The EU is going through a difficult phase: The euro and refugee crises are still unresolved, the solidarity between Member States is eroding, the UK stands on the brink of an exit, nationalist forces are gaining increasing support in many Member States, the support for European integration is diminishing and EU foreign policy is focused on combating crises. The union appears too heterogeneous and the economic and political interests of the 28 Member States too diverse to be able to tackle these challenges as a whole. Does the concept of differentiated integration offer a possible solution? Can such differentiation offer the European integration project a better and more stable future? Which measures of diversity and flexibility can the ever closer Union among the peoples of Europe endure? Or will such differentiation ultimately damage the joint European project? These questions and others were the focus of an international and interdisciplinary conference at the European Academy of Otzenhausen in April 2016 that was organized by Univ.-Prof. Dr. Thomas Giegerich. The results of this conference are contained in this volume.