"The European Union is without question the most densely instutionalised international organisation in the world, with a welter of intergovernmental and supranational institutions and a rapidly growing body of primary and secondary legislation. This paper examines the new institutionalisms in rational choice and historical analysis and their contributions to EU studies, briefly summarising the core assumptions of each approach before discussing specific applications to the study of the EU and the question of enlargement." (Quoted from paper)