 For philosophers, the special interest of this interdisciplinary inquiry lies in the ways moral psychology may help adjudicate between competing ethical theories. The plausibility of its associated moral psychology is not, of course, the only dimension on which an ethical theory may be evaluated; equally important are normative questions having to do with how well a theory fares when compared to important convictions about such things as justice, fairness, and the good life. Such questions have been, and will continue to be, of central importance for philosophical ethics. Nonetheless, it is commonly supposed that an ethical theory committed to an impoverished or inaccurate conception of moral psychology is at a serious competitive disadvantage. As Bernard Williams (1973, 1985; cf. Flanagan 1991) forcefully argued, an ethical conception that commends relationships, commitments, or life projects that are at odds with the sorts of attachments that can be reasonably expected to take root in and vivify actual human lives is an ethical conception with—at best—a very tenuous claim to our assent.