This article examines one of the most important developments in the history of human rights: the debates over human rights universality that took place between UNESCO and the Commission on Human Rights during the drafting of the Universal Declaration of Human Rights in 1947 and 1948. Based on new archival research, the article presents for the first time a revised history of this key episode in international relations. Beyond implications for our understanding of human rights, the role of Western institutions, and cultural diversity, the article provides an alternative understanding of how the early post-war international world was constructed. What this research shows is that the international system was very much an “unsettled firmament” with different perspectives on which institutions in the UN system should play which roles in rebuilding the post-war world. In fact, how this firmament eventually settled was very much ad hoc and dependent on circumstances. In other words, the international system could have developed otherwise, which holds lessons for the future.