James S. Coleman ranks among the most influential sociologists of the twentieth century. Coleman's scholarship pursued several linked lines of inquiry in parallel, but centered on understanding and improving the performance of social systems. He led a study of inequality in educational opportunity (Coleman, Campbell et al. 1966) that had a major impact on US educational policy and served as a model for much subsequent policy research in social science. Foundations of Social Theory (1990), his principal theoretical work, outlined an approach to understanding social phenomena resting on interdependent purposive actions. He viewed the rising prominence and power of large organizations (“corporate actors”) as the most distinctive feature of contemporary society, and contended that social science and social theory should help to develop new forms of social organization that are more attentive to the interests and welfare of natural persons. Coleman's work has enduring influence on social theory, educational research, organizational analysis, mathematical sociology, and policy research, among other fields.