Ideocracies (or: ideological dictatorships) such as the „Third Reich“, the Soviet Union and the People´s Republic of China have much more than any other kinds of autocracy characterized the history of the 20th century. Despite their undeniable loss of significance, they have not disappeared from the world in the 21st century, for example China, Cuba or North Korea. By way of case studies and systematic comparisons the authors of this volume, political scientists, sociologists, philosophers and historians, shed light on the specific ways of functioning of ideocracies. In the focus of their attention there is the typical interplay of legitimation, cooptation and repression when autocratic elites are struggling to stabilize their rule.