Abstract: Advocates of cosmopolitan ideals, to the extent that they engage with questions of institutional design, typically imagine replicating or refining existing, nation-state models of governance but on an international scale. This essay argues that cosmopolitan ethics need not go hand in hand with international government, and may be better served by a different approach. I explore the concept of degeneracy as a principle of institutional evaluation and design in international politics. Degeneracy is a characteristic of complex systems in which multiple components of the system offer overlapping (but not identical) functions, and is a key component in the robustness of such systems. Non-degenerate systems, by contrast, exhibit fragility in the face of adverse conditions. When applied to systems of governance, degeneracy commends polycentricity and allows for some evaluation of the robustness of different mechanisms and forms of polycentric governance. Cosmopolitan ideals are better served by providing alternatives to existing forms of governance than by building on them. I consider some concrete policy applications of this idea, focusing on immigration and intellectual property.