Moral systems, like normative systems more broadly, involve complex mental representations. Rational Rules argues that moral learning can be understood in terms of general-purpose rational learning procedures. Nichols offers statistical learning accounts of some fundamental aspects of moral development: how people come to think that a rule is act-based, that is, that the rule prohibits producing certain consequences but not allowing such consequences to occur or persist, and how people come to expect that a new rule will also be act-based; how people come to believe a principle of liberty, according to which whatever is not expressly prohibited is permitted; and how people come to think that some normative claims hold universally while others hold only relative to some group. The resulting account has both empiricist and rationalist features: since the learning procedures are domain-general, the result is an empiricist theory of a key part of moral development, and since the learning procedures are forms of rational inference, the account entails that crucial parts of our moral system enjoy rational credentials. Moral rules can also be rational in the sense that they can be effective for achieving our ends, given our ecological settings. Rational Rules argues that at least some central components of our moral systems are indeed ecologically rational: they are good at helping us attain common goals. The account extends to an explanation of moral motivation: a basic form of rule representation brings motivation along automatically, and so part of the explanation for why we follow moral rules is that we are built to follow rules quite generally.

Shaun Nichols, Cornell University

Shaun Nichols is Professor of Philosophy at Cornell University.

Preface
PART I: RATIONALITY AND RULES
1. Rationality and morality: Setting the stage
2. The wrong and the bad: On the nature of moral representations
PART II: STATISTICAL LEARNING OF NORM SYSTEMS
3. Scope
4. Priors
5. Closure
6. Status
PART III: PHILOSOPHICAL IMPLICATIONS
7. Moral empiricism
8. Rational rules and normative propriety
9. Rational rules, relativism, and universalism
10. Is it rational to be moral?