This paper discusses a philosophical issue in taxonomy. At least one philosopher has suggested the taxonomic principle that scientific kinds are disjoint. An opposing position is defended here by marshalling examples of nondisjoint categories which belong to different, coexisting classification schemes. This denial of the disjointness principle can be recast as the claim that scientific classification is “interest-relative”. But why would anyone have held that scientific categories are disjoint in the first place? It is argued that this assumption is needed in one attempt to derive essentialism. This shows why the essentialist and interest-relative approaches to classification are in conflict.

This essay is a philosophical evaluation of some of the findings of Wald and Penrose in which they claim to have supported an arrow (or the irreversibility) of time in quantum gravity. First, the notion of lawlike irreversibility (or anisotropy) of time is spelled out, then the general situation in quantum mechanics is briefly discussed. Finally, the findings in quantum gravity are evaluated against such a background. My conclusion is that the arrow of time found in quantum gravity is at best de facto (nonlawlike).

A conventional experiment is proposed to resolve the realist/idealist debate by challenging the premise that double blinding and an attitude of objectivity in general deter the corroborative influence which preconceptions exert on perception. The possibility that objectivity enhances corroboration would not contradict empirical findings, and would account for the success of science.

G. A. Cohen defends and Jon Elster criticizes Marxist use of functional explanation. But Elster's mechanical conception of explanation is, contrary to Elster's claims, a better basis for vindication of functional explanation than Cohen's nomological conception, which cannot provide an adequate account of functional explanation. Elster also objects that functional explanation commits us to metaphysically bizarre collective subjects, but his argument requires an implausible reading of methodological individualism which involves an unattractive eliminativism about social phenomena.

The inductive reliability of Bayesian methods is explored. The first result presented shows that for any solvable inductive problem of a general type, there exists a subjective prior which yields a Bayesian inductive method that solves the problem, although not all subjective priors give rise to a successful inductive method for the problem. The second result shows that the same does not hold for computationally bounded agents, so that Bayesianism is “inductively incomplete” for such agents. Finally a consistency proof shows that inductive agents do not need to disregard inductive failure on sets of subjective probability 0 in order to be ideally rational. Together the results reveal the inadequacy of the subjective Bayesian norms for scientific methodology.

According to a familiar argument, iterated prisoner's dilemmas of known finite lengths resolve for ideally rational and well-informed players: They would defect in the last round, anticipate this in the next to last round and so defect in it, and so on. But would they anticipate defections even if they had been cooperating? Not necessarily, say recent critics. These critics “lose” the backward-induction paradox by imposing indicative interpretations on rationality and information conditions. To regain it I propose subjunctive interpretations. To solve it I stress that implications for ordinary imperfect players are limited.

In Gemes (1990) I examined certain formal versions of hypothetico-deductivism (H-D) showing that they have the unacceptable consequence that “Abe is a white raven” confirms “All ravens are black”! In Gemes (1992) I developed a new notion of content that could save H-D from this bizarre consequence. In this paper, I argue that more traditional formulations of H-D also need recourse to this new notion of content. I present a new account of the vexing notion of the natural axiomatization of a theory. The notion is used to construct a form of H-D that allows for the type of selective confirmation without which Glymour (1980a,b) claims H-D is hopeless.

In Grünbaum (1989, 374, 390), I objected to Narlikar's (1977, 136–137) designation “event of ‘creation’” for a supposed first cosmic instant t = 0, which he imports into the big bang cosmology of the general theory of relativity (GTR). Narlikar (1992, 361–362) does reject a theological construal of the “creation”. But, endeavoring to justify his secular creationism, he now points out that, in the GTR, the usual derivation of matter-energy conservation from Hilbert's stationary action principle cannot be extended to include the putative first instant t = 0. Narlikar reasons that this “breakdown” in the derivation of energy conservation at t = 0 qualifies the putative initial event as the “creation event”. I argue that this inference is multiply fallacious.

Relying on an analysis of the case of gravitational lensing, Hacking argues for a “modest antirealism” in astronomy. It is shown here that neither his scientific arguments nor his philosophical doctrines imply an antirealist conclusion. An alternative, realistic interpretation of gravitational lensing, and of the nature and history of astronomy more generally, is suggested.

In the context of a discussion of time symmetry in the quantum mechanical measurement process, Aharonov et al. (1964) derived an expression concerning probabilities for the outcomes of measurements conducted on systems which have been pre- and postselected on the basis of both preceding and succeeding measurements. Recent literature has claimed that a resulting “time-symmetrized” interpretation of quantum mechanics has significant implications for some basic issues, such as contextuality and determinateness, in elementary, nonrelativistic quantum mechanics. Bub and Brown (1986) have shown that under the standard interpretation of the aforementioned expression, these claims employ ensembles which are not well defined. It is argued here that under a counterfactual interpretation of the expression, these claims may be understood as employing well-defined ensembles; it is shown, however, that such an interpretation cannot be reconciled with the standard interpretation of quantum mechanics.

Maher (1992b) advances an objection to dynamic Dutch-book arguments, partly inspired by the discussion in Levi (1987; in particular by Levi's case 2, p. 204). Informally, the objection is that the decision maker will “see the dutch book coming” and consequently refuse to bet, thus escaping the Dutch book. Maher makes this explicit by modeling the decision maker's choices as a sequential decision problem. On this basis he claims that there is a mistake in dynamic coherence arguments. There is really no formal mistake in classical dynamic coherence arguments, but the discussions in Maher and Levi do suggest interesting ways in which the definition of dynamic coherence might be strengthened. Such a strengthened “sequentialized” notion of dynamic coherence is explored here. It so happens that even on the strengthened standards for a Dutch book, the classic dynamic coherence argument for conditioning still goes through.

Alasdair MacIntyre's expression of the “profound gratitude we all owe to Althusser for having brought French Marxism back into dialogue with the rest of French philosophy” (as quoted by Elliott in his introduction to the selection under discussion, 1990, xi), important as it may be for a host of reasons, did not try to make Althusser's philosophy particularly attractive to philosophers of science. However, the present selection of essays does precisely this: It is almost ideally designed to mark the beginnings of an effective encounter of this particular brand of “French Marxism” with philosophy of science.

Shown here is that a constraint used by Popper in The Logic of Scientific Discovery (1959) for calculating the absolute probability of a universal quantification, and one introduced by Stalnaker in “Probability and Conditionals” (1970, 70) for calculating the relative probability of a negation, are too weak for the job. The constraint wanted in the first case is in Bendali (1979) and that wanted in the second case is in Popper (1959).

R. Laudan and L. Laudan (1989) have put forth a new model intended to solve the problem of disagreement, the problem of consensus, and the problem of innovation in science. In support of this model they cite the history of the acceptance of continental drift, or plate tectonics. In this discussion, I claim that this episode does not constitute an instance of their model. The historical evidence does not support this model. Indeed, closer examination seems to weaken it. I also sketch an alternative model.

Evidence for a hypothesis typically confirms the hypothesis more if the evidence was predicted than if it was accommodated. Or so I argued in previous papers, where I also developed an analysis of why this should be so. But this was all a mistake if Howson and Franklin (1991) are to be believed. In this paper, I show why they are not to be believed. I also identify a grain of truth that may have been dimly grasped by those Bayesians who deny the confirmatory value of prediction.

In a recent paper Stein (1991) makes a number of criticisms of an earlier paper of mine (Maxwell 1985) that explored the question of whether the idea that the future is genuinely “open” in a probabilistic universe is compatible with special relativity. I disagree with almost all of Stein's criticisms.

When Bloor's Knowledge and Social Imagery was first published in 1976, it was not the first time that a “strong programme” in the sociology of knowledge was treated to a hostile reception by philosophers. But never before has such a dialectically unproductive encounter with philosophers led to such a methodologically fruitful response, for, when an array of positivist, historicist, Popperian, and realist philosophers argued against Bloor and his Edinburgh colleagues that normative accounts of scientific rationality could not be refuted by empirical accounts of what scientists do (see Brown 1984), an entire line of research was launched that sought to explain science without having to make reference to the philosophers' cherished norms. This is the field now known as Science and Technology Studies (STS). Although STS is normally taken to be intellectually centered in sociology, its main practitioners are just as likely to have been drawn from philosophy and the natural sciences (as in the case of the original Edinburgh School) as from the social sciences proper. The unmistakable mark of Bloor's influence is that, unlike the sociology of science most recognizable to sociologists (e.g., Merton 1973), the STS practitioner is committed to studying science in the same spirit of analytic detachment and epistemic neutrality as she would any other aspect of society. In practice, this has amounted to a preference for methods that incorporate “ethnographic distance” (e.g., Latour and Woolgar [1979] 1986), although in recent years theoretical debate has increasingly focused on the appropriate attitude that STS practitioners should adopt toward science, given their findings to date (see Pickering 1992, Fuller 1992b). I will return to this debate at the end of this essay.