Historians of international law differ over Montesquieu's observation in the Spirit of Laws that ‘all countries have a law of nations, not excepting the Iroquois themselves, though they devour their prisoners: for they send and receive ambassadors, and understand the rights of war and peace’. One school of thought argues in opposition to Montesquieu that international law is essentially a European invention, although there are different emphases within this school as to whether international law commences with the ancient Greeks, with the Romans, with medieval Christendom, with early modernity, or with the Peace of Westphalia in 1648. Others, who object to the eurocentrism implicit or explicit in such views, assert that a truly universal system of international law is not apparent until the late nineteenth century. Yet another thesis, with the same starting point of resisting eurocentric interpretations, maintains that there was a universal international legal order roughly from the rise of Islam until the late eighteenth century but the nineteenth century doctrine of sovereignty and legal positivism, together with European imperialism, involved a shift away from the broad moral principles of natural law that underpinned the universal order towards a self-serving distinction between ‘civilised’ states, which could have legal obligations toward each other, and the rest, which were outside the legal system. Additional complications are to be found in claims that the true origins of international law are to be found in the ancient Middle East, or China, or India.