Differentiation has become a central topic of debate in the EU. Generally, it is considered a positive device for advancing integration in crucial policies, letting the unwilling states opt out from the new regimes. However, the debate has not sufficiently acknowledged that policy differentiation has been made possible by governance differentiation. It was the 1992 Maastricht Treaty's decision to inaugurate an intergovernmental regime for core state power policies, distinct from the

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... l regime regulating single market policies, that allowed differentiation to flourish. Differentiation and intergovernmentalism are thus inter-connected. During multiple crises of the last decade, intergovernmental governance has shown its undemocratic effects, thus soliciting a critical reappraisal of the differentiation logic. The federalisation of the EU appears a more promising alternative strategy for advancing integration and, at the same time, meeting the democratic expectations of the EU. This analytical exercise speaks to the Conference on the Future of Europe. | INTRODUCTION Differentiation (understood as differentiated integration) has become a central topic of scientific debate in the European Union (EU). 1 It is prized as a virtue of the process of integration which could proceed only by accommodating different national preferences and views around different policy regimes operating within the same Treaty's framework. According to Schimmelfennig and Winzen, "We speak of differentiated integration-as opposed to uniform integration-when the legally valid rules of the EU, codified in European treaties and EU legislation, exempt or exclude individual member states explicitly from specific rights or obligations of membership in the EU". 2 The EU has accommodated different forms of differentiation. The differentiation considered here concerns the formal opt-out of