This book is largely unpublished material from Popper’s literary remains regarding his The Open Society and Its Enemies that conveys some interesting stories about its publication and initial reception, throws light on its message, and complements it somewhat. It also contains much that Popper hardly discussed elsewhere.

Karl R. Popper is “the outstanding philosopher of the twentieth century” (Bryan Magee), even “the greatest thinker of the [twentieth] century” (Gellner). He felt affinity with thinkers of the Age of Reason and developed a new version of rationalism: critical rationalism. As a champion of science and of democracy he was the most influential philosopher of the post-WWII era. He was a close follower of Bertrand Russell and of Albert Einstein in that all three advocated problem-oriented fallibilism (during the peak (...) of the influence of Ludwig Wittgenstein who did not), valued commonsense, taking its theories to be approximations to the scientific truths of the day, and considered scientific truths as series of approximations to the absolute truth [Agassi, 1981, 112-16]. In particular, all three viewed science as the bold flight of the imagination checked and tempered by experience [Russell, 1931, 102]; [Einstein, 1949, 680]. Insofar as Russell adumbrated Popper’s philosophy, it may be fair to consider the latter a streamlined version of the former (the way both Berkeley and Hume deemed their philosophies streamlined versions of Locke’s [Hattiangadi, 1985]; [Wettersten, l985]. Russell raised the level of rational discourse in philosophy while remaining within the empiricist tradition; Popper continued and consolidated Russell’s achievements, adding a broad modification of the rationalist tradition [Popper, 1945, Ch. 24], thus forging new ways of philosophizing [Lakatos, 1978, 10]. Many sought a via media between rationalism and irrationalism, between individualism and collectivism, as well as between radicalism and traditionalism. Many sought a via media between empiricism and intellectualism. Popper’s philosophy is the only viable comprehensive rationalist suggestion in these directions (although it is open to modifications, of course), being thoroughly fallibilist and reformist, thus achieving a new and intensified commonsense philosophy, the only one that is integrated.. (shrink)

In this article I reply to criticism of my published work by N. Psarros (Journal for the General Philosophy of Science 28: 297–305,1997). I show that I had already answered the first criticism in my published work and not overlooked his supposed refutation. However I offer a plausible argument which he could have used to strengthen his claim. Psarros cites my work on Hopkins in his opening paragraph, but then makes no further reference to it in the text. I indicated (...) to Psarros verbally at Ilkley 1994 (and reiterate the message here) that Hopkins' work on Vitamins is the exemplar of a Popperian historical episode and must require addressing by the opponents of critical rationalism. (shrink)

Science seems to develop by inducing new knowledge from observation. However, it is hard to find a rational justification for induction. Popper offers one attempt to resolve this problem. Nursing theorists have tended to ignore or reject Popper, often on the false belief that he is a logical positivist (and hence hostile to qualitative research). Logical positivism claims that meaningful sentences containing any empirical content should ultimately be reducible to simple, observation statements. Popper refutes positivism by showing that there are (...) no such simple statements. He is not a positivist. For Popper, the scientist begins with problems and puts forward trial solutions. These are subjected to rigorous testing aimed at falsifying them. A new theoretical position is then reached in which the scientist knows either that the trial solutions are false or that they have not yet been falsified. Science is characterized by the fact that it tests its ideas through attempted falsification. Nonscience tests its ideas through attempted refutation. Nursing theory is a mixture of science and non-science. Popper’s method requires rigorous testing of theory in both realms. As such, some nursing theory should be discarded. Popper’s view faces at least two important criticisms. One is that a scientist can always reject an apparent falsification by instead altering some auxiliary hypothesis (e.g. denying the accuracy of the falsifying observation). Popper can deal with this argument by saying that defence of a theory in this way will eventually break down if the theory is false. The second criticism is that Popper’s method does ultimately draw upon induction. This criticism is true, but his method can be usefully adapted. An adapted from of Popper’s philosophy of science provides a good basis for nursing theory. (shrink)

Knowledge of residual perturbations in Uranus's orbit led to Neptune's discovery in 1846 rather than the refutation of Newton's law of gravitation. Karl Popper asserts that this case is untypical of science and that the law was at least prima facie falsified. I argue that these assertions are the product of a false, a priori methodological position, 'Weak Popperian Falsificationism' (WPF), and that on the evidence the law was not, and was not considered, prima facie false. Many of Popper's commentators (...) presuppose WPF and their views on this case and its implications for scientific rationality and method are similarly unwarranted or defective. (shrink)

Popper's account of refutation is the linchpin of his famous view that the method of science is the method of conjecture and refutation. This thesis critically examines his account of refutation, and in particular the practice he deprecates as avoiding a refutation. I try to explain how he comes to hold the views that he does about these matters; how he seeks to make them plausible; how he has influenced others to accept his mistakes, and how some of the ideas (...) or responses to Popper of such people are thus similarly mistaken. I draw some distinctions necessary to the provision of an adequate account of the so-called practice of avoiding a refutation, and try to rid the debate about this practice of at least one red herring. I analyse one case of 'avoiding' a refutation in detail to show how the rationality of scientific practice eludes both Popper and many of his commentators. Popper's skepticism about contingent knowledge prevents him from providing an acceptable account of contingent refutation, and so his method is really the method of conjecture and conjecture. He cannot do without the concepts of knowledge and refutation, however, if his account of science is to be plausible or persuasive, and so he equivocates between, amongst other things, refutation as disproof and refutation as the weaker notion of discorroboration. I criticise David Stove's account of this matter, in particular to show how he misses this point. An additional advantage Popper would secure from this equivocation is that if refutations were mere discorroborations they would be easier to achieve, and hence more common in science, than is the case. On Popper's weak notion of refutation, it would be possible to refute true theories since corroboration does not entail truth. There are two other related doctrines Popper holds about refutation which, if accepted, make some refutations seem easier to obtain than is the case. I call these doctrines 'Strong Popperian Falsificationism' (SPF) and 'Weak Popperian Falsificationism' (WPF). SPF is the false doctrine that if a prediction from some theory is refuted then that theory is refuted. Popper does not always endorse SPF. In particular, when confronted with a counterexample to it, he retreats to WPF, which is the false doctrine that if a prediction from some theory is refuted then that theory is prima facie refuted. WPF , or even SPF, can seem plausible if one has in mind predictions derived from theories in strong or conclusive tests of those theories, which I suggest Popper characteristically does. v Popper is disposed to describe any such case of predictive failure which does not lead to the refutation of the theory concerned as one in which that refutation has been avoided. To reinforce his portrayal of the refutation, or the attempted refutation, of major scientific theories as the rational core of scientific practice, Popper treats the so-called practice of avoiding a refutation as untypical of science, and much so-called avoidance he dismisses as unscientific or pseudo-scientific. I argue that his notion of avoiding a refutation is incoherent. Popper is further driven to believe that such avoidance is possible, however, because he conflates sentences with propositions and propositions with propositional beliefs. Also, he wishes to avoid being saddled with the relativisim that is a consequence of his weak account of refutation as discorroboration. Popper believes that ad hoc hypotheses are the most important of the unscientific means of avoiding a refutation. I argue that his account of such hypotheses is also incoherent, and that several hypotheses thought to be ad hoc in his sense are not. Such hypotheses appear to be so largely because of Popper's use of rhetoric and partly because these hypotheses are unacceptable for other reasons. I conclude that to know that a hypothesis is ad hoc in Popper's sense does not illuminate scientific practice. Popper has also attempted to explicate ad hocness in terms of some undesirable, or allegedly undesirable, properties of hypotheses or the explanations they would provide. The first such property is circularity, which is undesirable; the second such property is reduction in empirical content, which is not. In the former case I argue that non-circularity is clearly preferable to non-ad hocness as a criterion for a satisfactory explanation or explanans, as the case may be, and in the latter case that Popper is barking up the wrong tree. Some cases of so-called avoidance are obviously not unscientific. The discovery of Neptune from a prediction based on the reasonable belief that there were residual perturbations in the motion of Uranus is an important case in point, and one that is much discussed in the literature. The manifest failure of astronomers to account for Uranus's motion did not lead to the refutation of Newton's law of gravitiation, yet significant scientific progress obviously did result. Retreating to WPF, Popper claims that Newton's law was prima facie refuted. In general, astronomers have never shared this view, and they are correct in not doing so. I argue that the law of gravitation would have been prima facie refuted only if there had been good reason at the time to believe as false what is true, namely, that an unknown trans-Uranian planet was the cause of those Uranian residuals. Knowledge of the trans-Uranian region was then so slight that it was merely a convenient assumption, one which there was little reason to believe was false, that the known influences on Uranus's motion were the only such influences. I conclude that in believing vi or supposing that it was this assumption that was false, rather than the law of gravitation, Leverrier and Adams, the co-predictors of Neptune, were acting rationally and intelligently. Popper's commentators offer a variety of accounts of the alleged practice of avoiding a refutation, and of this case in particular. I analyse a sample of their accounts to show how common is the acceptance of some of Popper's basic mistakes, even amongst those who claim to reject his falsificationism, and to display the effects on their accounts of this acceptance of his mistakes. Many commentators recognize that anomalies are typically dealt with by changes in the boundary conditions or in other of the auxiliary propositions employed. Where many still go wrong, however, is in retaining the presupposition of WPF which encouraged Popper to hold the contradictory view about anomalies in the first place. Thus Imre Lakatos and others, for example, have developed a 'siege mentality' about major scientific theories; they see them as under continual threat of refutation from anomalies, and so come to believe that dogmatism is essential in science if such theories are to survive as they do. I examine various such doomed attempts to reconcile Popper with the history of science. It is a common failure in this literature to conflate or to fail to see the need to distinguish a belief from a supposition, and an epistemic reason from a pragmatic reason. I argue that only if one does draw these distinctions can one give an adequate account of how anomalies are rationally dealt with in science. The other important strand in Popper's thinking about 'avoidance' of refutation which has seriously misled some of his commentators is his unfounded belief in the dangers of ad hoc hypotheses. I examine the accounts that a sample of such commentators provide of the trans-Uranian planet hypotheses of Leverrier and Adams. These commentators imply or assert what Popper only hints at, namely, that there is something fishy about this hypothesis. I provide a further defence of the rationality of entertaining this hypothesis at the time. I conclude with a few remarks about Popper's dilemma in respect of scientific practice and his long standing emphasis on refutations. (shrink)

Abstract Evolutionary epistemologists from Popper to Campbell have appropriated the Darwinian principle to explain the apparent fit between the world and our knowledge of it. I argue that this strategy suffers from the lack of any principled distinction among various types of elimination. I offer such a distinction and show that there is a species of elimination that is really corrective, that is, which violates the Darwinian principle as Popper understands it.

Two suggestions are at the back of the present talk. First, toleration is obligatory, not criticism. So do not try to make people critically-minded: do not force them in any way to try to offer or accept criticism, to learn to participate effectively in the game of critical discussion. If they refuse, then they are within their right. Also, they will easily ad vance excuses for their refusal; admittedly some of these are unreasonable, but not all. Instead of trying to (...) make people critically-minded, try to help them become criticallyminded if and when they request help on this matter, but not otherwise. My second suggestion is that a simple, inconclusive, criterion should be used to distinguish with ease between proper and improper criticism — not by reference to validity, since proper criticism may turn out to be invalid, and some of the worst diatribes may inadvertently include valid criticism. This should hardly be expected of diatribes, and these are recognizable by their display of poor appreciation their target. (This was noted in a recent review by Stefano Gattei of the Italian edition of the Lakatos -Feyerabend correspondence: it largely concerns Popper, yet it displays boorish disrespect to him.) So much for my messages here. I also wish to present here the following ideas. (shrink)

The author submits that Popper's social philosophy rests on seven pillars: rationality (both conceptual and practical), individualism (ontological and methodological), libertarianism, the nonexistence of historical laws, negative utilitarianism ("Do no harm"), piecemeal social engineering, and a view on social order. The first six pillars are judged to be weak, and the seventh broken. In short, it is argued that Popper did not build a comprehensive, profound, or even consistent system of social philosophy on a par with his work in epistemology. (...) Still, he did make some important contributions to the field, such as unveiling the philosophical roots of totalitarianism and defending social engineering against both revolutionists and conservatives. (shrink)

In the present paper I shall first summarize Popper's criticism of the traditional method of definition, and then go on to comment critically on his own views on the form and function of so-called nominalist definitions.

One of the most original thinkers of the century, Karl Popper's work has inspired generations of philosophers, historians, and politicians. This collection of papers, specially written for this volume, offers fresh philosophical examination of key themes in Popper's philosophy, including philosophy of knowledge, science and political philosophy. Drawing from some of Popper's most important works, contributors address Popper's solution to the problem of induction, his views on conventionalism and criticism in an open society and explore his unique position in twentieth (...) century philosophy. Contributors also examine the current relevance of Popper to understanding liberal democracy, his critique of tribalism and offer new evaluations on Popper's relationship with analytic philosophy in general, and with Wittgenstein in particular as well as drawing on the studies of Isaac Newton and Albert Einstein to assess Popper's conception of science. This volume offers new insights on key topics from some of Popper's most important work and is essential reading for students of Popper and anyone interested in political philosophy and the philosophy of science. (shrink)

We compare Karl Popper’s ideas concerning the falsifiability of a theory with similar notions from the part of statistical learning theory known as VC-theory . Popper’s notion of the dimension of a theory is contrasted with the apparently very similar VC-dimension. Having located some divergences, we discuss how best to view Popper’s work from the perspective of statistical learning theory, either as a precursor or as aiming to capture a different learning activity.

This is a comprehensive introduction to the philosophical and political thought of Karl Popper, now available in English. It is divided into three parts, dealing with his biographical data, his works and recurrent themes, and finally his critics. It was approved of by Popper himself as a sympathetic and comprehensive study, and will be ideal to meet the increasing demand for a summary introduction to his work.

... THIRD WORLD EPISTEMOLOGY L. Jonathan Cohen . Sir Karl Popper's striking hypothesis about a third world of objective knowledge deserves careful scrutiny ...

In this paper I criticize Popper's conception of the rationality principle in the social sciences. First, I survey Popper's outlook on the role of a principle of rationality in theorizing in the social sciences. Then, I critically examine his view on the status of the principle of rationality concluding that the arguments supporting it are quite weak. Finally, I contrast his standpoint with an alternative conception. This, I show, helps us understand better Popper's reasons for adopting his perspective on rationality.

Popper's thesis that the growth of knowledge lies in the emergence of problems out of criticism and takes place in an autonomous world of products of the human mind (his so-called world-3) raises two questions: (1) Why does criticism lead to new problems, and (2) Why can only a limited number of tentative solutions arise at a given time? I propose the following answer: Criticism entails an overlooked evolutionary world-3 mechanism, namely, the migration of piece meal conceptual schemes from one (...) research tradition to another. Popper by passed the questions above because he relied very heavily on the selective power of criticism. (shrink)

Popper uses the "Humean challenge" as a justification for his falsificationism. It is claimed that in his basic argument he confuses two different doubts: (a) the Humean doubt (Popper's problem of induction), and (b) the "Popperean" doubt whether - presupposing that there are laws of nature - the laws we accept are in fact valid. Popper's alleged solution of the problem of induction does not solve the problem in a straightforward way (as Levison and Salmon have remarked before). But if (...) Popper's solution of the Humean challenge is re-interpreted as being close to Kant's it makes sense. Even though Popper explicitly rejects Kant's synthetic judgements a priori, it is claimed here that this is so because he misinterprets Kant's argument. If he had understood Kant correctly he should have been a modern "Kantianer"! (shrink)

Popper's critique of the philosophical doctrines underlying totalitarian ideology is powerful. Yet, having the regimes of Hitler and Stalin in full view before him, he did not give full and balanced consideration to the range of effects these doctrines can have within actually existing ideologies and regimes. The ideas he correlates with totalitarianism can and do exist in benign forms or tempered by other ideas and by institutions. Moreover, the struggle with totalitarianism is only partly a struggle of philosophical ideas. (...) Political argument and rhetoric appeal to feeling as well as intellect. This tends to be a blindspot of liberalism that often weakens it in the competition with its adversaries. (shrink)

Denkpsychologie has been important for the development of psychology as well as of philosophy during the last century. More specifically, cognitive psychology as well as Karl Popper’s evolutionary epistemology were both influenced by Otto Selz’s cognitive psychology. Without doubt, Selz played a role in the development of Popper’s thinking, but Michel ter Hark has not given convincing evidence for Popper’s idea of bold conjectures being influenced by Selz.

in Ian Jarvie, Karl Milford and David Miller (eds.): Karl Popper: A centenary assessment, Aldershot: Ashgate 2006, Chapter 45, pp. 57–70.

Popper [3] offers a qualitative definition of the relation “p q” = “p is (strictly) closer to the truth than (i.e., strictly more verisimilar than) q”, using the notions of truth (in the actual world) and classical logical consequence ( ), as follows.

Social science employs teleological explanations which depend upon the rationality principle, according to which people exhibit instrumental rationality. Popper points out that people also exhibit critical rationality, the tendency to stand back from, and to question or criticise, their views. I explain how our critical rationality impugns the explanatory value of the rationality principle and thereby threatens the very possibility of social science. I discuss the relationship between instrumental and critical rationality and show how we can reconcile our critical rationality (...) with the possibility of social science if we invoke Popper’s conception of limited rationality and his indeterminism. (shrink)

In their 1983 article, Popper and Miller present an argument against inductive probability. This argument is criticized by Redhead in his 1985 article. The aim of the present note is to state one form of the Popper-Miller argument, and defend it against Redhead's criticisms.

Reconstructing Popper's research programme for the Human Sciences, Noretta Koertge (Inquiry, Vol. 18 [1975]) has given a deductive?nomological account of explanations of actions by means of a Rationality Principle. It is argued here that such a Rationality Principle is fundamentally redundant. Neither is it logically necessary in order to deduce a cognitive action?explanandum, nor can it be given a semantic non?empty interpretation, at least not within Koertge's own syllogism. Any attempt to save the Rationality Principle as unfalsifiablc but nevertheless indispensable (...) for action explanations is rejected in the light of possible alternative action explanations by empirical and therefore in principle falsifiable psychological laws. (shrink)

Is Popper's philosophy alive or dead? If we make a judgment based on recent discussion in academic philosophy of science, he definitely seems to be fading. Popper is still seen as an important historical figure, a key part of the grand drama of 20th century thinking about science. He is associated with an outlook, a mindset, and a general picture of scientific work. His name has bequeathed us an adjective, "Popperian," that is well established. But the adjective is used for (...) very general ideas that, according to most current philosophers, Popper did not develop convincingly. His detailed account is often seen as attractive on first impression, but full of holes that become bigger rather than smaller as discussion continues. The picture and the name remain, which is more than 1 most philosophers can hope for. But the name attaches more and more to a set of instincts and intuitions, less and less to views that are seeing ongoing philosophical development. Inside science itself, Popper's standing is quite different. He continues to be just about the only philosopher who can seize the imagination and command the loyalty of successful professional scientists. And he is popular within science not only for purposes of general commentary and public relations. Popper's philosophy is a resource drawn on by scientists in their internal debates about scientific matters. This has been especially marked in some parts of biology (Hull 1999). From the point of view of philosophers, this affection on the part of scientists may have an unflattering explanation. Popper offers a rather heroic view of the scientific character, featuring an appealing combination of creativity and hard-headedness. It is no surprise that scientists like to be described this way. It is no surprise that they prefer this picture to the one often (though inaccurately) associated with Hempel and Carnap – the scientist as a sort of logic-driven pattern-recognition machine. The same applies to the picture associated with Kuhn, who presents the normal scientist as a narrow-minded, indoctrinated member of a peculiar collective enterprise, an enterprise devoted to solving tiny puzzles most of the time but prone to occasional fits of crisis and chaos.. (shrink)

The form of argument used by Popper and Miller to attack the concept of probabilistic induction is applied to the slightly different situation in which some evidence undermines a hypothesis. The result is seemingly absurd, thus bringing the form of argument under suspicion.

The article discusses some parallels between Weltanschauung analysis in contemporary philosophy of science and Rahner’s criticism of the context/content approach to theological pluralism.