In this paper I attempt to tie together a longstanding dispute between Henry Kyburg and Isaac Levi concerning statistical inferences. The debate, which centers around the example of Petersen the Swede, concerns Kyburg's and Levi's accounts of randomness and choosing reference classes. I argue that both Kyburg and Levi have missed the real significance of their dispute, that Levi's claim that Kyburg violates Confirmational Conditionalization is insufficient, and that Kyburg has failed to show that Levi's criteria for choosing reference class are problematic. Rather, the significance of the Petersen case is to show that other aspects of their respective systems are defective: for Levi his account of credal judgments other than direct inference, and for Kyburg his explanation of how indexes are associated with a body of knowledge.

Isaac Levi and I have different views of probability and decision making. Here, without addressing the merits, I will try to answer some questions recently asked by Levi (1985) about what my view is, and how it relates to his.

By reference to Maxwell's kinetic theory, one feature of hypothetico-deductivism is defended. A scientist need make no inference to a hypothesis when he first proposes it. He may have no reason at all for thinking it is true. Yet it may be worth considering. In developing his kinetic theory there were central assumptions Maxwell made (for example, that molecules are spherical, that they exert contact forces, and that their motion is linear) that he had no reason to believe true. In this paper I develop a position that explains why they were worth considering, and that rejects the retroductive position that a hypothesis is worth considering when, if true, it would explain the observed data.

Ferdinand Schoeman (1986) attempts to refute six arguments that I gave in The Probable and the Provable (1977, pp. 49–120) for not analyzing the standards of forensic proof in terms of any concept of probability that conforms to the familiar principles of the mathematical calculus of chance. But he evidently does not appreciate the strength of the case for rejecting the validity of any such analysis. In the course of discussing his criticisms, I shall add a seventh argument to fortify my position, though I concede that the second of my original arguments has to be discarded.

Is sociobiology a new paradigm? A number of people have claimed that it is. I argue that, sociologically speaking, it may well be. But epistemologically, it is not. The case rests on one's interpretation of the major Darwinian evolutionary mechanism, natural selection. In this note, it is shown that sociobiology relies on an orthodox understanding of selection. Thus, in crucial epistemological respects, sociobiology is continuous with the rest of Darwinian evolutionary theory.

There is renewed interest in the logic of discovery as well as in the position that there is no reason for philosophers to bother with it. This essay shows that the traditional, philosophical arguments for the latter position are bankrupt. Moreover, no interesting defense of the philosophical irrelevance or impossibility of the logic of discovery can be formulated or defended in isolation from computation-theoretic considerations.

Isaac Levi uses C. S. Peirce's fallibilism as a foil for his own “epistemological infallibilism“. I argue that Levi's criticisms of Peirce do not hit their target, and that the two pragmatists agree on the fundamental issues concerning background knowledge, certainty, revision of belief, and the aims of inquiry.

Urbach (1985) has concluded that the use of randomization in the design of clinical and agricultural trials is both inappropriate and ineffective. It is argued here that it is appropriate, as it eliminates the dependence of inference on the unknown precise physical model that underlies a set of observations, and effective, in that it is relatively simple to apply in practice compared with any competing method. Furthermore, it has been proven in practice.

John Dupré (1984) has recently criticized the theory of probabilistic causality developed by, among others, Good (1961–62), Suppes (1970), Cartwright (1979), and Skyrms (1980). He argues that there is a tension or incompatibility between one of its central requirements for the presence of a causal connection, on the one hand, and a feature of the theory pointed out by Elliott Sober and me (1983), on the other. He also argues that the requirement just alluded to should be given up. I defend the theory against Dupré‘s criticisms and conclude with comments on Dupré‘s appraisal of the bearing of his arguments on the nature of probabilistic causal laws.

In a recent discussion note Sober (1985) elaborates on the argument given in Sober (1982) to show the inadequacy of Ronald Giere's (1979, 1980) causal model for cases of frequency-dependent causation, and denies that Giere's (1984) response avoids the problem he raises. I argue that frequency-dependent effects do not pose a problem for Giere's original causal model, and that all parties in this dispute have been guity of misinterpreting the counterfactual populations involved in applying Giere's model.

Clark Glymour has argued that hypothetico-deductivism, which many take to be an important method of scientific confirmation, is hopeless because it cannot be reconstructed in classical logic. Such reconstructions, as Glymour points out, fail to uphold the condition of relevance between theory and evidence. I argue that the source of the irrelevant confirmations licensed by these reconstructions lies not with hypothetico-deductivism itself, but with the classical logic in which it is typically reconstructed. I present a new reconstruction of hypothetico-deductivism in relevance logic that does maintain the condition of relevance between theory and evidence. Hence, if hypothetico-deductivism is an important rationale in science, we have good reason to believe that the logic underlying scientific discourse is captured better by relevance logic than by its classical counterpart.

If the decades of the forties through the sixties were dominated by discussion of Hempel's “covering law“ explication of explanation (and its variants), that of the seventies was preoccupied with Salmon's “statistical relevance” conception, which emerged as the principal alternative to Hempel's enormously influential account. Readers of Wesley C. Salmon's Scientific Explanation and the Causal Structure of the World (Salmon 1984), therefore, ought to find it refreshing to discover that its author has not remained content with a facile defense of his previous investigations; on the contrary, Salmon offers an original account of different kinds of explications, advances additional criticisms of various alternative theories, and elaborates a novel “two-tiered“ analysis of explanation that tacitly depends upon a “two-tiered” account of homogeneity. Indeed, if the considerations that follow are correct, Salmon has not merely refined his statistical relevance account but has actually abandoned it in favor of a “causal/mechanistic“ construction. This striking development suggests that the theory of explanation is likely to remain as lively an arena of debate in the eighties as it has been in the past.

The aim of Stich's book is to further the controversial thesis that the conceptual framework of ‘folk’ psychology will have no significant role to play in a mature cognitive science. Skepticism about the scientific relevance of folk psychology has been voiced by others (behaviorists and nonbehaviorists alike); but Stich's critique is both novel and more fully developed than earlier ones. The charge is not–-or not simply–-that ‘folk theory’ is a “degenerating paradigm“ (Churchlands), or that, in general, the constructs of folk theory fail to refer altogether (Rorty; Dennett). Stich's thesis is subtler, and rests on the claim that the individuation of folk-psychological states is irremediably vague and context-and-observer relative in a way that makes a folk-psychological taxonomy ill-suited to the requirements of scientific explanation and systematization. Stich, of course, does not reject mentalism as such, as did the behaviorists: he merely rejects the assumption–-often tacitly accepted by cognitive scientists and by their philosophical interpreters–-that the mental states posited by a mature cognitive science will essentially correspond to the intentional, propositional attitude states of folk psychology. Thus, for Stich, there is no reason to suppose that cognitive science will turn out to be a sophisticated extension of folk psychology. The “Panglossian prospect” (p. 5) of a conceptual reunification of the scientific image of mind with the ‘manifest’ image under the banner of cognitivism is just what this book calls into question.

We argue that Horgan's program for nominalizing science fails, because its translation of quantitative statements destroys the inferential structures of explanations, predictions and retrodictions of nonquantitative scientific facts.

The likelihood justification of cladistic parsimony suggested in Sober (1984) is here shown to be incomplete. Even so, cladistic parsimony remains a counterexample to the principle of the common cause formulated by Reichenbach (1956) and Salmon (1975, 1979, 1984).

Although Hale and Resnik are correct in their specific objection to my proposal for nominalizing science, the proposal can be saved by means of a simple and plausible modification.