Why Isn’t There Only Physics?

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

In this thesis, I discuss the relations between descriptions of the world at dif-ferent levels: through the examination of case studies from condensed matter physics and quantum field theory, I argue that we may effect reductions and that such reductions provide bottom-up explanations of the autonomy and novelty – the emergence – of higher-level descriptions.
Philosophically, I make three principal contributions. First, I propose an approach to reduction which has not been considered in the existing literature – that of justifying the laws which connect descriptions of phenomena at dif-ferent levels; this involves focus on the underlying features which allow us to discard a tremendous amount of detail when we move from lower-level to higher-level descriptions. Second, I defend and develop an account of emer-gence which better captures the term’s use by scientists but which does not place it in opposition to reduction – this corresponds to the availability of novel explanatory strategies at higher levels that build on abstractions from lower-level descriptions; this also allows for a precise characterisation of the level structure itself. Third, I distinguish different types of autonomy, which correspond to invariance under different types of perturbations – this informs discussion of multiple realisability and underwrites my explanation of what makes Effective (Quantum) Field Theories (EFTs) such useful theories.
Each philosophical contribution is supported by examples from physics: I consider first order phase transitions, phonons in crystal lattices, the univer-sality of critical phenomena, and EFTs. By analysing these case studies, I con-tribute to conceptual and foundational debates about the theories discussed. In addition, in the latter two cases I clarify the explanatory function of the renormalisation group. In all cases, I identify the lower-level mechanisms and processes which allow for the discarding of detail when constructing higher-level descriptions.
Overall, I argue that the level structure of reality and the emergence of higher-level stability may be explained by identifying the physical structures which allow for abstraction from irrelevant detail.
Date of Award2019
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorEleanor Knox (Supervisor) & David Papineau (Supervisor)

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