Book excerpt: In this survey of early medieval thought and of the society that nurtured it, the author concentrates on three main epochs: the age of Alcuin, architect of the Carolingian Renaissance, when working copyists, libraries and schools established a tradition of learning and devotion which survived even the horrors of the tenth century; the age of Gerbert and the Ottos, when millennial fantasies and social disruption contrasted with real if limited achievements in the spread of Arab and Byzantine thought; and finally the heroic age of Abelard, which witnessed the rise of vernacular languages, the early Crusades and, in the Hildebrandine Revolution, the first great clash of Empire and Papacy.