Trashing Popper

Progress notes on an ebook describing the debilitated state of Popper scholarship.


Mission statement
Standard Errors
Popper’s Progress
Major contributions
Min requirement for treatment  (4 turns)
The Popperian legacy of programs and projects
Mistakes and unresolved issues
Popperian infrastructure and networks

The epidemiology of Popperism
My story
1989 Courses  Australian unis
1997 Courses  US unis
Public Libraries in Sydney
Fisher Library (Uni of Sydney)
Amazon Books

Major contributors to the standard errors
O’Hear, Chalmers, Stove, Stanford, Wiki

Main Text – Annotated bibliography of books

The Bayesian Retreat

Mission statement

What can be done when a major thinker has been buried in his own profession? When his work is either ignored or presented in such a mangled and distorted form that it is easily dismissed as fatally flawed, at best an interesting contribution to the history of ideas.

Very few scholars would want to risk their career progression and their image by developing  his or her ideas. Referees and publishers’ readers would not look kindly on the results. If a book was published, how many bookstores would stock it, how many people would see it and how many would spend tens of dollars to buy it?

The answer is the inexpensive ebook, an end run around the profession, the publisher s and the diminishing number of bookstores.



If Popper is an important philosopher then the current status of his ideas in the academic community is a warning sign on the standards of teaching and scholarship in the profession. It appears to be possible to spend a career in philosophy schools without meeting someone who can provide a straight feed on Popper’s ideas.

We have been told over and over again that analytical philosophy in the twentieth century achieved unprecedented standards of accuracy and precision. That claim is seriously challenged by the evidence compiled in this book.

The leading idea is that Popper is important in the philosophy of science and in several other fields as well, including political philosophy and the theory of rationality. Consequently the main lines of his work should familiar to all educated people. If ideas matter then the neglect of Popper’s ideas may be no small contribution to the political, social and economic travails of our time.

How the project evolved

Serious work started after a chance encounter in a local bookshop  with a new philosophy book containing a strange misrepresentation of Popper’s ideas. A check on the books in a  nearby public library turned up the same result in most cases. The search extended to the library at the University of Sydney and a pattern emerged.

There are several  standard criticisms of Popper’s “falsificationism” and these can be found in practically every philosophy text that that has been checked, not just introductory books but “state of the art” reviews of epistemology and the philosophy of science. In the last decade or so a growing number of philosophy books do not mention Popper at all. If Popper’s ideas are indeed as defective as the impression that is conveyed by the standard criticisms, that is quite understandable.


1.The falsifiability criterion is about meaning.
2.Falsification cannot be decisive.
3.Failure to draw the distinction between falsifiability (a matter of logic and the form of           statements) and falsification (a practical matter).
4.Scientists don’t practice falsification.
5.Falsificationism is refuted by the history of science.
6.Popper was subjected to effective criticism by Lakatos/Kuhn/Feyerabend.
7.The failure of Popper’s theory of verisimilitude casts doubt on his whole program.
8.There is no getting away from induction/justificcationism.
9.From Habermas: Popperism is a form of positivism, it is analytical and provides no        dialectic or effective theory of criticism. In addition Popper's dualism facts and values,        is/ought or propositions and proposals, provides no leverage for criticism of the status       quo.


Some of the above are really in the category of “schoolboy howlers” especially the first, and it is disconcerting to find them recycled by scholars of high repute, such as A C Grayling who wrote that statements falling foul of Popper’s demarcation are “vacuous”.

On 2 and 3, Popper pointed out that falsification cannot be decisive (p 49-50 of LSD) so it is hardly a criticism to raise this. Confusion on this point arises from (3), the failure to separate the logic of the situation from the practical problems and procedures of scientists at work. Quine endorsed the logic of the demarcation criterion (1974, x) and acceptance of this would have saved the positivists and logical empiricists from two or three decades of wasted effort on their verification criterion. Back in the real world, Popper made the turn to the critical appraisal of the conventions or “rules of the game” that are required to address the practical problems of testing theories.

4. “Scientists don’t practice falsification”, meaning they don’t want to subject their theories to criticism and tests. Some do and some do not. Those who do are likely to be more effective researchers than those who do not. Some people do not follow the advice of their doctor, their dentist or the instructions that come with their appliances. How smart is that? Scientists who do not criticize their own ideas will most likely find that other people will do so, hence the importance of the social aspect of science that Popper described in Chapter 23 of OSE (1945).

5. The idea that Popper’s ideas are refuted by the  history of science is based on the false assumption that Popper thought that a theory should be discarded at the first sign of adverse evidence.  Apparent refutations, negative evidence, “disconfirmations” signal that there is a problem. More work is required, maybe for years, decades or even centuries. Popper insisted that a new theory or research program takes time to demonstrate its fertility and a highly successful theory should only be supplanted by a better one.

6. As for the criticism from Lakatos, Kuhn and Feberaband: Lakatos invented “naïve falsificationism” to successfully confuse the issues. Kuhn at one point suggested that Popper should be criticized as a naïve falsificationist even though he was not a naïve falsificationist. When he retreated from his initial (and interesting) position to a more coherent (and less interesting) stance he conceded that Popper’s approach was correct at times of crisis, meaning a serious conflict between rival theories, which for Popper was practically all the time. Feyerabend abused Popper and his wife but in terms of substance he merely repeated Popper’s dictum that there is no such thing as “scientific method”.

7. Popper’s attempt to develop a formal measure of verisimilitude (truthlikeness) did not deliver and he gave it away as soon David Miller pointed out he error. This was one of Popper’s projects that did not work. Not for nothing was he a fallibilist!

8. There are four, or maybe five or six kinds of induction which permit writers like O’Hear to appeal to induction at every stage of the scientific enterprise. Popper’s target was the so-called logic of induction which is supposed to assign valid, meaningful or helpful numerical probabilities to explanatory general theories and his arguments on this topic have not been refuted. The last resort of inductivists (apart from the program of Bayesian subjectivism) is usually the claim that we need the “inductive” assumption that there are regularities or laws or propensities and patterns in nature. Popper pointed out (1935, 1959) that this is a metaphysical theory about the world and using the label “induction” is merely a verbal strategy to defend inductivism.

The claim by Habermas and others that Popper is just a slightly deviant positivist is not sustainable in view of the full extent of Popper’s “deviance” which can be explained by the four “turns” (conjectural, objective, social and metaphysical). As for Popper’s defence of the status quo, the distinction that he drew between factual propositions and social or moral proposals was explicitly designed to give reformers a lever to change the status quo.


Popper’s contribution has to be understood against the background of the ideas that dominated Anglo-Saxon philosophy in the early 20th century, largely under the influence of Bertrand Russell and Ludwig Wittgenstein. This history has largely dropped out of sight among the generations that grew up after the “philosophy of science” wars of the 1960s and 70s when Kuhn, Lakatos, Feyerabend and others became key players.

In the last hundred years or so philosophy became specialized and professionalized, losing a wide readership among the educated general public. This problem has persisted despite the massive postwar growth of the universities which produced waves of philosophy students who were inducted into the various fashions of the time while Popper’s ideas were usually encountered in a scarcely recognizable form if they appeared at all.

Popper’s Progress

Popper was born in Vienna in 1902, the third child of a prominent liberal lawyer with scholarly interests. He left school in 1919 without his matriculation and attended university lectures in topics that interested him, especially maths and physics. The University was an easy walk from home in the heart of the old city; an apartment that shared the floor with the rooms of his father’s legal practice. Also in walking distance were the main Cathedral, the Synagogue, the House of Parliament, the Opera House, several major museums and art galleries and Café Central.

The young Popper dabbled in radical politics and voluntary social work including a spell with Alfred Adler’s project in the slums. Inspired by Tolstoy’s views on the dignity of manual work he became a qualified cabinet maker. He contemplated a career in music but instead joined the teacher-training course established in the University to support the Austrian school reforms that were under way at the time. He qualified as a teacher in 1928 after majoring in psychology and writing two theses, one on habit formation in children and the other on the axioms of the various schools of geometry.

On the way he studied philosophy, maths and science independently, with some informal assistance from various academics, including some philosophers who were attached to the Vienna Circle of logical positivists. In the late 1920s he seriously engaged with the twin problems of induction and demarcation and commenced his long argument with the logical positivists and logical empiricists.

At that time only a handful of academics in that field in the world addressed the issues in the philosophy of science that are now the business of thousands of  academics  and students around the globe. They were the preserve of small groups of interested people, including working scientists such as Pierre Duhem and Charles Sanders Peirce.

The Vienna Circle of logical positivists gathered around Professor Moritz Schlick (1882-1936), Rudolph Carnap (1891-1970) and Otto Neurath (1883-1945). Their spiritual predecessor was Ernst Mach (1838-1916) a philosopher-physicist in the strong empiricist (knowledge based on sense data) tradition of David Hume whose mission was to purge science of metaphysics and place it on the firm "positive" foundations of sensation. Few philosophers have had such a deep and wide-ranging influence. Mach virtually became the official philosopher of Viennese progressivism through his influence in psychology, physics (the young Einstein), literature (Robert Musil), and painting (the Impressionists). 

The members of the Circle pursued Mach's positivism, with Russell's Principia (an attempt to reduce maths to logic) their inspiration and Wittgenstein's Tractatus providing the anti-metaphysical program. The war on metaphysics was pursued using the strict "verificationist" definition of meaning. They proposed that statements should be regarded as literally meaningless if they could not be confirmed or verified by evidence. The propositions of logic and mathematics were exempt from the requirement for verification on the understanding that they are true by definition and they do not pretend to convey information about the world. The positive part of the program was to explain how scientific knowledge is based on the foundations of evidence, data or sense impressions using the logic of induction in one or other of its manifestations.

One of Popper’s disciplines was to put his ideas into writing. This process became very focused, almost by accident, after a night-long conversation with a friend [name] who suggested that Popper should organise his ideas into a book.

“It had never occurred to me to write a book. I had developed my ideas out of sheer interest in the problems, and then written some of them down for myself because I found that this was not only conducive to clarity but necessary for self-criticism. Writing a book did not fit my way of life nor my attitude towards myself - my father was afraid that it would end in my becoming a journalist. My wife opposed the idea because she wanted me to use any spare time to go skiing and mountain climbing with her.”

A time of crisis

This was a book for a time of crisis in philosophy and physics. The crisis in philosophy was the failure to provide a justification for the logic of induction which was supposed to be the distinctive feature of science. Bertrand Russell described this failure as the “skeleton in the cupboard” of rationalism. Another looming disaster for the positivists was the failure of their “verification criterion” to provide a workable demarcation between science and metaphysics. In science there was the problem of understanding Einstein’s challenge to Newton and the tension between Bohr and Einstein on the interpretation of quantum theory.

The philosophy of science became institutionalised and professionalised in the 1930s, driven by the logical positivists on the Continent and later by the logical empiricists in the US. They had a formal program, drafted under the inspiration of Otto Neurath who was a tireless political operator on behalf of socialism and logical positivism. One part of their program was to solve the problem of induction and the other was to put down metaphysics. 

Popper addressed a different problem from that of meaning and metaphysics because he was concerned with the difference between science and pseudo-sciences such as astrology which appear to be based on observations but are actually unsinkable because they make vague predictions which sometimes work out and sometimes do not. His exemplar of science was Einstein's theory which might have been refuted by a particular set of observations on the eclipse of the sun. Inspired by this example Popper advanced his criterion of falsifiability to demarcate between testable statements on the science side of the line (The proposition 'All planets travel in ellipses’ which is logically refuted by the observation of a planet that travels in a circular or rectangular path) and various categories of statements on the other side of the line.

It is important to note that Popper from the beginning of his published work drew a distinction between the decisive logic of falsification which he described as the falsifiability of a general theory (the single fact that slays a grand theory) and the problems of testing and observation in practice which preclude decisive falsification. Ian Jarvie explained that these problems (insoluble by logic) prompted Popper’s turn to consider the indispensable function of conventions or “rules of the game” in the community of scientists, a theme that Popper did not consolidate and has been almost entirely overlooked prior to Jarvie’s work [ref].

In addition to astrology Popper was concerned about the attitude of dedicated followers of Marx, Freud and Adler who interpreted all events in terms of their favourite  theory so nothing could unsettle it in their minds. He did not doubt that there was much to be learned from all three men but their systems needed to be approached in a critical manner. He was quite comfortable with the idea that parts of Marism could be made scientific (testable) and he was amused by the joke that Musgrave inserted in the Index of Conjectures and Refutations with entries for “Mardism, unfalsifiable” and “Marxism, falsified”.

Popper wanted to explain what it was about science that enabled scientific knowledge to grow, in contrast with pseudosciences, and perhaps philosophy. Unfortunately there was a widespread belief that his criterion concerned meaning because the positivists were so preoccupied with meaning that they could only regard Popper's line of demarcation as a rival to their own verification principle. Carnap, one of the dominant members of the Circle, was initially receptive to Popper’s ideas and he wrote paper titled “Testability and meaning” which helped to perpetuate the misunderstanding of Popper's work.

As to the problem of induction, Popper claimed that he solved this by demonstrating that scientists can make their way using conjectural theories and deductive logic to test them. Many philosophers claim that this does not solve the problem but merely evades it, however it does solve the problem for working scientists.

The Logic of Scientific Discovery became one of the great “game changing” books of the 20th century. Originally published in 1935/5 as Logik de Forschung (The Logic of Scientific Investigation) it emancipated the philosophy of science from the program of the logical positivists and it provided philosophical support for several aspects of Einstein’s methods and his revolutionary program in physics.

The Reception of Popper - Out of step.

Popper’s work is so out of sight and out of step with the academic philosophers these days that some effort is required to understand why practicing scientists often have so much respect for it. This applied to scientists at the top of the tree and also to the humble soil scientists who Popper lectured in WEA classes in New Zealand. Einstein wrote to Popper after a look at the manuscript and advised that he would have a very good book when he fixed some details in the physics. He had less need than most for Popper’s work because he had already got over his early attachment to positivism. Peter Medawar, John Eccles and Jaques Monod all saluted his work. Medawar described Popper as possibly the greatest philosopher of science, and Monod commenced his introduction to the French translation with the words “This great and noble book…”.

As for the soil scientists, Popper wrote to Carnap from  New Zealand

“I have a course for research workers on Scientific Methods, with discussion of their practical research problems, which have led to considerable practical results, a kind of poly-clinical advisory agency for agricultural chemists etc. The course was very interesting and successful. It is comforting to find that philosophy can be of some practical use! My hatred against the empty verbalism and scholasticism of the vast majority of philosophical writings is increasing proportionally to the time I have to devote to teaching such matters.” (After the Open Society, eds Shearmur and Turner, 91)

The soil scientists helped Popper as well. One of them, Parton, suggested the term “corroboration” that Popper took up in place of “confirmation”. He also alerted his colleague Geoffrey Leeper in Melbourne to Popper’s work; Leeper in turn passed on the word to his student Keith Barley and when I went to study with Keith Barley in Adelaide years later he lent me The Open Society and its Enemies when I told him I was leaving to study Sociology.

What the book achieved – bring in the four turns here

Bartley summed up Popper’s major achievement in “The Popperian Harvest” which he contributed to a collection of papers In Pursuit of Truth (ed Levinson,  
The British edition of this book was pulped following legal action by an academic who was named in the book and described as incompetent on account of his radical misrepresentation of Popper’s ideas.

First “ Popper solved the problem of induction, in all its classic manifestations.” Bartley suggested that the same approach could be applied to all the main problems in epistemology and methodology, listed by Bertrand Russell in his classic work The Problems of Philosophy (1912), and by A. J. Ayer The Central Questions of Philosophy (1973).  These are  the is/ought problem; the problem of other minds, of the external world, of the uniformity of nature, of the existence of the past, of the existence of matter, of the existence of physical space, and of time independent of perception.

“Consequently classical epistemology is rendered obsolete and a new evolutionary epistemology is introduced with a new approach to knowledge, human society and cosmology.”

Another way to describe Popper’s achievement is to refer to four “turns” that he introduced (1) the “conjectural turn” to accept the inevitably fallible nature of our knowledge, (2) the turn from psychologism (psychological reduction of epistemology)  and the obsession with subjective beliefs to focus on scientific, public or inter-subjective knowledge, (3) the “social” or “conventional” turn to take account of the “rules of the game” in scientific investigation and (4) to rehabilitate metaphysics in the core of the philosophy of science..(others could be suggested, like the evolutionary turn and anti-essentialism).

The Poverty of Historicism and The Open Society

With Logik der Forschung in print, Popper turned his attention to the social sciences. As a man of the moderate left he was alarmed at the failure of the socialists to prevent the rise of fascism. Some Marxists even managed to convince themselves that this was inevitable, and so could not be resisted.

Malachi Hacohen’s biography of Popper describes his travels across Europe during the 1930s to find a way of escape from Austria. He found a lecturing position at the Canterbury College in Christchurch, New Zealand, and he arrived there in 1937. “The Poverty of Historicism”  became his “war work” when Hitler invaded Austria in 1938.

Popper later described The Poverty as his stodgiest piece of writing but there were several mitigating circumstances. He was still struggling with English as a third or fourth language. He had a very demanding teaching load because he was the sole lecturer in philosophy and the writing had to be done in his own time because his professor insisted that he was employed to teach, not to do research and writing. For several years the outcome of the war was in doubt and at home in Austria fourteen of his relatives perished in the Holocaust. He had to make do with primitive library facilities (his father’s house contained more books than the college library) and he was desperately short of colleagues who could discuss his ideas in depth.

The Poverty of Historicism refuted the major arguments which propped up the myth of historical determinism, possibly the most dangerous and damaging myth of modern times. It is a neglected classic because it was overshadowed by The Open Society and its Enemies which was published in 1945 while The Poverty did not appear in book form until 1957. One of his signature ideas spelled out in the book is “piecemeal social engineering” and another is the call for a study of institutions as the vital framework of  human action. [Footnote von Mises on social engineering and the work of North on institutions that won a Nobel Prize].

Popper’s aim in this work was to transform the social sciences in the same way that he transformed the philosophy of the natural sciences in Logik der Forschung (1935). This had a moral and political purpose because he believed that defective methods in the social sciences had contributed to the rise of fascism and communism. The book is dedicated to the victims of these movements.

He wanted the social sciences to develop a body of knowledge to enable social reforms to deliver peace, freedom and prosperity in the way that the natural sciences and technology increased the productive capacity of the earth. This knowledge and the kind of piecemeal reforms that he advocated would be subject to abuse, like science and technology, but not as much as grand schemes driven by dictators or “philosopher kings” who believe that “history is on our side”.

An Opportunity Lost

Popper put aside the manuscript of The Poverty to work on The Open Society. He then published  The Poverty  in a series of three articles in Hayek’s journal Economica in 1944/45.  The framework for analysis of social events that he offered was very similar to the approach suggested by Talcott Parsons in The Structure of Social Action and by Ludwig von Mises in Human Action which was completed in 1940 in German and published in English in 1949.  All three men offered a framework for the study of economics and the other human sciences which could have:

Maintained sociology and economics as an integrated discipline.

Sponsored partnerships between economists and students of all social institutions – law, politics, literature, religion and cultural studies at large.

Ensured that “high theory” and empirical studies informed, enriched and corrected each other.

Contributed to good public policy, especially by monitoring the results of increased regulation and intervention in the marketplace by large government agencies (like the military/industrial complex of the US) and the impact of the erosion of “civic virtues”. This work could have commenced when the role of government was much smaller and less entrenched.

There was a window of opportunity for these three leading figures in their respective fields, plus their followers, to form a united front across the disciplines of sociology, economics and philosophy to promote the ideas that they shared and to debate the views that they did not share. This did not happen and the defective ideas which all three identified in the 1930s became embedded in the rapidly growing community of  economists and sociologists after the war.

The Open Society and its Enemies

Popper's first book in English was his war effort, a major work which grew out of notes on essentialism that he made for one of the sections of The Poverty of Historicism. The Open Society and its Enemies is a systematic investigation of several powerful ideas which render our traditions of democracy, rationality and tolerance dangerously fragile under the pressure of social and political crises.

The book had a substantial impact in some quarters but several factors told against its wider popularity, among them its size, the prejudices of readers and its novelty and depth. The two volumes run to almost 800 pages with over 200 pages of footnotes, accumulated at the ends of the volumes in small print. It is interesting to note that it is hardly read on campus and it is kept in print by a lay readership.

Essentially a tract of moral and political philosophy, it is almost totally ignored by moral philosophers and by political scientists. Popper formulated the problems of morals and politics in a way that makes no sense to most scholars in those fields. Traditionally these problems are approached either by analysis of the meaning of the key concepts (the state, power, justice etc) or by simply describing the forms taken by states, power-structures, and systems of justice. Popper's approach, is eminently practical, but it does not appeal to people indoctrinated in the traditional methods.  [ref to essentialism and historicism]

On Popper's account, the central problem of moral and political philosophy is to formulate and criticise standards which act as 'rules of the game' in social life. [Footnote the comparison with the rules of the game of science] These rules of the game occur in all groups and they may be enforced informally or by due process of law. The question we have to face is not whether we will have rules but whether we will try to improve them by critical discussion and trial and error. This approach cuts through the verbalism that bogs down academic discussions of moral and politics and it is constantly in touch with practical problems and their possible solutions. This approach could have evolved out of Wittgenstein’s concern with games and forms of life if he or his followers had addressed practical problems in a critical manner.

Jarvie listed 19 principal ideas that Popper offered in three social sciences: history, sociology, and political science, not counting dozens of major contributions and critical arguments that are more strictly philosophical. These include the challenge to the “leader principle” (the problem of sovereignty), a critique of collectivist (social) justice, a demolition of the aim of revolutionary utopian reform, and, parallel to the “rules of the game” in science, the “language of political proposals” in politics.

The Postscript to The Logic of Scientific Discovery

During the1950s Popper wrote almost a thousand pages of manuscript planned as a companion volume to The Logic of Scientific Discovery. This work remained in preparation until the 1980s due to a series of delays with the proofreading and the distraction of other projects..

Conjectures and Refutations (1963)

Despite Popper’s activity during the 1950s there was little to show outside the academic journals apart from the very small and somewhat enigmatic Poverty of Historicism in 1957 and very technical The Logic of Scientific Discovery in 1959. Neither of those volumes gave any hint of the range of Popper’s interests or provided a helpful introduction to his thought.

The publication of Conjectures and Refutations in 1963 provided 21 papers on a very wide range of topics, starting with his first paper written in English in 1937 [CHECK]  including some that were fundamentally important to consolidate and extended the insights of The Open Society and The Logic of Scientific Discovery. One of the best is  “On the sources of knowledge and of ignorance” which challenged the authoritarian structure of western thought and inspired Bartley’s major program to unpack the implications of “non-justificationism”, the first of the “Popperian turns”. He advanced his first positive treatment of metaphysics and gave out the first hints of some important developments in his thinking on evolution and language that surfaced a decade later in Objective Knowledge.

In retrospect it is clear that Popper’s publication program did not work out well for the propagation of his ideas in the profession and for his own standing. Logik der Forschung (1935) was practically invisible in the English-speaking world while the Continental diaspora entrenched logical positivism and logical empiricism in the North American universities and others, with the help of Freddy Ayer did much the same in Britain. Ayer’s Language Truth and Logic became a big influence after the war, not just in the profession but even more among the general readership that still existed at that time.

During the 1950s various forms of linguistic philosophy became the major rivals to positivism for professional attention among those who were not interested in the so-called Continental schools of thought. Consequently The Logic of Scientific Discovery was published against the tide of thinking and it was soon overtaken by Kuhn’s The Structure of Scientific Revolutions (1962) which provided a much more exciting and accessible alternative to the establishment in the philosophy of science. This meant that Conjectures and Refutations came into an academic marketplace where Popper’s stocks were falling. Without the excitement and distraction caused by Kuhn, Conjectures might have been seen as an exciting and reader-friendly explanation and development of the somewhat intimidating ideas in The Logic of Scientific Discovery.

Objective Knowledge

In the 1960s Popper produced a series of conference papers which indicated a major concern with evolution and simultaneously articulated a much stronger account of objective knowledge than his critique of psychologism in The Logic of Scientific Discovery. These papers addressed a linked set of problems concerning biological evolution, human consciousness, language and the nature of abstract ideas. He proposed that the distinctive features of human society and culture resulted from our use of language for description and argument, functions that cannot be reduced to the expressive and signaling functions of language. Further, there is a kind of objective content to descriptions and arguments that cannot be reduced to purely materialistic or subjective terms. These ideas mount a serious challenge to the prevailing fashions of materialism in the philosophy of mind and the various combinations of expressionism and reductionism that dominate the theories of literature and textual analysis.

The Schillp Volume, Unended Quest and The Self and its Brain

In 1974 came the long-awaited Popper volume (actually two volumes) in the Library of Living Philosophers series, edited by P A Schillp. The format of this series is to provide an intellectual autobiography of the subject, followed by a collection of essays (x in this case) about the work and then the replies by the philosopher. Popper’s intellectual autobiography was published separately in 1976 as Unended Quest.

One of the significant outcomes of the volume came as a result of Bartley’s series of essay reviews. He planned a series of five essays but he only completed three before the died. More important, writing the reviews re-ignited his admiration for Popper’s work and he became reconciled with Popper and took on the task of editing The Postscript.

The Postscript to the Logic of Scientific Discovery

The Postscript finally emerged from Bartley’s editorial hands in three volumes during 1982 and 1983. The first volume is Realism and the Aim of Science, the second is The Open Universe: An Argument for Indeterminism and the third is Quantum Theory and the Schism in Physics.

The third volume contains a Metaphysical Epilogue that provides the keystone to the arch  of  Popper’s thought, the theory of metaphysical research programs. This explains the cluster of themes that unify Popper's work and account simultaneously for the power and depth of his thought, and for the difficulty that he has had in obtaining recognition for his ideas in the community of philosophers.

This is the fourth “turn”, in addition to the conjectural, objectivist social turns. It provides the rationale for Popper’s excursion into metaphysics (contra the positivists) and the beginning of an explanation for the pervasive influence of metaphysical ideas.