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PhD defence

An Ontology for Physical Necessity

  • J. Yu
Tuesday 26 March 2024
Academy Building
Rapenburg 73
2311 GJ Leiden


  • Prof.dr. J.W. McAllister
  • dr. V.A. Gijsbers
  • dr. M.S. van der Schaar


The central inquiry of this thesis revolves around how ontology can adequately accommodate the existence of necessary physical relations. Initially, the thesis demonstrates the imperative acknowledgment of necessary physical relations by showcasing the failure of Neo-Humean theories. Subsequently, it embarks on an investigation of the foundational explanation of physical necessity. This investigation scrutinizes two distinct accounts of necessary physical relations: dispositionalism and ontological structural realism (OSR), typically perceived as contrasting approaches to elucidating physical necessity. The thesis contends that the individuation regress inherent in dispositionalism compels its alignment with OSR. It then identifies a deficiency within the current OSR framework concerning the elucidation of the relationship between mathematical and physical necessity, attributing this shortfall to OSR's lack of ontological discussion regarding the nature of relations and structures. In response, this thesis endeavors to construct an ontological framework based on the relation of coexistence. This framework is demonstrated to encompass isomorphic counterparts of all mathematical structures within any mathematical reductionist program, as well as the isomorphic counterparts of all physical structures derived from these mathematical foundations. Such a framework facilitates the differentiation between mathematical and physical structures, thereby elucidating the distinction between mathematical and physical necessity.

PhD dissertations

Approximately one week after the defence, PhD dissertations by Leiden PhD students are available digitally through the Leiden Repository, that offers free access to these PhD dissertations. Please note that in some cases a dissertation may be under embargo temporarily and access to its full-text version will only be granted later.

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