Laudan's Reticulated Model of Scientific Rationality
Of those philosophers who have sought to find a "middle ground" on the spectrum of post-Kuhnian positions on scientific rationality, one of the most widely discussed is Larry Laudan. In his earlier 1977 work, Progress and Its Problems, Laudan took a more or less Kuhnian position on the holistic character of paradigms, each with its own data, its own successes, and its own standards for defining acceptable problems and acceptable solutions. Later on, in his 1983 Science and Values he altered his position and presented a naturalistic theory of scientific rationality that was based on a sustained critique of the holistic character of Kuhnian paradigms. In the "Preface" to that work, he characterizes the relation of his position to Kuhn's as follows:...this is a book about the role of cognitive values in the shaping of scientific rationality. Among recent writers, no one has done more to direct our attention to the role of cognitive standards and values in science than Thomas Kuhn. Indeed, for more than two decades, the views of Thomas Kuhn -and reactions to them- have occupied center stage in accounts of scientific change and scientific rationality. That is as it should be, for Kuhn's Structure of Scientific Revolutions caused us all to rethink our image of what science is and how it works. There can be no one active today in philosophy, history, or sociology of science whose approach to the problem of scientific rationality has not been shaped by the Gestalt switch Kuhn wrought on our perspective on science. This debt is so broadly recognized that there is no need to document it here.Less frequently admitted is the fact that, in the twenty-two years since the appearance of The Structure of Scientific Revolutions, a great deal of historical scholarship and analytic spadework has moved our understanding of the processes of scientific rationality and scientific change considerably beyond the point where Kuhn left it.Laudan takes the label of "pragmatist" for his view of rationality. He explicitly rejects what he calls the "Leibnizian ideal" of a logic which fully determines theory choice, of which the empiricist consensus has been the latest example. Yet he argues that the rush to the sociological thesis that theory choice is fully at the mercy of "external" factors is in no way necessitated, either by the relation between evidence and theory or by the historical record. His Popperian heritage is visible in his total acceptance of "Humean" underdetermination of theory choice: it is incontrovertible that there are logically possible an infinite number of theories which are consistent with any finite body of evidence. But this logical fact is largely irrelevant to scientific rationality because choice is never made from the field of all logically possible theories, with which no scientist is ever confronted, but always made relative to a choice among actually extant, competing rivals. Once this point is established, it by no means follows that of existing rivals, all will be equally in conformity with the accepted data. Furthermore, if one recognizes that the logical relations of deductive entailment between theory and evidence is only one evidential relation out of many possible relations. In a "pragmatic" spirit Laudan adds into the question of theory choice other such "ampliative" evidential relations as fertility, simplicity, causal connection, and unification. Thus when one goes beyond the purely logical relationship of deductive implication to include such pragmatic considerations relative to our interests, there is even less reason to believe that of competing rivals, all will be an equally rational choice. Nevertheless, Laudan is quick to point out that even though a "staggering proportion" of all scientific theory choice decisions can be made answerable to such a robust form of rationality, not all can. There will be cases where in fact existing methods do indeed underdetermine theory choice, but rather than regard this is a weakness of his account of rationality Laudan exploits the historical testimony of existence of protracted and irresolvable disputes (dissensus) as evidence for his view that an account of scientific rationality should not indeed always issue in consensus. We can expect dissensus precisely when more than one of existing rivals measure up equally well against existing methodological commitments.
Indeed, we are now in a position to state pretty unequivocally that Kuhn's model of scientific change, as developed in Structure and elaborated in The Essential Tension, is deeply flawed, not only in its specifics but in its central framework assumptions. It is thus time to acknowledge that, for all its pioneering virtue, Kuhn's Structure ought no longer be regarded as the locus classicus, the origin and fount, for treatments of these questions. It is time to say so publicly and openly, lest that larger community of scientists and interested laymen, who have neither the time nor the inclination to follow the esoteric technical literature of these fields, continues to imagine that Kuhn's writings represent the last (or at least the latest) word on these matters.
But just saying so is not enough. The decanonization of a discipline's patron saints is always a slow and arduous task, and one demanding that the case be carefully constructed and that it cut to the heart of the matter. This book is a contribution to that effort. So as not to have my intentions mistaken, let me stress that I did not set out to debunk Kuhn. My central concern in writing this essay has been from the outset to offer an account of scientific debate and scientific decision making that does as much justice as I can to what we have come to learn about how science works. Yet over and over again in that process, I have found myself denying theses and doctrines that many people (although usually not Kuhn himself, who tended to be rather tentative in his claims) regard Kuhn as having decisively established. For that reason, if for no other, Kuhn-or what Kuhn has been made into by his expositors-stalks the pages of this work as a presence to be both acknowledged and ultimately exorcised. Yet that is surely the wrong image. No one working in this field in this generation can get Kuhn entirely out of his system. Nor should we try, for he has posed an impressive range of important and fertile questions. What we can demand is that we honestly face up to the fact that his answers to most of those questions, never fully compelling, are no longer even plausible.
This book purports to provide better answers to some of Kuhn's questions than Kuhn himself did, and to diagnose why Kuhn, along with such fellow travelers as Feyerabend and Hanson, was never able to produce answers as compelling as his questions. There is no particular hubris involved in making that claim; indeed, something would be dreadfully wrong if, two decades after the appearance of Kuhn's masterpiece, one were not able to sustain such a claim. There is progress in philosophy just as surely as, if more slowly than, there is in science; although Kuhn himself, ever a believer in a sharp demarcation between science and everything else, might well dispute it. In any event it is not in my power, nor is it my intention, to detract from Kuhn's seminal contribution when I assert that we have by now built upon it and moved beyond it.
But Laudan has learned from Kuhn very well that methods themselves are not stable through time, for the methods we adopt are pragmatically understood as instruments for attaining desired ends. They have the logical form of "hypothetical imperatives" ("if...then" constructions in which the consequent is an imperative): "If you desire goal G, then employ method M." These goals thus justify the choice of methods in the same way that methods justify the choice of theories; they represent the "values" in Laudan's title, Science and Values. Such a set of values is termed an "axiology." When a conflict arises between competing methodological claims, then the rational choice to be made is the one which is the most effective instrument in attaining the desired goals. But goals are rational only to the extent that they are realizable, thus while the goals justify the choice of methods, methods, in their success "exhibit the realizability" of goals. As scientific beliefs change, goals once thought realizable may come to be regarded as impossible to realize; Laudan calls this "utopianism" in the pejorative sense of "unattainable." Utopian goals are considered clearly irrational to pursue. The demands of scientific rationality thus must "harmonize" with our theoretical beliefs about the world in the sense that our scientific world view is one in which the attainment of such goals is a rational possibility. As in the relation between methodological and theoretical beliefs, in which methods underdetermine theory choice, so in the relation between goals and methods, it may occur that different methods are equally efficient at attaining some desired goal, in which case a methodological dissensus will result. Finally, of course different goals may be equally attainable given any set of theoretical and methodological beliefs. In these cases one will also expect dissensus. Thus in this picture of a pragmatic scientific rationality there is no guarantee that the rational choice will always be determined for theories, methods, or goals, although it generally will; but it will always be highly constrained by its relations with the other two levels.
This gives Laudan a model of rationality in which all three "levels" of scientific beliefs, the theoretical, the methodological, and the axiological are changeable in the light of rational demands. No one goal is fixed or determined for scientific inquiry; in the future growth of scientific inquiry, any and all of present commitments on every level may be changed. Employing a triangular diagram to represent these relations, Laudan calls his model the "Reticulated Model of Scientific Rationality.
Laudan's position is "naturalistic" in that he holds that the subject of scientific rationality is as much a fit subject for scientific inquiry as any other aspect of human behavior, or, for that matter, any other natural phenomena. The naturalists' motto, "we learn how to learn" in effect expresses the point that our "canons" or "rules" of scientific rationality are as much open to revision in the process of the growth of knowledge as are our scientific theories about the natural world. As our knowledge of the world increases, methods which were once the best available ways of deciding on the acceptability of scientific theories, may become replaced by better methods which achieve the same ends more efficiently or with greater precision. Thus the methods employed at any stage in the development of science are used to justify the choice of the then accepted theories, but as the theoretical beliefs of one stage of human knowledge are replaced by new theoretical beliefs, thereby changing our beliefs about the world, which in turn constrains which beliefs regarding the efficiency of methods are deemed most acceptable.