 For example, suppose principles of justice were to impose a duty to practice impartial benevolence towards all people, and thus a duty to show no greater concern for the welfare of ourselves and loved ones than we do towards millions if not billions of others. This principle demands too much of human nature and would not be sustainable or even feasible—people simply would reject its onerous demands. But Rawls’s stability requirement implies more than just ‘ought implies can.’ It says that principles of justice and the scheme of social cooperation they describe should evince “stability for the right reasons” (PL xliii, CP 589). Recall here the higher-order interests of the parties in development and exercise of their capacities for justice. A just society should be able to endure not simply as a modus vivendi, by coercive enforcement of its provisions and its promoting the majority of peoples’ interests. Stability “for the right reasons” requires that people support society for moral reasons of justice; society’s basic principles must respond to reasonable persons’ capacities for justice and engage their sense of justice. Rawls regards our moral capacities for justice as an integral part of our nature as sociable beings. He believes that one role of a conception of justice is to accommodate human capacities for sociability, the capacities for justice that enable us to be cooperative social beings. So not only should a conception of justice advance human interests, but it should also answer to our moral psychology by enabling us to knowingly and willingly exercise our moral capacities and sensibilities, which are among the moral powers to be reasonable. This is one way that Rawls’s conception of justice is “ideal-based” (CP 400–401 n.): it is based in an ideal of human beings as free and equal moral persons and an ideal of their social relations as generally acceptable and justifiable to all reasonable persons whatever their circumstances (the ideal of a well-ordered society). 