Stephen Salkever in this Review (“Virtue, Obligation and Politics,” APSR 68 [March, 1974]) discusses two paradigms of politics: one based on the concept of virtue (ancient political philosophy), the other resting on obligation (modern political thought). We analyze the meaning and significance of these two paradigms in terms of the cognitive-developmental moral psychology common to Lawrence Kohlberg, John Dewey, and Jean Piaget. We first present the cognitive-developmental theory and its empirical findings. We then demonstrate that the politics of obligation falls within the virtue paradigm as a necessary stage in the development of virtue, which involves placing Plato, Aristotle, Machiavelli, Hobbes, Locke, Rousseau, and Rawls within our developmental scheme. Finally, we explore the nature of understanding moral principles from within the cognitive-developmental perspective. In all this, we agree with Salkever's basic assumption that any account of political good (public as opposed to private) must be based on moral psychology, i.e., it must deal with the question of “What is good for the most inclusive of all publics, the human species?” We go two steps beyond Salkever, however, by showing the significance of the question, and by providing an answer to it (both of which bear upon the understanding of morality). An underlying purpose of our research is to present and to promote the political relevance and significance of moral psychology in general and cognitive development in particular.