Multilateralism, defined as coordination between three or more states based on generalized principles (Ruggie 1992), is a central component of the contemporary international system. Multilateral organizations have grown in complexity, members, and mandates, performing different functions for the global community: overcoming collective action problems (Keohane 1990), providing public spheres for states and other actors to debate and generate common understandings (Johnstone 2011), institutionalize power and status relations (Gilpin 1981), and allow joint governance of shared problems (Rosenau and Czempiel 1992). This expanding participation in international life has also made organizations witnesses of history: major episodes of modern politics, from decolonization to climate change, unfolded in their plenaries. Likewise, they are today pressured to adapt processes and concepts to accommodate new facts, such as non-state conflicts, failed states, transnational crime, and the rise of non-Western powers with distinctive agendas and identities (Hurrell 2007). This research project is thus interested in multilateral organizations and their responsiveness, past and present, to global challenges.