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.

How are scientific concepts formed? This question was central for positivist and operationalist philosophers concerned to root scientific thought directly in experience (e.g., Hempel 1952, Bridgman 1927). Although the positivist program has been abandoned, the current interest in the philosophy of scientific discovery shows the need for a theory of conceptual development. This paper offers a theory of how new concepts can arise, not by abstraction from experience or by definition, but by conceptual combination. Such combination produces a new concept as a non-linear, non-definitional amalgam of existing concepts. After proposing rules intended to account for a variety of mundane cases of conceptual combination, the paper presents several illustrations of how scientific concepts have arisen through combination.

According to a strict empiricist position (Hume 1739), concepts are abstracted from experience or formed by definition. You form the concept of a dog by experiencing a number of examples of dogs and extracting the common features.

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.

Several 17th- and 18th-century natural philosophers and methodologists aimed to establish a body of positive scientific results which were more than hypothetical or conjectural. They made exaggerated claims for the truth and empirical pedigree of their scientific conclusions. Since the mid-19th century, investigators have been more circumspect; and, increasingly in the 20th century, reflective scientists have become explicit fallibilists. They frequently acknowledge that current results are unlikely to endure.

Seemingly in keeping with the working scientists own attitude, many, perhaps most, contemporary philosophers of science—in the wake of dramatic revolutions in several sciences and philosophical attacks on the quest for certainty—now take for granted the hypothetical, the conjectural nature of all Interesting scientific claims, particularly deep theoretical claims. According to these philosophers, the lesson we have learned from 19th-century methodologists is that 17th-century discovery programs, which aimed to justify theories by “deduction from the phenomena”, were only utopian dreams.

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.

Could there have been a more down to earth philosopher of science than Charles Saunders Peirce? His later years are characterized by metaphysical opinions that are speculative. Yet throughout his career, his view of scientific method was quintessentially pragmatic. For instance, he reckons the testability of scientific hypotheses by these oft-repeated standards: “money, time, energy, thought” (7.220). He came to the philosophy of science from the laboratory by a route involving a dispute with leading scientists, carried on in the scientific journals and congresses of his day, and reported to the International Geodetic Committee. The dispute concerned the soundness of the design of certain experiments carried out by Peirce and others to measure the strength of the gravitational field at the Earth's surface. (Peirce's own account of these events is given in 7.1 - 7.20.

Cognitivism is now rather clearly the dominant approach in psychology. Philosophers such as Putnam (1975), Dennett (1978), Lycan (1981), and Cummins (1983) have supported the cognitivist strategy by proposing that mental states are to be defined functionally in terms of their interactions with other mental states. One of the most prominent features of the cognitivist-functionalist position is the autonomy it is thought to bestow upon psychology. Psychology, as viewed from this perspective, describes the processing of mental representations within the mind-brain and does not need to concern itself with the neurological activity that underlies its operation.

The arguments that are raised to support the autonomy of psychology from neurophysiology are arguments against a strong reductionist position that makes psychology dispensable (a view held, for example, by P.S. Churchland (1980)). The arguments are designed to show that there are regularities in nature that are not captured in the laws of physics.

In an interesting recent paper, Geroch (1984) has sought to state the content of, “and to some extent to advocate” a view toward quantum mechanics which is at least closely akin to the view advanced by Everett, known popularly (but, arguably, misleadingly) as the many-worlds interpretation. While sensitive to objections along the lines of that by Stein quoted above, Geroch believes that these can adequately be answered. The key to answering such objections is to argue that physics is not responsible for accounting for our experience of physical phenomena—it is enough that it account for the physical phenomena themselves. It is this last argument that I wish to examine in this paper, both in general, and specifically in its application to Everett's interpretation of quantum mechanics.

What are the eplstemolog leal virtues that we value In scientific theories? In The Scientific Image. Bas van Fraassen (1980) argues that the preeminent virtue Is empirical adequacy: the capacity of a theory to “save the phenomena”. In an Intuitive sense a theory Is empirically adequate if “What It says about the observable things and events in this world is true.” This point of view, according to which the eplstemologlcal aim of science is to save the phenomena, van Fraassen calls constructive empiricism. In an earlier “constructive critique” of constructive empiricism (1983), I argued that there were serious problems In van Fraassen's proposal for extending the notion of empirical adequacy to statistical theories. In that paper I suggested an alternative definition for the empirical adequacy of a simple statistical hypothesis: roughly speaking, the idea Is that a simple statistical hypothesis Is empirically adequate provided that there does not exist another simple hypothesis which has a higher likelihood relative to the set of all phenomena (past, present, and future) In the actual world.

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.

Here follows a puzzle for those attempting to explain inductive inference. Suppose one hypothesis, H, implies another, I. Suppose further we obtain evidence, E, deemed sufficient to warrant the rejection of I. Is this evidence sufficient to warrant the rejection of H as well?

It is very tempting to answer this question affirmatively. The inference in question appears to be justified by a single use of modus tollens or denying the consequent:

A testament to the obvious plausibility of this sort of inference is the ubiquity of its endorsement in treatises on inductive inference. See, for example, Popper (Popper 1935, p. 76), Hempel (Hempel 1945, p. 31), Hacking (Hacking 1976, p. 33), or Savage (Savage 1954, p. 32). Indeed, a referee reporting on another paper called the following “rule of implication”:

(+) If hypothesis H implies hypothesis I, then evidence sufficient to warrant the rejection of I, in turn warrants the rejection of H.