Modal Logic Should Say More Than It Does

First-order modal logics, as traditionally formulated, are not expressive enough. It is this that is behind the difficulties in formulating a good analog of Herbrand’s Theorem, as well as the well-known problems with equality, non-rigid designators, definite descriptions, and nondesignating terms. We show how all these problems disappear when modal language is made more expressive in a simple, natural way. We present a semantic tableaux system for the enhanced logic, and (very) briefly discuss implementation issues.

• Type: Conference
• Year: 1991
• Where: BIRTHDAY
• Authors: Melvin Fitting
• Keywords: Applied Computing, BIRTHDAY 1991, Discuss Implementation Issues, First-order Modal Logics, Non-rigid Designators