Functionalism emerged as an alternative to federalist designs about the organization of the international system. Functionalism belongs to the liberal-idealist tradition of international relations theory and usually takes account of Immanuel Kant, John Jacques Rousseau, and Woodrow Wilson. The main figure of functionalism is David Mitrany (1888-1975). Mitrany’s seminal work entitled “A Working Peace System of 1944” has influenced many of his successors in European studies.