Problems of ethno-national and religious identity in violent conflict dominate modern politics, from the recent violent history of Northern Ireland, to current conflicts in Afghanistan and Iraq, to terrorism in Sri Lanka or the former Yugoslavia. Yet whilst politics and international relations struggle with these problems, sociology generally has made only a small contribution. It is the contention here that sociology, particularly social theory, should be a major tool in helping explain national, religious and identity problems. The classical sociologists directly addressed these problems in their sociology, which was fundamentally about the formation of integrated national societies. For 'nation', read 'society'. Durkheim, especially, was sponsored by the French State to mould a new French nation from competing religious, ethnic and linguistic groups and identities - one that would overcome all the internal revolutionary violence and divisions of her history from 1789 onwards to form a single enlightened, civic culture. This book demonstrates that he offers important lessons for today.