By Karl Popper, Routledge, March 2, 2001, 0415249929

Mostly modern essays from Popper, who is both writes germanically, and is characteristically ungermanic in his beliee that life’s “solutions” constantly evolve, and there are no fixed rules.

Each essay stands alone. The book can be read in any order.

I find Popper’s writing cogent, readable but challenging and not condescending. The questions he asks are intrigue me: How do we solve problems? What attitude is required.

Above all Popper believes we have a duty to be optimistic.

I read this about 15 years ago. These notes are from then.

The Logic and Evolution of Scientific Theory

[p9] I should now like to recall my three-stage model:

  1. problem;
  2. attempted solutions;
  3. elimination,

and my remark that this schema of how new knowledge is acquired is applicable all the way from the amoeba to Einstein.

[p9] The crucial novelty of the scientific method and approach is simply that we are actively interested and involved in elimination.

[p10] For example, instead of waiting until our environment refutes a theory or an attempted solution, we try to modify the environment in such a way that it is as unfavourable as possible to our attempted solution. We thus put our theories to the tesc - indeed, we try to put them to the severest test. We do everything to eliminate our theories, for we ourselves should like to discover those theories that are false.

[p11] There is nothing that can guarantee scientific progress.

My main thesis, then, is that the novelty of science and scientific method, which distinguishes it from the prescientific approach, is its consciously critical attitude to attempted solutions; it takes an active part in attempts at elimination, in attempts to criticize and falsify.

Conversely, attempts to save a theory from falsification also have their methodological function, as we have already seen. But my thesis is that such a dogmatic attitude is essentially characteristic of prescientific thinking, whereas the critical approach involving consciou attempts at falsification leads to scienceand governs scientific method.

Although the taking of sides undoubtedly has a function in scientific method, it is in m view important that the individual researcher should be aware of the underlying significance of attempts at falsification and of sometimes successful falsification. For the scientific method is not cumulative (as Bacon of Verulam and Sir James Jeans taught); it is fundamentally revolutionary.

[p13] You will perhaps have been surprised that I have so often mentioned my three-stage model. I have done this partly to prepare you for a very similar four-stage model, which is typical of science and the dynamics of scientific development.

[p14] we arrive at the four-stage model characteristic of scientific theory.[…]

  1. the old problem;
  2. formation of tenative theories;
  3. attemps at elimination through critical discussion, including experimental testing;
  4. the new problems that arise from the critical discussion of our theories.

Epistemology And The Problem Of Peace

[p38] But there is none; for knowledge – certain knowledge – is an empty word.

Science is the quest for truth. But truth is not certain truth.

  (5) Truth != certain truth
      Truth != certainty.

Everyone knows what truth is. It is the correspondence of a statement with the reality about which the statement says something:

  (6) Truth = correspondence with reality, or perhaps
      Truth correspondence of the alleged facts with the
      actual facts.

But definitions are not important. And quibbling over words is a menace.

[p44] Intellectuals know nothing. And their lack of modesty, their presumptuousness, is perhaps the greatest obstacle to peace on earth. The greatest hope is that, although they are arrogant, they may not be too stupid to realize it.

Adaptation and Darwinism: A Thought Experiment

[p48] A test tube is a very poor environment for life, and to keep life alive we shall have to develop special machinery. We shall thus have to adapt the environment to life. (Adaptation is indeed based upon reciprocity.) To adapt the environment to life, we must introduce at least one supermarket to feed the life. We also need a sewage system to remove the waste produced by life. And then we must also build schools to get the children out of the way, which is the only purpose of schools. And we must organize birth control – otherwise the life we have made in the test rube will be choked by its descendants.

Towards An Evolutionary Theory Of Knowledge

[p71] Observations (or ‘data’) may lead in scienceto the abandonment of a scientific theory and thereby induce some of us to think up a new tentative theory – a new trial. But the new theory is our product, our thought, our invention; and a new theory is only rarely thought up by more than a few people, even when there are many who agree on the refutation of the old theory. The few are those who see the new problem. Seeing a new problem may well be the most difficult step in creating a new theory.

On Freedom

[p84] When I speak of reason or rationalism, all I mean is the conviction that we can learn through criticism of our mistakes and errors, especially through criticism by others, and eventually also through self-criticism. 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. The emphasis here is on the idea of criticism or, to be more precise, critical discussion.

[p89] Kant’s solution was to demand that the state should limit individual freedom only to the extent made necessary by human coexistence, and that this necessary limitation should apply to all citizens as equally as possible. This genuinely Kantian principle shows that the problem of political freedom is at least conceptually solvable. But it does not provide us with a criterion of political freedom. For often in individual cases, we cannot establish whether a certain limitation of freedom is really necessary,nor whether it is a burden imposed equally on all citizens. We therefore need another criterion that can be more easily applied. My own proposal for one is the following. A state is politically free if its political institutions enable its citizens in practice to change a government without bloodshed when a majority wishes such a change. Or, more succinctly: we are free if we can get rid of our rulers without bloodshed.

Against The Cynical Interpretation of History

[p107] For if socialism must come about, it is obviously criminal to fight its coming. Indeed it is everyone’s duty to further the coming of socialism, so that what must come will encounter as little resistance as possible. Since you are not strong enough as an individual, you have to go with the movement, with the Party, and give it your loyal support, even if this means you support or at least swallow things you find morally repulsive. This is a mechanism that must lead to personal depravity. You swallow more and more intellectual trickery, excuses and lies. And once you go beyond a certain threshold, you are presumably prepared to accept anything. That is the road to political terrorism, to crime.

[p108] Everything turned upon the Marxist proof of the coming of a classless society, I learnt. But this broke down at the very point where Marx had seen and denied the possibility of a counter-argument. Clearly it is the party leaders who, with the party’s help, form the beginnings of a ‘new class’ and thereby negate Marx’s hopes. This ‘new ruling class’ deceives and mistrusts its future subjects, yet demands their trust. Already before victory and dictatorship, the leaders were rulers who expelled from the party anyone who posed awkward questions. (They could not yet kill such people.) This was their way of dealing with questions. This was the source of party discipline.

[p109] I am an optimist who has no knowledge of the future and therefore makes no predictions. We must make a very clear division between the present, which we can and should judge, and the wide-open future, which we are able to influence. We therefore have a moral duty to face the future quite differently from how we would if it were just a continu- ation of the past and present. The open future contains unforeseeable and morally quite different possibilities. So our basic attitude should not be ‘What will happen?’ but ‘What should we do to make the world a little better – even if we know that once we have done it, future generations might make everything worse again?’

[p110] Bertrand Russell, to whom I felt very close for many years until, as an old man, he fell under the sway of a communist secretary, wrote that the problem of our time is that our development has been too fast intellectually and too slow morally, so that when we discovered nuclear physics we did not achieve in time the necessary moral principles. In other words, according to Russell we are too clever – but morally, we are too bad. Many people, including many cynics, shared Russell’s view. I believe the exact opposite. I believe that we are too good and too stupid. We are too easily swayed by theories that appeal directly or indirectly to our moral sense, and our attitude to these theories is not sufficiently critical. We are not intellectually mature enough for them, and become their obliging victims, ready to make sacrifices of ourselves.

[p111] The prevailing ideology, which sees us living in a morally evil world, is a blatant lie. As it spreads, it discourages many young people and makes them despondent – at an age when they may not be able to live at all without some hope to support them. To repeat: I am not a optimist regarding the furnre. For the future is open. There is no historical law of progress. We do not know what tomorrow will be like. There are billions of possibilities, good and bad, that no one can foresee. I reject the prophetic goal-setting of the three interpretations of history, and I maintain that on moral grounds we should not put anything in their place. It is wrong even to try to extrapolate from history – for example, by inferring from present trends what will happen tomorrow. To see history as an at least partly predictable current is to build a theory out of an image or metaphor.

Waging Wars For Peace

[p116] Spiegel Herr Popper, the collapse of the Soviet Union has fulfilled a prophecy you made as much as half a century ago. Is this the triumph of critical rationalism over the enemies of the open society?

Popper I made no such prophecies, because I am of the view that no prophecies should be made. I think it is a completely wrong attitude to judge intellectuals by whether they make good prophecies.

The philosophy of history in Germany, at least since Hegel, has always thought it must somehow be prophetic. I think this is wrong. One learns from history, but history ends here and now. Our attitude to the future must be quite different from one of trying to extrapolate from history and, as it were, following the paths of history through into the future.

NOTE: He’s conflicted about forecasting. Above he says he does not like predictions or judging intellectuals by their prophecies. Yet, below he says he made a bold prediction and that it came (partially) true with AIDS.

Spiegel Already before Hiroshima, you wrote that man will one day disappear from the face of the earth.

Popper Why not? There are incalculable dangers. Just as all of us die, mankind too will probably die. Perhaps we will one day perish along with the solar system. But there is no point in talking, or even thinking, about such things. More likely is what I predicted long before AIDS – that some microbe will polish us off. That could happen very quickly. Any time. But there could still be many thousands of years to go until then.

The Collapse of Communism

[p133] One day in June 1919 a Party- sponsored demonstration of unarmed young comrades was fired upon by the police, and there were a number of deaths (eight if I remember rightly). I was outraged at what the police had done, but also at myself. For not only had I taken part; I had approved of the Party’s sponsorship and, perhaps, encouraged others to join in. Possibly some of them were among the dead. For what had they died? I felt responsible for them. I decided that although I had a right to risk my own life for the sake of my ideals, I certainly had no right to encourage others to risk their lifefor my ideals and even less for a theory like Marxism of whose truth there might be some doubt.

I asked myself whether I had seriously and critically examined the Marxist theory. And I was deeply depressed when I had to admit to myself that the answer was: ‘No’.

But when I returned to Party headquarters I found a very different attitude: the revolution demanded such sacrifices; they were unavoidable. And it meant progress, for it would make the workers furious with the police, and conscious of the class enemy.

[p135] First, we must break with the ridiculous habit of thinking that a wise man can predict what will happen. It seems that almost everybody believes it is characteristic of wisdom to make true prophecies. And almost everybody believes that a rational programme for the future must be based upon a true prediction.


History stops today. We can learn from it; but the future is never a prolongation of the past; nor is it an extrapolation. The future does not exist yet. Our great responsibility lies precisely in the fact that we can influence the future, that we can do our best to make it better.

To do this we must use all we have learnt from the past; and one very important thing we ought to have learnt is: to be modest.

[p137] 1. Strengthening Freedom, Controlled by Responsibility. We hope to achieve something like a maximum degree of personal freedom, but this is possible only in a civilized society - that is, a society devoted to a life of non-violence. […]

  1. World Peace. Now that the atom bomb and nuclear warheads have been invented, all civilized societies ought to cooperate in keeping the peace and closely monitoring the proliferation of atomic and hydrogen weapons. […]

  2. Fighting Poverty. Thanks to technology, the world is wealthy enough, at least potentially, to eliminate poverty and also to reduce unemployment to a tolerable minimum. Economists have found this very difficult – as no doubt it is; and they have ceased, rather suddenly (about 1965), to regard it as their main aim, as it was before. It seems a problem that has suddenly become unfashionable, and many economists behave as if there were a proof that it was insoluble. But on the contrary, there exists more than one proof that the problem is sol- uble, even though it may be very difficult to avoid some interference with the free market. But we interfere constantly with the free market, probably much more than necessary. […]

  3. Fight the Population Explosion. With the invention of abortion pills, in addition to other methods of birth control, biochemical technology has achieved a state where education on population control should be made available all over the world. […]

[p138] 5. Education to NonViolence. It is my considered opinion (though, of course, I may be wrong) that violence has lately been on the increase. At any rate, this is a hypothesis that can be investigated. And it should also be investigated whether we are educating our children to a toleration of violence.[…]

It is clear that this is closely connected with some of the previous points, such as the population explosion. I believe we should try to teach our children, if not the virtue of non-violence at least the truth that the greatest vice of all, the greatest of all evils, is cruelty. I do not say ‘unnecessary cruelty’, for cruelty is not only never necessary, it is never permissible. This includes mental cruelty, which we often commit out of thoughtlessness, that is, stupidity, laziness, or selfishness.

It has become unfashionable, I fear, to speak of these educational problems, both because of the fashionable freedom to do as one pleases (even if it is vicious according to unfashionable morals) and because, I admit, there is so much hypocrisy connected with morality. To this I say: Kant told us, ‘Dare to be wise!’ I may perhaps, more modestly, tell you: Dare to despise fashions, and be a little more responsible each day. This is, perhaps, the best you can do for freedom.

The Necessity of Peace

[p141] The idea that research, including scientific and theoretical research, consists of advancing bold hypotheses and testing them experimentally was thus already clear to me as a child. It is to Nansen that I owe this perhaps somewhat romantic view of science as consisting of experimental investigations and not of results assured for all time. True science, then, primarily consists of discoveries that have to be repeated over and over again it does not consist of so-called solid facts but of unsure hypotheses. The researcher must therefore sometimes take risks that put his intellectual responsibility severely to the test.

How I Became A Philosopher Without Trying

[p161] The constant consciousness of our own fallibility, and constant self-criticism combined with unlimited devotion to our main problem and its many problem-children and other subsidiary problems – this is what I can recommend to you with full conviction, from the bottom of my heart.

I wish to end with this advice: However happy you may be with a solution, never think of it as final. There are great solutions, but a final solution does not exist. All our solutions are fallible.

This principle has often been mistaken for a form of relativism, but it is the very opposite of relativism. We seek for truth, and truth is absolute and objective, and so is falsity. But every solution to a problem opens the way to a still deeper problem.

May my advice be a signpost on your way to a creative and happy life!