Kripke-style models with two accessibility relations, one intuitionistic and the other modal, are given for analogues of the modal systemK based on Heyting's prepositional logic. It is shown that these two relations can combine with each other in various ways. Soundness and completeness are proved for systems with only the necessity operator, or only the possibility operator, or both. Embeddings in modal systems with several modal operators, based on classical propositional logic, are also considered. This paper lays the ground for (...) an investigation of intuitionistic analogues of systems stronger thanK. A brief survey is given of the existing literature on intuitionistic modal logic. (shrink)

We investigate intuitionistic propositional modal logics in which a modal operator is equivalent to intuitionistic double negation. Whereas ¬¬ is divisible into two negations, is a single indivisible operator. We shall first consider an axiomatization of the Heyting propositional calculus H, with the connectives →,∧,∨ and ¬, extended with . This system will be called Hdn . Next, we shall consider an axiomatization of the fragment of H without ¬ extended with . This system will be called Hdn + . (...) We shall show that these systems are sound and complete with respect to specific classes of Kripke-style models with two accessibility relations, one intuitionistic and the other modal. This type of models is investigated in [2] and [3], and here we try to apply the techniques of these papers to an intuitionistic modal operator with a natural interpretation. The full results of our investigation will be published in [4] and [1]. (shrink)