Richard Jeffrey's generalization of Bayes' rule of conditioning follows, within the theory of belief functions, from Dempster's rule of combination and the rule of minimal extension. Both Jeffrey's rule and the theory of belief functions can and should be construed constructively, rather than normatively or descriptively. The theory of belief functions gives a more thorough analysis of how beliefs might be constructed than Jeffrey's rule does. The inadequacy of Bayesian conditioning is much more general than Jeffrey's examples of uncertain perception might suggest. The “parameter α” that Hartry Field has introduced into Jeffrey's rule corresponds to the “weight of evidence” of the theory of belief functions.

John Stuart Mill regards economics as an inexact and separate science which employs a deductive method. This paper analyzes and restates Mill's views and considers whether they help one to understand philosophical peculiarities of contemporary microeconomic theory. The author concludes that it is philosophically enlightening to interpret microeconomics as an inexact and separate science, but that Mill's notion of a deductive method has only a little to contribute.

The paper considers recent proposals by Armstrong, Dretske, and Tooley that revive the view that statements of laws of nature are grounded by the existence of higher order facts relating universale. Several objections to such a view are raised and an alternative analysis, recognizing general facts, is considered. Such an alternative is shown to meet a number of the objections raised against the appeal to higher order facts and it is also related to views of Hume and Wittgenstein. Further objections are then raised to all the non-Humean “realist” attempts to provide special facts to ground the laws of nature.

Although the theory of Jean Piaget is correctly characterized as genetic epistemology, its nature and scope remain unclear and controversial. An examination of Piaget's Introduction à l'épistémologie génétique indicates that Piaget relies heavily upon a model of comparative anatomy and, consequently, that genetic epistemology is about both the history of science and individual development. This biological model seems to be the basis for Piaget's view that the history of science can be seen as a (Kantian) history of scientific concepts whereas psychogenetic development is a history of these very same concepts on the individual level. Finally, although there are passages indicating a different interpretation of the scope of genetic epistemology, I give several reasons for preferring the more liberal interpretation.

This paper supplements an earlier one (Wassermann 1978b). Its views aim to reinforce those of Lewontin and other prominent evolutionists, but differ significantly from the opinions of some philosophers of science, notably Popper (1957) and Olding (1978). A basic distinction is made between ‘laws’ and ‘theories of mechanisms’. The ‘Theory of Evolution’ is not characterized by laws, but is viewed here as a hypertheory which explains classifiable evolutionary phenomena in terms of subordinate classifiable theories of ‘evolution-specific mechanisms’ (ESMs), each of which could apply to a host of species. Adaptations could result from ESMs that are rooted in molecular complementarities. The status of optimization theories that aim to predict best adapted states of organisms or populations is also discussed.

Most patterns of an organism develop reproducibly and predictably. Thus, most biological patterns are largely predetermined by the nature of the zygote and by the nature of the surrounding world. Some ontogenetic patterns can also be considered to be preformed. Eighteenth and nineteenth century definitions of ‘preformation’ suggested that all aspects of a precursor pattern—its elements and its configuration—are preserved during development. Today, the idea of preformed configurations has been lost. To revive this lost idea, we offer the following biologically contemporary definition for preformed ontogenetic patterns: preformed patterns are those patterns with topologies that have been conserved during their ontogenies. This definition is presented in precise mathematical language, and its application is demonstrated in a system of developing, abstract patterns.

This paper responds to a recent claim by Shrader-Frechette that current particle physics, with its essentially atomist paradigm, is in a state of Kuhnian crisis. We respond to Shrader-Frechette's claim in two ways: first, we argue directly against much of the evidence used by Shrader-Frechette as indicators of Kuhnian crisis; second, we question Shrader-Frechette's application of Kuhnian categories to current research in general, pointing out the dangers inherent in such an analysis.

This paper explores the status of the von Neumann-Lüders state transition rule (the “projection postulate”) within “real-logic” quantum logic. The entire discussion proceeds from a reading of the Lüders rule according to which, although idealized in applying only to “minimally disturbing” measurements, it nevertheless makes empirical claims and is not a purely mathematical theorem. An argument (due to Friedman and Putnam) is examined to the effect that QL has an explanatory advantage over Copenhagen and other interpretations which relativize truth-value assignments to experimental arrangements. Two versions of QL, the lattice-theoretic (LT) and partial-Boolean-algebra (PBA), are considered. It turns out that the projection postulate is intimately connected with the choice of conditional connective for QL. The effect of the projection postulate is obtained with the Sasaki conditional. However, this choice is found to require extra assumptions, on both the LT and PBA versions, which are either just as ad hoc as the projection postulate itself or indefensible from within the real-logic QL framework.