The Interaction of ‘If’ and ‘Would’: Semantics and Logic

Abstract

This chapter argues that the difference between indicative and counterfactual conditionals traces to the overt difference in verb forms and not to any alleged covert ambiguity or context-dependence in ‘if’. ‘Would’ has a life beyond conditionals; the best hypothesis is that it is a necessity modal restricted to contextually relevant worlds. In standard counterfactual conditionals, ‘would’ scopes over ‘if’; given the invariant truth-functional semantics of ‘if’, the compositional semantics then makes counterfactual conditionals contextually restricted strict conditionals. The chapter explores the consequences of this for the logic of counterfactuals: principles such as transitivity, contraposition, and strengthening the antecedent hold, with appearances to the contrary being explained by context-shifting caused by the application of the suppositional heuristic. However, modus ponens fails because the contextual restriction may exclude the actual world.