The concept of well-being is central to the subject matter of moral philosophy as well as economics. According to some moral theorists (particularly utilitarians) morality is about the maximization of social well-being. According to others, notably John Rawls (1972) we ought to give particular priority to the worst off members in society. Both these and other moral positions, whatever the priority they attach to different members of society in arriving at moral judgements, require an account of well-being or advantage. The concern with well-being is thus of foundational importance in moral philosophy, even if well-being is not thought of as all that matters. Furthermore, those who want to distinguish ‘morality’ from ‘self-interest’ must furnish us with an account of human interests, so that we can distinguish the moral realm from that of self-interest or prudence. The concerns of moral philosophers, here, clearly overlap with those of economists. Economists (particularly in welfare and development economics) are much concerned with questions of how well people are doing, with their ‘standard of living’ or ‘quality of life’. However, there are very different ways of thinking about each of these ideas. Indeed, we need to discriminate between different views of the quality of life and to decide which is the most appropriate for the purposes of moral theory and the normative parts of economics.