The outcome of the 2024 European Parliament elections highlights the need for the EU to underpin its functioning as a European democracy with a proper political theory. This article introduces the theory of democratic integration as a political philosophy of the EU. It aims to provide the EU with a philosophical foundation by analysing its evolution as a deviation from the Westphalian system of international relations and its doctrine of absolute sovereignty. The article finds that the EU is succeeding in creating a new democratic home for its citizens and its member states. In times of increasing support for parties which promote national sovereignty as the recipe for the future and which consequently call for the dismantling of the European Parliament and the deconstruction of EU democracy, the theory will empower the Union to defend its constitutional achievements and prevent it from backsliding into an undemocratic organisation of illiberal states.