
175The Quantum Revolution in PhilosophyAnalysis 80 (2): 381388. 2020.Richard Healey’s The Quantum Revolution in Philosophy is a terrific book, and yet I disagree with nearly all its main substantive conclusions.1 1 The purpose of this review is to say why the book is well worth your time if you have any interest in the interpretation of quantum theory or in the general philosophy of science, and yet why in the end I think Healey’s ambitious project fails to achieve its full goals.

57Interpreting the quantum mechanics of cosmologyIn A. Ijjas & B. Loewer (eds.), Philosophy of Cosmology: an Introduction, Oxford University Press. forthcoming.Quantum theory plays an increasingly significant role in contemporary earlyuniverse cosmology, most notably in the inflationary origins of the fluctuation spectrum of the microwave background radiation. I consider the two main strategies for interpreting standard quantum mechanics in the light of cosmology. I argue that the conceptual difficulties of the approaches based around an irreducible role for measurement  already very severe  become intolerable in a cosmological context, whereas the …Read more

67On the Plurality of Quantum Theories: Quantum theory as a framework, and its implications for the quantum measurement problemIn S. French & J. Saatsi (eds.), Scientific Realism and the Quantum, Oxford University Press. forthcoming.`Quantum theory' is not a single physical theory but a framework in which many different concrete theories fit. As such, a solution to the quantum measurement problem ought to provide a recipe to interpret each such concrete theory, in a mutually consistent way. But with the exception of the Everett interpretation, the mainextant solutions either try to make sense of the abstract framework as if it were concrete, or else interpret one particular quantum theory under the fiction that it is fundam…Read more

47I argue that wavefunction realism  the view that quantum mechanics reveals the fundamental ontology of the world to be a field on a highdimensional spacetime, must be rejected as relying on artefacts of toosimple versions of quantum mechanics, and not conceptually wellmotivated even were those toosimple versions exactly correct. I end with some brief comments on the role of spacetime in any satisfactory account of the metaphysics of extant quantum theories.

25In discussions of the foundations of statistical mechanics, it is widely held that the Gibbsian and Boltzmannian approaches are incompatible but empirically equivalent; the Gibbsian approach may be calculationally preferable but only the Boltzmannian approach is conceptually satisfactory. I argue against both assumptions. Gibbsian statistical mechanics is applicable to a wide variety of problems and systems, such as the calculation of transport coefficients and the statistical mechanics and ther…Read more

28Spontaneous symmetry breaking in quantum systems, such as ferromagnets, is normally described as degeneracy of the ground state; however, it is well established that this degeneracy only occurs in spatially infinite systems, and even better established that ferromagnets are not spatially infinite. I review this wellknown paradox, and consider a popular solution where the symmetry is explicitly broken by some external field which goes to zero in the infinitevolume limit; although this is formal…Read more

21I distinguish between two versions of the black hole informationloss paradox. The first arises from apparent failure of unitarity on the spacetime of a completely evaporating black hole, which appears to be nongloballyhyperbolic; this is the most commonly discussed version of the paradox in the foundational and semipopular literature, and the case for calling it `paradoxical' is less than compelling. But the second arises from a clash between a fullystatisticalmechanical interpretation of b…Read more

18Decoherence and Ontology, or: How I Learned To Stop Worrying And Love FAPPIn Simon Saunders, Jonathan Barrett, Adrian Kent & David Wallace (eds.), Many Worlds? Everett, Quantum Theory, and Reality, Oxford University Press. 2010.I make the case that the Universe according to unitary quantum theory has a branching structure, and so can literally be regarded as a "manyworlds" theory. These worlds are not part of the _fundamental_ ontology of quantum theory  instead, they are to be understood as structures, or patterns, emergent from the underlying theory, through the dynamical process of decoherence. That they are structures in this sense does not mean that they are in any way unreal: indeed, pretty much all higherleve…Read more

48The case for black hole thermodynamics part I: Phenomenological thermodynamicsStudies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics 64 5267. 2018.I give a fairly systematic and thorough presentation of the case for regarding black holes as thermodynamic systems in the fullest sense, aimed at students and nonspecialists and not presuming advanced knowledge of quantum gravity. I pay particular attention to the availability in classical black hole thermodynamics of a welldefined notion of adiabatic intervention; the power of the membrane paradigm to make black hole thermodynamics precise and to extend it to localequilibrium contexts; the …Read more

89Lessons from realistic physics for the metaphysics of quantum theorySynthese 116. 2018.Quantum mechanics, and classical mechanics, are framework theories that incorporate many different concrete theories which in general cannot be arranged in a neat hierarchy, but discussion of ‘the ontology of quantum mechanics’ tends to proceed as if quantum mechanics were a single concrete theory, specifically the physics of nonrelativistically moving point particles interacting by longrange forces. I survey the problems this causes and make some suggestions for how a more physically realistic…Read more

66Fundamental and Emergent Geometry in Newtonian PhysicsBritish Journal for the Philosophy of Science 71 (1): 132. 2020.Using as a starting point recent and apparently incompatible conclusions by Saunders and Knox, I revisit the question of the correct spacetime setting for Newtonian physics. I argue that understood correctly, these two versions of Newtonian physics make the same claims both about the background geometry required to define the theory, and about the inertial structure of the theory. In doing so I illustrate and explore in detail the view—espoused by Knox, and also by Brown —that inertial structure…Read more

10The working assumption amongst most philosophers of QFT appears to be that algebraic QFT, and not the "Lagrangian" QFT of the working physicist, is the proper object of philosophical and foundational study. I argue that this assumption is unmotivated, and fails to take into account important features of the post1960s development of Lagrangian QFT. From a modern perspective the two forms of QFT are better seen as rival research programs than as variant formulations of one theory; furthermore, th…Read more

43I provide a selfcontained introduction to the problem of the arrow of time in physics, concentrating on the irreversibility of dynamical processes as described in statistical mechanics.

110Diachronic Rationality and PredictionBased GamesProceedings of the Aristotelian Society 110 (3pt3): 243266. 2010.I explore the debate about causal versus evidential decision theory, and its recent developments in the work of Andy Egan, through the method of some simple games based on agents' predictions of each other's actions. My main focus is on the requirement for rational agents to act in a way which is consistent over time and its implications for such games and their more realistic cousins

132Protecting cognitive science from quantum theoryBehavioral and Brain Sciences 27 (5): 636637. 2004.The relation between microobjects and macroobjects advocated by Kim is even more problematic than Ross & Spurrett (R&S) argue, for reasons rooted in physics. R&S's own ontological proposals are much more satisfactory from a physicist's viewpoint but may still be problematic. A satisfactory theory of macroscopic ontology must be as independent as possible of the details of microscopic physics.

32Using the parametrised representation of field theory I demonstrate that in both local and global cases, internal and spacetime symmetries can be treated precisely on a par, so that gravitational theories may be regarded as gauge theories in a completely standard sense.

30Decoherence is widely felt to have something to do with the quantum measurement problem, but getting clear on just what is made diffcult by the fact that the "measurement problem", as traditionally presented in foundational and philosophical discussions, has become somewhat disconnected from the conceptual problems posed by real physics. This, in turn, is because quantum mechanics as discussed in textbooks and in foundational discussions has become somewhat removed from scientific practice, espe…Read more

115The relativity and equivalence principles for selfgravitating systemsIn Dennis Lehmkuhl (ed.), Towards a Theory of Spacetime Theories, . 2009.I criticise the view that the relativity and equivalence principles are consequences of the smallscale structure of the metric in general relativity, by arguing that these principles also apply to systems with nontrivial selfgravitation and hence nontrivial spacetime curvature (such as black holes). I provide an alternative account, incorporating aspects of the criticised view, which allows both principles to apply to systems with selfgravity.

35I explore the reduction of thermodynamics to statistical mechanics by treating the former as a control theory: a theory of which transitions between states can be induced on a system by means of operations from a fixed list. I recover the results of standard thermodynamics in this framework on the assumption that the available operations do not include measurements which affect subsequent choices of operations. I then relax this assumption and use the framework to consider the vexed questions of…Read more

41I review the role of probability in contemporary physics and the origin of probabilistic time asymmetry, beginning with the prequantum case but concentrating on quantum theory. I argue that quantum mechanics radically changes the prequantum situation and that the philosophical nature of objective probability in physics, and of probabilistic asymmetry in time, is dependent on the correct resolution of the quantum measurement problem.

206An investigation is made into how the foundations of statistical mechanics are affected once we treat classical mechanics as an approximation to quantum mechanics in certain domains rather than as a theory in its own right; this is necessary if we are to understand statisticalmechanical systems in our own world. Relevant structural and dynamical differences are identified between classical and quantum mechanics (partly through analysis of technical work on quantum chaos by other authors). These…Read more

242Epistemology quantized: Circumstances in which we should come to believe in the Everett interpretationBritish Journal for the Philosophy of Science 57 (4): 655689. 2006.I consider exactly what is involved in a solution to the probability problem of the Everett interpretation, in the light of recent work on applying considerations from decision theory to that problem. I suggest an overall framework for understanding probability in a physical theory, and conclude that this framework, when applied to the Everett interpretation, yields the result that that interpretation satisfactorily solves the measurement problem. Introduction What is probability? 2.1 Objective …Read more

47I give a brief account of the way in which thermodynamics and statistical mechanics actually work as contemporary scientific theories, and in particular of what statistical mechanics contributes to thermodynamics over and above any supposed underpinning of the latter's general principles. In doing so, I attempt to illustrate that statistical mechanics should not be thought of wholly or even primarily as itself a foundational project for thermodynamics, and that conceiving of it this way potentia…Read more

306Saunders and Wallace replyBritish Journal for the Philosophy of Science 59 (3): 315317. 2008.A reply to a comment by Paul Tappenden (BJPS 59 (2008) pp. 307314) on S. Saunders and D. Wallace, "Branching and Uncertainty" (BJPS 59 (2008) pp. 298306)

246Taking particle physics seriously: A critique of the algebraic approach to quantum field theoryStudies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics 42 (2): 116125. 2010.I argue against the currently prevalent view that algebraic quantum field theory (AQFT) is the correct framework for philosophy of quantum field theory and that “conventional” quantum field theory (CQFT), of the sort used in mainstream particle physics, is not suitable for foundational study. In doing so, I defend that position that AQFT and CQFT should be understood as rival programs to resolve the mathematical and physical pathologies of renormalization theory, and that CQFT has succeeded in t…Read more

62An extended analysis is given of the program, originally suggested by Deutsch, of solving the probability problem in the Everett interpretation by means of decision theory. Deutsch's own proof is discussed, and alternatives are presented which are based upon different decision theories and upon Gleason's Theorem. It is argued that decision theory gives Everettians most or all of what they need from `probability'. Contact is made with Lewis's Principal Principle linking subjective credence with o…Read more

57I investigate the consequences for semantics, and in particular for the semantics of tense, if time is assumed to have a branching structure not out of metaphysical necessity (to solve some philosophical problem) but just as a contingent physical fact, as is suggested by a currentlypopular approach to the interpretation of quantum mechanics.

373Gravity, Entropy, and Cosmology: in Search of ClarityBritish Journal for the Philosophy of Science 61 (3): 513540. 2010.I discuss the statistical mechanics of gravitating systems and in particular its cosmological implications, and argue that many conventional views on this subject in the foundations of statistical mechanics embody significant confusion; I attempt to provide a clearer and more accurate account. In particular, I observe that (i) the role of gravity in entropy calculations must be distinguished from the entropy of gravity, that (ii) although gravitational collapse is entropyincreasing, this is not…Read more

37I argue that the metaphysical import of the AharonovBohm effect has been overstated: correctly understood, it does not require either rejection of gauge invariance or any novel form of nonlocality. The conclusion that it does require one or the other follows from a failure to keep track, in the analysis, of the complex scalar field to which the magnetic vector potential is coupled. Once this is recognised, the way is clear to a local account of the ontology of electrodynamics ; I sketch a possi…Read more

120Who's afraid of coordinate systems? An essay on representation of spacetime structureStudies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics 67 125136. 2019.Coordinatebased approaches to physical theories remain standard in mainstream physics but are largely eschewed in foundational discussion in favour of coordinatefree differentialgeometric approaches. I defend the conceptual and mathematical legitimacy of the coordinatebased approach for foundational work. In doing so, I provide an account of the Kleinian conception of geometry as a theory of invariance under symmetry groups; I argue that this conception continues to play a very substantial r…Read more
Pittsburgh, Pennsylvania, United States of America
Areas of Specialization
Philosophy of Physical Science 
Areas of Interest
Philosophy of Physical Science 
General Philosophy of Science 