This concluding chapter of the third edition of European Integration Theory (OUP 2018) takes stock of the updated mosaic of integration theory. The chapter is organised in three sections. The first section offers a comparative perspective on the book’s chapters. To that end, it presents the preferences of each approach from a comparative perspective, against the backdrop of three leading metaphorical perceptions of the EU. The second section addresses the absence of security crises in the book’s contributions. To explore, how security crises may be brought into focus in integration theory, it distinguishes the impact of integration along two dimensions. These include first, the horizontal regional comparative perspective and the ‘litmus test’ of the applicability of integration theory to other regions; and second, the vertical dimension which connects normative crises in EU sub-units with global conflicts. And the concluding third section asks how integration theory fares sixty years on from the Treaty of Rome, and points out potential issues and themes for the future of European integration theory.