Relational Observables, Quiddities, and Structural Realism

Abstract: In this article, I argue that modern spacetime physics causes problems for a number of traditional accounts of modality, but also offers important new ideas about the connection between modal and non-modal features of reality. I suggest that recent work on relational observables in general relativity and quantum gravity can help us understand how non-modal features of reality could arise from modal features of reality within some form of modal ontic structural realism. In particular, I argue that the notion of an `internal view,' as employed in the partial/complete observables formalism and the quantum reference frame formalism, is an important conceptual insight which can help address outstanding problems in the philosophy of lawhood and modality.