The study of international ethics is marked by an overwhelming bias towards reasoned reflection at the expense of emotionally driven moral deliberation. For rationalist cosmopolitans in particular, reason alone provides the means by which we can arrive at the truly impartial moral judgments a cosmopolitan ethic demands. However, are the emotions as irrational, selfish and partial as most rationalist cosmopolitans would have us believe? By re-examining the central claims of the eighteenth-century moral sentiment theorists in light of cutting-edge discoveries in the fields of neuroscience and...