International Relations theories generally hold that increased interaction between units in an international system produces convergence in their forms through military competition, institutional emulation, or normative socialization. In contrast, we argue that diverse international systems can endure despite increasing interaction. The early modern Indian Ocean international system hosted a variety of statist, corporate, and imperial polities. Diversity endured for three reasons. First, powerful foreign and local actors held differing maritime and land-oriented preferences for conquest, which created the potential for coexistence between unlike polities. Second, congruent European and Asian ideas of heteronomy facilitated durable polity di...