This book explores the German idea of federalism denoting 'diversity within unity'. Historians, linguists and political scientists examine how federalism emerged in the Holy Roman Empire, was re-shaped by nineteenth-century cultural movements, and was adopted by the unified state in 1871 and again after 1945. The myth of federalism as a safeguard against totalitarianism is tested in regard to the Third Reich and the GDR. The book concludes with an outlook on German federalism's future in Europe.