The concluding chapter returns to consider implications of the experience of the OSCE over 50 years from 1975–2025 for theories of international relations. The early years of the CSCE/OSCE provide broad support for liberal institutionalist theories, as the CSCE developed as a normative institution in the last 15 years of the Cold War, and, as the OSCE in the first post-Cold War decade of the 1990s; the principles of the Helsinki Final Act and the Charter of Paris provided a normative foundation for dismantling authoritarian regimes throughout its region between 1975 and 1989, and building more democratic states afterward with special attention to promotion of human rights and the rights of persons belonging to national minorities. Internationally, it provided the basis for creating a pluralistic security community across its 57 participating States. However, following the Istanbul Summit in 1999, realist ideologies, a focus on individual national interests, and a return to authoritarianism in some regions, increasingly undermined the normative foundations of international cooperation in the OSCE region. The chapter concludes that neither liberal institutionalism nor political realism are inherent principles guiding international politics. From a constructivist perspective, it concludes that the OSCE, like most efforts at international cooperation, is what its participating States “make of it.” States have agency, and their changing political beliefs, normative values, perceptions, and decisions determine their behavior in international relations, including in international institutions like the OSCE.