“This heresy [filioque], which has united to itself many innovations, as has been said, appeared about the middle of the seventh century, at first and secretly, and then under various disguises, over the Western Provinces of Europe, until by degrees, creeping along for four or five centuries, it obtained precedence over the ancient orthodoxy of those parts, through the heedlessness of Pastors and the countenance of Princes. Little by little it overspread not only the hitherto orthodox Churches of Spain, but also the German, and French, and Italian Churches, whose orthodoxy at one time was sounded throughout the world, with whom our divine Fathers such as the great Athanasius and heavenly Basil conferred, and whose sympathy and fellowship with us until the seventh Ecumenical Council, preserved unharmed the doctrine of the Catholic and Apostolic Church. But in process of time, by envy of the devil, the novelties respecting the sound and orthodox doctrine of the Holy Ghost, the blasphemy of whom shall not be forgiven unto men either in this world or the next, according to the saying of our Lord (Matt. xii. 32), and others that succeeded respecting the divine Mysteries, particularly that of the world-saving Baptism, and the Holy Communion, and the Priesthood, like prodigious births, overspread even Old Rome; and thus sprung, by assumption of special distinctions in the Church as a badge and title, the Papacy. Some of the Bishops of that City, styled Popes, for example Leo III and John VIII, did indeed, as has been said, denounce the innovation, and published the denunciation to the world, the former by those silver plates, the latter by his letter to the holy Photius at the eighth Ecumenical Council, and another to Sphendopulcrus, by the hands of Methodius, Bishop of Moravia. The greater part, however, of their successors, the Popes of Rome, enticed by the antisynodical privileges offered them for the oppression of the Churches of God, and finding in them much worldly advantage, and “much gain,” and conceiving a Monarchy in the Catholic Church and a monopoly of the gifts of the Holy Ghost, changed the ancient worship at will, separating themselves by novelties from the old received Christian Polity. Nor did they cease their endeavors, by lawless projects (as veritable history assures us), to entice the other four Patriarchates into their apostasy from Orthodoxy, and so subject the Catholic Church to the whims and ordinances of men.”
Encyclical of the Eastern Patriarchs, 1848, sec. 6.
Signed, Patriarchs of Constantinople, Alexandria, Antioch and Jerusalem.