A Tree-Sequent Calculus for a Natural Predicate Extension of Visser's Propositional Logic

We study predicate logic that is interpreted in Kripke models similarly to intuitionistic logic except that the accessibility relation of each model is not necessarily reflexive. Unlike in Ruitenburg's Basic Predicate Calculus, which is previous work on logic of this kind, the notion of formula in our system is the standard one in predicate logic. We give an axiomatization for this logic in the style of tree-sequent calculus (a special form of labelled sequent calculus) and prove its completeness with respect to the class of Kripke models.