Abstract

The paper focuses on the modal argument that accounts of assertion in terms of constitutive norms are incompatible with conventionalism about assertion. The argument appeals to an alleged modal asymmetry: 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 this line of reasoning fails to establish any modal asymmetry, by invoking the distinction between the non-discriminating existence across possible worlds of types (practices, institutions) defined by constitutive rules, and the discriminating existence of those among them that are actually in force. The necessity of practices defined by constitutive rules that the argument relies on concerns the former, while conventionalist claims concern the latter. The paper concludes suggesting considerations that are relevant to deciding whether assertion is in fact conventional.