Modal Logic and Contingent Existence

March 14, 2025

Abstract: In this talk, I will defend contingentism, the idea that some things exist contingently. It might be surprising that this needs defence, but natural reasoning principles concerning possibility and necessity on the one hand, and the existential and universal quantifiers on the other, have led some to necessitism, the view that everything that exists, exists necessarily.

Almost all recent work on modal semantics makes essential use of possible worlds models. These models have proved useful for analysing the structural properties of modal logics, but it is less clear that they fix the meaning of our modal vocabulary, given that we have no grasp of what counts as a possible world, independent of our grasp of what counts as possible. In this talk, I describe an inferentialist semantics for modal and quantificational vocabulary, not as a rival to possible worlds models, but as an explanation of how the concepts we do employ can be modelled using possible worlds. I then use this inferentialist semantics to clarify the contingentist’s commitments, and offer answers to necessitist objections.

• This talk is a Presentation at the University of Calgary Philosophy Department.

• The slides for this talk are available here.

• There is a draft paper, which goes into the results I discuss in this talk in more length.