Development towards the Pentarchy
In the Apostolic Age (largely the 1st century) the Christian Church comprised an indefinite number of local churches that in the initial years looked to the first church at Jerusalem as its main centre and point of reference. But by the 4th century it had developed a system whereby the bishop of the capital of each civil province (the metropolitan bishop) normally held certain rights over the bishops of the other cities of the province (later called suffragan bishops).
Of the three sees that the First Council of Nicaea was to recognize as having such extraprovincial power, Rome is the one of which most evidence is discerned. The church in Rome intervened in other communities to help resolve conflicts. Pope Clement I did so in Corinth in the end of the 1st century. In the beginning of the 2nd century, Ignatius, Bishop of Antioch, speaks of the Church of Rome as "presiding in the region of the Romans" (ἥτις προκάθηται ἐν τόπῳ χωρίου Ῥωμαίων). In the end of that century, Pope Victor I threatened to excommunicate the Eastern bishops who continued to celebrate Easter on 14 Nisan, not on the following Sunday.
The first records of the exercise of authority by Antioch outside its own province of Syria date from the late 2nd century, when Serapion of Antioch intervened in Rhosus, a town in Cilicia, and also consecrated the third Bishop of Edessa, outside the Roman Empire. Bishops participating in councils held at Antioch in the middle of the 3rd century came not only from Syria, but also from Palestine, Arabia, and eastern Asia Minor. Dionysius of Alexandria spoke of these bishops as forming the "episcopate of the Orient", mentioning Demetrian, bishop of Antioch, in the first place.
In Egypt and the nearby African territories the bishop of Alexandria was at first the only metropolitan. When other metropolitan sees were established there, the bishop of Alexandria became known as the arch-metropolitan. In the mid-3rd century, Heraclas of Alexandria exercised his power as arch-metropolitan by deposing and replacing the Bishop of Thmuis.
Council of Nicaea
The First Council of Nicaea in 325, in whose sixth canon the title "metropolitan" appears for the first time, sanctioned the existing grouping of sees by provinces of the Roman empire, but also recognized that three sees, Alexandria, Antioch and Rome, already had authority over wider areas. In speaking of Antioch, it also spoke generically about "other provinces".
While the Council did not specify the extent of the authority of Rome or Antioch, it clearly indicated the area, even outside its own province of Egypt, over which Alexandria had authority, by referring to "the ancient customs of Egypt, Libya and Pentapolis, according to which the bishop of Alexandria has authority over all these places".
Immediately after mentioning the special traditions of wider authority of Rome, Alexandria and Antioch, the same canon speaks of the organization under metropolitans, which was also the subject of two previous canons. In this system, the bishop of the capital of each Roman province (the metropolitan) possessed certain rights with regard to the bishops of other cities of the province (suffragans).
In the interpretation of John H. Erickson, the Council saw the special powers of Rome and Alexandria, whose bishops were in effect metropolitans over several provinces, as exceptions to the general rule of organization by provinces, each with its own metropolitan. After the mention of the special traditions of Rome, Alexandria, Antioch and other provinces, canon 6 goes on immediately to speak of the metropolitan form of organization, which was also the topic of the two preceding canons.
This Council's recognition of the special powers of Rome, Alexandria and Antioch served as the basis of the theory of the three Petrine sees (Rome and Antioch were said to be founded by Saint Peter and Alexandria by his disciple Mark the Evangelist) that was later upheld, especially in Rome and Alexandria, in opposition to the theory of the five Pentarchy sees.
In its seventh canon, the Council attributed special honour, but not metropolitan authority, to the Bishop of Jerusalem, which was then called Aelia, and was in the province (Syria Palaestina) whose capital was Caesarea.
The First Council of Constantinople (381) decreed in a canon of disputed validity: "The Bishop of Constantinople, however, shall have the prerogative of honour after the Bishop of Rome; because Constantinople is New Rome." This "prerogative of honour" did not entail jurisdiction outside his own "diocese". The Emperor Theodosius I, who called the Council, divided the eastern Roman Empire into five "dioceses": Egypt (under Alexandria), the East (under Antioch), Asia (under Ephesus), Pontus (under Caesarea Cappadociae), and Thrace (originally under Heraclea, later under Constantinople).
The Council also decreed: "The bishops are not to go beyond their dioceses to churches lying outside of their bounds, nor bring confusion on the churches; but let the Bishop of Alexandria, according to the canons, alone administer the affairs of Egypt; and let the bishops of the East manage the East alone, the privileges of the Church in Antioch, which are mentioned in the canons of Nice, being preserved; and let the bishops of the Asian Diocese administer the Asian affairs only; and the Pontic bishops only Pontic matters; and the Thracian bishops only Thracian affairs." Jerusalem was not put at the head of any of the five dioceses.
The transfer of the capital of the empire from Rome to Constantinople in 330 enabled the latter to free itself from its ecclesiastical dependency on Heraclea and in little more than half a century to obtain this recognition of next-after-Rome ranking from the first Council held within its walls. Alexandria's objections to Constantinople's promotion, which led to a constant struggle between the two sees in the first half of the 5th century, were supported, at least until the Fourth Council of Constantinople of 869–870, by Rome, which proposed the theory that the most important sees were the three Petrine ones, with Rome in first place.
The Western bishops took no part in the First Council of Constantinople, and it was only in the mid-6th century that the Latin Church recognized it as ecumenical.
The Council of Ephesus (431) defended the independence of the Church in Cyprus against the supra-metropolitan interference by Antioch, but in the same period Jerusalem succeeded in gaining supra-metropolitan power over the three provinces of Palestine.
After the Council of Chalcedon (451), the position of the Pentarchy's Patriarchate of Alexandria was weakened by a division in which the great majority of its Christian population followed the form of Christianity that its opponents called Monophysitism.
The Council of Chalcedon (451), which marked a serious defeat of Alexandria, gave recognition, in its 28th canon, to Constantinople's extension of its power over Pontus and Asia in addition to Thrace. The Council justified this decision on the grounds that "the Fathers rightly granted privileges to the throne of old Rome, because it was the royal city", and that the First Council of Constantinople, "actuated by the same consideration, gave equal privileges to the most holy throne of New Rome, justly judging that the city which is honoured with the Sovereignty and the Senate, and enjoys equal privileges with the old imperial Rome, should in ecclesiastical matters also be magnified as she is, and rank next after her".
Pope Leo I, whose delegates were absent when this resolution was passed and who protested against it, recognized the council as ecumenical and confirmed its doctrinal decrees, but rejected canon 28 on the ground that it contravened the sixth canon of Nicaea and infringed the rights of Alexandria and Antioch. However, by that time Constantinople, the permanent residence of the emperor, had in reality enormous influence, and had it not been for the opposition of Rome, its bishop could easily have been given first place among all the bishops.
Canon 9 of the Council declared: "If a bishop or clergyman should have a difference with the metropolitan of the province, let him have recourse to the Exarch of the Diocese, or to the throne of the Imperial City of Constantinople, and there let it be tried." This has been interpreted as conferring on the see of Constantinople a greater privilege than what any council ever gave Rome (Johnson) or as of much lesser significance than that (Hefele).
Thus in little more than a hundred years the structural arrangement by provinces envisaged by the First Council of Nicaea was, according to John H. Erickson, transformed into a system of five large divisions headed by the bishops of Rome, Constantinople, Alexandria, Antioch, and Jerusalem. He does not use for these divisions the term patriarchate because the term patriarch as a uniform term for the heads of the divisions came into use only in the time of Emperor Justinian I in the following century, and because there is little suggestion that the divisions were regarded as quasi-sovereign entities, as patriarchates are in Eastern Orthodox ecclesiology. Because of the decision of the Council of Ephesus, Cyprus maintained its independence from the Antioch division, and the arrangement did not apply outside the empire, where separate "catholicates" developed in Mesopotamia and Armenia.
Map of the Pentarchy around the year 1000. White interior: conquered by the Islamic Caliphates. White lined: temporarily occupied by the Islamic Caliphates or Emirates. Arrows: expansion