Westphalianism is the belief that the world is inescabably divided into sovereign states, or ought to be so. The term is derived from the 1648 Treaty of Westphalia, which concluded the Thirty Years' War by dividing the Holy Roman Empire into a number of sovereign principalities along confessional lines.
A notable defence of Westphalianism is to be found in John Rawls' book from 1999, A Law of Peoples