Appiah's latest book is The Honor Code: How Moral Revolutions Happen, which examines the relationship between honor, morality, and social norms. Here is an excerpt from the New York Times review:

In “The Honor Code,” we accompany Detective Appiah as he tries to figure out who killed three morally repugnant practices: dueling among British gentlemen, foot-binding among the Chinese elite and slavery in the British Empire. In each case he shows how notions of honor sustained the practice for centuries, and how (spoiler alert) it was honor that later killed the practice in just a few decades, making these cases the “moral revolutions” referred to in his subtitle. Appiah also presents a fourth case: honor killings in present-day Pakistan, in which women and girls who are thought to have had sex outside of marriage, even in cases of rape, are murdered by male relatives to preserve the family’s “honor.” In this case the revolution has not yet happened, but Appiah draws on the other three cases to suggest how this horrific practice might someday meet its end.