As with desert, reciprocity inspires skepticism. On one hand, it seems obvious that when we return a favor to someone who has been good to us, we do something that (other things equal) is at least good, maybe even morally required. Yet, Allen Buchanan recently began an article by declaring, “There is a strain of thought in the history of ethics that surfaces from time to time in the work of powerful thinkers and that threatens to shatter the basic conceptual framework within which our legal system and commonsense morality formulate the problems of justice. This idea may be called justice as reciprocity.” To Buchanan, justice as reciprocity implies that duties of justice obtain only among those who can do each other favors.