The Council of Serdica, or Synod of Serdica (also Sardica), was a synod convened in 343 at Serdica (located in modern-day Sofia, Bulgaria) in the civil diocese of Dacia, by Emperors Constans I, Augustus in the West, and Constantius II, Augustus in the East. It attempted to resolve "the tension between East and West in the Church." "The council was a disaster: the two sides, one from the west and the other from the east, never met as one."

Calling of the Council "Constans decided to take the initiative ... His brother Constantius … agreed to permit, at the suggestion of Constans, that a grand Ecumenical Council should take place, with the intention of resolving the tension between East and West in the Church, at Serdica, modern Sofia, a city carefully chosen as standing between the Eastern and Western halves of the Roman Empire."Hanson RPC, The Search for the Christian Doctrine of God: The Arian Controversy, 318-381. 1988, page 293

Traditionally, it had been claimed that the council was convened by the two augusti at the request of Pope Julius I. However, RPC Hanson wrote:"The devisers of this meeting were certainly not Eastern bishops. Socrates (HE II.20) expressly says that they did not want to come. It was a small group of Western bishops, influential with Constans, who planned the Council: Maximinus of Trier, Protasius of Milan, Ossius of Cordova, Fortunatianus of Aquileia and Vincent of Capua. Julius of Rome was not a prime mover in the affair; he sent a comparatively minor delegation who kept a low profile."Hanson RPC, The Search for the Christian Doctrine of God: The Arian Controversy, 318-381. 1988, page 294Since the "devisers" of the council were a small group of bishops who had Constans' ear, the question arises to what extent they represent the general view of the West. After discussing the evidence, Ayres concludes that it is not accurate to describe it as an East/West or a Latin/Greek divide. He says it is an error to assume "that Greek-speaking areas of the east divided clearly in theology from the Latin-speaking west. … ‘East’ vs. ‘West’ is far too clumsy a tool of analysis for almost anything in the fourth century."Ayres, Lewis, Nicaea and its Legacy, An Approach to Fourth-Century Trinitarian Theology, 2004, page 123

Delegates "In 343 … about 90 bishops from the West and about 80 from the East set off to meet in Serdica. Constans himself, accompanied by Athanasius and several other Eastern bishops who had been deposed during the past twenty years, attended the encounter."Hanson RPC, pages 293-4 "Athanasius, Asclepas and Marcellus were present as Eastern bishops with a grievance."Hanson RPC, page 294 These Eastern bishops were deposed by Eastern courts. Their attendance under the protection of the Western emperor was a direct challenge and insult by Emperor Constans to the authority of the Eastern church.

At this time, "Constantius was on the Eastern frontier occupied with war against the Persians." He did not attend. "He sent the comes Strategius Musonianus and the castrensis Hesychius, to assist the Eastern bishops in their journey and ordered Philagrius (an official experienced in troublesome ecclesiastical matters, now comes in Thrace), to accompany them on their journey from Philippopolis to Serdica."

Consistent with the principle that a small group of Western bishops were the "devisers" of this council, the Western delegates came from a relatively small part of the Western Empire:"At least half of those attending the ‘western’ meeting were from areas to the east of northern Italy and the largest single block of attendees were the Greek and Balkan bishops. The ‘western’ council was as localized as most during this century."Julius I was represented by the priests Archidamus and Philoxenus, and the deacon Leo. Athanasius reported that bishops attended from Roman diocese of Hispania, Gaul, Britain, Italy, Africa, Egypt, Syria, Thrace and Pannonia. Constantius II was represented by Strategius Musonianus and Hesychius of Antioch.

The Council Never Met Later descriptions claim that the event was never a council.

"The council was a disaster: the two sides, one from the west and the other from the east, never met as one."Ayres, Lewis, page 123 "It was in fact a debacle rather than a Council, and it is absurd to reckon it among the General Councils."Hanson RPC, page 295

"The unwilling Eastern bishops ... on reaching Serdica were housed in a wing of the imperial palace and carefully kept from informal contact with the Western bishops."Hanson RPC, 295 They refused to allow Marcellus and Athanasius to participate in the discussions and the Westerners would not allow the meeting to continue without them:"The majority (of the ‘easterners’) refused to meet with the ‘westerners’ who wished Athanasius and Marcellus to be allowed normal participation in the meeting."Ayres, Lewis, page 124 These two bishops "had been tried, condemned and deposed by regularly convened and ordered Eastern councils." Athanasius had been found guilty of "tyrannical behaviour." "The Easterners had no intention of allowing the Westerners to review decisions which they were competent to make. … The Easterners had a perfectly good case, and this fact until recently has not been sufficiently realized. Western bishops had no right to review the verdicts of Eastern councils. … Metropolitan jurisdictions were fairly clearly established in the East but were still in an uncertain and unformed state in the West.""Athanasius was deservedly unpopular in the East. Serious attempts were made to overcome the impasse. Ossius more than ten years later said that he had gone so far as to offer to take back Athanasius with him to Spain if the Easterners would join him in discussion, but the distrustful Eastern bishops refused this suggestion."Hanson RPC, page 296

Both sides took the most imprudent measures towards the others: "The Western bishops examined the cases of Athanasius, of Marcellus, of Asclepas and of Lucius all over again and declared them innocent." They "stigmatized all the Easterners as Arians" and excommunicated Eastern leaders. "The ‘easterners’ ... excommunicated all the ‘western’ leaders at Serdica" and "branded all the Westerners as Sabellians." "Intended as a means of healing a dangerous rift which was developing between the Eastern and Western Church, it succeeded only in widening that rift to an apparently unbridgeable extent."Hanson RPC, page 306

Historical context

Council of Nicaea

This dispute that prevented the entire council from meeting already began at Nicaea, where Alexander formed an alliance with Marcellus and some other Sabellians:"Simonetti estimates the Nicene Council as a temporary alliance for the defeat of Arianism between the tradition of Alexandria led by Alexander and 'Asiatic' circles (i.e. Eustathius, Marcellus) whose thought was at the opposite pole to that of Arius. … Alexander … accepted virtual Sabellianism in order to ensure the defeat of Arianism."Hanson RPC, The Search for the Christian Doctrine of God: The Arian Controversy, 318-381. 1988, page 171 "Marcellus learnt the main lines of his theology from Eustathius."Hanson RPC, page 234 "Eustathius and Marcellus … certainly met at Nicaea. and no doubt were there able to join forces with Alexander of Alexandria and Ossius."Since Constantine had taken Alexander's part,Ayres, Lewis, Nicaea and its Legacy, An Approach to Fourth-Century Trinitarian Theology, 2004, page 89 Alexander's alliance was able to dominate the council, including to insert in the Creed the term homoousios which hitherto was preferred only by the Sabellians."Ossius of Cordoba probably chaired the meeting; Eustathius of Antioch, Marcellus of Ancyra, and Alexander must all have been key players in the discussions." "Marcellus of Ancyra … had been an important figure at the council and may have significantly influenced its wording."Ayres, Lewis, Nicaea and its Legacy, An Approach to Fourth-Century Trinitarian Theology, 2004, page 431"Athanasius was certainly present as a deacon accompanying Alexander of Alexandria. … But it is equally certain that he can have taken no prominent nor active part, in spite of later legends to this effect and the conviction of some scholars that he was the moving spirit in the Council."Hanson RPC, page 157

After Nicaea After Nicaea, Marcellus was deposed for Sabellianism.Williams, Rowan, Arius: Heresy and Tradition (Revised ed.). Grand Rapids, Michigan: Wm. B. Eerdmans Publishing. (2002), page 80 "Marcellus of Ancyra had produced a theology … which could quite properly be called Sabellian."Hanson RPC, page ix

After Alexander died in 328,Hanson RPC, page 175 Athanasius, who was still underage, became bishop of Alexandria. However, more or less at the same time as Marcellus, Athanasius was found guilty of violence and "tyrannical behaviour" and exiled. Both Marcellus and Athanasius were bishops in the eastern part of the Empire, were deposed by the Eastern Church, and were exiled to Rome. What is less well known, is that both Athanasius and Marcellus taught one single hypostasis. "Athanasius and Marcellus could come together in Rome. The perception that these two trajectories held to very similar beliefs would help to shape widespread eastern antipathy to both in the years after Nicaea." "The fragments of Eustathius that survive present a doctrine that is close to Marcellus, and to Alexander and Athanasius. Eustathius insists there is only one hypostasis."Ayres, Lewis, page 69 (Eustatius was another important Sabellian in the fourth century.)For that reason, Athanasius and Marcellus, while in Rome, were able to form an alliance against those who taught that the Father, Son, and Spirit are three hypostases (three Centres of Consciousness or three Minds):"They considered themselves allies."Ayres, Lewis, page 106 "Athanasius and Marcellus now seem to have made common cause against those who insisted on distinct hypostases in God."While in Rome, Athanasius also developed his polemical strategy:"Athanasius’ engagement with Marcellus in Rome seems to have encouraged Athanasius towards the development of" "an increasingly sophisticated account of his enemies;" "the full flowering of a polemical strategy that was to shape accounts of the fourth century for over 1,500 years;" "a masterpiece of the rhetorical art."Ayres, Lewis, page 106-7This included the claim that all of his enemies are Arians (followers of Arius), which they were not, and that Athanasius himself was deposed due to an Arian ‘conspiracy’, which is also not true.

Constantine was emperor of the entire Roman Empire and was able to limit religious disagreements between factions in the church. However, after he died in 337, his sons divided the empire between them. This created the opportunity for theologies to develop in different directions in the eastern and western parts of the empire.