Propositional quantification in logics of contingency

Abstract

In this work we define contingency logic with arbitrary announcement. In contingency logic, the primitive modality contingency formalises that a proposition may be true but also may be false, so that if it is non-contingent then it is necessarily true or necessarily false. To this logic one can add dynamic operators to describe change of (non-)contingency. Our logic has operators for public announcement and operators for arbitrary public announcement, as in the dynamic epistemic logic called...