Liberals have discovered the system level of analysis. Two somewhat competing strands of system-level liberal scholarship have emerged. The first emphasizes the system's normative dynamics and the democratic peace. The second has sought to conceive of capitalism as a property of the international system and theorize its effects. While a number of propositions and mechanisms have been identified, the literature has failed to develop an overarching account of system structure. Using Durkheim's distinction between mechanical and organic societies, and Waltz's tripartite definition of structure, this paper develops a liberal grand-theory that integrates these two strands of liberal systemic thinking. The theory generates a number of large propositions: the structure's dominant tendency is integration; it pushes states to specialize; and it induces a competitive normal politics. I also propose a typology of systems that vary according to liberal homogeneity and a liberal normative framework and mutual economic dependence, with important implications for the question of systemic stability. By way of conclusion, I offer a few thoughts on the value of grand-theorizing in International Relations.This article aims to deliver a systemic theory of international politics with distinctly liberal characteristics. This may seem like an impossible task because in its theoretical form, liberal theory is typically understood in three different ways: as centering on the domestic level of analysis (Milner 1997), as being dyadic (Doyle 1983), or as involving "bottom-up" preference aggregation (Moravcsik 1997). To date, it has been defined by its theoretical form, and not content.This contemporary understanding of liberal theory largely developed in opposition to top-down realist arguments centering on the system level of analysis. However, this dyadic and bottom-up understanding of liberal theory is fairly new. Consider, for example, the many nineteenth-century liberals such as Ricardo and Cobden who championed the idea that general prosperity could be created through freer trade at the regional or system level. Rosecrance (1986) has conceived of the system in terms of a trading world and a politico-military world. Others have argued that hegemonic power can contribute to the creation and maintenance of liberal order (Ikenberry 2001). Keohane and Nye (2001) have made the case that institutions and "complex interdependence" have modified the systemic tendencies of anarchy. Even Kant's Perpetual Peace, a work widely recognized as the foundation for the dyadic democratic peace, has been found to contain prominent "third image" implications (Huntley 1996;Harrison 2002). Defining theories in terms of assumptions and content-and