distinction. In 400 Romanization extended more fully into Gaul than into other parts of the north. Charlemagne's empire in 800 incorporated parts of Italy as well as Gaul. The crusades to the Holy Land drew their main impulse from France and Normandy. Western Christendom, which emerged in the twelfth century and after, covered north and south Europe, unified by acceptance of the authority of the papacy, by the interconnection of universities in France and Italy, by French conquests in Naples and Outremer, by the networks of Italian international commerce, by the use of Latin as the language of scholarship and diplomacy. Medieval history, from one point of view, is the story of the movement of the centre of gravity of civilization from one side of the Alps to the other. If we looked for possible centres in 400 we might choose Rome or Constantinople, later perhaps Baghdad or Cordoba. By 1300 north-west Europe, northern France, the Low Countries, and the Rhineland had the most advanced civilization the world had ever seen. It was physically wealthy because of its rich agriculture and cloth industries, intellectually and aesthetically complex because of its universities and cathedrals, its lay literature and its many centres of seigneurial and urban power.

But the division between north and south has great advantages. The Mediterranean was always to some extent a separate world. Most strikingly so in the earlier Middle Ages when the empires of Byzantium and the Arabs scarcely extended beyond the Alps and the Pyrenees. The intellectual and aesthetic efflorescence of the Italian cities in the Renaissance, though it greatly influenced the north, was based on essentially Italian roots in the independent cities, which had no real parallel in the north, in Mediterranean trade, and the Italian devotion to the memory of Rome. The distinction between the Mediterranean and the north, though it divides the western Europe which emerged, provides a convenient arrangement of our subject-matter.

Thomas Brown shows in the first chapter how the decline of Rome in the Mediterranean was promoted dramatically by the invasions of Barbarians and Muslims, in spite of the resurgence under Justinian, and more gradually by social and economic change and the development of Christianity. Edward James

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