A normal modal calculus between T and S4 without the finite model property

Abstract

Given separate though similar proofs of the finite model property for individual modal calculi such as S5, S4, S2, and the Feys-von Wright system T, the problem arises of generalising the arguments and establishing the property for modal calculi en masse. In other words, we would like to be able to show in one fell swoop that any modal calculus satisfying certain general syntactic conditions has the finite model property.