Well, don’t take a Catholic’s word for it, Marco. I have just finished reading “The Petrine Ministry: Catholics and Orthodox in dialogue“, the outcome of a 2003 symposium between Catholics and Orthodox held under the auspices of the Pontifical Council for Promoting Christian Unity.
The final paper was given by an orthodox theologian Ioannis Zizioulas, who is Metropolitan of Pergamon, and Orthodox president of the Joint International Commission for Dialogue between the Roman Catholic Church and the Orthodox Church as a Whole.
He cites the orthodox theologian Alexander Schmemann as saying:
A local church cut from the universal koinonia is indeed a contradictio in adjecto, for this koinonia is the very essence of the church. And it has, therefore, its form and expression: primacy. Primacy is the necessary expression of the unity and faith and life of all local churches, of their living and efficient koinonia.
He cites yet another orthodox theologian, John Meyendorff:
The very idea of the primacy was very much a part of ecclesiology itself: the provisional Episcopal Synod is needed a president, without who sanction no decision was valid. …I would venture to affirm here that the universal primacy of one bishop…was not simply an historical accident, reflecting pragmatic requirements … The function of the one bishop is to serve that unity on the world scale, just as the function of a regional primate is to be agent of unity on a regional scale.
Zizioulas himself says that the 34th “Canon of the Apostles” “requires that the protos is a sine qua non conditio for the synodical institution, hence an ecclesialogical necessity, and that the Synod is equally a pre-requisite for the exercise of primacy”. He adds that “synods without primates never existed in the Orthodox Church” and “primacy in the church has never been exercised by rotation”. He concludes:
The fact that all synods have a primate as an ecclesialogical necessity means that Ecumenical synods should also have a primus. This automatically implies universal primacy. The logic of synodality leads to primacy, and the logic of the ecumenical Council to universal primacy.