The abbots of the many abbeys of various orders built throughout this period were too enlightened to disregard the progress of their contemporaries, and they promptly applied the new principles to the construction or embellishment of their monasteries. [Illustration: 133. ABBEY OF CLUNY. GATEWAY] The Abbey of Cluny was founded in 909 by William, Duke of Aquitaine, and declared independent by Pope John XI., who in 932 confirmed the duke's charter. Its rapid development and growth in power is sufficiently explained by the social and political circumstances of its origin. At the beginning of the tenth century Norman invasions and feudal excesses had destroyed the work of Charlemagne. Western Christendom seemed to lapse into barbarism after the havoc made by the Saracens and Northern pirates among towns and monasteries. Civil society and religious institutions had alike fallen into the decay born of a conflict of rights and a contempt of all authority. Cluny rapidly became a centre round which all the intelligence which had escaped submersion in the chaos of the ninth century grouped itself. Its school soon attained a distinction equal to that which marked the first great seats of learning at the beginning of the Middle Ages. Thanks to the _Rule_ of St. Benedict, on which the Benedictines of Cluny had grounded their community, the abbey developed greatly in extent and wealth. Throughout the eleventh and twelfth centuries it seems to have been the prolific nursery-ground whence Europe drew not only teachers for other monastic schools, but specialists in every branch of science and of letters, notably architects, who aided in the expansion of Cluny and its dependencies, and further practically contributed to the construction of the numerous abbeys founded by the Benedictines throughout Western Europe, and even in the East, the cradle of Christianity. While this struggle of intelligence against ignorance was in progress, a social revolution had accomplished itself by the enfranchisement of the communes, a development of the utmost importance in its relation to science, art, and material existence, in a word, to the whole social system. Architecture, that faithful expression of the social state which had its origin in Pagan civilisation, became Christianised by its culture in the abbeys, and in its new development rose to that pre-eminence the marvels of which we have already studied in the first part of this work. But though the successes achieved by the architecture of this period were rapid and dazzling, its decadence was profound, for it was induced by too radical an emancipation from antique principles, the superiority of which had been established in the first centuries of the Middle Ages.