This essay will attempt to define an abstract model of the international system (or, more precisely, a model of the structure of that system), as a supplement to the types presented by Morton A. Kaplan. Before attempting such a construction, it is well to show the utility of the “multi-bloc system” as an alternative to his six models. Kaplan's “balance-of-power” and “unit veto” systems are essentially defined in terms of nation-states as “actors”; and his “universal” and “hierarchical” systems have essentially but one “actor,” though in the former the nation-state subsists as an administrative and local political unit. The two “bipolar” models (“loose” and “tight”) have, by definition, two major bloc “actors,” with uncommitted nation-states on the margin and an “international actor” such as the U.N. playing a limited role in the former model. It is true that his “unit veto” system may have blocs instead of nation-states for “actors,” but by this very token the difference between a system with a multiplicity of states and one with a multiplicity of blocs is not suggested by Kaplan's typology.The possibility of an international system composed of a multiplicity of blocs has been considered by a number of writers in the past few years. Even before the end of the Second World War, Walter Lippmann wrote:The question is whether some sixty to seventy states, each acting separately, can form a universal organization for the maintenance of peace. I contend that they cannot, and that single sovereign states must combine in their neighborhoods, and that the neighborhoods must combine into larger communities and constellations, which then participate in a universal society.