Abstract

Possible worlds are ways things might have been. They find applications in analysing possibility and necessity; propositions; knowledge and belief; information; and indicative and counterfactual conditionals. But possible worlds semantics faces the issue of hyperintensionality, generated by concepts that require distinctions between logical or necessary equivalents. The problems of distinguishing equivalent propositions, of logical omniscience, of information overload, of irrelevant conditionals, and of counterpossible conditionals, are all instances of the general issue. Adding impossible worlds promises to help with these puzzles. But can we genuinely think about the impossible? It is argued that we can.