Dominic J. Ryder

This thesis undertakes a philosophical analysis of the use of idealizations in contemporary theoretical physics, with a focus on domains for which we lack direct empirical evidence. The thesis focuses upon three domains of great importance to fundamental physics: Hawking radiation and black hole evaporation; beyond standard model physics; and quantum gravity. It asks how the use of idealized models can be justified in these domains without direct empirical evidence. The difficulty of justifying idealizations is illustrated through the identification of a paradox in mainstream derivations of Hawking radiation, which arises because of a particular idealization. This thesis then proposes a solution: embedding deidealization. This is a novel approach to deidealization that plays an important role in justifying idealizations. Embedding deidealization justifies idealizations by embedding them into a large complex of scientific knowledge, and is exemplified in this thesis through a case study: embedding deidealization can justify the use of idealizations in derivations of black hole evaporation, by drawing on facts from the large complex of scientific knowledge into which the model is embedded. This analysis is repeated for derivations of Hawking radiation, although the justificatory warrant is weaker in that case. Three further cases are then studied: the black hole information paradox, beyond standard model physics, and quantum gravity. First, it is argued that the use of idealizations in an important statement of the black hole information paradox undermines the grounds for the paradox. Thus, the paradox can be resolved by careful treatment of the idealizations. Second, it is argued that physicists are justified in expecting the standard model to break down, despite lacking direct empirical evidence. Finally, Dawid’s meta-empirical confirmation framework is analysed, and it is argued that the framework cannot license the confirmation of quantum gravity theories, including string theory.