Panentheism.  Revisionism.  Anarchocapitalism.



Essays by Me

Essays by Others

Process, Insight, and Empirical Method 

An Argument for the Compatibility of the Philosophies of Alfred North Whitehead and Bernard J. F. Lonergan and Its Implications for Foundational Theology.

A Dissertation Submitted to the Faculty of the Divinity School, The University of Chicago, for the Degree of Doctor of Philosophy

December 1983

Thomas Hosinski, C.S.C.

Chapter II:

The Tenability of Whitehead’s and Lonergan’s Interpretations of Scientific Method


This chapter is an interlude—though a necessary one—in the development of the main thesis and argumentation of my dissertation.  It is necessary in order to establish critically the status of Whitehead’s and Lonergan’s interpretations of empirical scientific method.  We have already seen in Chapter I the extent to which both of their philosophies depend on an accurate and tenable interpretation of empirical scientific method.

Fundamentally, then, if Whitehead’s and Lonergan’s interpretations of empirical method could not be judged tenable, this would seriously weaken their own philosophies and the foundations I believe their philosophies offer for theology, as well as the argument I wish to formulate concerning the compatibility of their philosophies.  Hence apart from any cogency and self-evidence their discussions, analyses, and arguments may have—and I, obviously, am of the opinion that such cogency and self-evidence is considerable—I must discover independent lines of evidence for judging that their interpretations of empirical scientific method are tenable.

Under normal circumstances such lines of evidence might be elicited by considering critical studies of their work done by philosophers of science. This procedure, however, cannot be followed in this case for the simple reason that critical studies of Whitehead’s and Lonergan’s interpretations of empirical scientific method are almost non-existent.

There is one critical study of Lonergan’s interpretation of empirical scientific method done by a noted philosopher of science: Mary Hesse, “Lonergan and Method in the Natural Sciences,” in Patrick Corcoran, ed., Looking at Lonergan’s Method (Dublin: The Talbot Press, 1975), pp. 59-72.  Unfortunately, this analysis is so riddled with basic misunderstandings of Lonergan’s thought that it is of negligible critical value.  There are also the following studies in Spirit as Inquiry: Studies in Honor of Bernard Lonergan, originally published in Continuum 2 (1964): 300-553: Patrick A. Heelan, “A Realist Theory of Physical Science,” pp. 334-342; and Edward M. MacKinnon, “Cognitional Analysis and the Philosophy of Science,” pp. 343-368.  Heelan’s study is not critical, but an appreciative attempt to argue against linguistic analysts’ interpretations of science.  MacKinnon’s study is mainly an attempt to “build bridges” between Lonergan’s analysis and the contemporary philosophy of science traditions.

In fact, with regard to the interpretation of scientific method, the work of both Whitehead and Lonergan has been virtually without influence in the community of philosophers of science.  One can understand why Lonergan, a professional theologian, might be unknown among philosophers of science, but it is surprising to discover that Whitehead also is by and large ignored by them.  With just a few exceptions, his work beyond 1922 is simply not referred to by philosophers of science.

For critical studies of Whitehead’s philosophy of science (i.e., the concepts of his philosophy of science) see Appendix IV and Bibliography of Palter, Whitehead’s Philosophy of Science, pp. 236-243.  While there are numerous studies of this sort, I can discover none which addresses Whitehead’s interpretation of the general method of empirical science.

This is probably the case because Whitehead nowhere engages in an extended analysis of empirical scientific method and also because his work after 1922 is “metaphysical” [See Thesis, p. 9.] and was thus considered irrelevant to the modes of interpretation then dominant in the philosophy of science.  In any event, there is a dearth of critical studies of Whitehead’s and Lonergan’s interpreta-tions of empirical scientific method, and so I must choose another form of analysis in order to develop independent lines of evidence.

The best procedure remaining to me seems to be that of comparison.  The task would be simple if there existed some widely accepted and agreed-upon statement and analysis of the structure of scientific method to which I could compare the interpretations of Whitehead and Lonergan.  Unfortunately, as anyone familiar with the state of contemporary philosophy of science knows, there is no such agreement. [See Frederick Suppe, ed., The Structure of Scientific Theories.]  Rather, there is a pluralism of positions within the community of philosophers of science yielding a wide spectrum of interpretations of scientific method.  Obviously, any attempt to compare Whitehead’s and Lonergan’s interpretations to the entire spectrum of contemporary interpretations in the philosophy of science would expand my necessary interlude into several dissertations in their own right.  The course I shall follow, then, is to pick two representative interpretations from the many available in contemporary philosophy of science and critically compare Whitehead’s and Lonergan’s interpretations to them.  This ought to be sufficient to enable me to illustrate that Whitehead’s and Lonergan’s interpretations of scientific method fall within the spectrum of interpretation offered by contemporary philosophy of science, and for my purposes this would be sufficient independent evidence to base the judgment that their interpretations are tenable.

Finally, though the two thinkers I have chosen for the purpose of comparison certainly need no introduction, perhaps something ought to be said about my reasons for choosing these two in particular.  First, both Karl Popper and Michael Polanyi have produced important interpretations of empirical scientific method and philosophies of knowing.  Their interpretations have been widely influential for a number of years.  On this topic, their names and work spring immediately to mind.  More important than this, however, is the apparent distance between their interpretations; that is, in several important respects the difference between their interpretations gives one a sense of the spectrum of interpretation that exists.  For example, it seems a long way from Polanyi’s “personal knowledge” to Popper’s “epistemology without a knowing subject.”  Thus Popper and Polanyi serve as good figures for a discussion that aims at being exemplary rather than exhaustive in its treatment. Thirdly, both Popper and Polanyi not only have thorough interpretations of empirical scientific method, but also full-fledged epistemologies situated within a larger philosophical outlook.  Their work is on roughly the same scale as that of Whitehead and Lonergan, and this will facilitate comparison of interpretations.  Finally, in the philosophy of Karl Popper we find a well-articulated interpretation of empirical scientific method that at least initially appears to be in serious disagreement with the interpretations of both Whitehead and Lonergan, while in the philosophy of Michael Polanyi we find one that has a marked resonance with them.  This, too, will facilitate a critical comparison of views.

The first section of this chapter will attempt to summarize Karl Popper’s interpretation of empirical scientific method and the philosophy of knowing; the second section will attempt to do the same for Michael Polyani’s interpretation; and the third section will be the critical comparison of Whitehead’s and Lonergan’s interpretations to these two.


Karl Popper on Scientific Method and Knowledge

Karl Popper’s interpretation of empirical scientific method and the nature of human knowledge has been developed over several decades and has drawn wide comment and criticism.

Popper’s major works are: The Logic of Scientific Discovery (New York: Basic Books, 1959; 2nd ed., 1968 hereafter cited as L.Sc.D.], a translation by the author of Logik der Forschung (Vienna: 1934); two collections of articles and papers, Conjectures and Refutations: the Growth of Scientific Knowledge (New York: Basic Books, 1962 hereafter cited as C.R.], and Objective Knowledge: An Evolutionary Approach (Oxford: At the Clarendon Press, 1972 hereafter cited as Ob. Kn.; and Popper’s “Intellectual Biography” and “Replies to My Critics” in Paul A. Schilpp, ed., The Philosophy of Karl Popper, 2 vols. [Vol. XIV of The Library of Living Philosophers] LaSalle, Ill.: Open Court, 1974), 1: 3-181 and 2: 961-1197 respectively.  There are two major collections of commentaries and critical studies: Mario Bunge, ed., The Critical Approach to Science and Philosophy (New York: The Free Press, 1 64 ; and the essays in Schilpp, ed., The Philosophy of Karl Popper.

As Popper himself has repeatedly stated, the ideas with which he interprets empirical scientific method and develops his philosophy of knowledge are quite simple.  In this section I will attempt to communicate the simplicity of his basic interpretation without becoming involved in the detailed, minute criticism his interpretation has provoked.


The General Context

It is perhaps best to begin with a brief consid-eration of the philosophical context from which Popper approaches the problem of knowledge and empirical method.  In the preface to the English edition of his major work, The Logic of Scientific Discovery, Popper states his conviction that the central problem for thought

is the problem of cosmology: the problem of understanding the world—including ourselves, and our knowledge, as part of the world.  All science is cosmology, I believe, and for me the interest of philosophy, no less than of science, lies solely in the contributions which it has made to it. [L.Sc.D., p. 15. Popper’s italics omitted.]

In its attempt to contribute to this understanding, in its search for truth, philosophy does not follow some method peculiar to itself.

There is no method peculiar to philosophy . . .

And yet, I am quite ready to admit that there is a method which might be described as “the one method of philosophy.”  But it is not characteristic of philosophy alone; it is, rather, the one method of all rational discussion, and therefore of the natural sciences as well as of philosophy.  The method I have in mind is that of stating one’s problem clearly and of examining its various proposed solutions critically. [Ibid., pp. 15, 16.  Popper’s italics.  All italics in subsequent quotations from Popper’s are his.]

Popper’s own concern is to contribute to an understanding of human knowledge, and he is convinced that the only way of arriving at an understanding of knowledge is to offer a solution to “the central problem of epistemology,” namely, “the growth of knowledge.”  Furthermore, “the growth of knowledge can be studied best by studying the growth of scientific knowledge.”  [Ibid., p. 15.  Popper’s italics omitted.] This is because scientific knowledge, in the problem situations it addresses and in the disciplined way it discusses reasons for accepting or rejecting a theory, offers an easier entry into the problems and issues involved in knowledge in general than does common-sense knowledge.

“The problem of epistemology may be approached from two sides: (1) as the problem of  ordinary or common-sense knowledge, or (2) as the problem of scientific knowledge.  Those philosophers who favour the first approach think, rightly, that scientific knowledge can only be an extension of common-sense knowledge, and they also think, wrongly, that common-sense knowledge is the easier of the two to analyse.”  Ibid., p. 18; see also pp. 18-22.  In formulating his discussion in this way, Popper is attempting to show why neither “logical analysis” nor “language analysis” can serve as the main method of epistemology.

Such, in brief, is the general context of Popper’s philosophy.

There are two possible ways of trying to summarize the main lines of Popper’s interpretation of science and knowledge.  One would be to construct a theoretical approach from the context I sum-marized above.  In this case we would begin by saying that since we are to study the growth of scientific knowledge from other sorts of knowledge, and then develop an analysis of how scientific knowledge changes or grows.  This is in fact how Popper proceeds in his discussion in The Logic of Scientific Discovery.  It is also possible, now that Popper has written his intellectual “Autobiography,” to summarize his central ideas by showing how he actually brought them together in his intellectual development.  It is the latter course that I shall choose, partly because I shall be dealing with Popper’s theoretical discussions below and partly because of the human interest in tracing the development of personal ideas into a public theory of knowledge. [Karl Popper, “Intellectual Autobiography,” in Schilpp, ed., The Philosophy of Karl Popper, 1: 3-181. (Hereafter cited as “Autobio.”)’

Popper attributes the birth of one of his central ideas to several crucial experiences that all took place in 1919, his seventeenth year. [For what follows, see ibid., pp. 23-29.] In the spring of that year he became convinced by communist propaganda and for a period of two or three months considered himself a communist.  But in the summer of that year several socialists and communists were killed in Vienna in an attempt to aid the escape of some communists under arrest by the police.  Popper felt that as a Marxist he bore part of the responsibility for this tragic incident. The revulsion he felt caused him to question Marxist theory (which was being presented as “scientific socialism”) and his own uncritical commitment to the creed of communism.  He decided that he had accepted the complex theories of Marxism and communism without subjecting those theories to critical examination so as to arrive at a personal understanding of them, and that he had also “repressed” his awareness of quite a bit that was wrong with both the theory and practice of communism.  He came to regard the Marxist and communist creed as dogmatic, and was horrified at how he had allowed this dogma to suppress his critical thought.  It was at this time, also, that he was investigating Freud’s and Adler’s theories of psychology, and came to similar conclusions about their dogmatism. See C.R., pp. 33-39 for another autobiographical account that treats Popper’s reaction to Freud and Adler.  In the same year, however, Popper learned of Einstein and his theory of relativity. He was most impressed with Einstein’s clear statement that if his theory should fail in certain specified empirical tests, he would regard it as untenable.

Here was an attitude utterly different from the dogmatic attitude of Marx, Freud, Adler, and even more so that of their followers. Einstein was looking for crucial experiments whose agreement with his predictions would by no means establish his theory; while a disagreement, as he was the first to stress, would show his theory to be untenable.

This, I felt, was the true scientific attitude. It was utterly different from the dogmatic attitude which constantly claimed to find “verifications” for its favorite theories.  Thus I arrived, by the end of 1919, at the conclusion that the scientific attitude was the critical attitude, which did not look for verifications but for crucial tests; tests which could refute the theory tested, though they could never establish it. [“Autobio.”, p. 29.]

In the next few years Popper developed his ideas about what separates or “demarcates” scientific theories from pseudoscientific theories.  [See ibid., pp. 31-33.]  What makes a theory scientific, he thought, is that it rules out or excludes the occurrence of some possible events; it predicts that some things will not happen.  Popper then concluded, “the more a theory forbids, the more it tells us.” [Ibid., p. 31. Italics omitted.] This is in contrast to pseudoscientific theories that seemed able to interpret any possible event as a “verification” of the theory.  Rather than simply dismissing dogmatic thought as “unscientific,” however, Popper concluded that it is “prescientific” and that it represents a necessary stage in the development of scientific thought.  Without dogmatic thought, critical thought would have nothing to criticize.

At roughly the same time (1922-1926) Popper was working on the psychology of learning, and his investigations led him to theorize that most, perhaps all, learning processes consist in the formulation of expectations (or theories) and the consequent modification of these expectations by the method of trial and error. [See ibid., pp. 34-41.] His investigations of learning in young children led him to reject the psychological theory of learning by induction (or repetition).  His research seemed to show that children have certain “inborn” needs for and expectations of structural invariants in their environment, and their learning (especially true of language acquisition) seemed to consist in repeated trials (attempting to meet their inborn expectations) and correction by the (critical) elimination of errors. This led Popper to theorize that learning, or the logic of discovery, does not take place by observing and then generalizing (inductive inference), but rather that observation is always guided by an aim, by problems needing resolution, by conjectures, by expectations.

All this led me to the view that conjecture or hypothesis must come before observation or perception: we have inborn expectations; we have latent inborn knowledge, in the form of latent expectations, to be activated by stimuli to which we react as a rule while engaged in active exploration. All learning is a modification (it maybe a refutation) of some prior knowledge and thus, in the last analysis, of some inborn knowledge.

Thus by 1926 Popper had developed several of the key ideas which he would use to interpret empirical scientific method and human knowledge, but at first he did not connect them.  It was not until after his Ph.D. examination in 1928 that he finally made the crucial connection in his ideas which has guided and dominated his interpretation ever since.  Since Popper describes this and summarizes all the points I shall discuss below, I will quote a lengthy passage from his “Autobiography.”

It was only after my Ph.D. examination that I put two and two together, and my earlier ideas fell into place.  I understood why the mistaken theory of science which had ruled since Bacon—that the natural sciences were the inductive sciences, and that induction was a process of establishing or justifying theories by repeated observations or experiments—was so deeply entrenched.  The reason was that scientists had to demarcate their activities from pseudoscience as well as from theology and metaphysics, and they had taken over from Bacon the inductive method as their criterion of demarcation. . . . But I had held in my hands for many years a better criterion of demarcation: testability or falsifiability.

Thus I could discard induction without getting into trouble over demarcation.  And I could apply my results concerning the method of trial and error in such a way as to replace the whole inductive methodology by a deductive one.  The falsification or refutation of theories through the falsification or refutation of their deductive consequences was, clearly, a deductive inference (modus tollens).  This view implied that scientific theories are either falsified or for ever remain hypotheses or conjectures.

Thus the whole problem of scientific method cleared itself up, and with it the problem of scientific progress.  Progress consisted in moving towards theories which tell us more and more—theories of ever greater content.  But the more a theory says the more it excludes or forbids, and the greater are the opportunities for falsifying it. So a theory with greater content is one which can be more severely tested.  This consideration led to a theory in which scientific progress turned out not to consist in the accumulation of observations but in the overthrow of less good theories and their replacement by better ones, in particular by theories of greater content.  Thus there was competition between theories—a kind of Darwinian struggle for survival.

Of course theories which we claim to be no more than conjectures or hypotheses need no justification (and least of all a justification by a nonexistent “method of induction,” of which nobody has ever given a sensible description). We can, however, sometimes give reasons for preferring one of the competing conjectures to the others, in the light of their critical discussion.  [Ibid., p. 62-63. ]

Thus by 1928 or 1929 the main ideas that Popper would use to develop his major interpretation of science and human knowledge in Logik der Forschung had already come together.  I will now turn to a more detailed consideration of this interpretation. 


The Problem and Criterion of Demarcation

Popper regards his solution to the problem of demarcation as the center of his philosophy and states that unless this idea is understood both in its simplicity and its complexity his philosophy will be misunderstood.  [“Replies to My Critics,” in Schilpp, ed., The Philosophy of Karl Popper, 2: 976, 979. (Hereafter cited as “Replies.”)]  The problem of demarcation, as we have see briefly above, has to do with what criterion is to be used in order to distinguish between science on the one hand and nonscience on the other.  It is important to recognize that this criterion does not distinguish between true and false scientific theories, but attempts rather to establish what can properly be called “science” (in the sense of empirical science) and what cannot.  [See ibid., p. 976.]  This allows Popper to place together in the category of “nonscience” such diverse forms of thought as logic, metaphysics, theology, psychoanalysis, astrology, and so forth, without the necessity of distinguishing between them.

The criterion of demarcation, obviously, must be derived from an understanding of what it is about science that makes it unique.  That is, this criterion presupposes an interpretation of science.  We can most easily understand Popper’s proposed criterion by recalling how impressed he was with Einstein’s statement that if his theory failed to meet certain specified empirical tests, he would regard it as untenable.  The view of science implicit in Popper’s criterion of demarcation is that science is bold theorizing or conjecturing, but conjecturing that states its consequences in such a way that the consequences may be tested and possibly refuted by the facts of experience.  Popper summarizes this view of science and his criterion of demarcation in this way.

There is a reality behind the world as it appears to us, possibly a many-layered reality, of which the appearances are the outermost layers.  What the great scientist does is boldly to guess, daringly to conjecture, what these inner realities are like.  This is akin to mythmaking. . . . The boldness can be gauged by the distance between the world of appearances and the conjectured reality, the explanatory hypothesis.

But there is another, a special kind of boldness—the boldness of predicting aspects of the world of appearance which so far have been overlooked but which it must possess if the conjectured reality is (more or less) right, if the explanatory hypotheses are (approxi-mately) true.  It is this more special kind of boldness which I usually have in mind when I speak of bold scientific conjectures.  It is the boldness of a conjecture which takes a real risk—the risk of being tested, and refuted; the risk of clashing with reality.

Thus my proposal was, and is, that it is this second boldness, together with the readiness to look out for tests and refutations, which distinguishes “empirical” science from nonscience, especially from prescientific myths and metaphysics.

Ibid., pp. 980-981.  In L.Sc.D., p. 27, Popper summarizes his view of science in this way: “A scientist, whether theorist or experimenter, puts forward statements, or systems of statements, and tests them step by step.  In the field of the empirical sciences, more particularly, he constructs hypotheses, or systems of theories, and tests them against experience by observation and experiment.”

As we shall see when we come to discuss the detailed interpretation of science and empirical scientific method Popper develops from this position, there are a number of qualifications which must be introduced for a full understanding of his criterion of demarcation.  First, however, I must discuss the more famous formulation of Popper’s criterion and then, in the following subsection, how he judges that it solves the closely related problem of induction.

Popper’s criterion of demarcation is more familiarly known as falsifiability, though it can also be called testability.  The simple statement of this criterion is as follows.

. . . I shall certainly admit a system as empirical or scientific only if it is capable of being tested by experience. . . . not the verifiability but the falsifiability of a system is to be taken as a criterion of demarcation.  In other words: . . . it must be possible for an empirical scientific system to be refuted by experience.

L.Sc.D., pp. 40-41.  It should be noted that it is incorrect to speak of Popper’s criterion as “falsification”; he does not require that a “scientific” or “empirical” statement actually be tested, only that it is capable of being tested.  See ibid., pp. 86-87.

Since Popper’s criterion has often been confused with the logical positivist criterion of meaningfulness which he in fact criticized from the beginning, it would be good to consider his criticisms of the logical positivist interpretation before we discuss several possible objections to his criterion.  This contrast with the logical positivist interpretation will also make the meaning of Popper’s criterion more clear.

Popper originally developed his ideas without knowledge of the logical positivist interpretation of science and its criterion of meaningfulness, but when he became acquainted with the ideas and the men of the Vienna Circle, he immediately saw how his ideas related to the problems they were addressing, and he was convinced that his ideas were better than theirs.

Popper discusses this in C.R., pp. 39-41; L.Sc.D., p. 40 note *3; “Autobio.,” pp. 63-71; and at some length in “Replies,” pp. 963-976.  A non-biographical or theoretical criticism of logical positivism is argued in L.Sc.D., pp. 34-39, 49-53, and passim; and in C.R., pp. 253-292.

As Popper saw, the logical positivists of the Vienna Circle were trying to solve the problem of demarcation by providing a criterion for distinguishing between science and nonscience.  Yet their method of approach, Popper argued, involved them in two major errors.  The first of these errors was their anti-metaphysical programme.  In attempting to lay the coup de grace to metaphysics, the logical positivists chose meaningfulness as the criterion of demarcation between science and metaphysics.  According to this criterion, the only meaningful statements are empirical scientific ones and all others (most especially metaphysical statements) are “meaningless.”  They were, in short, attempting “to prove that metaphysics by its very nature is nothing but nonsensical twaddle—’sophistry and illusion,’ as Hume says, which we should ‘commit to the flames.” [L.Sc.D., p. 35.]  This choice of criterion was bound to lead to trouble, in Popper’s estimation, since the history of science repeatedly illustrates that “metaphysical ideas are often the forerunners of scientific ones.

“Autobio.,” p. 63.  Popper has continually argued that metaphysics can make contributions to science and knowledge.  I will return to this point below.

It seemed inconsistent and unreasonable to Popper to label ideas meaningless at one stage of their development, but meaningful at a later stage.  It addition, it seemed obvious to him that metaphysical ideas were meaningful, but that whether or not they were scientific was a separate question.

The second major error of the logical positivists was this.  The criterion of meaningfulness merely shifted the problem, and then another criterion to distinguish between meaningfulness and meaninglessness was necessary.  The members of the Vienna Circle recognized this, and chose verifiability as their criterion of meaningfulness. Verifiability, as Popper says, “was taken as being the same as provability by observation statements. [Ibid.] This, however, was really just another way of restating the classic idea of induction.  Popper’s logical analysis of science (and his study of Hume) had already convinced him that there really was no such thing as inductive inference in empirical science, and that inductive inference was logically impossible:

. . . inference to theories, from singular statements which are “verified by experience” (whatever that may mean), is logically inadmissable.  Theories are, therefore, never empirically verifiable.  If we wish to avoid the positivist’s mistake of eliminating, by our criterion of demarcation, the theoretical systems of natural science, then we must choose a criterion which allows us to admit to the domain of empirical science even statements which cannot be verified.  [L.Sc.D., p. 40.]

Popper saw, and argued at length

[In L.Sc.D.and in numerous papers and articles.]

that his criterion of falsifiability avoided the pitfalls resulting from the use of meaningfulness and verifiability as the dual criteria of demarcation.

Because Popper has often been misunderstood as proposing falsifiability instead of verifiability as the criterion of meaningfulness, it must be emphasized that he disagrees entirely with the use of meaningfulness as a criterion. [Thesis, p. 132 note 2 for references.] He is careful to comment on numerous occasions that non-scientific statements are meaningful, and he finds any attempt to distinguish between science and nonscience on the basis of meaningfulness to be fruitless and to result in numerous difficulties and absurdities.  When he prepared the English edition of Logik der Forschung Popper included this note:

Note that I suggest falsifiability as a criterion of demarcation, but not of meaning.  Falsifiability separates two kinds of perfectly meaningful statements: the falsifiable and the non-falsifiable.  It draws a line inside meaningful language, not around it.  [L.Sc.D., p. 40 note *3.]

This should make it clear that Popper is in complete disagreement with the logical positivist interpretation of science and metaphysics.

Before moving to a consideration of Popper’s analysis and solution of the problem of induction, I will briefly discuss three possible objections to his criterion of demarcation.

Popper raises and answers these objections in ibid. , pp. 41-42.

Popper’s response to these objections clarifies the nature of his proposal.  The first objection is that if science is supposed to give us positive information about the world, how can it be characterized by a negative requirement, such as refutability?  Popper responds that this objection carries little weight, for he is able to argue that “the amount of positive information about the world which is conveyed by a scientific statement is the greater the more likely it is to clash, because of its logical character, with possible singular statements.” [Ibid., p. 41.  The detailed argumentation is on pp. 112-145.]  That is, the more it risks falsifiability, the greater is its actual informational content.

A second possible objection is that the criterion of falsifiability seems liable to the same sorts of objections raised against verifiability.  Popper argues that this is not the case, however, because his proposal “is based upon an asymmetry between verifiability and falsifiability; an asymmetry which results from the logical form of universal statements.” [Ibid.] A universal statement cannot be derived logically from singular statements, but it can be contradicted by singular statements.

Consequently it is possible by means of purely deductive inferences (with the help of the modus tollens of classical logic) to argue from the truth of singular statements to the falsity of universal statements.  Such an argument to the falsity of universal statements is the only strictly deductive kind of inference that proceeds, as it were, in the “inductive direction”; that is, from singular to universal statements. [Ibid.]

The third objection is that even if this asymmetry is admitted, it is impossible ever to falsify completely any theoretical system.  It is always possible to find some way of avoiding falsification, and this might seem to make the logical value of Popper’s criterion dubious at best.  Popper admits the truth of this objection, but argues that this does not destroy his proposal, because of the way he will characterize empirical method.

. . . empirical method shall be characterized as a method that excludes precisely those ways of evading falsification which, as my imaginary critic rightly insists, are logically possible.  According to my proposal, what characterizes the empirical method is its manner of exposing to falsification, in every conceivable way, the system to be tested.  Its aim is not to save the lives of untenable systems but, on the contrary, to select the one which is by comparison the fittest, by exposing them all to the fiercest struggle for survival.  [Ibid., p. 43.]

Thus the criterion of falsifiability ultimately is able to demarcate science from nonscience, in Popper’s view, because it can characterize empirical method as a radical commitment to testing.  Moreover, this makes it possible to distinguish between what is actually scientific and what is not.  It makes it possible, for example, to distinguish between a scientist’s scientific opinions and his or her nonscientific ones (including any dogmatic clinging to a theory that is no longer tenable).  The importance of this characterization of empirical method will become more evident in later discussions.


The Two Problems of Induction

Popper is of the opinion that his criterion of falsifiability and the understanding of human knowledge connected with it presents a solution to the age-old problem of induction, and he feels that this is the most widely neglected of his philosophical accomplishments.

See “Conjectural Knowledge: My Solution of the Problem of Induction,” Chapter 1, Ob. Kn., pp. 1-31.  See also Ob. Kn., pp. 85-105; “Autobio.,” pp. 112-118; and “Replies,” pp. 1013-1027.  These are the most extended analyses of the problem of induction, though Popper frequently discusses it briefly in all his books.

In his lengthier discussions of induction, Popper prefers to present the problem against the background of what he calls the “common-sense theory of induction.

See “Replies,” pp. 1016-1018; and Ob. Kn., p. 3.  I might also note that Popper draws an interesting distinction between “common-sense realism” and “the common-sense theory of knowledge.”  While he regards the former as true and as an idea of great importance, he argues that the latter (the source of the common-sense theory of induction) is thoroughly mistaken.  See especially Ob. Kn., pp. 32-84 and 341-361.

This is the view that all knowledge is the result of past observations, and that all expectations regarding the future occurrence of repeating phenomena (e.g., that the sun will rise tomorrow) are also due to past observations.  Popper argues that Hume rightly challenged this common sense view of induction, and showed by his analysis that

induction by repetition was logically untenable—that rationally, or logically, no amount of observed instances can have the slightest bearing upon unobserved instances. This is Hume’s negative solution of the problem of induction, a solution which I fully endorse.

But Hume held, at the same time, that although induction was rationally invalid, it was a psychological fact, and that we all relied on it. [“Replies,” p. 1018.]

There are, then, two separate problems of induction: the logical problem and the psychological problem.  The logical problem can be stated in this way: “Are we rationally justified in reasoning from repeated instances of which we have had experience to instances of which we have had no experience?  [Ibid.  Italics omitted.]  Hume argued that we are not rationally justified in so reasoning, no matter how many repetitions there are.  He further argued that the logical conclusion is the same even if we ask only for probability instead of for certain knowledge.  With this analysis Popper is in complete agreement.  The psychological problem of induction can be stated in this way: “How is it that nevertheless all reasonable people expect and believe that instances of which they have “had no experience will conform to those of which they have had experience?”  [Ibid.  Italics omitted.]  Or, to put it differently, why is it that we have such strong expectations to which we hold with such confidence?  Hume’s answer to this psychological problem was framed in terms of “custom” or “habit”: because of the power of association we are conditioned by repetition into a habitual or customary expectation that future occurrences will conform to those we have experienced in the past.  Popper holds that this analysis is mistaken.  In order to explain Popper’s solution of the psychological problem of induction, however, I must first discuss how he reformulates and solves the logical problem.

Popper’s main motivation for reframing the logical problem of induction is to show that irrationalism is not the necessary outcome of Hume’s logical analysis.  Rather, it was the combination of Hume’s correct logical and incorrect psychological solutions that led to an unintended irrationalism.

On this interesting analysis, which for reasons of brevity I cannot pursue here, see ibid., pp. 1019-1020; and Ob. Kn., pp. 4-5, 86-88, 93-95, and 99-101.

Popper reformulates the logical problem of induction by slightly generalizing and extending its wording: “Are we rationally justified in reasoning from instances or from counterinstances of which we have had experience to the truth or falsity of the corresponding laws, or to instances of which we have had no experience?  [“Replies,” p. 1020.  Italics omitted.  See also the slightly different formulation, Ob. Kn., p. 7.] Hume’s answer still holds: we are not justified in reasoning from an instance or any number of instances to the truth of the corresponding law. To this Popper adds an “equally negative” result:

we are justified in reasoning from a counterinstance to the falsity of the corresponding universal law (that is, of any law of which it is a counterinstance). . . . Induction is logically invalid; but refutation or falsification is a logically valid way of arguing from a single counterinstance to—or, rather against—the corresponding law. . . . there are logically valid negative arguments leading in the inductive direction: a counterinstance may disprove a law. [“Replies,” pp. 1020, 1021.]

The importance of this additional “equally negative” result is that it allows the development of “a positive theory of how, by purely rational arguments, we can prefer some competing conjectures to others’. [Ibid., p. 1021. See also Ob. Kn., pp. 7-8.] Popper’s theory of preference can be summarized quite simply.  Although Hume’s solution of the problem of induction implies that all theories or “laws” must always be regarded as hypothetical or conjectural, this does not mean that we have absolutely no basis for rational discussion.  Rather, the logically valid negative argument from counter-instances against the corresponding law (Popper’s contribution) provides the basis for rational preference.  Our theories and “laws” are nothing but conjectures or guesses, but they aim at the truth and, if they guess boldly, that is, if they contain a high degree of informational content and take the risk of being refuted, then we can subject them all to rigorous testing and rationally prefer those theories “whose falsity has not been established. [Ob. Kn., p. 8.  See pp. 13-23 for the detailed argumentation.] This does not mean that we ever possess the truth; but our theories do aim at the truth, and if we constantly subject them to the most stringent tests and prefer those whose falsity has not yet been established, then we are acting according to rational criteria.

This is the basis of Popper’s analysis of the “pragmatic problem of induction.” See ibid., pp. 21-23 and “Replies,” pp. 1024-1027.

This leaves us with Popper’s solution of the psychological problem of induction yet to be discussed.  Popper rejects Hume’s solution to this problem because a logical analysis reveals that Hume’s solution (conditioned expectation resulting from association of past repetitions) is actually inductive.  Popper argues that “repetition presupposes similarity, and similarity presupposes a point of view—a theory, or an expectation.” [Ob. Kn., p. 24.] Recall here Popper’s early conclusion that we have “inborn” expectations which we test against our experience from the moment of our births. What Popper is arguing is that in order to identify any occurrence as a “repetition,” we have to identify it as being similar to some other occurrence, and in order to identify it as similar we must have a (prior) expectation that there are similar occurrences. Hence the repetition theory that Hume proposes is untenable because, in fact, expectations come before any observations, and so there can be no inductive learning or conditioning such as Hume proposes.

Popper proceeds to solve the psychological problem of induction by invoking what he calls “the principle of transference from logic to psychology.” [“Replies,” p. 1024.  See also Ob. Kn., pp. 6, 23-27, 67-68 and note 30.] This principle is: “what is true in logic is true in psychology.”

Ob. Kn., p. 6. In “Replies,” p. 1024, Popper qualifies this by adding a phrase: “What is true in logic must, by and large, be true in psychology.” See also the qualification of this statement in Ob. Kn., p. 24.

Popper is arguing, in short, that Hume’s solution to the psychological problem is mistaken because it violates this principle in assuming that induction is a psychological fact even though it cannot be a logical fact.  Likewise, Popper holds, the unintended irrationalism following from Hume’s solution must be mistaken.

It will be clear that my principle of transference guarantees the elimination of Hume’s irrationalism: if I can answer his main problem of induction, including [the psychological problem], without violating the principle of transference, then there can be no clash between logic and psychology, and therefore no conclusion that our understanding is irrational. [Ob. Kn., p. 6.]

Following his principle of transference, Popper solves the psychological problem of induction by transferring his theory of preference from the logical world of ideas to the psychological world of learning.

As I shall discuss below, Popper draws a distinction between the world of physical objects, the world of subjective experience, and the world of objective knowledge.  He labels these “world 1,” “world 2,” and “world 3” respectively.  He does not consider his proposed solution to the psychological problem of induction to belong to, his objective (“world 3”) theory of knowledge, but holds that this objective theory of knowledge can shed light on the “world 2” psychological problem.  See Ob. Kn., pp. 25-26.

That theory of preference provided a method of preferring some competing conjectures to others by subjecting all conjectures to rigorous tests and preferring those conjectures that remain unfalsified in the face of all tests.  Popper asserts that the same rational method can be used in the psychological situation.  Why is it that we have such strong “beliefs” or expectations regarding the future occurrence of events?  The answer Popper proposes is that we cannot avoid such expectations: these beliefs or expectations “are partly inborn, partly modifications of inborn beliefs resulting from the method of trial and error-elimination.”  [Ob . Kn., P . 27.  For the argumentation in support of this conclusion see pp. 23-26.] But since the method of trial and error-elimination corresponds exactly with the logical problem, this means that our holding of such strong expectations regarding the future is not the irrational result or mere conditioning by repetition.  Rather, so long as we do subject our “inborn” expectations to testing and modify them when we detect errors, we are operating according to a “perfectly” rational method.

See ibid., pp. 24, 27.  For Popper’s analysis of how Kant contributed to the solution of this problem and of his own difference from Kant, see ibid., pp. 23-24, 91-93.

In this way Popper regards the psychological problem of induction as solved.

Before proceeding to the theory of the method of science Popper develops from his analysis of the problems of induction and demarcation, perhaps a few words are in order concerning what positions Popper is led to by these discussions.  One major position Popper adopts as a result of his analysis is that all attempts to justify our theories must be given up.  By this he means that there can be no justification for the claim that a theory is true.  Since there is no induction—no logically valid inductive inference—there can be no verification.  Hence all theories must always be regarded as hypotheses, and all may be refuted.

See, among many possible references, ibid., p. 29.  This conclusion, though widely accepted today, was not so when Popper it, and he regards it as one of his major contributions to philosophy.

This does not mean, however, that we must abandon the search for truth.

. . . our critical discussions of theories are dominated by the idea of finding a true (and powerful) explanatory theory; and we do justify our preferences by an appeal to the truth: truth plays the role of a regulative idea. We test for truth, by eliminating falsehood. That we cannot give a justification—or sufficient reasons—for our guesses does not mean that we may not have guessed the truth; some of our hypotheses may well be true. [Ibid., pp. 29-30.]

Thus, though we cannot justify theories, we can justify our preferences among theories, and we do so by means of the heuristic and regulative idea of truth.  The important conclusion from these positions is that while we may make contact with the truth, we can never be sure that we know the truth.  All our knowledge must always remain hypothetical and tentative.  I will discuss this theory of knowledge in more detail below, but first I will give more detailed consideration to Popper’s analysis of empirical scientific method.


The Method of Empirical Science

Popper’s solution of the problem of induction and his criterion of falsifiability lead to an analysis of empirical scientific method.  While for reasons of brevity I cannot enter into a detailed discussion of Popper’s analysis, I can in a reasonably brief compass describe the basic elements of his interpretation.

Popper offers the following summary of the theory of empirical scientific method his analysis leads to:

This solution of the problem of induction gives rise to a new theory of the method of science, to an analysis of the critical method, the method of trial and error: the method of proposing bold hypotheses, and exposing them to the severest criticism, in order to detect where we have erred.

From the point of view of this methodology, we start our investigation with problems.  We always find ourselves in a certain problem situation; and we choose a problem which we hope we may be able to solve.  The solution, always tentative, consists in a theory, a hypothesis, a conjecture.  The various competing theories are compared and critically discussed, in order to detect their shortcomings; and the always changing, always inconclusive results of the critical discussion constitute what may be called “the science of the day.”

Thus there is no induction: we never argue from facts to theories, by way of refutation or “falsification.” [“Autiobio.,” p. 68.  See also the summary offered in C.R., p. 313.]

As is already clear from what we have seen of Popper’s analysis, one major feature of his interpretation is that scientific method is completely deductive in character; it consists in methods of (deductively) testing the consequences of theories or hypotheses. [See L.Sc.D., pp. 32-33.] The first questions likely to be raised by someone familiar with the more traditional characterizations of science are, what of the role of observation; and, if there is no induction, then how do theories and hypotheses come to be formulated?  Observation (and its associated operation of description) are reinterpreted by Popper as ways of checking or testing hypotheses.  This interpretation of the role of observation is closely related to Popper’s argument that all observations are preceded and directed or guided by theory, that all observations are in fact “theory-laden.”

See, among numerous possible references, L.Sc.D., pp. 94-95, 106, 423-424; C.R., pp. 23, 46-48, 55, 127-129; Ob. Kn., pp. 71-72, 145-146, 258-259, 342-347.

The command to observe, Popper often notes, cannot be obeyed until we are told what we are to observe, what we are to look for.  This is an example of how observation in fact always presupposes a particular point of view.

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 its turn presupposes interests, points of view, and problems. . . . It is quite true that any particular hypothesis we choose will have been preceded by observations—the observations, for example, which it is designed to explain.  But these observations, in their turn, presupposed the adoption of a frame of reference: a frame of expectations: a frame of theories.  If they were significant, if they created a need for explanation and thus gave rise to the invention of a hypothesis, it was because they could not be explained within the old theoretical framework, the old horizon of expectations.  There is no danger here of an infinite regress.  Going back to more and more primitive theories and myths we shall in the end find unconscious, inborn expectations.

C.R., pp. 46, 47.  Note in this passage Popper’s appeal to the notion of “inborn” expectations, which he also used to resolve the psychological problem of induction, as the basis for his interpretation of the role of observation.

Thus observation, which in the inductivist inter-pretation of empirical scientific method is the starting point, is in Popper’s deductivist interpretation shifted to the end stage of the application of scientific method where it plays the crucial role of being the actual means of testing theories for errors.  The starting point for empirical scientific method in Popper’s interpretation is a problem (or a p~oblem situation) which has occurred because of the clash of the investigator’s expectations (hypotheses) with his or her subsequent experience (observations). [See Ob. Kn., pp. 257-265, 287-289; C.R., p. 222; “Autobio.,” pp. 105-106.]

With regard to the question of how theories come to be formulated, Popper dismisses this question as one of great interest for psychology but not for an objective theory of knowledge.

. . . the work of the scientist consists in putting forward and testing theories.

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. The question how it happens that a new idea occurs to a man—whether it is a musical theme, a dramatic conflict, or a scientific theory—may be of great interest to empirical psychology; but it is irrelevant to the logical analysis of scientific knowledge. [L.Sc.D., p. 31.]

While Popper is willing to allow for important roles for imagination and intuition in the formation and even the testing of theories,

See, for example, C.R., p. 28: “Neither observations nor reason are authorities.  Intellectual intuition and imagination are most important, but they are not reliable: they may show us things very clearly, and yet they may mislead us.  They are indispensable as the main sources of our theories; but most of our theories are false anyway.  The most important function of observation and reasoning, and even of intuition and imagination, is to help us in the critical examination of those bold conjectures which are the means by which we probe into the unknown.”

he simply does not think that there is any place for an “objective” analysis of these faculties in a theory of knowledge, and so he does not discuss how theories come to be formulated.  His analysis begins with a discussion of problems and then moves to a discussion of how the guesses, conjectures, hypotheses, and theories we propose as solutions of problems are tested.

With regard to the character of hypotheses or theories, Popper’s interpretation ought to be clear enough from what I have already said.  Hypotheses and theories are tentative conjectures, guesses, which scientists construct in the hope of solving the problems they are investigating.  It is clear that in his view hypotheses, when they are initially proposed and forever after, have the logical status of conjectures or guesses.  This is another major result of Popper’s solution to the problem of induction and his logical critique of the criterion of verifiability. Some guesses, however, are better than others.  The bulk of Popper’s analysis is devoted to a close study of how empirical science determines whether its guesses are good or not; in other words, the bulk of his analysis concerns the procedures of testing.

It is not necessary to enter into a discussion of Popper’s detailed analysis of the scientific methods of testing.  He develops at some length an analysis of the logical conditions necessary for the deduction of predictions from theories; he analyzes the logical status of the “basic statements” or observations actually used to test a theory’s predictions; he develops a theory for comparing various scientific hypotheses in terms of their degree of testability (which is identical with their degree of empirical or informational content); and he expands his theory of preference, especially by formulating his theories of corroboration and verisimilitude.

With the exception of the theory of verisimilitude, these are all discussed in L.Sc.D. as well as later writings.  For the notion of verisimilitude see especially Ob. Kn., pp. 44-60.

While all of these developments are interesting and have provoked widespread comment in the philosophy of science, I will not enter into a discussion of them, given my purpose, since they are all subsumed under Popper’s general interpretation of empirical scientific method; it is with this general interpretation that I am concerned.

One conclusion of Popper’s analysis of testing I ought to mention in passing is that what is tested is a system of statements, and that if falsification does occur, it is falsification of the whole theoretical system.  It may be extremely difficult and even impossible to determine which particular statement or subsystem of statements is responsible for the error, that is, which has actually been exposed to the falsifying experimental test.  To attribute responsibility for error to a particular statement or subsystem of statements is, Popper insists, conjectural. (See L.Sc.D., pp. 75-77; “Replies,” p. 982.)  This analysis has an important result for Popper’s epistemology: it means that if a falsification does occur, the falsification does not give us knowledge of exactly what the error is, only knowledge that there is an error somewhere in the system.

We have already seen Popper’s basic interpretation of empirical scientific method: it is a critical, method, one that subjects all proposed theories to the most stringent of tests and one that by its radical commitment to testing systematically prohibits or excludes all procedures by which a theory might be “immunized” against falsification or refutation.  The principal purpose of the detailed developments I alluded to in the previous paragraph is to establish the ways in which empirical method prohibits immunizing tactics and manifests its commitment to critical testing of hypothetical knowledge.  Thus Popper continually refers to the method of science as critical method, the method of boldly proposing hypotheses and criticizing them by trial and error-elimination.  However, as we saw briefly above [See Thesis, p. 126.] and shall discuss at more length below, Popper argues that this is the method of all rational discussion.  What characterizes empirical scientific method is that is prohibits “immunization” of hypotheses against falsification by its commitment to empirical testing.  This, in turn, means that empirical scientific method, in contrast to rational discussion in general, demands the prediction of empirical states of affairs which are excluded by the hypotheses.  It demands that the implications of the hypotheses be tested against the facts of experience in a “crucial experiment” specifically designed to try to falsify the hypotheses.  In short, though all critical discussion might strive to eliminate “immunizing” tactics, empirical science alone possesses the means of systematically assuring that these tactics will be avoided, and these means are the intersubjective testing of hypotheses by experimentation and observation.

Before moving to a discussion of the character of scientific knowledge and its growth, we might ask whether Popper’s interpretation of empirical scientific method is meant to be a description of how scientists actually proceed, or whether it is a theoretical model of what scientific method ought to be like. This question has in fact become a matter of some debate in the discussion between Popper, his students, and Thomas Kuhn.

See Thomas Kuhn, “Logic of Discovery or Psychology of Research?,” in Schilpp, ed., The Philosophy of Karl Popper, 2: 798-819, and Popper’s response, “Replies,” 2: 1144-1148.  Kuhn’s article also appears in Imre Lakatos and Alan Musgrave, eds., Criticism and the Growth of Knowledge (Cambridge: Cambridge University Press, 1970), pp. 1-23, with another response from Popper, “Normal Science and Its Dangers,” pp. 51-58, and Kuhn’s reply, “Reflections on My Critics,” pp. 231-278. (Hereafter cited as Criticism.)  See also John W. N. Watkins, “Against ‘Normal Science’,” in Lakatos & Musgrave, eds., Criticism, pp. 25-37; and J. O. Wisdom, “The Nature of ‘Normal’ Science,” in Schilpp, ed., The Philosophy of Karl Popper, 2: 820-842, and Popper’s response to Wisdom, “Replies,” 2: 1148-1153.

Kuhn argues that Popper’s interpretation of scientific method takes characteristics of what, Kuhn calls “extraordinary” or “revolutionary” science and applies them to the entire scientific enterprise, thus overlooking the actual procedures and characteristics of what Kuhn calls “normal” science. While he grants that Popper’s description of empirical scientific method does apply in what Kuhn terms “crisis” situations (situations in which an old, accepted theory has irretrievably broken down, situations that give rise to “extraordinary” or “revolutionary” science), he denies that Popper’s interpretation is a description of how scientists normally proceed.

The following statements of Kuhn will give a sense of his criticism of Popper’s interpretation.

“I suggest then that Sir Karl has characterized the entire scientific enterprise in terms that apply only to its occasional revolutionary parts. . . . neither science nor the development of knowledge is likely to be understood if research is viewed exclusively through the revolutions it occasionally produces.  For example, though testing of basic commitments occurs only in extraordinary science, it is normal science that discloses both the points to test and the manner of testing. . . . a careful look at the scientific enterprise suggests that it is normal science, in which Sir Karl’s sort of testing does not occur, rather than extraordinary science which most nearly distinguishes science from other enterprises.  If a demarcation criterion exists (we must not, I think, seek a sharp or decisive one), it may lie just in that part of science which Sir Karl ignores.”  

And later:

“The criteria with which scientists determine the validity of an articulation or an application of existing theory are not by themselves sufficient to determine the choice between competing theories.  Sir Karl has erred by transferring selected characteristics of everyday research [e.g., logic] to the occasional revolutionary episodes in which scientific advance is most obvious and by thereafter ignoring the everyday enterprise entirely.  In particular, he has sought to resolve the problem of theory choice during revolutions by logical criteria that are applicable in full only when a theory can already be presupposed.”  Kuhn, “Logic,” in Schlipp, ed., The Philosophy of Karl Popper, 2: 802, 813 (in Lakatos & Musgrave, eds., Criticism, pp. 6, 19).  

Kuhn further argues (quoting C.R., p. 51) that Popper’s programme actually contains—though Popper does not recognize them as such—”social-psychological imperatives” of the sort Kuhn thinks might help to explain scientific choices made on bases other than logic and experiment alone.  See “Logic,” 2: 813-816 (in Lakatos & Musgrave, eds., Criticism, pp. 19-22).  See also Kuhn’s “Reflections on My Critics,” in Lakatos & Musgrave, eds., Criticism, pp. 231-278.

Popper, on the other hand, admits the actuality of what Kuhn calls “normal” science, but regards it as a relatively recent phenomenon and judges it to be a very real danger to science and the growth of knowledge.  Popper is convinced that he has described scientific method as it ought to be practiced, and is of the opinion that a major disaster would occur should a sociological criterion of science (such as Kuhn proposes) ever replace a rational criterion (namely, Popper’s criterion of demarcation: falsifiability).

See Popper, “Normal Science and Its Dangers,” in Lakatos & Musgrave, eds., Criticism, pp. 51-58, and “Replies,” 2: 1144-1148, both directed against Kuhn; and compare with another statement (“Replies,” p. 1036): “I am inclined to say that we should attempt to find out what [scientists] ‘ought’ to do.  This ‘ought’ is . . . the ‘ought’ of a hypothetical imperative.  The question is: ‘How should we proceed if we wish to contribute to the growth of scientific knowledge?’.  And the answer is:  ‘You cannot do better than proceed by the critical method of trial (conjecture) and the elimination of error, by trying to test, or refute, your conjectures.’  The argument supporting this reply belongs to situational logic.  I do not think that we should turn to the (sociological) question of what scientists actually do or say, except perhaps to refute certain competing answers.”  It is on this position that strong currents in the contemporary philosophy of science are moving away from Popper’s analysis, but also away from Kuhn’s.  See Frederick Suppe, “Afterword,” in Suppe, ed., The Structure of Scientific Theories, pp. 633-728, especially pp. 643-649 on contemporary criticisms of Kuhn’s “sociological” interpretation as extreme, and pp. 682-704 on the work of Dudley Shapere, who is critical of the positions of both Popper and Kuhn.

I cannot hope to resolve this controversy here, nor even to enter into the details of the discussion. One of my purposes in alluding to it, however, is to illustrate that within the community of philosophers of science there are fundamental differences of opinion on the nature of scientific inquiry and its basic method.  While Popper is convinced that he is describing scientific method at its best, others of his peers judge that he is ignoring important aspects of how science is actually conducted.  Moreover, this disagreement over what the actuality of scientific method is does not appear to be amenable to any final resolution.  While all solutions thus far proposed have been found wanting in some respect, arriving at an adequate analysis of scientific method remains an open question in the ongoing work of the philosophy of science community.

A number of years ago, Langdon Gilkey noted that the interpretation of scientific inquiry is actually an open question which has provoked a pluralism of interpretations in the philosophy of science. .” . . when a theologian becomes discouraged by the inability of theology to give a reasoned defense or even a rationally articulated explication of the fundamental terms of religious faith, it is some relief to find that philosophers of science encounter the same inability, the same confusion, and the same disagreements when they seek to understand precisely what it is that is going on in scientific inquiry.”  Religion and the Scientific Future (New York: Harper & Row, 1970), p. 42.  The developments in the philosophy of science in the succeeding decade have only confirmed Gilkey’s observation.


The Nature and Growth of Objective Knowledge

The topic I must now consider is the nature of the knowledge arrived at by science and other forms of thought.  Throughout his writings Popper characterizes all human knowledge as hypothetical, but he also speaks of some knowledge as objective. Since we have already seen in some detail why Popper regards all knowledge as inherently hypothetical, in this subsection I will restrict my attention to what Popper means by “objective knowledge.”  The term “objective knowledge” carries several related meanings in Popper’s thought.  Its initial meaning is the one he gives it in discussing scientific objectivity: objective knowledge is knowledge arrived at by faithfulness to the critical method and presented in a form that remains open to the application of critical method.  In The Logic of Scientific Discovery Popper distinguishes between “our subjective experiences or our feelings of conviction” and “the objective logical relations” within scientific statements and between systems of such statements.  Objectivity concerns these objective relations, not subjective feelings or expressions.  Thus Popper says that “the objectivity of scientific statements lies in the fact that they can be inter-subjectively tested.” [L.Sc.D., p. 44.]  By “objective knowledge,” then, Popper does not mean knowledge that is true or certain; rather, he means hypotheses, theories, conjectures, and universal statements formulated in “public” language and open to critical analysis.  It ought to be noted that this definition of objectivity does not claim that only scientific statements are objective; it does not exclude philosophy, metaphysics, and so forth, from objective discourse.  Just as Popper insists that the criterion of falsifiability does not draw a line around meaningful discourse but within it, so his definition of scientific objectivity does riot draw a line around objective discourse but within it.  He generalizes the definition of objectivity to mean “inter-subjective criticism,” or discourse that is open to “mutual rational control by critical discussion.” [Ibid., p. 44 note *1, and further references there.] In this way he can argue that all human statements, when subject to this general method of critical discussion, can be considered objective.  What distinguishes scientific objectivity is the more narrow definition that scientific statements can be inter-subjectively tested (i.e., they are able to be falsified).  In either the special case of science or the more general case of rational discussion, the basic meaning of “objective knowledge” is the same: the theories, hypotheses, and conjectures we formulate in public language and which we hold open to critical analysis (or inter-subjective criticism).

Popper later developed this position into a significant part of his philosophy. [See especially “Epistemology Without a Knowing Subject,” and “On the Theory of the Objective Mind,” both in Ob. Kn., pp. 106-152; 153-190 respectively.] He argues that epistemology as well as common sense has overlooked objective knowledge and “mistakenly took it for granted that there was only one kind of knowledge—knowledge possessed by some knowing subject. [Ob. Kn. p. 73] Popper, in contrast, distinguishes between “subjective knowledge,” which he defines as consisting of “the dispositions of organisms,” and “objective knowledge,” which he defines as consisting of “the logical content of our theories, conjectures, [and] guesses.” [Ibid.] He then asserts that on the basis of this distinction we may speak of three “worlds”:

first, the world of physical objects or of physical states; secondly, the world of states of consciousness, or of mental states, or perhaps of behavioural dispositions to act; and thirdly, the world of objective contents of thought, especially of scientific and poetic thoughts and works of art.

Ob. Kn., p. 106.  See also ibid., pp. 73-74.  In several essays Popper refers to these as the “first,” “second,” and “third” worlds, but he later changes the terminology to “world 1,” “world 2,” and “world 3.”  See ibid., p. 31 and “Autobio.,” pp. 143-149 and notes 7a and 293 on pp. 157 and 180 respectively.

Popper calls these “world 1,” “world 2,” and “world 3” respectively, and includes as some of the more important “inmates” of “world 3” theoretical systems, problems, problem situations, critical arguments, the state of a discussion or the state of a critical argument, and the contents of books, journals, and libraries.  He wants to argue against the position that all of these entities are essentially (perhaps merely)

symbolic or linguistic expressions of subjective mental states, or perhaps of behavioural dispositions to act; further, that these entities are means of communication—that is to say, symbolic or linguistic means to evoke in others similar mental states or behavioural dispositions to act. [See Ob. Kn., p. 107.]

Against this, Popper argues that “world 3” entities have an independent existence of their own, “more or less” independent of “world 2.”  The major criticism he has of most epistemologies is that in attempting to reduce the “world 3” entities to mere expressions or communications of “world 2” states of consciousness, they miss precisely that which makes objective knowledge objective, and so undercut that which makes it possible to formulate criticism.  The concentration on the “world 2” states of consciousness undercuts the ground for the application of the critical method of rational discussion.

See ibid., p. 31: .” . . only a formulated theory (in contradistinction to a believed theory) can be objective, and . . . it is this formulation or objectivity that makes criticism possible; [this led me] to my theory of a ‘third world’ . . .”See ibid., pp. 108-150, 153-168 for his arguments against classic epistemologies.

Criticism, Popper appears to argue, can have a firm basis only if we can show that the objective knowledge of “world 3” is relatively independent of subjective states of consciousness.

Popper’s argument on this issue is a development of the positions he initially presented in The Logic of Scientific Discovery.  In a later work he presents the argument in the form of three main theses, all of which are concerned with a proper understanding of “objective knowledge.”

My first thesis involves the existence of two different senses of knowledge or of thought: (1) knowledge or thought in the subjective sense, consisting of a state of mind or of consciousness or a disposition to behave or to react, and (2) knowledge or thought in an objective sense, consisting of problems, theories, and arguments as such.  Knowledge in this objective sense is totally independent of anybody’s claim to know; it is also independent of anybody’s belief, or disposition to assent; or to assert, or to act.  Knowledge in the objective sense is knowledge without a knower: it is knowledge without a knowing subject. [Ob. Kn., pp. 108-109; see also pp. 115-119 on the objectivity and autonomy of “world 3.”]

Popper’s second thesis is that epistemology, which he understands to be “the theory of scientific knowledge,” [Ibid., p. 108] can be properly developed only if it restricts itself to the study of objective knowledge, that is; the “largely autonomous” “world 3,” instead of centering its attention on “world 2” subjective states of consciousness. [See ibid., p. 111] His third thesis is that an objectivist epistemology developed in this way will shed light on the “world 2” subjective processes of understanding, but that the converse is not the case.  [See ibid., p. 112] In other words, Popper argues that one can only work out a cognitional theory after one has developed an adequate epistemology.

The theory of knowledge Popper discovers in his analysis of the “inmates” of “world 3” is exactly the same as the theory underlying all we have seen of his thought: that knowledge grows according to the method of conjecture and refutation.  Popper generalizes and summarizes this theory (which he also calls the method of problem solving) in the following schema: P1 TT EE P2, where P1 is the problem from which one starts, TT (for “tentative theory”) is the proposed conjectural solution to P1, EE (for “error elimination”) is the severe critical evaluation of the proposed theory, and P2 is the problem situation as it emerges from the initial attempt to resolve P1. [See ibid., pp. 119, 121, 144, 164, 168, 243.]  An important point in Popper’s argument for the autonomy of “world 3” is the observation that the contents of objective knowledge have implications and tend to generate problems that were not foreseen by any person.  This leads Popper to assert that objective knowledge really has a life of its own; it has logical relations and implications that do not depend for their existence on their being thought by a knowing subject.  This is what he means when he says that objective knowledge is knowledge without a knowing subject.  It is a product of knowing subjects, but it is autonomous.  Popper’s favorite example is the discovery of natural numbers.  Once the theory of natural numbers is produced by human subjects, it creates its own autonomous problems never before entertained by a knowing subject and which are gradually discovered.  For example, the existence of prime numbers is discovered, and the problem of whether the sequence of prime numbers is infinite arises.  This was not intended when the theory of natural numbers was produced; it is an unintended consequence of the logical relations in the “world 3” theory of natural numbers discovered as subjects operate on and with the contents of this autonomous “world 3.” Objectivity, then, has an ontological referent: the logical relations and implications of the contents of “world 3.” These relations and implications unfold according to the scheme Popper proposes: P1 TT EE P2.  This is a schema for the growth of knowledge.

Once it is seen that objective knowledge is produced, is related, unfolds, and grows according to this pattern, then it can be seen that human understanding also follows this same pattern in the basic method of problem-solving.

I might note here that Popper argues that this same pattern of problem-solving can be detected in or used to interpret the whole of biological evolution, so that human understanding and the growth of knowledge is, while an immense achievement, a special case of an activity common to all life. See ibid., pp. 113-115, 145-150, 241-255, 256-284; “Autobio. ,” pp. 141-143.

The subjective processes that occur in the human search for understanding are all operations on and with “world 3” objects, and objectivity in understanding means faithfulness to the method of problem-solving (the critical method) or subjecting to rational criticism all our proposed solutions to the problems we address. [See Ob. Kn., pp. 162-168, and compare pp. 136-137.] Thus Popper argues that the schema he proposes is not only a schema of how knowledge grows (epistemology), but also an analytic description of what we are doing when we try to understand (cognitional theory). [See ibid., p. 165.] This leads to two important observations.  First, the world of objective knowledge and its effect on us is really what is responsible for our rationality: “we thus owe to the third world especially our rationality—that is, our subjective mind, the practice of critical and self-critical ways of thinking, and the corresponding dispositions.” [Ibid., p. 147.]  Even more importantly, however, the interaction between the autonomous world of objective knowledge and our subjective (“world 2”) search for understanding is the cause of our self-transcendence.

. . . I suggest that everything depends upon, the give-and-take between ourselves and our work; upon the product which we contribute to the third world, and upon that constant feed-back that can be amplified by conscious self-criticism.  The incredible thing about life, evolution, and mental growth, is just this method of give-and-take, this interaction between our actions and their results by which we constantly transcend ourselves, our talents, our gifts. . . .

The process of learning, of the growth of subjective knowledge, is always fundamentally the same.  It is imaginative criticism.  This is how we transcend our local and temporal environment by trying to think of circumstances beyond our experience: by criticizing the universality, or the structural necessity, of what may, to us, appear (or what philosophers may describe) as the ‘given’ or as ‘habit’; by trying to find; construct, invent, new situations—that is, test situations, critical situations; and by trying to locate, detect, and challenge our prejudices and habitual assumptions.

This is how we lift ourselves by our bootstraps out of the morass of our ignorance; how we throw a rope into the air and then swarm up it—if it gets any purchase, however, precarious, on any little twig.

What makes our efforts differ from those of an animal or of an amoeba is only that our rope may get a hold in a third world of critical discussion: a world of language, of objective knowledge.  This makes it possible for us to discard some of our competing theories.  [Ibid., pp. 147, 148; see p. 119.]

In this way the growth of subjective knowledge leads us to self-transcendence, but this is possible only because our search for understanding is related in every way and at every point to the structure and growth of objective knowledge.  It is the feed-back from the autonomy and objectivity of “world 3” that enables our “world 2” subjective cognitional process to be self-transcending.

This raises the question of the relationship between Popper’s three worlds.  Popper argues that “world 2”, the world of subjective experience, is the mediating link between ‘world 1’ and “world 3.” ‘World 1’ and “world 3” are liked only indirectly through the mediation of the subject.

. . . all our actions in the first world are influenced by our second world grasp of the third world. This is why it is impossible to understand the human mind and the human self without understanding the third world (the ‘objective mind’ or ‘spirit’); and why it is impossible to interpret either the third world as a mere expression of the second, or the second as the mere reflection of the third. [Ibid., pp. 148-149.]

Popper wants to argue for “the objective reality of all three worlds,” [Ibid., p. 156; see p. 155, and “Autobio.,” p. 147.] with the world of the human subject (the mind) at the pivot of articulation. Thus it is the reality of the objective and autonomous “world 3” [Ob. Kn., p. 185.] that provokes or calls forth the self-transcendence of the human subject in “world 2”, and at the same time it is the activity of the human subject in “world 2” which produces “world 3” and also enables “world 3” to affect physical reality (“world 1”).  It is because the world of human subjectivity is of such pivotal importance that Popper stresses that the growth of subjective knowledge occurs only in relation to objective knowledge and follows the same pattern of development.

As I mentioned above, Popper argues that the method of growth he has described for both objective and subjective knowledge applies to all forms of human thought.  “Labouring the difference between science and the humanities has long been a fashion, and has become a bore.  The method of problem solving, the method of conjecture and refutation, is practised by both.” [Ob. Kn., p. 185.]  Beyond such disciplined forms of thought as science and the humanities, Popper argues the critical method of conjecture and refutation is the method underlying all human knowledge, including common sense, and can even be detected as the principal way in which all life forms relate to their environments.

The method of learning by trial and error—of learning from our mistakes—seems to be fundamentally the same whether it is practised by lower or higher animals, by chimpanzees or by men of science.  My interest is not merely in the theory of scientific knowledge, but rather in the theory of knowledge in general.  Yet the study of the growth of scientific knowledge is, I believe, the most fruitful way of studying the growth of knowledge in general.  For the growth of scientific knowledge may be said to be the growth of ordinary human knowledge writ large . . . .

C.R., p. 216. See also L.Sc.D., pp. 15-23.  For the development of this position into an interpretation of biological evolution, see references in Thesis, p. 152 note 1.

Popper is convinced that at root there is one basic method shared by all forms of learning and governing the growth of all forms of knowledge.  Science is distinguished (or demarcated) from all other forms of knowledge by the fact that its conjectures can be empirically tested; that is, by the use of special methods empirical science can subject its conjectures to empirical tests designed to falsify them.  But science shares its basic method, the critical method of conjecture and refutation, with all other forms of thought and knowledge.

Thus we may note how thoroughly Popper disagrees with the logical positivist interpretation of science and other modes of thought.  Not only does Popper argue that the humanities have a legitimate claim to speak meaningfully (Thesis, pp. 132-134), not only does he defend the possibility of objectivity in non-scientific discourse (Thesis, pp. 148-149), he also argues that non-scientific disciplines employ the same general method as do the natural and physical sciences.

There is one topic I have not yet discussed which has remained of central importance over Popper’s long career; the relation of scientific knowledge and knowledge in general to truth.  To state Popper’s position in brief, he argues that while there must be objective truth, we can never know if we have grasped the truth in any of our conjectures.  Yet the idea of truth and the desire and search for truth play important heuristic and regulative roles in the growth of knowledge.  Moreover, there are ways in which the notion of truth can be formalized so as to be of logical assistance in the testing of conjectures in empirical science.

We find an early statement of this position at the end of the main text of The Logic of Scientific Discovery:

Science is not a system of certain, or well-established, statements nor is it a system which steadily advances towards a state of finality.  Our science is not knowledge (episteme); it can never claim to have attained truth, or even a substitute for it, such as probability.

. . . Although it can attain neither truth nor probability, the striving for knowledge and the search for truth are still the strongest motives of scientific discovery. [L.Sc.D., p. 278.]

Shortly after this was written, Popper met Alfred Tarski, who had developed a logical analysis Popper regards as a valid rehabilitiation of the correspondence theory of truth (i.e., statements are true if they correspond to the facts).  Popper’s subsequent work was deeply influenced by Tarski’s theory.

Popper has recounted in numerous places the influence on his thought of Tarski’s theory.  See “Autobio.,” pp. 78, 112-114; L.Sc.D., p. 274 note *1; C.R., pp. 223-227; Ob.Kn., pp. 44-51, 59-60, 314-318, 319-39.

It is beyond the scope of my study to enter into a discussion of Tarski’s theory and its influence on Popper’s work, short of noting that it is Tarski’s analysis that allows Popper to develop his theory of verisimilitude, to argue on behalf of metaphysical realism, and to speak of the idea of truth as an important regulative idea in the growth of knowledge. I will restrict my comments here to Popper’s argument for metaphysical realism and the idea of truth as a regulative idea.

Popper agrees with idealism that all theories are our constructs which we try to impose on the world of nature and our experience.  He departs from idealism, however, in holding that “the question whether our man-made theories are true or not depends upon the real facts; real facts which are, with very few exceptions, emphatically not man-made.” [Ob. Kn., p. 328.]  How is it, though, “that we know there are “real facts”?  What is the evidence for arguing in support of realism?  While such an argument is in Popper’s classification metaphysical, not empirical, Popper believes there is sound evidence for the realist position.  The evidence is found in the very ideas of error, mistakes, and fallibility.  “The very idea of error, or of doubt (in its normal straightforward sense) implies the idea of an objective “truth which we may fall to reach.” [C.R., p. 226.] Thus the idea of truth acts as a regulative idea in our search for understanding, and also implies the existence of a real world independent of our thought processes and theories.

It is only the idea of truth which allows us to speak sensibly of mistakes and of rational criticism, and which makes rational discussion possible—that is to say, critical discussion in search of mistakes with the serious purpose of eliminating as many of these mistakes as we can, in order to get nearer to the truth.  Thus the very idea of error—and of fallibility—involves the idea of an objective truth as the standard of which we may fall short.  (It is in this sense that the idea of truth is a regulative idea.)  [Ibid., p. 229.]

Moreover, if we actually test a conjecture and succeed in falsifying it, “we see very clearly that there was a reality—something with which it could clash. [Ibid., p. 166.] Hence it is through falsification that we actually have experience of reality.

Our falsifications thus indicate the points where we have touched reality, as it were. [Ibid.]

It is through the falsification of our suppositions that we actually get in touch with “reality.”  It is the discovery and elimination of our errors which alone constitute that “positive” experience which we gain from reality.

Ob. Kn., p. 360.  Popper’s italics omitted.  Popper thus holds that while we can act in reality, while we can manipulate “world 1” and affect it with our “world 3” theories in experiments and technology, we can never be sure that we know reality.  Our experience of reality gives us no “positive” information except for the knowledge that our conjectures and theories can be (and often are) erroneous.  This does not mean that we have no knowledge, but it does mean that all knowledge must forever be hypothetical and severely limited in nature.

Popper summarizes his position in this way:

Theories are our own inventions, our own ideas; they are not forced upon us, but are our self-made instruments of thought; this has been clearly seen by the idealist.  But some of these theories of ours can clash with reality; and when they do, we know that there is a reality; that there is something to remind us of the fact that our ideas may be mistaken.  And this is why the realist is right. [C.R., p. 117.  For an extended treatment of realism see Ob. Kn., pp. 37-44.]

In sum, Popper argues on behalf of metaphysical realism and the importance of the idea of truth, even though his conclusions regarding the hypothetical character of all knowledge and the impossibility of verifying any of our conjectures cause him to deny that we can attain any certain knowledge.  Our knowledge of reality, even in the empirical sciences, always remains uncertain, conjectural, and hypothetical.  

This does not mean, however, that there can be no progress or growth in knowledge.  Popper does not like to speak of the growth of scientific knowledge as cumulative because in his opinion most people will take that to mean the mistaken inductivist ideal of the gradual accumulation of observations leading necessarily (if the observer is patient enough) to the discovery of the laws of nature. [See, e.g., L.Sc.D., pp. 279-280.] He does, however, support the interpretation that there is progress and growth in scientific knowledge.  To be sure, Popper is no naive progressivist and is under no illusion that progress is inevitable and certain. [See C.R., pp. 215-216.] Yet, he insists, the method of science does enable progress to be made if scientists are faithful to the demands of that method.  Popper usually prefers to characterize the growth or progress of scientific knowledge as growth by means of criticism, or growth by the “revolutionary” method of the overthrow (refutation) of false theories and the construction of new, better theories. [See, e.g., ibid., pp. 129, 215-216.] The model Popper proposes is actually a cumulative model (so long as one does not interpret this in the Baconian inductivist sense): “our latest and best theory is always an attempt to incorporate all the falsifications ever found in the field, by explaining them in the simplest way . . . .” [Ibid., pp. 116-117.] The present state of scientific knowledge (that is to say, the present state of scientific opinion) is always built on the past, and occurs in the context of a scientific tradition.  The growth and progress, however, is never automatic; it depends on taking the risk of bold conjecturing and the risk of severe criticism of those conjectures.

If we can never know the truth with certainty, the major question that arises is: how, then, do we know that we are making progress toward the truth?  By what criteria are we able to judge that our new conjectures are “better,” that they are closer approximations to the truth?  Popper wants to argue that we have more than subjective (“world 2”) conviction to support the idea of progress toward truth.  As we will see in the next subsection, Popper argues that it is possible to develop objective criteria of progress toward truth even in metaphysical discussions, but it is in arguing this position for the empirical sciences that he develops a good part of his philosophy of science.  Popper argues that his theories of testability and verisimilitude provide the criteria for the appraisal of theories, criteria that enable us to recognize (objectively) that one theory is a better approximation to the truth than another.

For a good short statement of this position, see Ob. Kn., pp. 143-145.  For a more detailed argument see ibid., pp. 47-60, 304-318, 319-335; and C.R. Chapter 10 “Truth Rationality and the Growth of Scientific Knowledge,” pp. 215-250, esp. pp. 228-236; 240-248.

It is here, particularly with regard to the develop-ment of the theory of verisimilitude, that Tarski’s work has been so influential on Popper.  I need not enter into a discussion of this part of Popper’s work, interesting though it is.  For my purposes, it is enough to observe that Popper argues for objective criteria for judging progress in the growth of knowledge and that all these criteria are connected to the criticism or testing of conjectures and theories.  Popper summarizes his position well in the following passage:

. . . one great advantage of the theory of objective or absolute truth [i.e., truth as correspondence with the facts] is that it allows us to say . . . that we search for truth, but may not know when we have found it; that we have no criterion of truth, but are nevertheless guided by the idea of truth as a regulative principle . . . ; and that, though there are no general criteria by which we can recognize truth—except perhaps tautological truth—there are something like criteria of progress towards truth . . . [C. R., p. 226.]


Metaphysics and Its Relation to Science

As I discussed above, Popper has from the beginning rejected any attempt to characterize metaphysics as meaningless.  The line of demarcation between science and metaphysics is not an impassable wall or an unbridgable gulf.  Rather, the line of demarcation marks the point, more or less clear, at which our discourse becomes empirical (which for Popper, we recall, means testable).  The reason Popper refused to dismiss metaphysics as meaningless is that very often in the past metaphysical ideas have been the forerunners of scientific (empirical) theories.

. . . most of our scientific theories originate in myths.  The Copernican system, for example, was inspired by a Neo-Platonic worship of the light of the Sun who has to occupy the “centre” because of his nobility.  This indicates how myths may develop testable components. They may, in the course of discussion, become fruitful and important for science.  In my Logic of Scientific Discovery I gave several examples of myths which have become most important for science, among them atomism and the corpuscular theory of light.  It would hardly contribute to clarity if we were to say that these theories are non-sensical gibberish in one stage of their development, and then suddenly become good sense in another. [Ibid., p. 257; see L.Sc.D., pp. 277-278.]

Moreover, the scientific quest for knowledge is inspired and guided by convictions that Popper must classify as metaphysical.  Science and the quest for knowledge, Popper held; depend on “the unscientific, the metaphysical . . . faith in laws, in regularities which we can uncover—discover.” [L.Sc.D., p. 278; see also pp. 252-253.] Metaphysics, then, cannot be meaningless, and is even of positive value for science: it is very often a source for interpretative ideas that in the course of time can become testable, and it is the source of our faith and conviction that science is possible, that there are regularities to be discovered.  

It might be helpful to recall that Popper’s use of the word “metaphysics” is much broader than its customary designation of a particular sub-discipline of philosophy.  By “metaphysics” Popper means all non-testable forms of thought, including religion, art, poetry, etc.

In The Logic of Scientific Discovery Popper was of the opinion that metaphysics is entirely subjective, or to use his later terminology, that all of metaphysics is in “world 2” and not subject to critical discussion.  The limits of arguability, he believed, coincide with the limits of science.  He later decided, however, that he was wrong on this point, and argued that although metaphysical theories are non-testable (i.e. irrefutable and hence nonscientific), they may be rationally and critically discussed.  [See Ob. Kn., p. 40 note 9.]

Although Popper does not say this, his position on the arguability of metaphysical theories seems to be a consequence of his broadening of the notion of objectivity from inter-subjective testing to inter-subjective criticism (see Thesis, pp. 148-149).  The connection seems clear.

His argument runs as follows. [See ibid., pp. 193-200.] If we accept the criterion of demarcation (or, as Popper calls it in this place, the criterion of refutability), then metaphysical theories are irrefutable by definition: their statements are such that they cannot be empirically tested.  They are compatible with any given empirical state of affairs, and they cannot predict an empirical state of affairs which would be incompatible with the theory. 

For an interesting, if brief, application of the criterion to the psychoanalytic theories of Freud and Adler, see “Replies,” pp. 984-985.

Such theories, in Popper’s analysis, can neither be proven nor disproven: they share with all theories the inability to be verified, but they differ from scientific theories in that they also cannot be falsified.  Yet, Popper argues, there can be rational, critical discussions of these metaphysical theories which allow us to conclude that some of these theories are false and others better approximations to the truth. How is it possible to argue rationally (critically) about theories which we know to be neither demonstrable nor refutable?  How can we conclude that a metaphysical theory is false when it is impossible actually to falsify it?  Popper’s solution is to point out that metaphysical theories are not isolated assertions about the world but rather are developed in a context: they address problems and are designed to resolve those problems.  Popper calls this context the “problem-situation” and argues that critical discussion of metaphysical theories can occur if we direct attention to the problem situation.

. . . every rational theory, no matter whether scientific or philosophical, is rational in so far as it tries to solve certain problems.  A theory is comprehensive and reasonable only in its relation to a given problem-situation, and it can be rationally discussed only by discussing this relation. [C. R., p. 199.]

When attention is directed to the problem and the problem situation, it is then possible to ask about the theory such questions as:

Does it solve the problem?  Does it solve it better than other theories?  Has it perhaps merely shifted the problem?  Is the solution simple?  Is it fruitful?  Does it perhaps contradict other philosophical theories needed for solving other problems? [Ibid.]

Such questions constitute the criteria of critical discussion and progress toward truth in nonscientific or metaphysical discourse. 

Popper is thus arguing that something like a theory of preference can be applied to critical discussions of nonscientific theories.  For example, in studying Hume’s philosophy, we might characterize its problem as the grounding of realism; and we might note that Hume’s conclusions led to an idealism because he was unable to ground realism in his sensationalist theory of perception, learning, and knowledge. It is then reasonable, Popper argues, to criticize Hume’s idealism

It is more customary to characterize Hume’s position as radical skepticism, but Popper speaks of Hume’s “idealism.”  See Ibid.

by pointing out the inadequacies of his theory of learning and knowledge and, by judging that there exist “less inadequate” theories of learning and knowledge which do not lead to idealistic consequences,

Popper clearly has his own theory of learning in mind.  See Thesis, pp. 128-129.

conclude that Hume’s idealism is false and metaphysical realism is a better approximation to the truth.

For similar criticisms of determinism and irrationalism, see C. R., pp. 199-200.

Thus even though all metaphysical theories are by definition irrefutable, it is nevertheless possible by attention to the problem situation to carry on rational and critical discussions which can conclude that some metaphysical theories are false (though this cannot be demonstrated ) empirically and others are less inadequate approximations to the truth.

Popper does not develop his position any further. For instance, apart from the critical questions he asks, he does not suggest any specific criteria by which one might judge a metaphysical theory “false,” and propose another as less inadequate. Still, Popper’s position does imply that it is possible to formulate arguments of “relative adequacy” or at least “relative inadequacy.”

Popper summarizes his position in this way:

The discovery of a philosophical problem can be something final; it is made once, and for all time.  But the solution of a philosophical problem is never final.  It cannot be based upon a final proof or upon a final refutation: this is a consequence of the irrefutability of philosophical theories. . . . Yet it may be based upon the conscientious and critical examination of a problem-situation and its underlying assumptions, and of the various possible ways of resolving it. [C. R., p. 200.]

There is one other development in Popper’s estimation of metaphysics which is of some interest for my topic.  In the early 1950’s, in a work that remained unpublished until quite recently,

“Postscript: After Twenty Years.”  This work, in galley proofs since 1957, has been circulated and has had much influence in Popper’s circle.  See “Autobio.,” pp. 118-120.  A quotation relevant to the topic in the text is given in Lakatos and Musgrave, eds., Criticism, p. 183 note 3.  This work has recently been published as Karl Popper, The Postscript to the Logic of Scientific Discovery, ed. W. W. Bartley, 3 vols., Totawa, N.J.: Rowman and Littlefield, 1982), Vol. 1: The Open Universe: An Argument for Indeterminism; Vol. 2: Quantum Theory and the Schism in Physics; Vol. 3: Realism and the Aim of Science.

Popper described and analyzed the role played by what he calls “metaphysical research programmes”, that is, metaphysical theories and world-views that guide and influence the development of science.  In the course of his analysis, and by means of historical examples, Popper argued that the changes in our ideas of what constitutes a satisfactory explanation in science have been mediated by these metaphysical research programmes.  These ideas changed and developed over the ages under the pressure of criticism, and even though such ideas are not testable, they have been of great importance in the development of science.  This has led Popper to propose his own metaphysical view of the world and a correlative research programme, [See "Autobio.," pp. 120, 133-143; and Obj. Kn., Chapters 6 & 7, pp. 206-284.] but what is of interest for my topic is Popper’s recognition of the role of metaphysics in the explanation of explanation.  By this I mean that apparently Popper would agree with Whitehead and Lonergan that one of the functions of metaphysics is to explain how it is that the sciences can explain.  At the very least, Popper is arguing that the changes in metaphysical worldview can affect what scientists accept as constituting a satisfactory explanation of the world.


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Chapter II: The Tenability of Whitehead’s and Lonergan’s Interpretations of Empirical Scientific Method: Michael Polanyi on Scientific Method and Knowledge

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