This is an extensively revised and expanded version of the first edition of 1975. The book focuses on the political pluralism of J. N. Figgis, discussing its roots in the whig ideas of Acton, and the legal theories of Maitland and Gierke, reviewing its development in the writings of Harold Laski, G. D. H. Cole, Bertrand Russell and others. Pluralism rests on three pillars: liberty as a fundamental political value, best preserved by a division of power; a rejection of state sovereignty; and a belief in the personality of groups. Pluralist ideas of the relationship of state, group and individual are critically examined, and a chapter is devoted to authority within the group, taking the church as an instance. The book discusses the ideological and institutional conditions necessary for sustaining a pluralist and secular state. It is argued that pluralist theory is highly relevant to an age which has lost faith in the omnicompetent state, and to a situation where ethnic distinctions are becoming increasingly salient.