The changing structure of European order poses, for any student of international relations, some fundamental questions about the evolution of world politics. Concepts of European order and of the European state system are, after all, central to accepted ideas of international relations. Out of the series of conflicts and negotiations—religious wars, coalitions to resist first the Hapsburg and then the Bourbon attempt at European hegemony—developed ideas and practices which still structure the contemporary global state system: the equality of states; international law as regulating relations among sovereign and equal states; domestic sovereignty as exclusive, without external oversight of the rules of domestic order. The ‘modern’ state system, modern scholars now agree, did not spring fully-clothed from the Treaty of Westphalia at the close of the Thirty Years' War; it evolved through a succession of treaties and conferences, from 1555 to 1714. It remains acceptable, nevertheless, to describe the European state order as built around the Westphalian system.