Within a couple of generations, in 858, a new situation came to pass. The Eastern Emperor Michael III removed [[Ignatius of Constantinople|Ignatius I]] as patriarch of Constantinople. The emperor replaced him with a layman, St. [[Photius the Great]], who was the first Imperial Secretary and Imperial Ambassador to Baghdad. However, Ignatius refused to abdicate. Michael and Photius invited Pope [[Nicholas I of Rome]] to send legates to preside over a synod in Constantinople to settle the matter. With the council, the legates confirmed the patriarchate of Photius, much to Nicholas's chagrin, who then declared that they had "exceeded their authority."
In opposition to this removal of Ignatius, the bishop of Rome supported Ignatius as legitimate patriarch. Moreover, contrary to existing canons, Photius had been ordained to the office of bishop very quickly. Some scholarship suggests that violation of these canons was the main reason the bishop of Rome rejected the appointment of Photius, though other major actions by Nicholas to bolster his
power and position as pope puts his intervention in Eastern ecclesiastical matters more firmly in the context of his general programme of the growth of papal monarchy.
Therefore, after the arrival of an embassy from Ignatius, in 862, Nicholas said that Photius was deposed, as well as the bishop who ordained him and all the clergy Photius had appointed. The sheer temerity of this action did not even generate a response from Constantinople. However, several years later in 867, Photius finally rejected the Pope's assertion, particularly because of the activities of Latin missionaries in Bulgaria, who were, as St. Photius says, turning the Orthodox Christians there away from their pure Orthodox faith and leading them into [[heresy]]—most notably, the ''filioque''. Photius' response cited the ''filioque'' as proof that Rome had a habit of overstepping its proper limits.
Thus, over nearly six centuries, dispute over the ''filioque'' had not divided the Church definitively; for the most part, in spite of cultural and linguistic conflicts, the Eastern and Western Churches remained in [[full communion]].
In 1054, however, the argument contributed to the [[Great Schism]] of the East and West, and the West went so far as to accuse the East of heresy for not including the ''filioque'' in the Creed. There were many other issues involved, in large part based on misunderstandings between Greek and Latin traditions, as well as the irascible temperament of the antagonists. These were Cardinal [[Humbert]] from Rome and Patriarch [[Michael I Cerularius of Constantinople|Michael Cerularius]] of Constantinople. In addition to the actual difference in wording and doctrine in the ''filioque'', a related issue was the right of the Pope to make a change in the [[Nicene-Constantinopolitan Creed]] on his own, apart from an [[Ecumenical Council]].
===Attempted reunions and the ''Filioque'' after the Schism===
In the thirteenth century, Thomas Aquinas was one of the dominant Scholastic theologians. He dealt explicitly with the processions of the divine Persons in his ''Summa Theologica''. While the theology of Aquinas and other Scholastics was dominant in the Western Middle Ages, for all its apparent clarity and brilliance, it remains theology, not official [[Roman Catholic Church]] teaching.
In 1274, the Second [[Council of Lyons]] said that the [[Holy Spirit]] proceeds from the [[God the Father|Father]] and the [[Christ|Son]], in accord with the ''filioque'' in the contemporary Latin version of the [[Nicene Creed]]. Reconciliation with the East, through this council, did not last. Remembering the Crusaders' sack of Constantinople in 1204, Orthodox Christians did not want to be reconciled with the West in terms of capitulation to Latin [[Triadology]] and [[ecclesiology]]. In 1283, Patriarch [[John Beccus]], who supported reconciliation with the Latin Church, was forced to abdicate; reunion failed.
The Crusaders in question were the Venetians of the [[Fourth Crusade]], who had earlier been excommunicated for attacking other Christians. In 1204, they were getting even for a slaughter of Venetian merchants, in rioting, that took place in 1182. Pope Innocent III had sent them a letter, asking them not to attack Constantinople; after hearing of the sack of the city, he lamented their action and disowned them. Nevertheless, the people of Constantinople had a deep hatred for the people they called the "Latins" or the "Franks," and of course the Western church's major "endowment" from the spoils carried away now still largely rests in the hands of the Vatican.
===Recent discussions and statements===
Dialogue on this and other subjects is continuing. The ''filioque'' clause was the main subject discussed at the 62nd meeting of the [[North American Orthodox-Catholic Theological Consultation]], which met at [[Holy Cross Greek Orthodox School of Theology (Brookline, Massachusetts)]] from [[June 3]] through [[June 5]], 2002, for their spring session. As a result of these modern discussions, it has been suggested that the Orthodox could accept an "economic" ''filioque'' that states that the Holy Spirit, who originates in the Father alone, was sent to the Church "through the Son" (as the [[Paraclete]]), but this is not official Orthodox doctrine. It is what the Fathers call a ''[[theologoumenon]]'', a theological opinion. (Similarly, the late Edward Kilmartin, S.J., proposed as a ''theologoumenon'' a "mission" of the Holy Spirit to the Church.)
Recently, an important, agreed statement has been made by the North American Orthodox-Catholic Theological Consultation, on [[October 25]], 2003. This document ''The Filioque: A Church-Dividing Issue?'', provides an extensive review of [[Scripture]], history, and [[theology]]. Especially critical are the recommendations of this consultation, for example:
*Rome resisted the inclusion of the ''filioque'' for centuries. Leo III, the Pope of Rome at the time the ''filioque'' began its history in Western theology, strongly advised against its inclusion, even though he agreed with the soundness and validity of the doctrine contained in ''filioque''. Later, however, Rome contradicted its previous more Orthodox stance by the promulgation of the ''filioque'', thus anathematizing its own spiritual forebears.