Doctor of Philosophy
One recent debate in philosophy of physics has centered whether quantum particles are individuals or not. The received view is that particles are not individuals and the standard methodology is to approach the question via the structure of quantum theory. I challenge both the received view and the standard methodology. I contend not only that the structure of quantum theory is not the right place to look for conditions of individuality that quantum particles may or may not satisfy, but also that there is an important role for traditional metaphysics to play. Consequently, my work brings together the philosophy of physics and traditional metaphysics literatures to shed new light on the debate over the individuality of quantum particles. I defend a set of conditions of individuality and argue that quantum particles satisfy these conditions thereby defending the view that particles are individuals in opposition to the received view. I also challenge a second feature of the standard methodology insofar as I challenge the significance of the Principle of the Identity of Indiscernibles in terms of which much discussion in the philosophy of physics literature is framed. My work is significant in a number of additional ways as well. My work implies that the dominant explanation for quantum statistics in terms of non-individuality is incorrect and it also undermines the ontic-structural realists metaphysical underdetermination challenge to the scientific realist.
Summary for Lay Audience
One recent debate in philosophy of physics has centered on whether quantum particles are individuals or not. It is commonly thought that particles are not individuals because the formulas governing their behavior don’t care which particle is which when we have multiple particles of the same kind. The standard way to determine whether particles are individuals or not is to assume that being an individual requires possessing identity (in some sense) and looking at the structure of quantum theory to try to determine whether quantum particles have some form of identity. I challenge the common view by rethinking what it means for something to be an individual. I also challenge the standard approach of looking at the structure of quantum theory because quantum theory gives us both reasons to think that particles have some form of identity as well as reasons to think that particles don’t have any sort of identity. So, the structure of quantum theory underdetermines the answer to our question of whether particles are individuals or not. By rethinking what it means to be an individual we can avoid this underdetermination by providing an account of individuality in which the structure of quantum theory gives us a clear answer. I also think that there is an important role for traditional metaphysics to play given that we can’t extract a unified account of individuality from quantum theory itself. Consequently, my work brings together the philosophy of physics and traditional metaphysical literatures to shed new light on the debate. I defend a set of conditions of individuality independently of any considerations regarding quantum theory and argue that quantum particles satisfy those conditions and are, therefore, individuals. My work challenges several additional positions as well. It challenges the dominant explanation for certain aspects of the behavior of quantum particles where those aspects are explained by viewing quantum particles as non-individuals. It also allows the scientific realist (the view that the theoretical entities posited by science exist) to respond to a challenge from ontic-structural realists (the view that we should only accept the existence of structural features of our scientific theories).
Moore, Nathan, "Rethinking Individuality in Quantum Mechanics" (2019). Electronic Thesis and Dissertation Repository. 6401.
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