 Both Scanlon’s and Darwall’s views emphasize the social nature of morality, taken in the normative sense: Scanlon, by reference to justification to others; Darwall, by appeal to the relevance of second-personal reasons. But Darwall builds a responsiveness to second-personal reasons into the relevant notion of rationality, while Scanlon simply makes the empirical claim that many people are motivated by a desire to justify themselves to others, and notes that his definition of morality will yield rules that will allow one to do this, if one follows them. The sort of definition described in  section 5.1  also makes the social nature of morality essential to it, since it centrally features the notion of a response to the behavior of others. The definitions described in sections  5.2  and  5.3  do not entail the social nature of morality, since it is possible to accept, and even to advocate, a code that concerns only self-regarding behavior. But on any plausible account of rationality a code that would be advocated by all moral agents will govern interpersonal interactions, and will include rules that prohibit causing harm without sufficient reason. Only the definition offered in  section 5.3  therefore can be taken as realistically compatible with an egoistic morality.