Supervenience, Logic, and Empirical Content: Commentary on Hans Halvorson, The Logic in Philosophy of Science

Halvorson’s book’s real achievement is that it is both a source and a challenge, and not just for philosophers of science. I will begin with some notes to add to Halvorson’s discussion of supervenience and definability. Then secondly I will engage the book’s way of dealing with empirical content. Extension of formal methods to the relation of theory to world, as mediated by experiment and measurement, seems to me crucial to its value, and I will make three suggestions for this. Then thirdly I will turn to the tantalizing hints Halvorson gives us of an overall view of logic and language, and speculate about how that would answer questions about scientific representation and more specifically about the object language / metalanguage relation

Supervenience, Logic, and Empirical Content: Commentary on Hans Halvorson, The Logic in Philosophy of Science

Halvorson’s book’s real achievement is that it is both a source and a challenge, and not just for philosophers of science. I will begin with some notes to add to Halvorson’s discussion of supervenience and definability. Then secondly I will engage the book’s way of dealing with empirical content. Extension of formal methods to the relation of theory to world, as mediated by experiment and measurement, seems to me crucial to its value, and I will make three suggestions for this. Then thirdly I will turn to the tantalizing hints Halvorson gives us of an overall view of logic and language, and speculate about how that would answer questions about scientific representation and more specifically about the object language / metalanguage relation

Diachronic Metaphysical Building Relations: Towards the Metaphysics of Extended Cognition

In the thesis I offer an analysis of the metaphysical underpinnings of the extended cognition thesis via an examination of standard views of metaphysical building (or, dependence) relations. In summary form, the extended cognition thesis is a view put forth in naturalistic philosophy of mind stating that the physical basis of cognitive processes and cognitive processing may, in the right circumstances, be distributed across neural, bodily, and environmental vehicles. As such, the extended cognition thesis breaks substantially with the still widely held view in cognitive science and philosophy of mind, namely that cognitive processes and cognitive processing take place within the skin-and-skull of individual organisms. The standard view of metaphysical building relations can be expressed as the conjunction of two theses. First, that a metaphysical building relation – such as composition, constitution, realization, supervenience or emergence – is a relation of ontological dependence, because if a metaphysical building relation holds between X (or the Xs) and Y, then it is in virtue of X (or the Xs) that Y exists. Second, metaphysical building relations are synchronic (durationless) relations of ontological dependence. In the thesis, I propose an alternative diachronic framework by which to extend the standard synchronic accounts of metaphysical dependence relations, and by which to reformulate the metaphysical foundation of the extended cognition thesis. The project fills an important gap between analytical metaphysics (in particular, the metaphysics of dependence relations) and naturalistic philosophy of mind (especially the extended cognition thesis). To my knowledge there has been no attempt to establish a robust diachronic account of metaphysical building (or, dependence) relations such as, e.g., composition and constitution. However, this is precisely what I argue is required to properly advance and ground the metaphysics of extended cognition. Ultimately, my aim of reformulating the metaphysics of extended cognition consists in taking several steps toward a third-wave of extended cognition

En Route to Reduction: Lorentzian Manifolds and Causal Sets

I present aspects of causal set theory (a research programme in quantum gravity) as being en route to achieving a reduction of Lorentzian geometry to causal sets. I take reduction in philosophers' sense; and I argue that the prospects are good for there being a reduction of the type envisaged by Nagel. (I also discuss the prospects for the stronger functionalist variant of Nagelian reduction, that was formulated by Lewis.) One main theme will be causal set theory's use of a physical scale (viz. the Planck scale) to formulate how it recovers a Lorentzian manifold. This use illustrates various philosophical topics relevant to reduction, such as limiting relations between theories, and the role of analogy. I also emphasise causal set theory's probabilistic method, viz. Poisson sprinkling: which is used both for formulating the reduction and for exploring its prospects

Appearing Out of Nowhere: The Emergence of Spacetime in Quantum Gravity

Quantum gravity is understood as a theory that, in some sense, unifies general relativity (GR) and quantum theory, and is supposed to replace GR at extremely small distances (high-energies). It may be that quantum gravity represents the breakdown of spacetime geometry described by GR. The relationship between quantum gravity and spacetime has been deemed "emergence", and the aim of this thesis is to investigate and explicate this relation. After finding traditional philosophical accounts of emergence to be inappropriate, I develop a new conception of emergence by considering physical case studies including condensed matter physics, hydrodynamics, critical phenomena and quantum field theory understood as effective field theory. This new conception of emergence is independent of reduction and derivation. Instead, a low-energy theory is understood as emergent from a high-energy theory if it is novel and autonomous compared to the high-energy theory, and the low-energy physics is dependent (in a particular, minimal sense) on the high-energy physics (this dependence is revealed by the techniques of effective field theory and the renormalisation group). These ideas are important in exploring the relationship between quantum gravity and GR, where GR is understood as an effective, low-energy theory of quantum gravity. Without experimental data or a theory of quantum gravity, we rely on principles and techniques from other areas of physics to guide the way. As well as considering the idea of emergence appropriate to treating GR as an effective field theory, I investigate the emergence of spacetime (and other aspects of GR) in several concrete approaches to quantum gravity, including examples of the condensed matter approaches, the "discrete approaches" (causal set theory, causal dynamical triangulations, quantum causal histories and quantum graphity) and loop quantum gravity.Comment: PhD thesis submitted to the University of Sydne

Essays on the Metaphysics of Quantum Mechanics

What is the proper metaphysics of quantum mechanics? In this dissertation, I approach the question from three different but related angles. First, I suggest that the quantum state can be understood intrinsically as relations holding among regions in ordinary space-time, from which we can recover the wave function uniquely up to an equivalence class (by representation and uniqueness theorems). The intrinsic account eliminates certain conventional elements (e.g. overall phase) in the representation of the quantum state. It also dispenses with first-order quantification over mathematical objects, which goes some way towards making the quantum world safe for a nominalistic metaphysics suggested in Field (1980, 2016). Second, I argue that the fundamental space of the quantum world is the low-dimensional physical space and not the high-dimensional space isomorphic to the ``configuration space.'' My arguments are based on considerations about dynamics, empirical adequacy, and symmetries of the quantum mechanics. Third, I show that, when we consider quantum mechanics in a time-asymmetric universe (with a large entropy gradient), we obtain new theoretical and conceptual possibilities. In such a model, we can use the low-entropy boundary condition known as the Past Hypothesis (Albert, 2000) to pin down a natural initial quantum state of the universe. However, the universal quantum state is not a pure state but a mixed state, represented by a density matrix that is the normalized projection onto the Past Hypothesis subspace. This particular choice has interesting consequences for Humean supervenience, statistical mechanical probabilities, and theoretical unity