behaviour of atomic objects and the interaction with the measuring instruments which serve to define the conditions under which the phenomena appear'. 3 Heitler elaborates the point in some detail. 'One may ask', he writes, 'if it is sufficient to carry out a measurement by a self-registering apparatus or whether the presence of an observer is required.' And he arrives at the conclusion that the self-registering apparatus is insufficient, and that 'the observer appears, as a necessary part of the whole structure, and in his full capacity as a conscious being'.

Every test of a theory, whether resulting in its corroboration or falsification, must stop at some basic statement or other which we decide to accept. If we do not come to any decision, and do not accept some basic statement or other, then the test will have led nowhere. But considered from a logical point of view, the situation is never such that it compels us to stop at this particular basic statement rather than at that, or else give up the test altogether. For any basic statement can again in its turn be subjected to tests, using as a touchstone any of the basic statements which can be deduced from it with the help of some theory, either the one under test, or another. This procedure has no natural end.