In my humble opinion, I feel that this best answers Wandile's question, at least, in a basic straightforward way. No personal opinions from my part about what I think constitutes an Ecumenical Council. In case you did not see it the first time, here it is again:
I'm curious to known what makes a council ecumenical in Eastern Orthodoxy and Oriental Orthodoxy?
In Eastern Orthodoxy, just like the Mysteries ("Sacraments"), we cannot really say we have 7 "concretely" but many more Mysteries ("Sacraments"). The same goes for the canon of Scripture being "concretely" reduced to 47 (or so OT books) and the 27 NT books. In Orthodoxy, there were other synods which were convened -after the 7th, which could also be considered as "Ecumenical" in nature. Here is some information regarding the "8th Ecumenical Synod" which may answer some -if not all- of your questions.
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Let us return, though, to the Eighth OEcumenical Synod. The Synod convened under the presidency of the “most holy OEcumenical Patriarch Photios”; around three hundred and ninety Bishops and Episcopal representatives took part; Pope John VIII appointed three delegates; and representatives of the three Patriarchates of the East also participated. The proceedings of the Synod commenced in November of 879 and concluded in March of 880. Seven sessions were held in all, and the transactions of this historic Synod in Hagia Sophia, “composed in Greek and preserved,” and published in 1705 by the illustrious Patriarch Dositheos of Jerusalem (1669-1707), as witnessed by a manuscript in the Athonite Monastery of Iveron.
The Holy Synod of 879-880 “was one of the most important Synods in the history of the Church,” and, being comprised of three hundred and ninety “Fathers, both Eastern and Western, representing the five Patriarchates, presented an imposing spectacle such as had not been seen since the time of the Fourth OEcumenical Synod of Chalcedon.”
The Synod of Hagia Sophia under St. Photios the Great bears all of the hallmarks of an OEcumenical Synod, both outwardly and inwardly, and consequently “it is not at all surprising that it was regarded as the Eighth OEcumenical Synod by [Patriarch Euythmios I (907-917)], Theodore Balsamon, Neilos of Thessalonica, Neilos of Rhodes, Symeon of Thessalonica, Mark of Ephesus, Gennadios Scholarios, Dositheos of Jerusalem, Constantine Oikonomos, and” many “others,” such as the important “Dialogue of a Certain Hieromnemon,” and by our contemporaries, St. Nectarios of Pentapolis, Archbishop Chrysostomos Papadoupoulos, Francis Dvornik, Archimandrite Basileios Stephanides, Father John Romanides, Protopresbyter George Metallinos, Metropolitan Hierotheos Blachos, et al. And this Synod also called itself OEcumenical in many places in its Proceedings and Canons, and Archimandrite Basileios Stephanides writes that “since it has not been officially recognized as the Eighth OEcumenical Synod, any OEcumenical Synod that may be convened in the future ought to deal with this issue.”
It is, however, time for us to identify “all of the canonical elements necessary for the convocation, work, and decisions of an OEcumenical Synod,” which elements, indeed, the illustrious and clearly anti-Papist Synod of Constantinople bring together in:
1. “Its convocation as an OEcumenical Synod, at which the five ancient Patriarchal thrones were represented”;
2. “its convocation by Emperor Basil I the Macedonian (867-886),” who “in fact, together with his sons, was the first to sign the dogmatic decree (Ὅρος) of the Synod and its Acts”;
3. “the large number of its members (338-390 Bishops)”;
4. “the functioning of the Synod in conformity with the traditional canonical functioning of the OEcumenical Synods”;
5. “its canonical regulations” (it promulgated three Canons);
6. “its stipulations about matters of Faith,” wherein, on pain of anathema, it designated that the Sacred Symbol of Faith (the Creed) was unalterable and inviolable;
7. “its clear awareness of its authenticity as an OEcumenical Synod,” as this is expressed “in its decision to number the Seventh OEcumenical Synod with the preceding OEcumenical Synods, which only OEcumenical Synods were entitled to do”;
8. and “the decisions made in this Synod, which were consonant with the decrees of the previous OEcumenical Synods, in accordance with the Tradition of the Church.”
The work accomplished by the great Synod of 879-880 was momentous both for that troubled period and for the future of the Church: it functioned in a unitive spirit on the basis of dogmatic Truth and ca-nonical Tradition; it condemned the alteration of the Symbol of Faith through the addition of the Filioque; ratified the Sacred Symbol as it was handed down to us by the first two OEcumenical Synods; and rejected the distortion of the simple Primacy of Honor due to the Bishop of Rome, who had transformed this into an administrative Primacy of Power over the entire Church.
St. Photios the Great also acted in a unitive spirit, refuted the Papal Primacy of Power and the adulteration of the Symbol of Faith with incontrovertible arguments, set forth the Orthodox positions with candor and clarity, and called upon the representatives of Pope John VIII to renounce their errors, which had led to the schism of 867.
St. Nectarios of Pentapolis states emphatically that
[t]he Eighth OEcumenical Synod has great importance [because] in this Synod Photios was triumphant..., his struggles for the independence of the Eastern Church were crowned with total success, and the Truth of Orthodoxy, for which he had toiled so hard, prevailed.... In a word, the triumph was complete: it was a political, an ecclesiastical, and a personal triumph.
hope that was helpful!
