I have discussed the Second Council of Nicea (787) and the dogmatising of the veneration of images a couple of times on this blog, including:
What is rather interesting is that the Second Council of Nicea is another stumbling block for the Catholic apologist vis-à-vis Vatican I’s dogmatic teachings about the Bishop of Rome. Commenting on this council, the Abbé Guettée wrote:
The legates of the Pope and those of the Patriarchal churches of Alexandria, Antioch, and Jerusalem, having gone to Constantinople, Nicea was appointed as the place of assembling the council. The first session took place September twenty-fourth, 787. This second Council of Nicea is reckoned the seventh oecumenical, both by the Eastern and Western churches. Adrian was represented by the Archpriest Peter, and by another Peter, Abbot of the monastery of St. Sabas at Rome. The Bishops of Sicily were the first to speak, and said, “We deem it advisable that the most holy Archbishop of Constantinople should open the council.” All the members agreed to this proposition, and Tarasius made them an allocution upon the duty of following the ancient traditions of the Church in the decisions they were about to make. Then those who opposed these traditions were introduced, that the council might hear a statement of their doctrine. Then were read the letters brought by the legates of the Bishops of Rome, Alexandria, Antioch, and Jerusalem, for the purpose of ascertaining what the faith of the East and the West might be. The Bishop of Ancyra had shared the error of the iconoclasts. He now appeared before the council to make his confession of faith, and commenced with the following words, well worthy of being quoted: “It is the law of the Church, that those who are converted from a heresy, should abjure it in writing, and confess the Catholic faith. Therefore do I, Basil, Bishop of Ancyra, wishing to unite myself with the Church, with Pope Adrian, with the Patriarch Tarasius, with the Apostolic sees of Alexandria, Antioch, and Jerusalem, and with all Catholic bishops and priests, make this confession in writing, and present it to you, who have power by apostolic authority.”
This most orthodox language clearly proves that at the time the Pope of Rome was not regarded as the sole centre of unity, the source of Catholic authority; the unity and authority were only recognized in the unanimity of the sacerdotal body.
The letter of Adrian to the Emperor and Empress, and the one he had written to Tarasius were then read, but only in so far as they treated of dogmatic questions. His complaints against the title of oecumenical and his demands concerning the patrimony of St. Peter, were passed over in silence. Nor did the legates of Rome insist. The council declared that it approved of the Pope’s doctrine. Next were the letters from the Patriarchal sees of the East whose doctrine agreed with that of the West. That doctrine was compared with the teaching of the Fathers of the Church, in order to verify not only the present unanimity, but the perpetuity of the doctrine; and the question was also examined, whether the iconoclasts had on their side any true Catholic tradition. After this double preparatory examination, the council made its profession of faith, deciding that according to the perpetual doctrine of the Church, images should be venerated, reserving for God alone the Latria or adoration, properly so called.
The members of the council then adjourned to Constantinople, where the last session took place in the presence of Irene and Constantine and the entire people. The Acts of the seventh oecumenical council, like those of the preceding ones, clearly prove that the Bishop of Rome was only first in honour in the Church; that his testimony had no doctrinal weight, except in so far as it might be regarded as that of the Western Church; that there was at yet no individual authority in the Church, but a collective authority only, of which the sacerdotal body was the echo and interpreter.
This doctrine is diametrically opposed to the Romish system. Let us add, that the seventh oecumenical council, like the six that preceded it, was neither convoked, presided over, nor confirmed by the Pope. He concurred in it by his legates, and the West concurred in the same way, whereby it acquired its oecumenical character. (Abbé Guettée, The Papacy: Its Historic Origin and Primitive Relations With the Eastern Churches [New York: Carleton, 1867], 262-64, italics in original, emphasis in bold added)