Xariskai, it seems to me that there must be some such criteria for determining if a synod is indeed an ecumenical council, or merely a synod. And it seems to me, that these criteria are still themselves rather murkily identified.
"...a doctrine did not become orthodox because a council said it was, but a council was orthodox -and therefore binding- because the doctrine it confessed was orthodox" (Jaroslav Pelikan, The Spirit of Eastern Christendom
(University of Chicago Press), p. 24.
The idea of the necessity of rationalist criteria as "grounding" theology so characteristic of medieval epistemological foundationalism does not derive from early Christianity and is not, of course, characteristic of the Eastern Church.
On the other hand we do know very well what genuine union and Orthodox ecumenicity is NOT:
No council vehemently repudiated by the vast majority of Orthodox Christians in its own time is, in our view, a genuine Orthodox Ecumenical Council.
No "union" which enraged the theological sensibilities of the vast majority of Orthodox Christians in its own time is, in our view, a genuine union.
No council which no living Orthodox Christian regards as an Ecumenical Council is, in our view, an Orthodox Ecumenical Council, nor can such a council be reasonably said to be truly ecumenical or unifying, in our view.
Florence fails all of these criteria. We do not here have a failure the breath of a hair but a massive, colossal, stupendous failure of absolute epic proportions to achieve union. It was thus from the beginning centuries ago:
The Serbs were not represented at Florence. The vast majority of Russians rejected Florence as soon as they learned of it. The vast majority of Byzantines rejected Florence as soon as they learned of it. The very delegates that signed the agreement rejected it and claimed they were forced into signing. The Patriarchates of Jerusalem, Antioch, and Alexandria formally repudiated Florence forthwith. The Orthodox Church convened to formalize its rejection of Florence in 1872. Herein one with eyes to see may discover the criterion of false union and non-ecumenicity Jedi claims to objectively seek.
"The Ferrara agreement proved to be a shell of paper, and all the parade and rejoicing at the conclusion of the proceedings were made ridiculous by the utter rejection of its articles in Constantinople. On their return, the delegates were hooted as Azymites, the name given in contempt to the Latins for using unleavened bread in the Eucharist. Isidore, after making announcement of the union at Of en, was seized and put into a convent, from which he escaped two years later to Rome. The patriarchs of Jerusalem, Antioch, and Alexandria issued a letter from Jerusalem, 1443, denouncing the council of Florence as a synod of robbers and Metrophanes, the Byzantine patriarch as a matricide and heretic" Schaff, History of the Christian Church, Volume VI § 18. The Council of Ferrara-Florence. 1438–1445.
The Council at Florence sought to establish its ecumenicity by noting it's identity to be such in the openings, and then having everyone sign on to that. Of course, as you bring up, there were other issues.
While a particular council may declare itself to be ecumenical, it may later be regarded by the Church as being a Robber Council (e.g. http://en.wikipedia.org/wiki/Second_Council_of_Ephesus
Florence is in our view such a Robber Council, however badly amateur apologists wish to insist it really is an "Orthodox Ecumenical Council" (ignoring the "minor problem" of no Orthodox Christians believing it is an Ecumenical Council).
"Many of those who signed at Florence revoked their signatures when they reached home. The decrees of the Council were never accepted by more than a minute fraction of the Byzantine clergy and people." -Bishop Kallistos, op cit. The RC view here seems to be that overwhelming and vehement rejection by a majority of Orthodox Christians does not mean there is not Actual Total Union with the Orthodox Church despite almost no one believing it then or now.
“‘I can’t believe that!’ said Alice. ‘Can’t you?’ the Queen said in a pitying tone. ‘Try again: draw a long breath, and shut your eyes.’ Alice laughed. ‘There’s no use trying,’ she said: ‘one can’t believe impossible things.’ ‘I daresay you haven’t had much practice, said the Queen. ‘When I was your age, I always did it for half-an-hour a day. Why, sometimes I believed as many as six impossible things before breakfast.'” -Lewis Carroll, Through the Looking Glass
But if we need consensus from the whole Church prior to a council being identified as ecumenical, would't this effectively hinder it's function
It is not in this case that a total consensus was needed -no council ever achieved that- but it is the case that the vast majority of Orthodox Christians worldwide rejecting something, including the delegates that signed the agreement, the leadership and laity of every major trajectory of Orthodox Christianity soon forthwith, and the universal consensus of contemporary Orthodox Christians rejecting something nullifies the presumption of non-Orthodox apologists that true "unity" and "ecumenicity" really was reflected in this council after all; in fact such a presumption would completely empty such words of their meaning.
Oἰκουμένη/oikouménē, lit. means "inhabited"; it was an ancient Greek term for all the known world, the inhabited world, or the habitable world. If effectively the whole inhabited Orthodox world of its time rejected a council it does not by definition reflect the oikoumene/oἰκουμένη and is not in this original sense of the word ecumenical.
St Vincent of Lerins defined true catholic doctrine as marked by universality, antiquity, and consent. Florence fails all three of these criteria as it fails to embody the original meaning of oἰκουμένη. It is rejected by all Orthodox Christians today as it was by the vast majority of Orthodox Christians in its own time as soon as they learned of it. It is not for us an Ecumenical Council. With reasonable warrant we opine that it never was. No argument in this thread remotely suggests good reason for Orthodox Christians to suppose otherwise. My advice to RCs is live with it and move on to defending more important and somewhat more believable things.