Informational dynamics of ‘might’ assertions

Abstract

We investigate, in a logical setting, the proposal that assertion primarily functions to express and coordinate doxastic states and that ‘might’ fundamentally expresses lack of belief. We provide a formal model of an agent’s doxastic state and precise assertability conditions for an associated formal language. We thereby prove that an arbitrary assertion (including a complex of ‘might’ and ‘factual’ claims) always succeeds in expressing a well-defined doxastic state. We then propose a fully general and intuitive doxastic update operation as a model of an agent coming to accept an arbitrary assertion. We provide reduction axioms for some novel update operations related to this proposal.