The Euro Area, the Schengen Area, and Airbus - the 'Anglosphere', the Franco-German 'motor' and Nordic cooperation - each illustrates how differentiation has become a pervasive feature of European integration. Which Europe? offers an authoritative and comprehensive examination of differentiated integration in its functional and its territorial aspects. It focuses on its implications for both the practice and the theory of European integration. Is it strengthening or weakening the EU and its Member States? Are territorial identities being undermined or strengthened? Are new theories of integration required? In particular, this book looks at the relationship between the growth in use of differentiated integration and the widening of European Union membership, the broadening in its policy scope, and the deepening in integration.