The 4th-Century Councils

What Is This?

The standard story is simple: the Council of Nicaea settled the question in 325, the Council of Constantinople confirmed it in 381, and the church moved on. But that story skips 56 years of bitter theological warfare — years during which anti-Nicene positions dominated the church, more councils rejected Nicaea than affirmed it, and the pro-Nicene champion Athanasius was exiled five times by successive emperors.

The largest council of the entire period — Ariminum, with roughly 400 bishops — was coerced into repudiating Nicaea. The aged Hosius of Cordoba, who had presided over Nicaea itself, was broken by imperial pressure and forced to sign a creed that banned Nicaea's key term. For most of the 56-year interval, to hold the Nicene position was to be in the minority, facing exile, deposition, and state coercion.

This is not obscure history. It is central to understanding whether "three persons in one God" was the original Christian belief or a later development that won out through political power. Every tradition in the Christological debate must account for these decades, and each does so very differently.

The Four Theological Parties

The 4th-century debate was not a simple two-sided affair. Four distinct theological parties competed for influence, and the boundaries between them shifted constantly as alliances formed and broke apart under political and theological pressure.

Understanding Arius

The name "Arian" is so familiar that most people assume there was a unified movement founded by and following Arius of Alexandria. The reality is quite different.

Arius's core argument was simple and exegetically grounded. He held that unbegottenness (agennēsia) is a fundamental and essential attribute of God. God, by definition, is uncreated, unoriginate, and without cause. The Son, by contrast, is explicitly described in Scripture as "begotten" — the "only-begotten Son" (monogenēs). If the biblical text itself is the authority, then a begotten being cannot be the unbegotten God. The conclusion followed directly: "there was when the Son was not." This was not philosophical speculation imported from Greek thought — it was an attempt to take the biblical language of "begetting" seriously without muddying the waters with philosophical categories that the text itself does not use.

Arius wrote to his bishop Alexander: "Before he was begotten or created or determined or established, he did not exist. For he is not eternal or co-eternal or unbegotten with the Father." The Son, for Arius, was the first and greatest of all created beings, immensely exalted above all others, the one through whom God made the world — but a creature nonetheless, because he was begotten and therefore had a beginning.

The one-letter difference between homoousios and homoiousios has often been ridiculed as a trivial distinction. It was not. The difference between "same substance" and "similar substance" was the difference between saying the Son is what the Father is and saying the Son is like what the Father is — between identity and resemblance. Everything turned on that single Greek letter, the iota.

The Timeline

What follows is a detailed chronological account of the councils, synods, and political events that shaped the outcome. It is long because it needs to be. The standard narrative — Nicaea decided, Constantinople confirmed — survives only because most people never look at what happened in between.

Phase 1: The Reaction (325–341)

The Council of Nicaea in 325 was convened by Emperor Constantine, who wanted theological unity in his newly unified empire. Roughly 300 bishops attended, overwhelmingly from the East. The council produced a creed containing the word homoousios — "of the same substance" — to describe the relationship of the Son to the Father. The term was controversial from the start. It had no biblical pedigree. It had been used by Paul of Samosata, a condemned heretic. Many Eastern bishops signed it under imperial pressure rather than genuine conviction. The "consensus" of Nicaea was thinner than it appeared.

Within a decade, the reaction began. The Council of Tyre in 335 was the first major anti-Nicene council. It deposed Athanasius from his see in Alexandria on charges of misconduct — charges widely understood to be politically motivated. Athanasius was sent into his first exile. The same year, the Synod of Jerusalem (335) readmitted Arius himself to communion, effectively reversing Nicaea's condemnation of the man whose theology had provoked the council in the first place.

The Council of Rome in 340 saw the Western church rally behind Athanasius. Pope Julius I examined the charges against Athanasius and declared them unfounded. This set the pattern for the next two decades: the West generally supported Nicaea, while the East — where the vast majority of bishops resided — increasingly moved against it.

The Council of Antioch in 341, also called the Dedication Council, was a landmark. Ninety-seven Eastern bishops gathered and produced not one but four creeds — all of them deliberately avoiding the word homoousios. The council explicitly asserted "three in hypostasis, one in agreement" — three distinct realities united by will and harmony rather than by shared substance. This was a direct and self-conscious repudiation of the Nicene formula. The bishops at Antioch were not fringe radicals. They were the mainstream Eastern episcopate, and they rejected Nicaea's central theological term just sixteen years after it had been adopted.

Phase 2: The Split (343–355)

The Council of Sardica in 343 was meant to heal the growing rift between East and West. It failed catastrophically. The Eastern and Western delegations could not even agree to sit in the same room. The Easterners refused to participate if Athanasius and Marcellus of Ancyra were seated. The Westerners refused to exclude them. The two groups met separately, each excommunicating the other's leaders. The church was, for practical purposes, split.

The First Council of Sirmium in 351 produced an anti-Nicene creed. Sirmium, in modern Serbia, was one of the imperial capitals, and its councils were shaped directly by imperial policy. Constantius II, who had become sole emperor after defeating his brothers, was committed to a theological settlement that would bypass the controversial homoousios. Sirmium was his vehicle.

The Council of Arles in 353 marked the turning point in the West. Under direct pressure from Constantius II, Western bishops who had previously supported Athanasius and the Nicene faith were compelled to condemn Athanasius. The emperor made it clear that refusing would mean exile. Most submitted.

The Council of Milan in 355 extended the capitulation. More Western bishops were forced to condemn Athanasius. Those who refused — including Dionysius of Milan, Eusebius of Vercelli, Lucifer of Cagliari, and, most significantly, Pope Liberius himself — were deposed and exiled. By the end of 355, virtually every major pro-Nicene bishop in both East and West had been exiled or forced to submit. The Nicene position had no institutional support anywhere in the church. It survived in the person of Athanasius, hiding in the Egyptian desert, and a handful of other exiles.

Phase 3: The Arian Triumph (357–360)

The Third Council of Sirmium in 357 produced what came to be called "the Blasphemy of Sirmium" — a name given by its opponents, but one that stuck. This creed went further than any previous anti-Nicene statement. It banned both homoousios ("same substance") and homoiousios ("similar substance") as unscriptural. It declared that the Father is "greater" than the Son "in honour, renown, and deity." It stripped away every remaining shred of the Nicene settlement.

The creed was signed by Hosius of Cordoba. Hosius was nearly a hundred years old. He had been Constantine's theological advisor. He had presided over the Council of Nicaea itself. He was the living embodiment of the Nicene settlement — and he was broken. After months of imperial pressure and physical confinement, the man who had led Nicaea signed a creed that repudiated its central term. This was not an anonymous bureaucrat capitulating. It was the architect of Nicaea himself.

The Council of Ancyra in 358 represented a homoiousian reaction against Sirmium's extremism. Basil of Ancyra and his allies pushed back, insisting that the Son was at least "of similar substance" to the Father. This alarmed the homoeans and anomoeans but also demonstrated that the theological middle was not willing to follow Sirmium's radical conclusions.

The Fourth Council of Sirmium in 358 attempted another compromise, producing the so-called "Dated Creed" (it was dated to the current consuls, an unusual feature). The Dated Creed adopted a homoean position: the Son is "like" the Father, but all ousia-language is set aside. This was designed to satisfy everyone by saying as little as possible. Constantius intended it as the basis for a universal settlement.

To achieve that universal settlement, Constantius convened twin councils in 359: one in the West at Ariminum (modern Rimini, Italy) and one in the East at Seleucia (in modern Turkey). The councils were meant to ratify the homoean creed simultaneously, presenting a united front.

What happened at Ariminum is one of the most revealing episodes in the entire history of Christian doctrine. Roughly 400 Western bishops gathered — making it larger than Nicaea. Initially, they voted unanimously to reaffirm the Nicene Creed and reject the homoean formula. The bishops were then held at Ariminum for months, forbidden to leave. Imperial commissioners applied relentless pressure. Delegations were sent to the emperor and kept waiting. One by one, the bishops were worn down. Eventually, the exhausted council signed a homoean creed that omitted homoousios. A council larger than Nicaea, which had initially voted unanimously for Nicaea, was coerced into repudiating it.

"The whole world groaned and was astonished to find itself Arian."

— Jerome, Dialogue Against the Luciferians, 19

At Seleucia, the Eastern council was similarly contentious but more fragmented. The homoiousians, homoeans, and anomoeans fought among themselves. No clear consensus emerged, but the homoean party, backed by imperial authority, claimed victory.

The Council of Constantinople in 360 ratified the homoean creed as the official faith of the church. It banned the word ousia entirely from theological discussion. Nicaea was, to all appearances, dead. The homoean settlement was the established orthodoxy of the Roman Empire, enforced by imperial power and affirmed by the largest councils the church had ever assembled.

Phase 4: Recovery and Imperial Settlement (361–381)

Everything changed with the death of Constantius II in 361. His successor, Julian (later called "the Apostate"), was a pagan who had no interest in Christian theological disputes. Julian recalled all exiled bishops, both pro-Nicene and anti-Nicene, with the apparent hope that restoring them all simultaneously would generate enough internal conflict to weaken the church. The policy of recall was cynical, but its effects were consequential: Athanasius returned to Alexandria, and the pro-Nicene movement had breathing room for the first time in years.

The Synod of Alexandria in 362 was a pivotal moment. Athanasius, now returned from his third exile, convened a small but strategically critical gathering. For the first time, he extended an olive branch to the homoiousians. He recognised that many who used the language of "similar substance" were not Arians. They affirmed the Son's genuine divinity; they merely distrusted the word homoousios, which they feared implied that Father and Son were identical rather than merely co-equal. Athanasius agreed that homoousios did not mean identity of person, only identity of nature. This was the beginning of the coalition that would eventually win — a coalition built not on theological uniformity but on recognising that different verbal formulas could express the same underlying conviction.

The progress was far from linear. Under the reign of Valens (364–378), another homoean emperor, persecution of pro-Nicene bishops resumed. Athanasius was exiled again (his fourth and fifth exiles fell in this period, though the fourth was brief). The Cappadocian Fathers — Basil of Caesarea, Gregory of Nazianzus, and Gregory of Nyssa — emerged as the new intellectual leaders of the pro-Nicene cause, refining Trinitarian language with a precision that Athanasius's generation had lacked. It was the Cappadocians who developed the formula that would become standard: one ousia (substance/essence), three hypostaseis (persons/subsistences). This formula resolved a longstanding confusion in which ousia and hypostasis had often been used interchangeably, leading Eastern and Western theologians to talk past each other.

The decisive turning point was military, not theological. In 378, Emperor Valens died at the Battle of Adrianople, one of the worst military disasters in Roman history. His successor in the East was Theodosius I, who became emperor in 379. Theodosius was a baptised Nicene Christian — the first emperor since Constantine to hold the pro-Nicene position with genuine personal conviction.

In February 380, Theodosius issued the Edict of Thessalonica. This edict declared Nicene Christianity — specifically the faith confessed by Pope Damasus of Rome and Peter of Alexandria — to be the official religion of the Roman Empire. All other forms of Christianity were declared heretical. This was an extraordinary act of imperial power. The emperor did not wait for a council. He did not seek the consensus of bishops. He simply declared, by imperial decree, what the correct faith was. The Nicene position, which had been a beleaguered minority for most of the preceding decades, became the state religion by executive fiat.

The First Council of Constantinople in 381 followed the edict. It was convened by Theodosius to confirm what his edict had already established. One hundred and fifty Eastern bishops attended — no Western bishops were present. The council reaffirmed the Nicene Creed with some expansions (notably on the Holy Spirit) and declared the Nicene faith to be the faith of the church. It was smaller than Ariminum. It was smaller than several of the anti-Nicene councils that had preceded it. Its authority was established not by the breadth of its representation or the universality of its consensus but by the power of the emperor who convened it and enforced its decisions.

Why This Matters for the Debate

Every tradition must account for these 56 years. The historical facts are not in dispute. What is fiercely disputed is what they mean.

Trinitarian view: The resistance to Nicaea was not uniformly motivated by heresy. Many Eastern bishops, particularly the homoiousians, genuinely affirmed the Son's full divinity while resisting homoousios as non-scriptural and potentially Sabellian (collapsing Father and Son into one person). Their theological concerns were legitimate, and the eventual pro-Nicene victory required the Cappadocians' careful refinement — distinguishing ousia (shared essence, one) from hypostasis (distinct person, three) in ways Nicaea itself had not. The 4th-century turmoil reflects the difficulty of articulating a profound truth with precision, not the imposition of a new one. The theology behind homoousios was sound, even though the term needed theological clarification before it could command broad assent. The council that settled the question at Constantinople (381) represented a synthesis of Nicene and homoiousian positions, not a simple vindication of 325. The imperial involvement is regrettable but not decisive. Emperors supported anti-Nicene positions too — Constantius, Valens — and those positions did not endure. The Nicene faith survived exile, persecution, and imperial hostility precisely because it was true. Trinitarians often argue that the Holy Spirit guided the church through decades of confusion to the correct articulation of what Scripture teaches — though it should be noted that this is a theological interpretation of the historical events, not a historical argument in itself. The claim that the settlement endured because it was grounded in revelation rather than imposed by force is a faith commitment that must be weighed against the documented role of Theodosius's edict, which declared Nicaea the state religion before the Council of Constantinople was even convened.

Biblical Unitarian view: The 4th-century history proves that the Trinity was not the original Christian belief. It was a contested theological development that required decades of imperial coercion to establish. If homoousios had been the clear teaching of the New Testament, it would not have needed to be imposed by Constantine, defended by a handful of exiles, abandoned by the vast majority of bishops, and finally re-established by imperial decree before a council was even convened. The anti-Nicene positions commanded majority support for most of the period — among bishops who were far closer in time and culture to the apostolic era than modern interpreters are. The pattern is unmistakable: every time imperial power favoured the anti-Nicene position, the anti-Nicene position dominated; every time imperial power favoured the Nicene position, the Nicene position dominated. The theology followed the emperor. The eventual "victory" at Constantinople was not a theological consensus arriving at last but a political settlement imposed by a sympathetic emperor. If the Trinity had been clearly taught in the New Testament, 56 years of political warfare would not have been necessary to establish it.

Logos Theology view: The pre-Nicene position — the Son is genuinely divine but derivatively so, the Logos emanating from the Father as source — was the natural reading of the available texts and the dominant theology before Nicaea forced a binary choice. The homoiousian position, which affirmed "similar substance," was closer to what Justin Martyr, Origen, and Tertullian had actually taught than what Nicaea declared. These earlier theologians had consistently described the Son as a "second God" or a "second divine being" — genuinely divine, but subordinate to and derived from the Father. Nicaea's homoousios went beyond what the texts warranted, which is precisely why it was resisted so fiercely by theologians who knew the earlier tradition. The Nicene settlement was a narrowing of the theological tradition, not its culmination. It excluded positions that had been perfectly orthodox for centuries and replaced them with a formula that the earliest Christian writers would not have recognised.

Go Deeper

For rigorous engagement with the 4th-century councils and the development of Nicene theology:

• R.P.C. Hanson, The Search for the Christian Doctrine of God (the definitive scholarly treatment)
• Lewis Ayres, Nicaea and Its Legacy
• Rowan Williams, Arius: Heresy and Tradition
• Richard Rubenstein, When Jesus Became God (accessible popular account)
• John Behr, The Nicene Faith (2 vols)
• Dale Tuggy, "Trinity" in Stanford Encyclopedia of Philosophy