Abstract

The paper offers a model for the conventionality of illocutionary forces. It focuses on the argument that accounts of assertion in terms of constitutive norms are incompatible with conventionalist claims about assertion. The argument appeals to an alleged modal asymmetry, and is in that respect related to well-known arguments that the notion of truth by convention is misguided: while constitutive rules are essential to the acts they characterize, and therefore the obligations they impose necessarily apply to every instance, conventions are arbitrary and thus can only contingently regulate the practices they establish. The paper argues that there is no such modal asymmetry, by appealing to a distinction between the non-discriminating "existence" across all possible worlds of practices defined by constitutive rules, and the discriminating sense in which only some of them are actually "in force" in the actual world; the necessity of practices defined by constitutive rules concerns the former, while conventionalist claims concern the latter.