Abstract

For the modal logic |$\textsf {S4}^{C}_{I}$|⁠, we identify the class of completable |$\textsf {S4}^{C}_{I}$|-algebras and prove for them a Stone-type representation theorem. As a consequence, we obtain strong algebraic and topological completeness of the logic |$\textsf {S4}^{C}_{I}$| in the case of local semantic consequence relations. In addition, we consider an extension of the logic |$\textsf {S4}^{C}_{I}$| with certain infinitary derivations and establish the corresponding strong completeness results for the enriched system in the case of global semantic consequence relations.