Logical necessity, physical necessity, ethics, and quantifiers

Abstract

Some philosophers, for example Quine, doubt the possibility of jointly using modalities and quantification. Simple model‐theoretic considerations, however, lead to a reconciliation of quantifiers with such modal concepts as logical, physical, and ethical necessity, and suggest a general class of modalities of which these are instances. A simple axiom system, analogous to the Lewis systems S1 —S5, is considered in connection with this class of modalities. The system proves to be complete, and its class of theorems decidable.