Abstract: What is it for an expression to have a meaning in a community’s language? David Lewis can be taken to argue in his “Languages and Language” that it is for there to be a conventional regularity of using the expression in certain conditions (e. g. when one has a certain belief) and reacting in a certain way (e. g. trustfully). I will argue that this view cannot accommodate certain aspects of language use as a rational and voluntary action. Instead, I will defend the idea that meaningfulness has to do with rules that permit using the expression in certain conditions and outline two ways in which this can be the case.