Abstract

In [2] we have presented sequent formulations of the modal logics S5 and S4 based on sequents of higher levels: sequents of level 1 are like ordinary sequents, sequents of level 2 have collections of sequents of level 1 on the left and right of the turnstile, etc. The rules we gave for modal constants involved sequents of level 2, whereas rules for other customary logical constants of first–order logic involved only sequents of level 1. Here we show starting from the same sequent rules of higher level we can obtain sequent formulations of intuitionistic analogues of S5 and S4. We presuppose for this paper an acquaintance with [2]