Richard Jeffrey espoused an antifoundationalist variant of Bayesian thinking that he termed ‘Radical Probabilism’. Radical Probabilism denies both the existence of an ideal, unbiased starting point for our attempts to learn about the world and the dogma of classical Bayesianism that the only justified change of belief is one based on the learning of certainties. Probabilistic judgment is basic and irreducible. Bayesian conditioning is appropriate when interaction with the environment yields new certainty of belief in some proposition but leaves one's conditional beliefs untouched (the ‘Rigidity’ condition). Although Richard Jeffrey denied the general applicability of this condition, one of his main contributions to probabilistic thinking is a form of belief updating—now typically called ‘Jeffrey conditioning’ or ‘probability kinematics’—that is appropriate in circumstances in which Rigidity is satisfied, but where the interaction causes one to reevaluate one's probability judgments over some partition of the possibility space without conferring certainty on any particular element. The most familiar occasion for Jeffrey conditioning is receipt of uncertain evidence: things partially perceived or remembered. But it also serves to illuminate belief updating occasioned by a change in one's degrees of conditional belief, a kind of belief change largely ignored by classical Bayesianism. I argue that such changes in conditional belief can also be basic (in the sense of not being analyzable as a consequence of conditioning on factual information) and offer a kinematical model for a particular kind change in conditional belief. Both are applied to changes in preference. Finally, I argue that Rigidity can fail when changes of belief give inferential grounds for changes in conditional belief (and vice versa). These failures show that conditioning methods are properly regarded, not as valid rules of inference, but as tools in the ‘art of judgment’.

The method in human genetics of ascribing causal responsibility to genotype by the use of heritability estimates has been heavily criticized over the years. It has been argued that these estimates are rarely valid and do not trace genetic causation. Recent contributions strike back at this criticism. I present and discuss two opposing views on these matters represented by Richard Lewontin and Neven Sesardic. I suggest that the conflicting perspectives are based in differing concepts of genetic causation and differing motivations and contexts of discussion. I use the distinction between structuring and triggering causes to clarify the basis for the opposing views.

The famous ethological maxim known as ‘Morgan's Canon’ continues to be an object of interpretive controversy. I reconsider Morgan's Canon in light of two questions: First, what did Morgan intend? Second, is this, or perhaps some reinterpretation of the Canon, useful within cognitive ethology? As for the first issue, Morgan's distinction between higher and lower faculties is suggestive of an early supervenience concept. As for the second issue, the Canon, both in its original form and in various recent rereadings, offers nothing useful to cognitive ethology.

In our 1993 paper, “A Critical Look,” Elliott Sober and I concluded that the famous claim about model formulation and constraints made by Richard Levins in his influential 1966 article on model building in population biology is neither true nor normative. Here, I comment upon the claim of Odenbaugh (2003) that the conclusions of “A Critical Look” are incorrect. My conclusions remain that Levins’ claim about the tradeoff between model properties (1) lacks logical coherence, (2) generates an arbitrary model classification, and (3) lacks normative utility. Accordingly, I view his claim as providing no useful insight into the nature of models and model building in population biology.

We introduce a dynamic model for evolutionary games played on a network where strategy changes are correlated according to degree of influence between players. Unlike the notion of stochastic stability (Foster and Young, 1990), which assumes mutations are stochastically independent and identically distributed, our framework allows for the possibility that agents correlate their strategies with the strategies of those they trust, or those who have influence over them. We show that the dynamical properties of evolutionary games, where such influence neighborhoods appear, differ dramatically from those where all mutations are stochastically independent, and establish some elementary convergence results relevant for the evolution of social institutions.

The “usual story” regarding molecular chemistry is that it is roughly an application of quantum mechanics. That is to say, quantum mechanics supplies everything necessary and sufficient, both ontologically and epistemologically, to reduce molecular chemistry to quantum mechanics. This is a reductive story, to be sure, but a key explanatory element of molecular chemistry, namely molecular structure, is absent from the quantum realm. On the other hand, typical characterizations of emergence, such as the unpredictability or inexplicability of molecular structure based on quantum mechanics, do not characterize the relationship between molecular chemistry and quantum mechanics well either. A different scheme for characterizing reduction and emergence is proposed that accommodates the relationship between quantum mechanics and molecular chemistry and some initial objections to the scheme are considered.

This paper tries to get a grip on two seemingly conflicting intuitions about reductionism in quantum mechanics. On one hand it is received wisdom that quantum mechanics puts an end to ‘reductionism’. Quantum entanglement is responsible for such features of quantum mechanics as holism, the failure of supervenience, and emergence. While I agree with these claims, I will argue that it is only part of the story. Quantum mechanics provides us with thoroughgoing reductionist explanations. I will distinguish two kinds of microexplanation (or micro-‘reduction’). I will argue that even though quantum entanglement provides an example of the failure of one kind of microexplanation, it does not affect the other. Contrary to a recent paper by Kronz and Tiehen, I claim that the explanation of the dynamics of quantum mechanical systems is just as reductionist as it used to be in classical mechanics.

Two views of scientific theories dominated the philosophy of science during the twentieth century, the syntactic view of the logical empiricists and the semantic view of their successors. I show that neither view is adequate to provide a proper understanding of the connections that exist between theories at different times. I outline a new approach, a hybrid of the two, that provides the right structural connection between earlier and later theories, and that takes due account of the importance of the mathematical models of a theory (the semantic component) and of the various distinct formulations that pick out these models (the syntactic component).

The present paper examines the role of exact results in the theory of many-body physics, and specifically the example of the Mermin-Wagner theorem, a rigorous result concerning the absence of phase transitions in low-dimensional systems. While the theorem has been shown to hold for a wide range of many-body models, it is frequently ‘violated’ by results derived from the same models using numerical techniques. This raises the question of how scientists regulate their theoretical commitments in such cases, given that the models, too, are often described as approximations to the underlying ‘full’ many-body problem.

Batterman has recently argued that fundamental theories are typically explanatorily inadequate, in that there exist physical phenomena whose explanation requires that the conceptual apparatus of a fundamental theory be supplemented by that of a less fundamental theory. This paper is an extended critical commentary on that argument: situating its importance, describing its structure, and developing a line of objection to it. The objection is that in the examples Batterman considers, the mathematics of the less fundamental theory is definable in terms of the mathematics of the fundamental theory, and that only the latter need be given a physical interpretation—so we can view the desired explanation as drawing only upon resources internal to the more fundamental physical theory.

I respond to Belot's argument and defend the view that sometimes ‘fundamental theories’ are explanatorily inadequate and need to be supplemented with certain aspects of less fundamental ‘theories emeritus’.

Albert (2000) provides a sketch of an entropy account of the causal and counterfactual asymmetries. This paper critically examines a proposal that may be thought to fill in some of the lacunae in Albert's account.