This book was originally published in 1974 when there were many theories attempting to explain the problems of international political integration. This book provides a critical analysis of the theories, relating them to relevant hypotheses in politics, economic and sociology. It treats separately functionalism, federalism and contemporary neo-functionalism. The author offers a number of hypotheses which place more stress on the conflicts inherent in late 20th Century international politics and in the domestic politics of Western European societies. Written for postgraduate and undergraduate alike, any terminology is carefully explained or used in a self-explanatory context