ABSTRACT
Differentiated integration is a core feature of European integration. It allows the EU to manage heterogeneity while avoiding integration deadlock. Differentiated integration follows two basic logics. Instrumental differentiation is a pragmatic, short-term tool to overcome distributional conflicts and efficiency concerns. By contrast, constitutional differentiation accommodates persistent diversity among its member states regarding the desired level and scope of European integration. It reflects a post-functional logic of concerns about self-determination, affects predominantly the integration of core state powers, and gives rise to a durable (but permeable) core-periphery structure in European integration. Differentiated integration is a largely unintended, still not fully recognized but highly beneficial constitutional principle of European integration. It has been a facilitator of integration and a fundamental institution of a ‘demoi-cratic’ union. Yet it only accommodates territorially structured heterogeneity, and it has not established itself as a strategy to support the self-determination of sub-state demoi in European integration.
