For centuries, philosophers have been puzzled by the fact that people often respect moral obligations as a matter of principle, setting aside considerations of self-interest. In more recent years, social scientists have been puzzled by the more general phenomenon of rule-following, the fact that people often abide by social norms even when doing so produces undesirable consequences. Experimental game theorists have demonstrated conclusively that the old-fashioned picture of economic man, constantly reoptimizing in order to maximize utility in all circumstances, cannot provide adequate foundations for a general theory of rational action. The dominant response, however, has been a slide toward irrationalism. If people are ignoring the consequences of their actions, it is claimed, it must be because they are making some sort of a mistake. In Following the Rules, Joseph Heath attempts to reverse this trend, by showing how rule-following can be understood as an essential element of rational action. The first step involves showing how rational choice theory can be modified to incorporate deontic constraint as a feature of rational deliberation. The second involves disarming the suspicion that there is something mysterious or irrational about the psychological states underlying rule-following. According to Heath, human rationality is a by-product of the so-called language upgrade that we receive as a consequence of the development of specific social practices. As a result, certain constitutive features of our social environment-such as the rule-governed structure of social life-migrate inwards, and become constitutive features of our psychological faculties. This in turn explains why there is an indissoluble bond between practical rationality and deontic constraint. In the end, what Heath offers is a naturalistic, evolutionary argument in favor of the traditional Kantian view that there is an internal connection between being a rational agent and feeling the force of one’s moral obligations.