Piaget's social psychology is not widely discussed among psychologists, partly because much of it is still contained in untranslated French works. In this article I summarize the main lines of Piaget's social psychology and briefly indicate its relation to current theories in social psychology. Rejecting both Durkheim's sociological holism and Tarde's individualism, Piaget advances a sociological relativism in which all social facts are reducible to social relations and these, in turn, are reducible to rules, values and signs. Piaget's theory of (...) social values takes the form of a social exchange theory characterized in an abstract logical way. Piaget claims social exchange requires normative principles of reciprocity and that individual social development results in such an equilibrium because rationality itself is social and based upon social cooperation. These views, in turn, derive from Piaget's orthogenetic views concerning the course of evolution: development can be characterized as an increase in equilibrium manifested both in individual action and in social interaction. (shrink)