Bounded Inquisitive Logics: Sequent Calculi and Schematic Validity

TL;DR

This paper develops cut-free labelled sequent calculi for bounded inquisitive logics, exploring schematic validity and demonstrating how certain formulas behave differently under boundedness assumptions.

Contribution

It introduces new sequent calculi for $n$-bounded inquisitive logics and analyzes schematic validity in predicate inquisitive logic.

Findings

Casari formula is atomically valid but not schematically valid in $ extsf{InqBQ}$

Schematic validity depends on the use of specific rules in the calculus

Derivations are valid when a particular rule is not applied

Abstract

Propositional inquisitive logic is the limit of its $n$-bounded approximations. In the predicate setting, however, this does not hold anymore, as discovered by Ciardelli and Grilletti, who also found complete axiomatizations of $n$-bounded inquisitive logics $\mathsf{InqBQ}_{n}$, for every fixed $n$. We introduce cut-free labelled sequent calculi for these logics. We illustrate the intricacies of \textit{schematic validity} in such systems by showing that the well-known Casari formula is \textit{atomically} valid in (a weak sublogic of) predicate inquisitive logic $\mathsf{InqBQ}$, fails to be schematically valid in it, and yet is schematically valid under the finite boundedness assumption. The derivations in our calculi, however, are guaranteed to be schematically valid whenever a single specific rule is not used.