Many persons would defend a sharp comparison of public policy and public science with judgments uniformly unfavorable to policy. Science is pure, policy is not. Science is essentially theoretical, policy is not. Science is rational, policy is not. Science deals in the factual and uncontroversial, policy does not. Although it is not my claim that public science and public, policy are the same thing, it will be a central thesis of what I have to say that the resemblances between public science and public policy are much closer than they seem, and consequently the philosophy of science and the philosophy of public policy are not widely divergent.

There is one meaning of philosophy of public policy, however, that I want to stay clear of. It is also associated with a meaning that can be attached to the philosophy of science.

Philip Kitcher and his program committee hoped to stimulate a lively debate this evening on the role which philosophers of science might play as advisors to government and the professional institutions of scientists. It is my guess that they had two changes in mind. They wanted more philosophers of science advising in Washington's science policy decisions. They also want you philosophers of science to develop those aspects of your field which are relevant to such decisions. They believe (I would guess) that not all of the scholarship of this association has such relevance, but that much of it does; that the relevant parts can still retain a genuinely epistemological,focus; and that science policy advice is better done by philosophers of science than by any other profession (e.g., the sociology of science). Perhaps I have merely projected these beliefs on to the program committee. They are, in any event, ones I hold and hope that they share.

According to the relational theory of space-time, the physical world contains spatio-temporal aggregates of matter (spatio-temporally extended physical objects, spatio-temporal parts’ of such objects, and aggregates consisting of spatio-temporal parts of different objects); these aggregates of matter are interrelated in various ways by various geometric (and also non-geometric) relations, but the physical world does not contain a space-time over and above these aggregates of matter and their interrelations.

It is tempting to put this doctrine by saying that there are no space-time regions, but only aggregates of matter. This formulation might be faulted, for a relationalist might want to “logically construct” regions out of aggregates of matter, and given such a “logical construction” the relationalist will assert that regions do exist.

In the late 1940s Gödel (1949a) made a fundamental contribution to relativity theory by finding an important new solution to Einstein's equation. It represents a possible universe with quite remarkable properties. For one thing, the entire material content of the Gödel universe Is In a state of uniform, rigid rotation. For another, free test particles in it exhibit a kind of boomerang effect Most striking of all, the Gödel universe allows for the possibility of “time travel” in a certain sense. It is this third feature I want to discuss today.

Of course one can mean various things by “time travel“. In traditional science fiction stories a classical background time structure is presupposed, and the time traveler is described as jumping from the present to the past (or to the future). In a spacetime diagram his worldline would appear as discontinuous.

It is certainly not unreasonable to try to account for patterns of variation in nature in terms of evolution by natural selection. But there are more or less “avid” proponents of this way of understanding nature who are, according to critics, more or less reasonable in inverse proportion. Attempts to understand nature in terms of evolution by natural selection can, according to these critics, be pushed too far. Just how far such pursuits can reasonably be pushed is the central problem of this paper.

I will discuss this issue in the context of an episode in the history of evolutionary biology that has been labelled by Stephen Gould, “the hardening of the evolutionary synthesis” (Gould 1980, 1982, 1983). In the course of the hardening of the synthesis, evolutionists attributed a greater and greater role to natural selection, and correspondingly less and less a role to alternative evolutionary agents—minimizing in particular the role of so-called “random drift”.

Molecular biologists are not accustomed to the attention of philosophers. Ours is a “normal” sort of science, operating very much within the neo-Darwinian paradigm, to flesh out a central dogma (DNA makes RNA makes protein) which is but an articulation, albeit a very important one, of that paradigm (Kuhn 1970). Our success in this enterprise has been remarkable, and we have not until recently had to address our prejudices.” Here I will present my own views on the nature of these prejudices and the troubles they have led us into.

Transposabie elements are a special kind of DNA. Evidence leading directly to an appreciation of their prevalence and an understanding of their behavior began to appear in the early 1960s, from studies of spontaneous mutations in bacteria.

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.

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.

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.

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.

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.