 These potential problems include the following. (1) Rules of inference are normative rather than descriptive. They tell us what inferences are permissible; they do not purport to provide an empirical account of what inferences people actually make. It is not clear how a description of the causal interactions between mental states can capture this normative element (Williams 1990; for a critique of the idea that mental content is normative, see Glüer and Wikforss 2009). (2) One might wonder whether there is something backward about the view that conceptual role determines meaning. In the case of propositional logic, a standard view is that the meaning of logical connectives such as conjunction is given by a truth table, which shows how the truth or falsity of a compound sentence is determined by the truth values of its component sentences. The adequacy of a system of inference rules is then determined by whether it permits derivations of all and only those arguments that are semantically valid. Similarly, perhaps the causal roles of mental states should be explained in part by their semantics, instead of the other way around. (3) Conceptual role semantics seems more plausible for logical connectives than for other sorts of representations. It is one thing to regard the meaning of a mental symbol for conjunction as determined by the inferences a subject will make between mental representations that contain the symbol and those that do not. After all, that is what conjunction is for. It is another and much bolder thing to regard more empirical mental representations as having their meanings determined in this way.