Charles was equally interested in two other religious controversies of his time, and he made his personal point of view predominant in spite of the weight of church authority on the other side. At the Council of Frankfort the bishops had received from Pope Hadrian the acts passed at the Second General Council of Nicæa dealing with the subject of image worship, a matter that had been debated with much violence in the East and in Italy for several generations. At Frankfort it was supposed, owing to an inability to understand the precise meaning of certain Greek words, that the Nicene Council had formally ordered the adoration of images, and its decrees were therefore rejected. The Emperor undertook the defense of the Western point of view, and in doing so did not hesitate to differ with Rome itself. He also took up an independent position on a more vital point. It seems that during Leo III’s pontificate certain French monks residing in the East were charged with heresy because they inserted in the so-called Nicene Creed, in the article dealing with the procession of the Holy Spirit, i.e., where it is stated that the Holy Spirit proceeds from the Father, the crucial word “filioque” (and from the Son). The matter was taken up by Charles, and after this recondite theological point had been studied, the action of the monks was officially sanctioned by the Council of Aix-la-Chapelle, in 809, although the Pope refused to approve of any addition to the historic formula of Christian belief. In considering the Frankish ruler’s attitude towards the Papacy, it is well to remember that the later administrative system of the Curia, which made so clear-cut the antagonism between the secular prince and the ecclesiastical hierarchy in the medieval times after the age of Hildebrand, had not yet been developed. Charles reverenced the Papacy; indeed, the Pope’s counsel and the Pope’s words often played a decisive part in influencing his motives. He was a convinced believer in the Pope’s right to teach the faithful, and he saw in him the guardian of apostolic tradition. It was to this tradition that he appealed when he condemned the Adoptionists at the Council of Frankfort. The specific rights of the Papacy, from this point of view, lay in its teaching function and in its liturgical usages, which were to be taken by the Christians of Charles’ dominions as the correct norm of their practice. There was also a full recognition of the prerogatives of the Papacy in phases of administration and discipline, wherever ancient precedents could be cited. So we find Charles appealing, in the renewed disputes between the sees of Arles and Vienne, to the ancient directions of the Roman bishops governing this question.