Plausibility, necessity and identity: A logic of relative plausibility*

Abstract

We construct a Hilbert style system RPL for the notion of plausibility measure introduced by Halpern J, and we prove the soundness and completeness with respect to a neighborhood style semantics. Using the language of RPL, we demonstrate that it can define well-studied notions of necessity, conditionals and propositional identity.

Keywords

relative plausibility, necessity, propositional identity, ordered neighborhood semantics