In order to formulate a comparative model of political cultures, a theory that integrates psychological, sociological and economic variables is developed. Within societies dominant political cultural themes stress particular patterns of right and obligation. These patterns simultaneously undergird social solidarity and justify an unequal distribution of rewards. Differences among political cultures exist vertically on an historical dimension of increasing moral comprehensiveness and horizontally on a dimension of moral content. Internal tensions deriving from technological development and from social discourse about the moral adequacy of norms stimulate change. A case study of American political culture, with its contrasting emphases on egalitarianism and individualism, assesses the theoretical claims.