The paths taken by historians and political scientists intersect less frequently thantheir subject matter might indicate. Both sets of scholars, for example, have a mutualinterest in the formation and evolution of the modern state. However, while thisinterest has made the ‘Westphalian system’ the common currency of exchangesamong political scientists, few historians refer to the concept, and some would notrecognize it—even at close range and in full sunlight. Practitioners of the two disciplinesoften pass like ships in the night because they are unaware of another largepresence on a parallel course. In an age of intense specialization we readily becomeseparated, like Alfred Marshall's noncompeting wage groups, from a common bodyof information. A more formally acceptable justification for discrete enquiries intosimilar problems lies in the claim that the disciplines have different purposes. Thedistinction is not, as is still so often said, that historians are interested in the uniqueand social scientists in the general; it is rather that the analytical issues forming thegeneralizations that necessarily accompany statements about large issues are of adifferent order. Political scientists assign significance to the Westphalian systemmainly because they wish to generalize about the principles governing the internationalregime of sovereign states after 1648. Historians, on the other hand, are lessinterested in testing the merits of realism and its rivals than in charting changingrelativities in international relations. Accordingly, they are more likely to set theWestphalian settlement in the context of already evolving state systems and of subsequentchanges of equal or greater moment, such as the upheavals caused by theFrench and American revolutions.