University of Cambridge
Real commitment: a coarse-grained approach to reality via alternative theories in physics
Abstract
dc:description.abstractThis dissertation is about the problematic kind of underdetermination: the existence of alternative theories that make the same observable predictions as established theories do but provide different ways the world is like. Acknowledging the longstanding debate on resolving underdetermination -- which has reached an impasse at a general level -- I opt for a shift towards fully detailed case studies. I dive into three such cases in physics. First, I consider the freedom in electrodynamic gauge theories to interpret some or all gauge variables as physical variables, posing the question whether, and to what extent, the electromagnetic potentials can be considered as physically real. I argue it should be an ontology that is signal local, achieved by picking the Lorenz gauge. Second, I consider the torsionful but non-curved alternative to general relativity called teleparallel gravity, posing the question whether curvature should be considered a physically real property of spacetime. I argue against claims -- most prominently by Eleanor Knox (2011) -- that teleparallel gravity should be ruled out on independent grounds (such as via functionalism, simplicity, or non-visualisability). Third, I consider a novel approach to geometric conventionalism, where trade-offs between geometric structure and so-called `universal forces' are treated rigorously, initiated through a proof by Jim Weatherall and J.B. Manchak (2014). I defend the value of this proof against several misconceptions (most prominently by Patrick Dürr and Yemima Ben-Menahem 2022) and suggest extensions. Each of these cases concern different interpretations of ontologically committing to some parts of a mathematical formalism rather than other parts. I put forward a framework that treats different interpretations as different choices of `semantic grain'. According to the problem at hand, we can opt for a more semantically fine-grained or semantically coarse-grained approach to distribute our ontological commitment. The more fine-grained the approach, the logically stronger the scientific realist's claims, providing ontological clarity. The more coarse-grained the approach, the logically weaker the claims, providing interpretative options to undermine underdetermination. Returning to the case studies, for the electromagnetic potentials I argue that ontologically committing to a particular gauge is a fine-graining, making logically stronger claims about nature. In the case of teleparallel gravity I argue instead for a coarse-graining, where we neither commit to curvature nor torsion, but to their conceptual common core of `failure to be invariant under parallel transport around a loop' (mathematically associated with the Lie bracket), logically weakening our interpretation of `Textbook Curvature'. For the underdetermination of geometric models and universal forces an analogous coarse-graining is apt, provided we are content with ontologically committing to a logically weaker concept of physical geometry, which is relative to differential forces only. The dissertation does not solve the problem of underdetermination: it cannot be solved in general. I give an Apologia by characterising the specification of ontology as an ill-structured problem: there is no algorithm to derive an interpretation from a formalism. I propose a philosophically pluralist methodology where multiple (relevant) philosophical frameworks of realism cooperate rather than conflict. The goal is an interpretative equilibrium. I call this `Iterative Interpretation', looking underdetermination in the eye and potentially overcome some of them to the best of our human interpretative abilities.
Degree
thesis:*- Name dc:type.qualificationname
- Doctor of Philosophy (PhD)
- Level dc:type.qualificationlevel
- Doctoral
- Grantor dc:publisher.institution
- University of Cambridge
- Year dc:date.issued
- 2024
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Mulder, Ruward Arthur
- Advisors dc:contributor.advisor
-
- Dewar, Neil
- Butterfield, Jeremy
- Chang, Hasok
Subjects
dc:subject × 7Rights
dc:rightsIdentifiers
dc:identifier.*- DOI dc:identifier.doi
- https://doi.org/10.17863/CAM.116676
- OAI identifier oai:identifier
- oai:www.repository.cam.ac.uk:1810/381526