The simplest case of quantum field theory on curved spacetime—that of the Klein–Gordon field on a globally hyperbolic spacetime—reveals a dilemma: In generic circumstances, either there is no dynamics for this quantum field, or else there is a dynamics that is not unitarily implementable. We do not try to resolve the dilemma here, but endeavour to spell out the consequences of seizing one or the other horn of the dilemma.

A polemical account of Australian philosophy up to 2003, emphasising its unique aspects (such as commitment to realism) and the connections between philosophers' views and their lives. Topics include early idealism, the dominance of John Anderson in Sydney, the Orr case, Catholic scholasticism, Melbourne Wittgensteinianism, philosophy of science, the Sydney disturbances of the 1970s, Francofeminism, environmental philosophy, the philosophy of law and Mabo, ethics and Peter Singer. Realist theories especially praised are David Armstrong's on universals, David Stove's on logical probability (...) and the ethical realism of Rai Gaita and Catholic philosophers. In addition to strict philosophy, the book treats non-religious moral traditions to train virtue, such as Freemasonry, civics education and the Greek and Roman classics. (shrink)

Since the onset of logical positivism, the general wisdom of the philosophy of science has it that the kantian philosophy of (space and) time has been superseded by the theory of relativity, in the same sense in which the latter has replaced Newton’s theory of absolute space and time. On the wake of Cassirer and Gödel, in this paper I raise doubts on this commonplace by suggesting some conditions that are necessary to defend the ideality of time in the sense (...) of Kant. In the last part of the paper I bring to bear some contemporary physical theories on such conditions. (shrink)

Although the philosophical literature on the foundations of quantum field theory recognizes the importance of Haag’s theorem, it does not provide a clear discussion of the meaning of this theorem. The goal of this paper is to make up for this deficit. In particular, it aims to set out the implications of Haag’s theorem for scattering theory, the interaction picture, the use of non-Fock representations in describing interacting fields, and the choice among the plethora of the unitarily inequivalent representations of (...) the canonical commutation relations for free and interacting fields. (shrink)

I argue that the best interpretation of the general theory of relativity has need of a causal entity, and causal structure that is not reducible to light cone structure. I suggest that this causal interpretation of GTR helps defeat a key premise in one of the most popular arguments for causal reductionism, viz., the argument from physics.

I argue that the extended simples picture (ESP) is compatible with supersubstantivalism under the quantum holism model, and that reevaluating our limits on the ways an object may be located by fusing the two ontologies can benefit our understanding of modern physics. I first illustrate the explanatory utility of extended simples, using examples of superposition and entanglement. Second, I advocate the use of supersubstantivalism as a way to understand the interface between objects and spacetime, and argue that the ESP suitably (...) fits into a supersubstantivalist interpretation of quantum field theory. In the last section, I propose quantum holism as a framework to reconcile supersubstantivalism with extended simples, and conclude that the causal relationship that interweaves material objects and spacetime render the two ontologies compatible. I will demonstrate that a combined ontology is useful for its parsimony, and for our understanding of quantum field theory. (shrink)

Many mechanisms, functions and structures of life have been unraveled. However, the fundamental driving force that propelled chemical evolution and led to life has remained obscure. The second law of thermodynamics, written as an equation of motion, reveals that elemental abiotic matter evolves from the equilibrium via chemical reactions that couple to external energy towards complex biotic non-equilibrium systems. Each time a new mechanism of energy transduction emerges, e.g., by random variation in syntheses, evolution prompts by punctuation and settles to (...) a stasis when the accessed free energy has been consumed. The evolutionary course towards an increasingly larger energy transduction system accumulates a diversity of energy transduction mechanisms, i.e. species. The rate of entropy increase is identified as the fitness criterion among the diverse mechanisms, which places the theory of evolution by natural selection on the fundamental thermodynamic principle with no demarcation line between inanimate and animate. (shrink)

In his recent book, Jaegwon Kim argues thatpsychophysical supervenience withoutpsychophysical reduction renders mentalcausation `unintelligible'. He also claimsthat, contrary to popular opinion, his argumentagainst supervenient mental causation cannot begeneralized so as to threaten the causalefficacy of other `higher-level' properties:e.g., the properties of special sciences likebiology. In this paper, I argue that none ofthe considerations Kim advances are sufficientto keep the supervenience argument fromgeneralizing to all higher-level properties,and that Kim's position in fact entails thatonly the properties of fundamental physicalparticles are causally efficacious.

The conceptual relation between objective becoming and the direction of time is explored by discussing an ontologically asymmetric notion of causation. It is claimed that such a notion, in terms of which Stein defined objective becoming in Minkowski spacetime, has either a purely metaphysical status or is reducible to physical concepts. In the former case, it is adequate for Stein's purpose but irrelevant to physical theories. In the latter, the causal asymmetry can be related to irreversible physical processes only in (...) an extrinsic way. This dilemma creates additional difficulties both to a unified theory of the direction of time and to the project of making room for becoming in the physical world. (shrink)

I argue against a priori objections to the view that causation may be reducible to some micro-structural process in principle discoverable by physics. I distinguish explanation from causation, and argue that the main objections to such a reduction stem from conflating these two notions. Explanation is the collection of pragmatically relevant, possibly counterfactual information about causation; and causation is to be identified in a necessary a posteriori way with whatever physical processes underwrite our explanatory claims.

Most philosophical discussion of the particle concept that is afforded by quantum field theory has focused on free systems. This paper is devoted to a systematic investigation of whether the particle concept for free systems can be extended to interacting systems. The possible methods of accomplishing this are considered and all are found unsatisfactory. Therefore, an interacting system cannot be interpreted in terms of particles. As a consequence, quantum field theory does not support the inclusion of particles in our ontology. (...) In contrast to much of the recent discussion on the particle concept derived from quantum field theory, this argument does not rely on the assumption that a particulate entity be localizable. (shrink)

Philosophical accounts of causation have traditionally been framed as attempts to analyze the concept of a cause. In recent years, however, a number of philosophers have proposed instead that causation be empirically reduced to some relation uncovered by the natural sciences: e.g., a relation of energy transfer. This paper argues that the project of empirical analysis lacks a clearly defined methodology, leaving it uncertain how such views are to be evaluated. It proposes several possible accounts of empirical analysis and argues (...) that the most promising approach would treat it as a contingent identity discovered by identifying the relation (or relations) that most nearly approximate the inferential role of causal concepts in a psychological theory of causal judgment. (shrink)

The paper takes a detailed look at a surprising new aspect of the dynamics of rigid bodies. Far from the usual consideration of rigid body theory as a merely technical chapter of classical physics, I demonstrate here that there are solutions to the conservation equations of mechanics that imply the spontaneous, unpredictable splitting of a rigid body in free rotation, something that has direct implications for the problem of causality. The paper also shows that the instability revealed in indeterminist splitting (...) processes does not depend solely on the bodies’ inertial properties but also on the number of dimensions of the physical space they inhabit. The paper concludes with a conjecture on the behavior of rigid bodies in four-dimensional space. (shrink)