Huw Price

Agency and Probabilistic Causality

Probabilistic accounts of causality have long had trouble with ‘spurious’ evidential correlations. Such correlations are also central to the case for causal decision theory—the argument that evidential decision theory is inadequate to cope with certain sorts of decision problem. However, there are now several strong defences of the evidential theory. Here I present what I regard as the best defence, and apply it to the probabilistic approach to causality. I argue that provided a probabilistic theory appeals to the notions of agency and effective strategy, it can avoid the problem of spurious causes. I show that such an appeal has other advantages; and argue that it is not illegitimate, even for a causal realist.

How to stand up for non-cognitivists

(1996). How to stand up for non-cognitivists. Australasian Journal of Philosophy: Vol. 74, No. 2, pp. 275-292.

Boltzmann's Time Bomb

Since the late nineteenth century, physics has been puzzled by the time‐asymmetry of thermodynamic phenomena in the light of the apparent T‐symmetry of the underlying laws of mechanics. However, a compelling solution to this puzzle has proved elusive. In part, I argue, this can be attributed to a failure to distinguish two conceptions of the problem. According to one, the main focus of our attention is a time‐asymmetric lawlike generalisation. According to the other, it is a particular fact about the early universe. This paper aims (i) to distinguish these two different conceptions of the time‐asymmetric explanandum in thermodynamics; (ii) to argue in favour of the latter; and (iii) to show that whichever we choose, our rational expectations about the thermodynamic behaviour of the future must depend on what we know about the past: contrary to the common view, statistical arguments alone do not give us good reason to expect that entropy will always continue to increase.

Does time-symmetry imply retrocausality? How the quantum world says “Maybe”?

Abstract It has often been suggested that retrocausality offers a solution to some of the puzzles of quantum mechanics: e.g., that it allows a Lorentz-invariant explanation of Bell correlations, and other manifestations of quantum nonlocality, without action-at-a-distance. Some writers have argued that time-symmetry counts in favour of such a view, in the sense that retrocausality would be a natural consequence of a truly time-symmetric theory of the quantum world. Critics object that there is complete time-symmetry in classical physics, and yet no apparent retrocausality. Why should the quantum world be any different? This note throws some new light on these matters. I call attention to a respect in which quantum mechanics is different, under some assumptions about quantum ontology. Under these assumptions, the combination of time-symmetry without retrocausality is unavailable in quantum mechanics, for reasons intimately connected with the differences between classical and quantum physics (especially the role of discreteness in the latter). Not all interpretations of quantum mechanics share these assumptions, however, and in those that do not, time-symmetry does not entail retrocausality.

Against causal decision theory

Proponents of causal decision theories argue that classical Bayesian decision theory (BDT) gives the wrong advice in certain types of cases, of which the clearest and commonest are the medical Newcomb problems. I defend BDT, invoking a familiar principle of statistical inference to show that in such cases a free agent cannot take the contemplated action to be probabilistically relevant to its causes (so that BDT gives the right answer). I argue that my defence does better than those of Ellery Eells and Richard Jeffrey; and that it applies, where necessary, to other types of Newcomb problem.

New Slant on the EPR-Bell Experiment

The best case for thinking that quantum mechanics is nonlocal rests on Bells Theorem, and later results of the same kind. However, the correlations characteristic of Einstein–Podolsky–Rosen (EPR)–Bell (EPRB) experiments also arise in familiar cases elsewhere in quantum mechanics (QM), where the two measurements involved are timelike rather than spacelike separated; and in which the correlations are usually assumed to have a local causal explanation, requiring no action-at-a-distance (AAD). It is interesting to ask how this is possible, in the light of Bells Theorem. We investigate this question, and present two options. Either (i) the new cases are nonlocal too, in which case AAD is more widespread in QM than has previously been appreciated (and does not depend on entanglement, as usually construed); or (ii) the means of avoiding AAD in the new cases extends in a natural way to EPRB, removing AAD in these cases too. There is a third option, viz., that the new cases are strongly disanalogous to EPRB. But this option requires an argument, so far missing, that the physical world breaks the symmetries which otherwise support the analogy. In the absence of such an argument, the orthodox combination of views—action-at-a-distance in EPRB, but local causality in its timelike analogue—is less well established than it is usually assumed to be. 1 Introduction   1.1 Background   1.2 Outline of the argument 2 The Experiments   2.1 Standard EPRB   2.2 Sideways EPRB   2.3 Comparing the experiments   2.4 The need for beables 3 The Symmetry Considerations   3.1 The action symmetry   3.2 Time-symmetry in SEPRB 4 The Basic Trilemma   4.1 An intuitive defence of Option III? 5 Avoiding the Trilemma? 6 The Classical Objection 7 Defending Option III   7.1 The free will argument   7.2 Independence and consistency 8 Entanglement and Epistemic Perspective 1 Introduction   1.1 Background   1.2 Outline of the argument   1.1 Background   1.2 Outline of the argument 2 The Experiments   2.1 Standard EPRB   2.2 Sideways EPRB   2.3 Comparing the experiments   2.4 The need for beables   2.1 Standard EPRB   2.2 Sideways EPRB   2.3 Comparing the experiments   2.4 The need for beables 3 The Symmetry Considerations   3.1 The action symmetry   3.2 Time-symmetry in SEPRB   3.1 The action symmetry   3.2 Time-symmetry in SEPRB 4 The Basic Trilemma   4.1 An intuitive defence of Option III?   4.1 An intuitive defence of Option III? 5 Avoiding the Trilemma? 6 The Classical Objection 7 Defending Option III   7.1 The free will argument   7.2 Independence and consistency   7.1 The free will argument   7.2 Independence and consistency 8 Entanglement and Epistemic Perspective

Naturalism without representationalism

1. The relevance of science to philosophy What is philosophical naturalism? Most fundamentally, presumably, it is the view that natural science constrains philosophy, in the following sense. The concerns of the two disciplines are not simply disjoint, and science takes the lead where the two overlap. At the very least, then, to be a philosophical naturalist is to believe that philosophy is not simply a different enterprise from science, and that philosophy properly defers to science, where the concerns of the two disciplines coincide. Naturalism as spare as this is by no means platitudinous. However, most opposition to naturalism in contemporary philosophy is not opposition to naturalism in this basic sense, but to a more specific view of the relevance of science to philosophy. Similarly on the pro-naturalistic side. What most self-styled naturalists have in mind is the more specific view. As a result, I think, both sides of the contemporary debate pay insufficient attention to a different kind of philosophical naturalism — a different view of the impact of science on philosophy. This different view is certainly not new — it has been with us at least since Hume — but nor is it prominent in many contemporary debates. In this paper I try to do something to remedy this deficit. I begin by making good the claim that the position commonly called naturalism is not a necessary corollary of naturalism in the basic sense outlined above. There are two very different ways of taking science to be relevant to philosophy. And contrary, perhaps, to first appearances, the major implications of these two views for philosophy arise from a common starting point. There is a single kind of core problem, to which the two kinds of naturalism recommend very different sorts of answer.

THE THERMODYNAMIC ARROW: PUZZLES AND PSEUDO-PUZZLES

For more than a century, physics has known of a puzzling conflict between the T-asymmetry of thermodynamic phenomena and the T-symmetry of the underlying microphysics on which these phenomena depend. This paper provides a guide to the current status of this puzzle, distinguishing the central issue from various issues with which it may be confused. It is shown that there are two competing conceptions of what is needed to resolve the puzzle of the thermodynamic asymmetry, which differ with respect to the number of distinct T-asymmetries they take to be manifest in the physical world. On the preferable one-asymmetry conception, the remaining puzzle concerns the ordered distribution of matter in the early universe. The puzzle of the thermodynamic arrow thus becomes a puzzle for cosmology.

Burbury's last case: The mystery of the entropic arrow

Does not the theory of a general tendency of entropy to diminish [sic 1 ] take too much for granted? To a certain extent it is supported by experimental evidence. We must accept such evidence as far as it goes and no further. We have no right to supplement it by a large draft of the scientific imagination.

Time Symmetry in Microphysics

Physics takes for granted that interacting systems without common history are independent, before interaction. This principle is time asymmetric, for no such restriction applies to systems without common future, after interaction. The time asymmetry is normally attributed to boundary conditions. I argue that there are two such independence principles at work in contemporary physics, one of which cannot be attributed to boundary conditions, and therefore conflicts with the assumed T-symmetry of microphysics. I note that this may have interesting ramifications in quantum mechanics.