Possible Worlds Semantics

The subject of this chapter is the most popular analysis of counterfactuals, i.e., possible worlds semantics. The chapter begins with a general characterization of this semantics, along with the key question of the philosophy of modality (Sect. 3.1). This aims to provide a basis for the analysis of counterfactuals in terms of possible worlds. In virtue of the standard (so-called ‘orthodox’) approach, every counterpossible is vacuously true. This motivates introducing a modification that results in extending the domain of worlds to include impossible worlds. Section 3.2 provides the details of the modified view, i.e., the semantics and metaphysics of impossible worlds. It also shows how the extension of the domain of worlds affects the analysis of one of the key notions of possible worlds semantics for counterfactuals, i.e., the notion of similarity between worlds. Since some advocates of orthodoxy have argued that the problem of counterpossibles should be shifted from the semantic question of truth-value to the pragmatic question of assertability, Sect. 3.3 examines these arguments and provides arguments against a pragmatic-oriented approach to counterpossibles.