The ecumenical movement is primarily the result of an internal dynamic arising from religious convictions, but it is also in part a response to social forces and historical developments. It is more inclusive than the major Protestant denominations in the American tradition and broader than the organizations which promote co-operation among the churches. The churches are not seeking to establish a monolithic church structure under centralized authority and control. The councils, in which they achieve order and at the same time maintain their freedom, may be suggestive to other institutions which desire to keep freedom and order in balance in modern mass society. Distinctions must be drawn between unity and uniformity, between agreement and mutual understanding. The community of interest among Christians rests primarily on common presuppositions derived from their faith. Intensive study of differences in doctrine and church polity improves mutual understanding and enlarges the areas of agreement. Participation in the ecumenical movement is changing the perspective of American churches with regard to national and world problems. Extensive association in international consultations and specialized agencies dealing with international affairs, in the missionary enterprise, and in interchurch aid and disaster relief corrects provincialism.