The bishops of Rome Calixtus (217-222 AD) and Stephenus (254-257 AD) were the first representatives of the clerical authorities to claim the primacy of the bishops of Rome over the rest of the Christian churches in the world. In their opinion, the bishops of Rome should be recognized by the entire Christian world as de jure followers of the Apostle Peter, who died in Rome. The claim is based on an ambiguous text from Matthew’s Gospel (16:18), namely Jesus’ discussion with the apostle Peter in Caesarea-Philippi in northern Palestine (today: Banjas, Israel), with the entrustment of the symbolic succession key:
And I tell you: you are Peter (pun kephas-petrus = rock-stone) and on this rock I will build my ecclesia (ecclesia = assembly, not church in the later interpreted sense) (the word church comes from the Latin word basilica = temple, place of worship in Romans).
The ambiguity of the text was one of the reasons why the Orthodox and Reformed churches never recognized the primacy of the pope in Rome.
The great theologians of the 2nd and 3rd centuries A.D. accepted, admittedly, the special role of the apostle Peter in Rome, but they also advocated the idea of equal rights of all bishops in the West and patriarchs in the East.
The Ecumenical Council of Nicaea (325 AD) recognized the equality of the four episcopates and patriarchates of the Christian world: Rome (Italy), Alexandria (Egypt), Jerusalem (Palestine) and Antiochia (Turkey).
In 375 AD the bishop of Rome Damasus I (366-384 AD) again ruled for the primacy of the bishop of Rome, based on the same ambiguous argument in the Gospel of Matthew (16:18), elevating the episcopate of Rome to the rank of apostolic see.
In 383 AD there was the dismemberment of the Roman Empire into 2 parts: the western part (with the capital in Rome) and the eastern part (with the capital in Constantinople). The title of Apostolic See for the bishop of Rome was immediately recognized by the emperor of the western part of the empire (Theodosius, 383-395). The Bishop of Rome (Siricius, 384-399) accordingly issued the Decretalia constituta, by which he established the primacy of the bishops of Rome.
Bishop Leo I (440-461) was the first pope. The emperor of the western part of the empire (Valentinians III, 425-455) officially confirmed by an edict of 445 the so-called Primate of the bishops of Rome, but only for the western countries (Italy, Spain, southern France, North Africa).
In 451, Pope Leo I protested against the decision of the Ecumenical Council of Chalcedon, to which the bishops of Rome and Constantinople were equally entitled in religious matters. After this date, the struggle for power and for the division of spheres of influence and primacy in the Christian world began between the 2 heads of the Western (Rome) and Eastern (Constantinople) churches, a struggle that continues to this day.
Pope Symmachus (498-514) decreed by Ordinance Constitutum silvestri that holders of the Apostolic See of Rome could not be tried and condemned by ordinary people.
Pope Gregory I (590-604) extended the influence of the episcopate of Rome to political affairs, first in Italy and then throughout the world, further deepening the discrepancy and misunderstanding between the Western and Eastern churches.
At the Council of Whitby (England, 664) Rome again repeated its claim to supremacy over Constantinople.
At the Ecumenical Council of Constantinople in 680, the claim of papal primacy was refuted, with a large proportion of the participants declaring themselves for the equality of all bishops and patriarchs.
Pope Stephen II (752-757) founded the world’s first religious state (Patrimony Petri) based in Rome, thereby moving further away from the eastern churches.
A serious disagreement between the 2 competing churches (west and east) occurred in 863, during the lawsuit filed by the Western Catholic Church against the Eastern Orthodox Patriarch Photius.
In the 10th-11th centuries the Christianization of the majority of the Russian population took place. The Russian Church immediately subordinated itself to the Orthodox Patriarchate of Constantinople.
Pope Leo IX (1049-1054) and Patriarch Michael Cerularius of Constantinople (1004-1058) completed the definitive rupture between the two churches in 1054, following irreconcilable disagreements (struggle for supremacy in the Christian world, theological differences, etc.). This split has gone down in history as the Great Schism.
The Eastern Orthodox churches declared themselves autocephalous churches after the Great Schism, with the Patriarch of Constantinople considered by the Eastern churches to be the head of the Orthodox Church.
In 1589, however, the patriarch of the Russian Orthodox Church in Moscow also claimed to take on the leading role of Orthodox churches around the world, which produced new complications.
The Orthodox Church recognizes only the first 7 Christian Ecumenical Councils, rejects primacy and the papal institution, has its own liturgy and icon worship.
This church claims to be the only one that would have preserved unchanged over the centuries the dogmas, tradition, worship and organization of the Christian church, as they were in the first 8 centuries after Jesus.
The name Orthodoxy became definitively established after the Great Schism of 1054.
The Orthodox churches are governed by the synodal hierarchical principle, forming regional, autocephalous and autonomous churches.
The Romanian Orthodox Church declared itself autocephalous in 1864 (in 1925 it became a Patriarchate).