Andrew Wayne

Bayesianism and Diverse Evidence

A common methodological adage holds that diverse evidence better confirms a hypothesis than does the same amount of similar evidence. Proponents of Bayesian approaches to scientific reasoning such as Horwich, Howson and Urbach, and Earman claim to offer both a precise rendering of this maxim in probabilistic terms and an explanation of why the maxim should be part of the methodological canon of good science. This paper contends that these claims are mistaken and that, at best, Bayesian accounts of diverse evidence are crucially incomplete. This failure should lend renewed force to a long-neglected global worry about Bayesian approaches.

Expanding the Scope of Explanatory Idealization

Many explanations in physics rely on idealized models of physical systems. These explanations fail to satisfy the conditions of standard accounts of explanation. Recently, some philosophers have claimed that idealizations can be used to underwrite explanation nonetheless but only when they are what have variously been called representational, Galilean, controllable, or harmless idealizations. This article argues that such a half-measure is untenable and that idealizations not of this sort can have explanatory capacities.

Emergence and Singular Limits

Recent work by Robert Batterman and Alexander Rueger has brought attention to cases in physics in which governing laws at the base level “break down” and singular limit relations obtain between base- and upper-level theories. As a result, they claim, these are cases with emergent upper-level properties. This paper contends that this inference—from singular limits to explanatory failure, novelty or irreducibility, and then to emergence—is mistaken. The van der Pol nonlinear oscillator is used to show that there can be a full explanation of upper-level properties entirely in base-level terms even when singular limits are present. Whether upper-level properties are emergent depends not on the presence of a singular limit but rather on details of the ampliative approximation methods used. The paper suggests that focusing on explanatory deficiency at the base level is key to understanding emergence in physics.

Causal Relations and Explanatory Strategies in Physics

Many philosophers now regard causal approaches to explanation as highly promising, even in physics. This is due in large part to James Woodwards influential argument that a wide variety of scientific explanations are causal, based on his interventionist approach to causation. This article argues that some derivations describing causal relations and satisfying Woodwards criteria for causal explanation fail to be explanatory. Further, causal relations are unnecessary for a range of explanations, widespread in physics, involving highly idealized models. These constitute significant limitations on the scope of causal explanation. We have good reason to doubt that causal explanation is as widespread or important in physics as Woodward and other proponents maintain.

Quantum java: The upwards percolation of quantum indeterminacy

Despite a general, if often provisional, acceptance of quantum indeterminacy, and a now orthodox physicalism on which macroscopic states are held to depend in some sense on microscopic states, many philosophers of mind and of science continue to work under the assumption that macro states, such as brain states, evolve deterministically from prior macro states. Frequently this presumption is implicit and undefended, or explicit but given minimal defense. 1 In neither case is the tension between quantum indeterminacy, macro-micro dependence and macro determinism given full recognition. Sometimes the tension is recognized, but it is held that there is at least a legitimate hope that quantum indeterminism need not percolate up to the macro level. 2 Finally, some philosophers of mind address the issue and defend the view that, for one reason or another, quantum indeterminacy not only need not, but in fact does not, percolate to the macro level. 3 In this paper we demonstrate that micro indeterminism leads to macro indeterminism unless macro states are effectively independent from micro states. We show this is so whether the relationship between realizing and realized states is, in orthodox fashion, deterministic, or, in unorthodox fashion, indeterministic. The price of macroscopic determinism is that one must give up the dependence of the macro on the micro, a dependence upon which physicalism rests. A puzzle about the very idea of macroscopic determinism must be addressed at the outset. Macro determinism is an example of what is sometimes called partial determinism (Earman, 1986). We call a system partially deterministic with respect to a class of its properties just in case the state of the system at any particular time with regard

Point-particle explanations: the case of gravitational waves

This paper explores the role of physically impossible idealizations in model-based explanation. We do this by examining the explanation of gravitational waves from distant stellar objects using models that contain point-particle idealizations. Like infinite idealizations in thermodynamics, biology and economics, the point-particle idealization in general relativity is physically impossible. What makes this case interesting is that there are two very different kinds of models used for predicting the same gravitational wave phenomena, post-Newtonian models and effective field theory models. The paper contends that post-Newtonian models are explanatory while effective field theory models are not, because only in the former can we eliminate the physically impossible point-particle idealization. This suggests that, in some areas of science at least, models invoking ineliminable infinite idealizations cannot have explanatory power.

Chapter 1 A Trope-Bundle Ontology for Field Theory

Publisher Summary Field theories have been central to physics over the past 150 years, and there are several theories in contemporary physics in which physical fields play key causal and explanatory roles. This chapter discusses a novel field trope-bundle (FTB) ontology on which fields are composed of bundles of particularized property instances called “tropes.” It presents a dominant view about the ontology of fields. Ontological parsimony, flexibility, and moderate nominalism are attractive features of field trope-bundle ontologies for field theories in physics. FTB approaches have significant advantages over traditional substance-attribute approaches, and the chapter explains the way such trope-bundle ontologies can be constructed for classic and quantum field theories.

DEGREES OF FREEDOM AND THE INTERPRETATION OF QUANTUM FIELD THEORY

Nick Huggett and Robert Weingard (1994) have recently proposed a novel approach to interpreting field theories in physics, one which makes central use of the fact that a field generally has an infinite number of degrees of freedom in any finite region of space it occupies. Their characterization, they argue, (i) reproduces our intuitive categorizations of fields in the classical domain and thereby (ii) provides a basis for arguing that the quantum field is a field. Furthermore, (iii) it accomplishes these tasks better than does a well-known rival approach due to Paul Teller (1990, 1995). This paper contends that all three of these claims are mistaken, and suggests that Huggett and Weingard have not shown how counting degrees of freedom provides any insight into the interpretation or the formal properties of field theories in physics.