Abstract

This chapter defends an account of metaphysical possibility which is based on the idea that there is a close connection between metaphysical possibility and the ‘just is’-operator. The discussion centers on two main results. First, it is shown that a limited class of ‘just is’-statements can be used to fix a truth-value for every sentence in a first-order modal language. (This is the Extension Theorem.) Second, it is shown that the truth-conditions of arbitrary sentences in a modal language can be specified using only the fragment of the language that does not contain modal operators. (This is the Reduction Theorem.) The chapter also contains an extend discussion of a rival account of metaphysical possibility, defended by David Lewis.