Concern with the nature and status of scientific knowledge is more or less coeval with the Western philosophical tradition. Both Plato and Aristotle, in different ways, made the explication of the distinction between "scientific knowledge" and "mere opinion" central to their theories of knowledge or "epistemologies." The questions posed by these ancient giants, and much of the terminology they developed for dealing with them, have been picked up by subsequent thinkers of the Western tradition over the centuries, thereby creating an almost continuous "conversation" across the ages, a conversation which continues into the present day.
Indeed, the connection between philosophy and scientific knowledge is even closer, for most of today's independent mature sciences had a long gestation within the womb of philosophy herself, the effects of which are often still visible. In fact, although the concept of scientific knowledge is ancient, the very word "scientist" is of relatively recent coinage. Most of the older heroes enshrined in today's science texts were known in their own day as "natural philosophers." And this is not merely a matter of names, for many of what are regarded as "scientific theories" today began life as philosophical speculations. The conceptual schemes which allowed most sciences to emerge were themselves products of philosophical world-views developed for other purposes.
But the relation of influence is not unidirectional, from philosophy to science, for once the various sciences have attained their independence from philosophy they have become major constraints on the further development of philosophy. Thus what are today regarded as the scientific achievements of men like Galileo, Newton, Darwin, or Einstein have all exerted profound effects on the philosophers of their day, and ours as well. All the great thinkers of the "modern period" since the Enlightenment have in one way or another had something to say about the scientific world-view that emerged during this period. The philosophies of the "continental rationalists," Descartes, Spinoza, and Leibniz, the "British empiricists," Locke, Berkeley, and Hume, and the synthesis of these strands in Kant's critical philosophy, and the idealist tradition which issued therefrom, all represent philosophical responses to the authority of the kind of knowledge provided by natural science. Furthermore, the responses of those who came later were often direct reactions to the philosophical interpretation accorded scientific knowledge by those who came before. This "historical dialogue" carries directly down to our own times, and is even now a matter of intense intellectual debate.
We do not here have the luxury of tracing this story from ancient times. If we go back briefly to the Enlightenment we would find that many philosophers were explicitly aware of the fact that the sequence of developments from Copernicus through Newton constituted a "scientific revolution" which called for a new set of answers to the question of the authority of the scientific description of nature. Two different approaches were associated with "rationalism" and "empiricism". On the one hand rationalists answered this question by saying that the conclusions of science are justified by "Reason." The mathematical description of motion, begun in astronomy already in ancient times was extended to all motion in the culminating achievement of Newtonian mechanics and gravitation. This suggested that the authority of science is akin to that of mathematical demonstration, or as we would say today, "proof" within a "formal deductive system." Thus it is deductive reasoning from necessarily true postulates which is the foundation of the authority of science. On the other hand, empiricists saw the authority of the scientific description of nature as based upon careful observation of particular phenomena, observations which often provided the measurements that made the connection between a mathematical representation of nature and a description of the empirical world. The authority accorded the laws and theories which make the scientific description of nature possible is then -according to empiricists- justified by reasoning inductively from observation.
Given the subdivision of labor characteristic of the contemporary intellectual world, this age old conversation has become the special concern of a subdiscipline known as "philosophy of science" and those who work in this field are called "philosophers of science." Many such scholars today are highly trained in, and often contribute to, the sciences which they study, thereby putting the lie to the common, but at least these days unjustified, complaint that philosophers who expound on such matters are ignorant of the subjects about which they proclaim.
Like most fundamental partings of the way in philosophy, disputes between rationalist and empiricist approaches to scientific knowledge have never been resolved in favor of one way or another. The issues were battled back and forth throughout the eighteenth and nineteenth centuries. But by the late nineteenth century the new subdiscipline of philosophy of science began to emerge around a consensus view that the authority of science cannot be guaranteed by reason but relies instead on what is held to be known directly in human sensory experience. Philosophers who hold this view are called empiricists; thus this outlook can be conveniently called the "empiricist consensus." A great deal of intellectual achievement was put into the analysis of science from this point of view.
Drawing on the long tradition of British empiricism, Bertrand Russell sought to use the powerful tools of the new symbolic logic, which he had learned from the German mathematician Gottlob Frege, to show how the scientific description of the world was erected upon what is given directly in experience. For all his innovations, Russell held to the Enlightenment ideal of justifying the authority of science by showing that it is a representation of what is real, which is one possible way of defining the view known as "realism." (Unfortunately philosophers use thos term, "realism," in a variety of quite different ways.) In America, the pragmatist philosophers C.S.Peirce and John Dewey developed an alternative analysis which relocated the authority of the scientific description of nature in its pragmatic virtues rather than regarding its goal as the representation of nature. After the First World War a group of philosophers generally known as the "logical positivists" became the dominant proponents of the empiricist consensus. Their views became the most influential single force in articulating and developing in detail this consensus. But the positivists never enjoyed an undisputed monopoly even within the empiricist consensus. Most conspicuously, they were challenged on nearly every point by Karl Popper's defense of "falsificationism," even though Popper himself was a solid adherent of the empiricist consensus.
Thus there were a variety of philosophical paths which intersected in their response to the question of the authority of science, and by saying that this formed an "empiricist consensus" I want of course to call attention to their area of agreement. At the same time, I also want to emphasize that the extent of that agreement was limited to a finite set of views over which they agreed and that there were also very many topics over which they also disagreed. It was, in short, not a dogmatic philosophy as much as a loose confederation of criss-crossing alliances that allowed its members a certain sort of agreement as to the rules and goals of the game of philosophy of science. But within those bounds there was strenuous competition over many hotly contested topics, many of which led into highly technical discussions more or less inscrutable to readers outside the walls of philosophy of science.
Thus the consensus was strained by intramural dissension which gradually led to a weakening of the alliances which bound together those within the walls. Further research tended to proliferate problems rather than solve them, and the character of those problems seemed ever more removed from the concerns of science. And then there were also always some philosophers who were concerned with natural science but never within the fold and adopted an extramural point of critical attack. Thus by the 1960's the consensus began to disintegrate from pressure within and without. The story of the breakup of this consensus and what has come in its wake will be our central concern in this course. It is a complex, many faceted, sometimes technical, but very fundamental intellectual story.
In 1962 Thomas Kuhn's now classic work, The Structure of Scientific Revolutions, without doubt one of the most influential books to have been published in the last 50 years, came to be the touchstone work in the debates which dismantled the dying consensus. It is a mistake to think that Kuhn's work caused these developments; it was as much a symptom of them. But Kuhn's book hit the wave of change at just the moment it broke and thus enjoyed a long ride in the forefront of discussion. However, while Kuhn and like minded critics of the empiricist consensus effectively overthrew the consensus view that had dominated philosophy of science from the 1930's to the 60's, Kuhn's own alternative was never crowned its successor within philosophy of science. It is now generally recognized by most philosophers to be inadequate as an account of many of the features of science to which Kuhn himself called attention. Thus in the last forty years philosophy of science has gone from a field formerly dominated by a single "received view" to an arena of volatile debate with no single dominant contender for a new acceptable model of scientific knowledge. This fact has made it one of the most lively and pivotal domains of philosophy, for the issues now occupying center stage in philosophy of science touch upon basic questions of epistemology, metaphysics, and axiology.
Through these debates the nature of philosophy of science has changed tremendously from the attempt to build a formal model of an idealized perfect science quite apart from any historical account of what scientists really do, to the attempt to build a philosophically acceptable view of science based upon a detailed historical examination of the actual patterns of reasoning employed in concrete episodes in the advance of science. En route these discussions have called into question such basic presuppositions as the belief that there is some pattern of reasoning which justifies acceptance of scientific theories, that there is some methodology called "the scientific method," that science has anything at all to say about the nature of reality, and that science can be examined apart from the social, cultural context in which it actually evolves. Because of the central role that science plays in contemporary culture, these upheavals in philosophy of science have reverberated in a variety of disciplines including history, political science, sociology, art, religious studies, and other disciplines too numerous to name.
To be specific, throughout the sixties and into the seventies, stimulated by what were thought to be implications of Kuhn's work, philosophers, historians, and sociologists of science found themselves engaged in a profound discussion over the rationality involved in the acceptance and rejection of scientific theories. In the eighties this discussion evolved into a renewed examination of the perennial philosophic question of realism vs. anti-realism in the interpretation of science. By the nineties, philosophers of science are now forced to come to grips with the questions of the values that motivate the acquisition of scientific knowledge and the role they play in human culture. Thus in contemporary philosophical analyses of scientific knowledge must be sensitive not only to the history of science but also to the social structures within which scientific knowledge is acquired, from the narrow confines of the laboratory to the broader context of the whole of modern Western culture within which science has assumed so central a role. This cluster of disciplines which all take science as their central object of study has come to be called "Science Studies," and at the hands of some, though not by any means all, authors has led to the radicalization of a variety of themes originally popularized (though not necessarily endorsed) by Kuhn's work and in the debates which led to the revolution in philosophy of science of which it was a part. The picture of science painted by these authors has led many scientists, rightly or wrongly, to feel under hostile attack, by what they regard as scientifically uninformed humanistic dilettantes. This debate has appeared under the name of "The Science Wars" in the popular press and is certainly one of the most lively, while at the same time ill understood, discussions in current philosophy.
But I am now rushing too far ahead of our story. It is time to stop and start over and tell the story step by step of how we got from the empiricist consensus to the science wars. And telling that story should take us just about a semester.