We all think that science is special. Its products—its technological spin-off—dominate our lives which are thereby sometimes enriched and sometimes impoverished but always affected. Even the most outlandish critics of science such as Feyerabend implicitly recognize its success. Feyerabend told us that science was a congame. Scientists had so successfully hood-winked us into adopting its ideology that other equally legitimate forms of activity—alchemy, witchcraft and magic—lost out. He conjured up a vision of much enriched lives if only we could free ourselves from the domination of the ‘one true ideology’ of science just as our ancestors freed us from the domination of the Church. But he told us these things in Switzerland and in California happily commuting between them in that most ubiquitous product of science—the aeroplane.

Karl Popper attempted to give an account of scientific research as the rational pursuit of the truth about nature without any appeal to what he took to be the fictitious notion of non-demonstrative or inductive support. Deductive inference can be seen to be inference enough for science, he claimed, once we appreciate the power of data to refute theory. Many of the standard objections to Popper's account purport to show that his deductivism actually entails a radical scepticism about the possibility of scientific knowledge. Some of these objections appear unanswerable in the context of the traditional analysis of knowledge as justified true belief; but this is neither a conception of knowledge that Popper himself accepted nor one that is currently in fashion. Reliabilism, the view that knowledge is a true belief generated by a reliable method, is now a popular replacement for the traditional analysis and one that is closer to Popper's own conception of knowledge. My aim in this essay is to consider in brief compass the prospects of a reliabilist reading of Popper's account of science. Such a reading makes it possible to turn some of the standard objections and helps to show which of Popper's views should be accepted and which rejected.

In this paper I shall venture into an area with which I am not very familiar and in which I feel far from confident; namely into phenomenology. My main motive is not to get away from standard, boring, methodological questions like those of induction and demarcation; but the conviction that a phenomenological account of the empirical basis forms a necessary complement to Popper's falsificationism. According to the latter, a scientific theory is a synthetic and universal, hence unverifiable proposition. In fact, in order to be technologically useful, a scientific hypothesis must refer to future states-of-affairs; it ought therefore to remain unverified. But in order to be empirical, a theory must bear some kind of relation to factual statements. According to Popper, such a relation can only be one of potential conflict. Thus a theory T will be termed scientific if and only if T is logically incompatible with a so-called basic statement b, where b is both empirically verifiable and empirically falsifiable. (We shall see that neither the verifiability nor the falsifiability of b was meant, by Popper, in any literal sense.) In other words: T is scientific if it entails ¬b; where b, hence also ¬b, is an empirically decidable proposition.

Science, and in particular the process of theory-change in science, formed the major inspiration for Karl Popper's whole philosophy. Popper learned about the success of Einstein's revolutionary new theory in 1919 (the same year in which his discontent with Marxism and Freudianism reached crisis-point), and Einstein ‘became a dominant influence on my thinking—in the long run perhaps the most important influence of all.’ Popper explained why:

In May, 1919, Einstein's eclipse predictions were successfully tested by two British expeditions. With these tests a new theory of gravitation and a new cosmology suddenly appeared, not just as a mere possibility, but as an improvement on Newton—a better approximation to the truth … The general assumption of the truth of Newton's theory was of course the result of its incredible success, culminating in the discovery of the planet Neptune … Yet in spite of all this, Einstein had managed to produce a real alternative and, it appeared, a better theory … Like Newton himself, he predicted new effects within (and without) our solar system. And some of these predictions, when tested, had now proved successful. (‘IA’, p. 28)

Popper's writings cover a remarkably wide range of subjects. The spectrum runs from Plato's theory of politics to the foundations of quantum mechanics. Yet even amidst this variety the philosophy of probability occupies a prominent place. David Miller once pointed out to me that more than half of Popper's The Logic of Scientific Discovery is taken up with discussions of probability. I checked this claim using the 1972 6th revised impression of The Logic of Scientific Discovery, and found that of the approximately 450 pages of text, approximately 250 are to do with probability. Thus Miller's claim is amply justified. It seems indeed that the philosophy of probability was one of Popper's favourite subjects, and, as we shall see, Popper certainly enriched the field with several striking innovations. In this area, as in others, Popper held very definite views, and criticized his opponents in no uncertain terms. Popper was an objectivist and anti-Bayesian, and his criticisms were directed against subjectivism and Bayesianism.

In these prefatory remarks, which are designed to locate my topic within the complex and wide-stretching field of Popper's thought and writings, I shall not say anything that those familiar with his work will not already know. Moreover, what I do say will take as understood many of the problems and theories, not to mention the terminology, that I shall later be doing my best to make understandable. My apologies are therefore due equally to those who know something about Popper's discussions of indeterminism and of the propensity interpretation of probability, and to those who know nothing.

There is no doubt at all that the issue of determinism versus indeterminism was a central, dominating theme of Popper's thought. By his own account he saw his criticism of the thesis of determinism as crucial to his defence not only of the reality of human freedom, moral responsibility and creativity but also as equally fundamental to his account of human rationality and to his theory of the content and growth of science as an objective, rational and most importantly demonstrably rational enterprise. Consequently a great deal of his writings discussing both the content and methodology of the natural and the social sciences alternately bear upon and presuppose his defence of indeterminism.

Popper wrote extensively on the quantum theory. In Logic der Forschung (LSD) he devoted a whole chapter to the topic, while the whole of Volume 3 of the Postscript to the Logic of Scientific Discovery is devoted to the quantum theory. This volume entitled Quantum Theory and the Schism in Physics (QTSP) incorporated a famous earlier essay, ‘Quantum Mechanics without “the Observer”’ (QM). In addition Popper's development of the propensity interpretation of probability was much influenced by his views on the role of probability in quantum theory, and he also wrote an insightful critique of the 1936 paper of Birkhoff and von Neumann on nondistributive quantum logic (BNIQM).

Karl Popper's work is of great diversity. It touches on virtually every intellectual activity. But he himself considered his philosophy of science one of his most important achievements. And indeed his achievement here is revolutionary. It destroyed the philosophy of inductivism which held sway over science for hundreds of years.

The first Darwin Lecture was given in 1977 by Karl Popper. He there said that he had known Darwin's face and name ‘for as long as I can remember’ (‘NSEM’ p. 339); for his father's library contained a portrait of Darwin and translations of most of Darwin's works (‘IA’, p. 6). But it was not until Popper was in his late fifties that Darwin begin to figure importantly in his writings, and he was nearly seventy when he adopted from Donald Campbell the term ‘evolutionary epistemology’ as a name for his theory of the growth of knowledge (OK, p. 67). There were people who saw evolutionary epistemology as a major new turn in Popper's philosophy. I do not share that view. On the other hand, there is a piece from this evolutionist period which I regard as a real nugget.

There is a sort of scepticism, or, at least, epistemological pessimism, that is generated by appealing to Darwin's theory of evolution. The argument is that nature, that is the selective pressures of evolution, has clearly fitted us for certain sorts of learning and mundane understanding, directly beneficial in point of individual survival and chances for reproduction. Very likely then, it is argued, nature has not fitted us for arcane intellectual accomplishments remote from, or quite disconnected from, those ends. So, it is suggested, perhaps we cannot understand, perhaps never will understand, because we are not made to understand, such matters as consciousness, its nature and causes, the origins of life, the beginning of the universe, or astro-physics in its more finalist pretensions. Sometimes, taken with the claim that manifestly we do understand some of these things, the argument becomes a reductio, and its exponents claim that consequently Darwinism must be false, or of only limited application. More commonly, however, in ‘naturalized epistemology’, it is made the vehicle of a claim about the limits of science, limits imposed by the evolutionarily derived frailty of human understanding. Popper, the late Popper, is one of the progenitors of naturalized epistemology. I want to ask what Popper's response would be, or ought to be, to this epistemological nihilism (to purloin a phrase of Quine's) conjured out of Darwinism.

It is one of Karl Popper's great distinctions that he has an intense—some would say too intense—awareness of the history of philosophy within which he works. He knows not only its patterns, but also its comedies, and sometimes he plays rhetorically against their grain. He knows, for example, that the drive to consistency tends to turn philosophy into compositions of related doctrines, each seeming to involve the others. Religious belief, for example, tends to go with idealism and free will, religious scepticism with materialism and determinism. Popper does not believe in a religion, was for long some kind of a socialist, and takes his bearings from the philosophy of science. Aha! it seems we have located him. Here is a positivist, a materialist, probably a determinist. But of course he denies he is any of these things. Again, like many modern thinkers, he wants to extend scientific method not only to the social sciences but also to history. So far so familiar, until we discover that he regards nature as no less ‘cloudy’ than human societies.

In his seminal The Poverty of Historicism (hereafter PH) Sir Karl Popper deployed a number of arguments to prick the pretensions of those who thought that they were, or could come to be, in possession of knowledge of the (social) future. These ‘historicists’ assumed that they could lay bare the law of evolution of a society, and that their possession of knowledge of such a law justified (large-scale) political action which had the aim of removing obstacles to the progress of history. In arguing against historicism Popper was clearly motivated by his interest in removing the intellectual backing for such revolutionary political practice. My first reading of PH was in the company of people who were extremely dismissive of the anti-revolutionary message, and who tended to argue that if that was the conclusion of Popper's theoretical argument, then obviously the argument was flawed. Within their context, that of the implementation of apartheid policy in South Africa, there was much to be said for this attitude. There is no doubt that Popper's message was insufficiently contextualised, or rather that he did not signpost very clearly whether he intended the anti-revolutionary political prescription to have limited or universal application. In this paper I want to reconsider some of these issues, particularly whether the truth of anti-historicism, in the sense intended by Popper, has such conservative consequences for political action.

Some years acquire symbolic status, and one such year is 1968. All over Europe and the United States university students exploded into violent rebellion. Insofar as this would-be revolution had an ideology it was unquestionably Marx-inspired, even if the Marxism was not always orthodox. It so happens that in the years 1970–1971 I was teaching philosophy at Balliol College, Oxford. And because of Oxford University's system, almost unique, of individual tuition for undergraduates, this meant I found myself in a continuing one-to-one relationship with bright students who were in the throes of revolutionary fervour.

If an economist or an economic historian speaks about ethical or moral problems, one should be suspicious. Karl Popper continually repeated that he did not want to preach, and I believe that his deep-rooted distrust of modern philosophical moralists, who usually preach water and drink cognac, led to his not writing a greater work on ethics. Nevertheless he was a moral person, and perhaps we can learn more about his cosmology, his methodology, and about his philosophy in general if we probe into some of the ethical foundations of his life and his thinking. It may become apparent to you that I do not refer primarily to Popper's Open Society and Its Enemies or other works of his political writings alone. In choosing not to do so, it is my intention to demonstrate that all his thinking is deeply rooted in ethics.