We investigate the thesis of Aharonov, Bergmann, and Lebowitz that time-symmetry holds in ensembles defined by both an initial and a final condition, called preand postselected ensembles. We distinguish two senses of time symmetry and show that the first one, concerning forward directed and time reversed measurements, holds if the measurement process is ideal, but fails if the measurement process is non-ideal, i.e., violates Lüders's rule. The second kind of time symmetry, concerning the interchange of initial and final conditions, fails (...) even in the case of ideal measurements. Bayes's theorem is used as a primary tool for calculating the relevant probabilities. We are critical of the concept that a pair of vectors in Hilbert space, characterizing the initial and final conditions, can be considered to constitute a generalized quantum state. (shrink)
Some desiderata for scientific confirmation are formulated in the light of a tentative scientific world view. Bayesian confirmation theories generically satisfy most of these desiderata, but one of them, "the strategy of ascent," fits best in a tempered personalist version of Bayesianism. There are both empirical and rational components, dialectically combined, in tempered personalism. The question of explanation vs. prediction is treated in a Bayesian manner, and it is found that both operations are susceptible to characteristic systematic errors. If these (...) are eliminated, however, then explanation and prediction provide equally good evidential support for hypotheses. (shrink)
Abner Shimony is one of the most eminent of present-day philosophers of science, whose work has exerted a profound influence in both the philosophy and physics communities. This two-volume collection of his essays written over a period of forty years explores the interrelations between science and philosophy. Shimony regards the knowing subject as an entity in nature whose faculties must be studied from the points of view of evolutionary biology and empirical psychology. He maintains that the twentieth century is one (...) of the great ages of metaphysics, given the deep implications of quantum mechanics, relativity theory, and molecular biology. Nevertheless he rejects the thesis that mentality is entirely explicable in physical terms and argues that mind has a fundamental place in nature. Though distinguishing between values and scientifically established facts, Shimony holds that the sense of wonder cultivated by the natural sciences is one of the noblest of human values. The first volume, Scientific Method and Epistemology, deals with the dialectic of subject and object, epistemic probability, induction and scientific theories, perception and conception, and fact and values. The focus of the second volume, Natural Sciences and Metaphysics, is on quantum mechanical measurement and non-locality, parts and wholes, time, and mind and matter. (shrink)
If quantum mechanics is interpreted as an objective, complete, physical theory, applying to macroscopic as well as microscopic systems, then the linearity of quantum dynamics gives rise to the measurement problem and related problems, which cannot be solved without modifying the dynamics. Eight desiderata are proposed for a reasonable modified theory. They favor a stochastic modification rather than a deterministic non-linear one, but the spontaneous localization theories of Ghirardi et al. and Pearle are criticized. The intermittent fluorescence of a trapped (...) atom irradiated by two laser beams suggests a stochastic theory in which the locus of stochasticity is interaction between a material system and the electromagnetic vacuum. (shrink)
The theory of natural selection is a rich systematization of biological knowledge without a first principle. When formulations of a proposed principle of natural selection are examined carefully, each is seen to be exhaustively analyzable into a proposition about sources of fitness and a proposition about consequences of fitness. But whenever the fitness of an organic variety is well defined in a given biological situation, its sources are local contingencies together with the background of laws from disciplines other than the (...) theory of natural selection; and the consequences of fitness for the long range fate of organic varieties are essentially applications of probability theory. Hence there is no role and no need for a principle of the theory of natural selection, and any generalities that may hold in that theory are derivative rather than fundamental. (shrink)
Noncontextual hidden variables theories, assigning simultaneous values to all quantum mechanical observables, are inconsistent by theorems of Gleason and others. These theorems do not exclude contextual hidden variables theories, in which a complete state assigns values to physical quantities only relative to contexts. However, any contextual theory obeying a certain factorisability conditions implies one of Bell's Inequalities, thereby precluding complete agreement with quantum mechanical predictions. The present paper distinguishes two kinds of contextual theories, ‘algebraic’ and ‘environmental’, and investigates when factorisability (...) is reasonable. Some statements by Fine about the philosophical significance of Bell's Inequalities are then assessed. (shrink)
A combination of methodological considerations and propositions about the causal structure of spacetime provides a reply to Fine's criticisms of the "factorizability requirement" used in several versions of Bell's theorem. His proposal of "action in harmony" is criticized. Experimental tests are proposed for both the "synchronization models" and the "prism models", which Fine has invented as loopholes to Bell's theorem. A theorem of Suppes and Zanotti which purports to show the impossibility of hidden variables is criticized. One of their crucial (...) premisses seems to be justifiable only if one accepts a Parmenidean metaphysics. (shrink)
