Popper is often perceived as an eccentric kind of positivist who adopted a slightly different take on the demarcation of science with the criterion of falsification in place of verification. People like Habermas and the late Richard Rorty regarded Popper as a positivist for all practical purposes.
That view does not do justice to the full extent of Popper’s program, starting with the first step which can be described as a full-blooded “conjectural turn”, to claim that even our best theories may be rendered problematic by new evidence, new criticisms and new theories. This anticipated the “hermeneutic turn” when appreciation of the theory-dependence and framework-dependence of observations and arguments became more widespread in the wake of Kuhn and the modern French theorists.
Consequently to understand Popper it is necessary to take on board the “conjectural turn” which dates from 1935 with the original German version of The Logic of Scientific Discovery and some other moves as well. These include the “objectivist turn” to break with the obsession with the justification of beliefs and instead to focus on the strengths and weaknesses of theories that are stated in a public, inter-subjective or “objective” form. Then there is Popper’s “social turn” to examine the function of institutions, traditions, conventions and “rules of the game” in science and society. this has been spelled out by Ian Jarvie. And finally the “metaphysical turn” to recognse the pervasive influence of philosophical or metaphsical ideas which are the framework assumptions or presuppositions of thought.
It will help to explain more about each of these “turns”, starting with the turn to conjectural objective knowledge. In traditional epistemology the central concern was (and remains) the justification of beliefs . In “Epistemology without a knowing subject” Popper wrote
This [traditional approach] has led students of epistemology into irrelevancies: while intending to study scientific knowledge, they studied in fact something which is of no relevance to scientific knowledge. For scientific knowledge simply is not knowledge in the sense of the ordinary usage of the words ‘I know’. While knowledge in the senses of ‘I know’ belongs to what I call the ‘second world’, the world of subjects, scientific knowledge belongs to the third world, to the world of objective theories, objective problems and objective arguments…Thus my first thesis is that the traditional epistemology, of Locke, Berkeley, Hume, and even of Russell, is irrelevant, in a pretty strict sense of the word. It is a corollary of this thesis that a large part of contemporary epistemology is irrelevant also.” (Popper, 1972, p.108).
In the course of explaining Popper’s turn from “justificationism” to critical rationalism, Bartley pointed out that all attempts to justify beliefs end up in an infinite regress. The alternative to the quest for justified beliefs is to form tentative critical preferences for theories (or policies) on the basis of their capacity to solve their problems and stand up to various forms of criticism, including experimental and practical tests.
Moving on to the “social turn”. The discovery of the social factor in science is often attributed to Kuhn and the sociologists of knowledge, however Jarvie identified what he called the social turn in Popper’s earliest published work, and especially in the chapter on the sociology of knowledge in The Open Society. In the way that Hayek wrote about the constitution of liberty, Jarvie found in The Logic of Scientific Discovery the framework for a “constitution for science”, that is, a set of conventions or rules to ensure that theories are exposed to criticism, especially empirical tests. Popper’s focus on the institutional framework of science is explicit in the chapter on the sociology of knowledge in The Open Society and its Enemies and in the final sections of The Poverty of Historicism on situational logic and the institutional theory of progress.
Finally, the little-noticed metaphysical turn, possibly the most striking difference between the later Popper and the original logical positivists, whose signature idea was to render all talk of metaphysics strictly meaningless. Popper briefly mentioned the theory of metaphysical research programs in the autobiography written for the Library of Living Philosophers (Popper 1974, and 1976) but it was several years before it appeared in more detail in the Metaphysical Epilogue to the third volume of The Postscript to the Logic of Scientific Discovery.
The three books of the “Postscript” are “Realism and the Aim of Science” (Volume 1), “The Open Universe: An Argument for Indeterminism” (Volume 2) and “Quantum Theory and the Schism in Physics” (Volume 3). They contribute to Popper’s long campaign in support of realism, indeterminism and objectivism which in turn support human freedom, creativity and rationality.
“Realism” has two parts, the first pursues various forms of inductivism and the second attacks the subjective interpretation of the probability calculus. “The Open Universe” critiques both scientific and metaphysical determinism and traces the linkage between metaphysical determinism and subjective probability theory. This volume carries the defence of realism and objectivism into the heart of quantum theory to challenge the dominant assumptions of the Copenhagen interpretation. Bartley points out in the editor’s introduction that this is a profoundly cosmological work, where “the basic theme of Karl Popper’s philosophy – that something can come from nothing – obtains its basis in physics”.
The book contains a ‘Metaphysical Epilogue’ that is remarkable (in addition to being the basis of Lakatos’s theory of scientific research programmes) because it provides a key to understanding a set of themes that unify Popper’s whole system of thought (the keystone to his arch of thought it you like). This gives some clues as to the depth of his thinking and the reason why it has been so badly received in the profession at large.
Popper’s theory of MRPs flows from his theory that we should look at the history of a subject, and its current status, in terms of its problem situations.
In science, problem situations are the result, as a rule, of three factors. One is the discovery of an inconsistency within the ruling theory. A second is the discovery of an inconsistency between theory and experiment – the experimental falsification of the theory. The third, and perhaps the most important one, is the relation between the theory and what may be called the “metaphysical research programme.
By raising the problems of explanation which the theory is designed to solve, the metaphysical research programme makes it possible to judge the success of the theory as an explanation. On the other hand, the critical discussion of the theory and its results may lead to a change in the research programme (usually an unconscious change, as the programme is often held unconsciously, and taken for granted), or to its replacement by another programme. These programmes are only occasionally discussed as such: more often, they are implicit in the theories and in the attitudes and judgements of the scientists.
I call these research programmes “metaphysical” also because they result from general views of the structure of the world and, at the same time, from general views of the problem situation in physical cosmology. I call them “research programmes” because they incorporate, together with a view of what the most pressing problems are, a general idea of what a satisfactory solution of these problems would look like.
The theme of the book is the way that the Copenhagen interpretation of quantum physics has been influenced by unstated and uncriticised metaphysical assumptions, especially determinism, subjectivism and instrumentalism. Of course the Copenhagen people are scientific indeterminists but Popper argues that there is a metaphysical form of determinism that they have not eliminated from their thinking.
The book contains four chapters after a 1982 Preface and an Introduction. The Preface makes a case for a realistic and commonsense interpretation of quantum theory to overcome the crisis in physics which Popper attributes to two things, the intrusion of subjectivism and the “end of the road” idea that quantum theory has reached the complete and final truth. In the Introduction he argues for an interpretation of quantum physics without the observer and he sharply formulated thirteen thesis to challenge the Copenhagen interpretation of the observer as an integral part of the system.
In Chapter I, ‘Understanding quantum theory and its interpretations’ Popper updated his ideas from the formulations in “The Logic of Scientific Discovery”. He still maintained that the problem of interpreting quantum theory is bound up with the interpretation of probability theory, and he argued that the theory of propensities that he described in the first and second volumes of The Postscript should be applied to the interpretation of quantum theory, thus resolving the difficulties that arise in the Copenhagen interpretation.
Chapter II ‘The objectivity of qauntum theory’ returned to the issue of the observer in the system and confronted the doctrine that experiments have to be interpreted with the observer, and especially the consciousness of the observer, as one of the variables. The discussion includes the nature of quantum jumps and the existence or non-existence of particles.
Chapter III attempts a resolution of the paradoxes of quantum theory, using the propensity interpretation of probability, applied to (1) the indeterminacy relations, (2) the expirement of Einstein, Podolsky and Rosen, and (3) the two-slit experiment.
The long fourth chapter is the Metaphysical Epilogue. This covers a lot of ground, starting with a brief statement of the theory of metaphysical research programs (above). He then ran through a series of ten research programs. First the block universe of Parmenides, then Atomism and Geometrization, followed by Essentialism and Potentialism (from Aristotle), then Renaissance Physics (Copernicus, Bruno, Kepler, Galileo), The Clockwork Theory (Hobbes, Descartes), Dynamism (Newton), Fields of Force (Faraday, Maxwell), Unified Field Theory (Riemann, Einstein, Schrodinger) and finally The Statistical Interpretation of Quantum Theory. After a discussion of schism, programs and metaphysical dreams he went on to indeterminism and the reduction of the wave packet and a model of a universe of propensities to account for the leading featues of all the ten programs that he sketched previously. After touching on some open problems he concluded with some comments on the role of metaphysical systems and the possibility of a demarcation within metaphysics, between good and bad systems.
The proper aspiration of a metaphysician…is to gather all the true aspects of the world (and not merely its scientific aspects) into a unifying picture which may enlighten him and others, and which may one day become part of a still more comprehensive picture, a better picture, a truer picture.