The idea that events in nature are, somehow, governed by natural laws, and that to understand those laws would be a key to understanding the events—is a very old one. Whether abstracted from a religious context, or arrived at through independent reflection about nature, this idea first became prominent in the early days of what we now call science. Since the time geometry was worked out in axiomatic form, some 2,300 years ago, the combination of its deductive power, together with the understanding it yielded of the fundamental physical realm of space, I think it is fair to say geometry has stood as the very model of what we ought to expect laws of nature to look like, as well as how they ought to function.

This phenomenon can be seen in the work of Euclid himself, especially that in mechanics (Clagett 1955).

One of the dominant interests of the philosophers of science has always been the problem of theory construction. How is a new theory established? To what extent can a theory be changed? Do theories change gradually or are they replaced during revolutions?

Most of the theorizing on these questions has been done with theories of the physical sciences, but there are indications that, for several reasons, Darwin's theory of evolution does not fit in the traditional framework. For instance, the number of theories still competing with each other in the 80 year period from the Darwinian revolution (1859) to about 1940 is quite extraordinarily large, and it was not one of these competing theories that was ultimately victorious, but rather an eclectic theory in which the best components of several opposing theories were synthesized in the 1940s.

A symposium is an occasion for broad brush strokes, and bold theses. We can qualify, indeed repent of these theses at leisure. But i t is only by bringing them into full view in their strongest form, that we may see where the issues lie , and be. instructed about our mistakes by our betters. I certainly count this distinguished company as my betters on the present subject, so I am unwilling to miss this opportunity to be instructed. I shall make claims with which all my fellow-symposiasts should disagree. (Indeed, in a cool hour, I may come to repudiate them too.)

One subject on which I shall have nothing to say is Darwinism-Yesterday, the historical and scholarly questions about what exactly Darwin said or thought. I am also not concerned with the social, psychological, or ideological causes of his and his successors’ beliefs.

Accounts of the structure of scientific theories in twentieth century philosophy of science have tended to focus on epistemological questions to the near exclusion of the metaphysical consequences of their solutions. This emphasis can be understood as resulting from the interest and concerns of the logical positivist movement and continued by proponents of the so-called “received view” of theories (Suppe 1977). One area where this division of interest has been a barrier to progress is understanding the growth of scientific knowledge.

While philosophers as diverse as Nagel, Hempel, Kuhn, and Lakatos have attempted to explain the historical course of science, they have largely built their views on foundations designed to explicate the relation between theories (paradigms, scientific research programs) and the world. Thus, the received view's model of progress via theory (or indeed, whole science) reduction (e.g., Nagel 1961) rests on its largely syntactic/logical account of theory structure.

Bas van Fraassen has formulated a semantical or model theoretic analysis of the structure of scientific theories. He contrasts his semantical approach with the syntactic approach of the logical positivists and argues that his theory is preferable on a number of grounds. My aims in this paper will be threefold. First, I will present a brief description of van Fraassen's approach. Secondly, I will compare his theory with that of the logical positivists and, in so doing, identify the virtues that van Fraassen believes recommend, his theory over the positivist theory. Finally, I will raise an objection that is positivist in spirit which suggests that, epistemically, his account is indistinguishable from classical historicism.

For van Fraassen, “To present a theory is to specify a family of structures, its models; and secondly, to specify certain parts of these models (the empirical substructures) as candidates for the direct representation of observable phenomena.

Philosophers concerned with the nature of rational decision making have distinguished two paradigms for rational deliberation. According to evidential decision theory, one, should, when faced with alternative courses of action, perform an act whose performance would constitute the best possible evidence that one will, get the good outcomes and not get the bad outcomes. On this paradigm, therefore, deliberation consists in trying to figure out which of the available actions is such that performing it should cause one's beliefs to be altered in such a way that the good outcomes will be as subjectively probable as possible and the bad outcomes as subjectively improbable aspossible, given the constraints imposed by one's prior beliefs. According to causal decision theory, on the-other hand, one should be explicitly concerned with the causal relations between the available acts and the possible outcomes.

One of the central problems of Kuhn's theory of scientific development is its reductionistic and local approach, i.e., its application of one basic pattern of scientific development—Kuhnian revolutions or K-revolutions—to only one area of science, the physical sciences. But the question arises as to why significant developmental episodes in the history of physics and chemistry only should be taken as paradigm cases, especially inasmuch as Kuhn himself claims to be describing and explaining the development of science generally. As Kuhn says, scientific revolutions “are at the heart of the most significant episodes of scientific development.“(Kuhn 1962, p. 140).

I shall take a somewhat radical position. First, I shall argue that the concepts of paradigm shift and scientific revolution are asymmetrical. That is, paradigm shifts represent a genus, and scientific revolutions are species within that genus; and whereas all K-revolutions are paradigm shifts, the converse does not hold.

There is a conflict between the intuition of scientists, and even many nonscientists, who see science as making progress, as being, in fact, the paradigm case of what it means to have progress in knowledge, and the writings of many philosophers of science who may be labeled ‘historicists’. For the most part the historicists do not deny progress outright. However, they have undercut previously accepted accounts of how science progresses.

Most methodological writing on economics is by economists. Although the bulk is produced by lesser members of the profession, almost all leading economists have at one time or another tried their hand at methodological reflection. The results are usually poor. If one read only their methodology, one would have a hard time understanding how Milton Friedman or Paul Samuelson could possibly win Nobel Prizes. It thus is less surprising that the economics profession professes such scorn for philosophizing than that its members spend so much of their time doing it.

Methodological reflections on economics pose other puzzles, too. Although this literature is heavily influenced by philosophy—both current and, especially, out-dated—, it is cut off from philosophical discourse. This quasi-autonomy is puzzling, since this literature is concerned with questions that appear to be instances of, if not the same as the questions with which philosophers of science are concerned.

Thomas Kuhn (1962) proposed that there are theories which are not only incompatible but also semantically incommensurable in order to explain historical evidence that scientists who hold consecutive theories often fail to come to terms with each other, being unable to resolve differences by appeal to evidence, authority or convention. Despite Kuhn's objections, this thesis has generally been interpreted by friends and foes alike so as to preclude direct rational communication across revolutionary divides in science. In this paper, I will sketch a weaker form of incommensurability which allows eventual comparison of incommensurable theories, but is consistent with Kuhn's model of science.

According to Kuhn, mature science normally operates within a disciplinary matrix which determines the nature of both scientific problems and their solutions. Such a matrix is composed of an articulated formalism, together with a set of standard problems called “exemplars”, and a set of preferred analogies for extending the exemplars to new applications.

A number of evaluations of the general prospects of Carnap's program of inductive logic have been presented on different occasions (e.g., Adler 1980, Jeffrey 1973, Kuipers 1984a, Lakatos 1968, Niiniluoto 1982). Niiniluoto's and my own account are the most positive about the internal strength of the program, provided one includes open systems of inductive probability, i.e., systems with non-zero probabilities for contingent universal generalizations. As is well-known, this was done for the first time by Hintikka.

This paper will not add a new evaluation to the list. Instead, I will show that the internal heuristic of Carnap's restricted program is already strong enough to solve one of its major problems, i.e., the problem of integrating analogy influences in systems of inductive probability.

Carnap has given considerable attention to the problem of analogy; to be precise, to what he called analogy by similarity, or analogy influences based on a distance function between the predicates.

It is natural to invoke geological metaphors to describe the impact and the lasting significance of Gödel's incompleteness theorems. Indeed, how better to convey the impact of those results - - whose effect on Hilbert's program was so devastating and whose philosophical reverberations have yet to subside - - than to speak of tremors and shock waves? The image of shaken foundations is irresistible.

Some of those, including the present writer, who criticize standard models of explanation, such as Hempel's D-N model or Salmon's S-R model, do so on the grounds that explanation is a “pragmatic” or “contextual” concept—an idea which the standard models seem to reject. Yet the sense in which explanation is, or is not, pragmatic is not always made clear by the critics or champions of the models. Indeed, some critics and some champions may even mean different things by “pragmatic” or “contextual”. In this paper I want to try to clarify a sense in which explanations might reasonably be considered pragmatic, discuss a couple of theories that are or are not pragmatic in this sense, argue the advantages of a pragmatic account, and briefly note some consequences of this for those seeking models of explanation.

In their classic work on the logic of explanation Hempel and Oppenheim (1948) claim that to explain the phenomena in the world of our experience is to answer the question “why?”, rather than the question “what?”. But there is a source of embarrassment, viz., the underdeveloped logic of why-questions itself. In this paper I want to explore some recent advances which, I shall argue, help us to overcome some of the embarrassment.

One way in which the logic of questions could help is proposed by Jaakko Hintikka. According to Hintikka (1981a) we can look upon scientific inquiry as a series of questions put to nature. For instance a scientist who tests a theory first derives its consequences C1,...,Cn and then asks nature questions of the form “Is CQ true?”. The inquirer (querier) here attempts to induce from nature one of the conclusive answers “Co is true” or “Co is not true”.

When one takes a long look at the concept (or concepts) of scientific explanation, it is possible and plausible to distinguish three fundamental philosophical views. These might be called the epistemic, modal, and ontic. They can be discerned in Aristotle's Posterior Analytics and they are conspicuous in the twentieth-century literature. In its classic form—the inferential version—the epistemic conception takes scientific explanations to be arguments. During the period of almost four decades since the publication of the landmark Hempel-Oppenheim article, “Studies in the Logic of Explanation” (1948), the chairman of this symposium (Carl G. Hempel) has done more than anyone else to articulate, elaborate, and defend this basic conception and the familiar models that give it substance (Hempel 1965), though it has, of course, had many other champions as well. According to the modal conception, scientific explanations do their jobs by showing that what did happen had to happen.

It has been suggested by Larry Laudan and others that scientific inquiry be conceptualized as a problem-solving and question-answering activity. This approach will be called here the interrogative conception of scientific inquiry. The logic of such a conception of scientific inquiry has not been studied systematically, however. In this paper, some of the main aspects of the logic on which the interrogative conception of science is based will. be briefly outlined on certain simplifying assumptions.

It is in fact natural to think of the typical task that confronts a scientist as a question-answer process in two different senses. Our scientist - I shall call her or him the Inquirer - is given a theory T as a starting-point and a question “C or C?” to be answered. Theory T is here assumed to be a truly general theory, i.e., it is assumed not to contain any individual constants.

Among objects and events in the world some have been or eventually will be observed. Others never have been and never will be. Current wisdom has it that among these latter are those that are nonetheless observable. Furthermore, the class of observable, not just observed, phenomena determines the empirical import of science. As van Fraassen tells us, a theory is empirically adequate if “what the theory says about what is observable (by us) it true.” (1980, p. 18). If there are quibbles with this picture, they are with the feasibility of a nonarbitrary or a theory-neutral distinction between the observable and the unobservable, but not with the idea that there are observable yet forever unobserved objects and events.

This, however, is precisely my quibble. Concrete items of the world—events and objects—are either observed or unobserved but, I urge, are not in addition observable or unobservable. This is not because I deny that a nonarbitrary or theory-neutral distinction can be drawn.