Social humanism is both a moral and a political philosophy. As a political philosophy, it requires the establishment and development of a kind of welfare state, and it proposes a framework for a series of agreements between states on global social and moral issues. As a moral philosophy, it provides a theory for the development of charters of human rights, which could reasonably be expected, over time, to command something approaching universal assent. To develop this moral and political theory, it has been necessary to revisit some basic questions concerning the metaphysics of morals, and to construct a new basic theory. This new theory is one of social idealism, which is like Kant’s rational idealism in some ways, but it is metaphysically realistic and based on the social ideals of ordinary, rather than perfectly rational, individuals. It is argued that there are two sorts of social ideals relevant to moral and political philosophy, ideals of character and ideals of society, corresponding roughly to the distinction between morals and politics. But the two are not really distinct, and it is a serious mistake to try to develop either one without an adequate theory of the other. An ideal society needs good people who are motivated and able to service and develop its institutions, and good people need a good society in which to live and work-one that will encourage them to express their natural virtues and to develop their natural talents for the good of all.