Abstract:

This paper discusses an inference rule called by modified modus ponens, which is used in the logical system LPC+Ch which is first order (or lower) predicate calculus equipped with additional axiomatization of modifier operators. This basic forms a system like generalized modal system with several pairs of modal operators. The main properties of the system LPC+Ch necessary for introducing this topic are considered. It suffices well a propositional system PC+Ch for these purposes. The modal version of modified modus ponens is proved to hold in standard modal systems.