The barbarian invasions, which swept away the last vestige of imperial greatness, introduced the heretical doctrines of Arius into Southern Europe. The religious antagonism resulting from the incessant clash of adverse opinions was perpetuated by the mutual jealousies of king and bishop, until the accession of Charlemagne practically united in the hands of that emperor the temporal and sacerdotal powers,--the dominion of the earth, and the control of an order whose members were universally regarded as mediators with heaven. With his death the exercise of the exalted prerogative of spiritual jurisdiction reverted to the Papacy. The claim to its enjoyment was never afterwards successfully urged by any monarch who was entitled, by right of inheritance, to the dignities and privileges of the Carlovingian empire. By degrees, the resistless influence of intellectual superiority, quietly, but none the less powerfully exerted, began to manifest itself. It was to the fact that the Church monopolized all the learning of early mediæval times, even more than to the reverence that attached to the holy calling of its ministers, that its boundless power over the most truculent and merciless barbarians is to be attributed. A mysterious and exaggerated importance was ascribed to that profession whose members held communion with past ages; who called down the blessings or the maledictions of celestial beings in a tongue unknown to the vulgar; who communicated, in unintelligible characters, with the learned and the wise of distant nations; and who, in the seclusion of the laboratory, indulged in pursuits condemned by the canons of their faith, but occasionally productive of results whose character, remarkable for that epoch, not infrequently acquired for the monkish chemist the unenviable and perilous title of conjuror. The literary and scientific attainments acquired in the cloister bore, however, no comparison to the erudition of those countries where Saracen energy and munificence had long promoted the exercise and expansion of the highest faculties of the human intellect. The knowledge possessed by the clergy was only extensive by contrast with the impenetrable ignorance by which they were surrounded, and which it was their interest to diligently propagate and maintain.