We are the funny organisms that make and follow rules. To understand us, one must understand what is it to institute and follow a rule, to perform correctly or in error. This question is more important than it might at first seem for linguistic meaning is (partly) constituted by rules that govern uses of expressions. For example, the fact that 'squid' is correctly applied to squid and incorrectly applied to cuttlefish is part of what makes 'squid' mean what it does. Philosophers sometimes argue further that all representations are rule-governed so that a theory of representation must explain the possibility of misrepresentation. The rule-following problem makes an explanation of correctness surprisingly difficult. Philosophers have also ...