The Council of Nicaea: A Historical Explainer

 The Council of Nicaea: A Historical Explainer

This year is, among other things, the 1700th anniversary of the Council of Nicaea. Ecumenical commemorations have already begun, focusing for the most part on the dual institutions of the Papacy and the Ecumenical Patriarchate of Constantinople--institutions both deeply entwined, though in different and somewhat ironic ways, with the event. 

Later this year, two men will meet in Nicaea: Pope Leo XIV-- an American born in Chicago who spent his ministry in Peru, places that none of the bishops at Nicaea had ever heard of, but the latest sitter on what was already in the fourth century the ancient and venerable seat of the bishop of the Church of Rome, and Patriarch Bartholomew--an ethnic Greek whose see was, at the time of Nicaea, a minor suffragan of Heraclea, who today presides over a tiny, purely vestigial Christian flock in what was, in the 4th century, the population heartland of Christianity, but which now resides within the borders of an ethnic nation-state named after Central Asian nomads and populated by the largely secularized followers of Islam, a Christian offshoot that would emerge centuries later from a portion of the world that nearly all the bishops of Nicaea would have regarded as a minor scrap of territory stuck rather awkwardly between two great Empires. These two men will no doubt issue appropriate statements of fraternity and commemoration for what both traditions they represent regard as the first Ecumenical Council of the undivided Christian Church of the first millennium. 

Accompanying these commemorations will come many, many explanations by the popular press the world around, designed to communicate to ordinary folks from America to Siberia to India and back again just what the Council of Nicaea is, anyway, and why it's important enough to make the Chicagoan Pope go all the way to Turkey. Alas, the popular press being what it is, the vast majority of these explanations will be wrong. This event will also be accompanied, no doubt, by many intelligent and intellectual explanations of just what the Council of Nicaea is, in podcasts, tweets, blueskys and the like: and as is frequently the case, these will be even more wrong. 

Hence, to get out ahead of these takes, I wanted to issue, as a scholar who has published an academic volume among other things on Nicaea and its context and legacy, a brief explainer on the historical event of the Council of Nicaea. This will be a deliberately broad take, deliberately designed to skirt most controversial scholarly questions; but nevertheless unavoidably based on my own opinions and scholarly judgments. 

As such, I am confident it will contain a great deal of information that will come as a surprise to most moderately-informed people, and an even higher percentage of information that both ordinary, good people and wicked take-having intellectuals have never heard of. I hope it will prove both informative and reasonably diverting.

What is the Council of Nicaea?

The Council of Nicaea was a council or gathering of Christian bishops held in the year 325 AD. It is named for the city in which it was held, a city which is now in the nation-state of Turkey, but which then was in the province of Bithynia in the diocese of Pontus in Asia Minor of the Roman Empire. 

Bishops are Christian religious leaders, the highest grade of the threefold clerical structure of Bishops-Priests-Deacons found in ancient Christianity and in modern Catholicism and Orthodoxy. They typically hold spiritual leadership over all the Christian priests, deacons, pastors, and Church properties in a given area, and are usually headquartered in a Cathedral Church found in a city after which their diocese is named. 

From at least the third century onwards, bishops from different cities would meet in central locations to discuss, debate, and come to collective decisions on matters of doctrine or discipline. These gatherings were known as councils or synods.

The Council of Nicaea was without a doubt the largest council of bishops held up to its time. It produced doctrinal statements and canons (disciplinary rules) that over the course of the fourth century came to be accorded very high authority by Christians around the Roman Empire and beyond, at least some of which are still considered authoritative by the vast majority of Christian believers today. 

Nicaea is considered the first "Ecumenical Council" by most ancient Christian bodies, including most notably the Catholic Church, the Eastern Orthodox churches, the Oriental Orthodox churches, and the Church of the East. In the Catholic tradition Ecumenical Councils are considered to be gatherings of at least a significant or representative sampling of all the bishops in the world, directed or at least approved by the bishop of Rome, known in Catholicism as the Pope. Other traditions lack as clear or universally-accepted definitions, but tend to be similar.

Within the Catholic tradition, the doctrinal definitions of Ecumenical Councils are held to be "infallible," or free from error. Within all ancient traditions, these definitions are taken as among the most authoritative statements of Christian faith outside of the Scriptures themselves.

Within modern Christianity, the Council of Nicaea is most known for its association with the so-called "Nicene Creed," a doctrinal text recited by Catholics and Byzantine Orthodox during every Sunday liturgy, and occasionally recited or at least treated as authoritative by many Protestants as well. 

The modern "Nicene Creed" is not, however, the original text of the creed promulgated at Nicaea: the original anathemas have been removed, the language altered, and additional sections added. This modified creed is generally known to scholars as the "Niceno-Constantinopolitan Creed" due to the tradition that it was first promulgated (though not necessarily first composed) at the Council of Constantinople in 381 AD. It is most likely in origins a local variant of the creed promulgated at Nicaea, originating in the Church of Constantinople and spread throughout the Eastern and eventually Western Church due to the influence of the Byzantine Empire. 

Nevertheless, the "Niceno-Constantinopolitan Creed" is accurately a "Nicene" Creed inasmuch as contains and centers the distinctive theological terminology first adopted at Nicaea, and would never have existed in its present form without the Council.

Who attended the Council?

Around 300 bishops (a more precise but possibly inaccurate number is 318) attended the Council of Nicaea, accompanied by larger but unknown numbers of priests and deacons. We also know from contemporary accounts that many Christian laypeople, both inhabitants of Nicaea and visitors, were present in the city during the Council and participated in various events held before or in tandem with the bishops' meetings. There also seems to have been large numbers of non-Christians who gathered to observe and participate in various public aspects of the Council, including professional rhetoricians and philosophers. The Council was also notably attended by the Roman Emperor Constantine. Constantine was accompanied by at least some Roman Imperial officials, including most likely his three eldest sons Crispus, Constantine II, and Constantius.

Those who attended the Council were not all or even most bishops in the world at this time, though they were most likely a significant proportion. Nor were those who attended a representative sampling of all the bishops in the world. Virtually all the bishops at the Council came from the Eastern Empire recently ruled by Licinius, and most from areas close to Nicaea, with bishops from the modern-day Middle East (especially Asia Minor, Syria, Palestine, and Egypt) predominating. The Council was attended by legates of the bishop of Rome, though the bishop of Rome did not attend in person. Besides these legates, however, less than ten bishops from the Western Empire attended. There was perhaps one bishop present from the Persian Empire, which possessed already sizable Christian communities. One bishop appears to have attended from the Novatian Church, a widespread and organized group originating in a 3rd century schism between rival claimants to the office of bishop of Rome and considered heretical for their denial of absolution to people guilty of adultery or murder; this bishop appears to have agreed to all the Council's decisions while continuing to refuse to hold communion with the more mainstream Church.

What happened to Christianity in the decades leading up to the Council?

Though the 4th century is usually seen as a crucial period for the Christian Church, the 3rd century AD is arguably both more important and more mysterious. The 3rd century AD had seen explosive growth, institution-building, and theological debate in the Christian Church, fostered by a relatively tolerant Empire mostly too busy with never-ending civil wars to do anything about the officially illegal religion in its midst. 

It is in this period, notably, that surviving "secular" Roman sources dwindle, and are replaced by proliferating (though often fragmentary) texts by Christian authors: texts diverse in genre and perspective, ranging from corpuses of letters by prominent bishops to theological treatises to apologetics to polemic to the acta of councils. 

As was long ago pointed out, nearly all the Christian phenomena that we tend to associate with the 4th century are in fact already attested in the 3rd century: including monumental Church buildings, Church choirs, elaborate liturgies, ornate artwork, a regular and attested sacramental and ecclesiological system, the concept and practice of canon law, massive networks of bishops in regular communion and communication with each other, regular and explicit appeals to the preeminent authority of the Church of Rome, episcopal and Papal bureaucracies, regular provincial Church councils, metropolitan structures, large-scale theological conflicts, large Church councils featuring bishops from multiple provinces, extensive and elaborate heresiologies, the deposition of bishops both by councils and by the bishop of Rome, centralized persecution of the Church by the Roman Emperor, the explicit recognition by the Roman Emperor of the Church as a legal entity capable of owning property, and the explicit appeal by bishops to the Roman Emperor to enforce their judgments. The third century also featured sophisticated theological debates over Trinitarian theology, the nature of God and of the Father, Son, and Spirit, and the relationship between Christ's human and divine natures that in basic contours foreshadow the conflicts of the 4th and 5th centuries. 

If there is a sense of discontinuity between the 3rd and 4th century Church, however, it is in large part due to several extreme and (to contemporaries) nearly apocalyptic events that took place in the early 4th century, and established for Christians around the Empire a clear dividing line between before and after. The first event was the Great Persecution enacted by Diocletian and succeeding Emperors from 302 AD onwards, most likely the largest and most widespread outbreak of political violence against Roman citizens in Roman history. 

Even here, it should be noted that what set apart the Great Persecution from previous Roman persecutions of Christians is more subtle than is often appreciated. From the reign of Nero onwards, being a Christian was for all individuals, citizens or otherwise, a crime punishable with death--albeit normatively via a unique process that offered even proven Christians the ability to clear their name by offering sacrifice and/or cursing Christ. The basic structure of Roman law, however, was such that Roman officials did not usually seek out and prosecute most crimes on their own initiative; rather, most malefactors were accused by their fellow citizens. In practice, what this meant was that the persecution of Christians from the 1st through the 3rd centuries was usually localized and individualized and tied to particular grudges and conflicts, with larger-scale outbreaks of violence very often driven by popular agitations and pogroms. Even the Decian Persecution in the 3rd century, the first universalized persecution of Christians actively instigated by the central Imperial administration, focused on individual status and actions: all Roman citizens were required to offer sacrifice and obtain a certificate testifying to this fact, and were punished for not complying.

The Great Persecution, however, was conceived of and implemented as a self-conscious and rational attempt by the Roman Imperial central government to dismantle the institution of the Christian Church. It began with purges of Christians from the Imperial administration and army, and was inaugurated by the seizure and razing of a church building in Diocletian's capital of Nicomedia. The initial universal decree focused on the seizure of all Church property and the banning of collective Christian worship, as well as legal disabilities against Christians as a class: all measures that, unlike the 1st century legal precedent, targeted Christianity not primarily as an individual crime but as a seditious organization. Later decrees focused on the arrest and imprisonment and forced sacrifice of all Christian clergy, another measure designed primarily to destroy institutional practice and leadership. Only the very last decree issued by Diocletian attempted to enforce universal participation in sacrifice on all citizens under pain of death, though in a much more collective and less organized way than under Decius. While even at earlier stages of this process violence against individual lay Christians was likely widespread, much of it was carried out by magistrates as punishments for failure to comply with the more central anti-institutional measures.

The death toll for the Persecution is nearly impossible to estimate and is still fiercely debated by scholars, with an older tradition indebted to Gibbon fanatically dedicated to the idea that early Christians somehow "exaggerated" the Persecution and more recent schools generally pushing back against this and emphasizing the unprecedented social impact and widespread violence of the Persecution. Nonetheless, there can be little question, in my judgment, that the Persecution had devastating effects on the basic institutional structure of Christianity throughout the Empire; a reality eloquently testified to by the schisms experienced by nearly every major Church during and following the Persecution. 

The Church of 325 AD, then, should very much not be characterized as an embryonic institution only barely feeling its way into widespread social influence and power, but nearly the opposite: a centuries-old, highly-developed institution recently dismantled by force and struggling to rapidly rebuild itself. 

What effects did Constantine's rise to power have on Christianity before the Council?

The Persecution took place in the backdrop of the collapse of the Roman Empire into a complex, multi-sided civil war which I will not attempt to cover in detail here. What may be said, though, is that the various sides of this conflict eventually formed themselves into broadly pro- and anti-Christian factions. In particular, from the very beginning of his reign as (usurping) Emperor, Constantine appears to have been publicly dedicated to a policy of the full civil and institutional legitimacy of Christianity and the Christian Church; and he was gradually followed by other Emperors, including his principal Western rival Maxentius. At the same time, the architect of the Persecution Galerius was replaced in the East by the even more fanatically anti-Christian Maximinus Daza, who appears to have made the continuation of the Persecution a central goal of his administration.

In the end, of course, Constantine and Licinius were triumphant in 313 AD, and together established a new legal order in which Christianity was for the first time treated explicitly both as a recognized institution and as a licit individual status. Even more importantly, Constantine in the West, and to a lesser degree Licinius in the East, began to patronize the Christian Church, funding Christian dioceses, granting legal privileges to Christian clergy, and beginning a building campaign of churches.

It should be clearly recognized, however, that the effects of this patronage, while beneficial in aiding the rapid rebuilding of institutions, were also frequently a source of destabilization themselves. The essential irony, not lost on many contemporaries, was that the same Imperial administration that had recently done its best to dismantle the Christian Church was now taking the lead in its rebuilding, with all the unusual influence that implied. While older narratives of groups like the Donatists have often seen them as inspired in part by anti-Imperial sentiment, they, like virtually all other similar groups around the Empire, in practice competed eagerly for Imperial favor and patronage, and were quite successful at gaining it. As my book project argues, Imperial patronage frequently provided less institutionally- or theologically-established Christian groups and individuals with alternate means of accessing power and influence and authority; and this could be in certain respects even more institutionally destabilizing than open persecution.

This was even more true where Emperors were in conflict with each other. In the early 320s, Constantine and Licinius came ever closer to open warfare, an event with massive potential impacts for Christians in the Empire. Constantine repeatedly accused Licinius during these years of persecution of Christians. The extent or even reality of these persecutions are much debated, but inasmuch as they existed, they most likely do not reflect any innate hostility of Licinius towards Christianity, but rather his politicized suspicions that Christian clergy in the East favored Constantine and might be in communication with him or acting on his behalf. This demonstrates well the political destabilization to which Christianity was now vulnerable.

In 324, the year before the Council of Nicaea, Constantine began his long-planned civil war with Licinius. Less than a year before the Council of Nicaea opened, Constantine defeated Licinius and became the sole Augustus of a newly-united Roman Empire. 

Why did the Council take place? Who called it?

A commonly-believed, but inaccurate idea about the Council of Nicaea is that it was instigated and called by Constantine. There is a sense in which this is literally true, but substantively and in its most common connotations it is false. While Constantine was clearly involved in issuing invitations to the eventual Council and funding bishops' travel to it, it is nonetheless nearly certain that a large council would have been called in the East regardless, probably with participation from the bishop of Rome and at least a limited number of bishops in the West, by the year 325.

The origins of this council arose from the so-called Arian Controversy. This controversy is also commonly misunderstood. This is especially true in its earliest stages, about which we have few good sources. 

It is clear that Arius was a Libyan, at least by descent, a scholar who had been taught by the priest Lucian in Antioch but who seems to have spent most of his life in Alexandria in Egypt. The Church of Alexandria was by far the most important Christian center in the East, a massive metropolis and the center of Christian and pagan philosophy alike. As an initially urban and Greek-speaking faith, Christianity had spread from Alexandria to the rest of Egypt and Libya, and as such the bishop of Alexandria also held authority over the whole of Egypt and Libya, with more than fifty bishops under his direct governance. 

In the early 4th century, however, the Church of Alexandria was riven, like most major churches, by internal conflicts brought about by the Great Persecution's targeting of clergy. In 306, at the height of the Persecution, the bishop of Alexandria Peter was challenged by Meletius, another Egyptian bishop who claimed the see of Alexandria, allegedly over his concerns that Peter and/or bishops associated with him had apostatized under persecution and/or were too lenient towards those who had. Arius seems to have initially sided with Meletius, and was excommunicated by Peter; however, after Peter's martyrdom, Arius apparently switched sides to his successor, Achillas, and was rewarded by being ordained a deacon and then a priest. As a priest, Arius seems to have been quite popular and to have had a following of his own, as well as significant ecclesial responsibilities; he was purportedly a prominent candidate for election as bishop upon Achillas' death. 

The election, however, was won by Alexander, who does not seem to have been a particular rival of Arius; by one account, he had even interceded with Achillas for Arius' reinstatement. It was in the aftermath of this election that Arius seems to have begun engaging in theological controversy with Alexander, accusing him of heresy for his belief that the Son was eternal. After a series of poorly-documented conflicts within Alexandria between followers of Arius and Alexander, Arius was excommunicated by Alexander and fled Egypt to Palestine, where he was received with honor by the primate of Palestine Eusebius of Caesarea.

Eusebius of Caesarea was among the most gifted Christian writers of the 4th century, a polymath who produced the first Church History, the first universal Chronology, and numerous apologetic and theological works. Despite the well-established canonical principle that a priest excommunicated by his bishop should not be received by another bishop, Eusebius appears to have been unstinting in his support for Arius and his theology. With his help, a council was held in Palestine that supported Arius against Alexander. 

At the same time, Arius had written a letter (that survives) to Eusebius of Nicomedia, an even more powerful and influential bishop and a "fellow Lucianist," who appears to have studied with Arius under Lucian of Antioch. This Eusebius was not much of a writer or theologian, but was very politically well-connected, as he had transferred his see to Nicomedia, the central Tetrarchic capital of Diocletian and now the frequent abode of Licinius. He also seems to have held a council supporting Arius; and both Eusebiuses engaged in extensive canvasing and letter-writing to gather followers to their cause and refute what they saw as Alexander's heretical theology. Letters by both men to this effect also survive.

In this way, a quarrel between a priest and his bishop rapidly was transformed into a conflict between two networks of bishops. From Alexander's surviving writings from this period, it seems clear that he regarded his principal opponent not as Arius, but rather as Eusebius of Nicomedia, who, he accused, was not merely proclaiming a heretical doctrine but also violating the canons and attempting to assert his personal control over the Church. 

At the same time, Alexander, assisted by his traditionally-influential position, was quickly able to put together a much larger and more influential network of bishops of his own. Petitions and documents against Arius and Eusebius were circulated and subscribed to by bishops around the East in impressive numbers. More than a hundred Egyptian and Libyan bishops participated in Alexander's excommunication of Arius; and many more were tied to him by more indirect networks. Alexander was also successful in gaining the support of the Church of Antioch, the other most prominent and well-connected see in the East; as well as of Marcellus of Ancyra, a well-connected bishop in Asia Minor who had presided over the important Council of Ancyra in 314. 

Between Alexandria, Antioch, and Ancyra, the numerical domination of the anti-Arius bishops was overwhelming; and it seems clear that their preferred strategy was to canvas and organize and network and eventually hold a large council to depose their principal adversaries. This basic strategy seems to have closely followed that which had culminated, in the 3rd century, in the deposition of the unpopular bishop of Antioch Paul of Samosata at the first large Council of Antioch; a process that had featured a great deal of networking leading to a large council whose results had been finalized by the direct participation of the bishop of Rome and the bishops of Italy.

If this did not take place before 325, it was not, likely, for lack of trying, but because Licinius had passed a decree forbidding Christian assemblies and councils. While the relationship between Licinius and Eusebius of Nicomedia is unclear, Constantine and others would later accuse Eusebius of having been a close participant in Licinius' "tyranny." The most likely conclusion is that Licinius in fact favored Eusebius, and that his decree was intended to forestall existing plans to hold a large council at which Eusebius would be condemned. 

With Licinius' civil war and defeat, this obstacle was removed, and Alexander and co seem to have moved quickly to cement their position. Licinius was defeated in September of 324, and by the end of the year the new bishop of Antioch, Eustathius, had already held a council at which he deposed Eusebius of Caesarea and other prominent members of the pro-Arius alliance in Syria and Palestine, but permitted them to appeal to a forthcoming, larger council to be held at Ancyra.

What was the theological question debated before and at the Council?

The answer to this question is difficult to answer given the relative paucity of sources, and the extremely detailed and technical nature of these sources. It is partially for this reason that the debate is understood popularly in very inaccurate terms.

Christians already in the 1st century regularly worshipped and invoked three divine realities in both individual and collective liturgies and prayers: 'God the Father,' Jesus the human Messiah identified with a pre-existent entity referred to as God and also known as 'the Son of God' the 'Word of God,' and the 'Spirit of God' or 'Holy Spirit.' The fundamental question, then, was how to reconcile the 'threeness' of Christian worship with the accompanying polemical and traditional assertion of monotheism, or 'oneness,' in the Christian tradition. 

By at least the early 3rd century, but almost certainly during the 2nd century, Christians throughout the Empire referred to these aspects of their faith by the complimentary abstract terms 'The Holy Threeness' and 'the Holy Oneness,' in the likely original Greek Hagia Trias and Hagia Monas (or sometimes Monarchia), quickly Latinized as Sancta Trinitas and Sancta Unitas. By the early fourth century, these terms and formulas were traditional and universal; they were never disputed by anyone in fourth-century debates, including Arius. Arius emphatically believed in and confessed what he called "the Holy Trinity," and indeed would have regarded it as heretical not to do so.

Already in the third century, though, bitter debates had emerged over how to understand the relationship between these terms and concepts. To give a full delineation of these debates would take a great deal of time, but it should be noted that they already took place between very hierarchical and distanced ideas of the relationship between Father, Son, and Spirit and more united and close conceptions, debated via Scriptural passages and traditions and often underlain by very different underlying metaphysics drawn from Platonism, Stoicism, and more eclectic sources. 

Central episcopal networks seem to have largely embraced a relative "centrist" position, anathematizing both the so-called Ebionitic position that denied Christ's divinity and the so-called "Sabellian" or "Patripassian" position that Father, Son, and Spirit were simply modes or names for a single divine person. Still, strong tensions were frequently visible between different traditions, perhaps best exemplified in the relative contrast between the Roman tradition, which tended towards the monadic, and the Alexandrian tradition, which tended towards a more hierarchical and even liturgical understanding of the relationship of the Trinity. In the late third century, the bishop of Alexandria was publicly censured by the bishop of Rome Dionysius for, among other things, denying that the Son was 'the same in substance' (homoosious) with the Father, calling the Son the creation and servant of the Father, and so (as Dionysius of Rome accused) "tearing apart and destroying the most revered proclamation of the Church of God, the Monarchy, into three powers of some sort and divided hypostases and three divinities.” The bishop of Alexandria in response largely capitulated, producing an elaborate retraction that declared that the Son was in fact eternal and intrinsic to divinity and could be described as homoousios with the Father, while likely still retaining some theological features with which Rome was barely comfortable. 

These tensions were certainly not a mere matter of East vs West, as far more monadic theologians were prominent in the East, and more hierarchical theologians in the West; and these tensions could just as easily emerge within Churches. If these tensions emerged with more fierceness in the fourth century, it was not because these questions had never been debated before in great detail, but, I would suggest, due both to a growing technical sophistication and consensus in philosophy (produced in part by Neo-Platonism) and due to the institutional disruptions and conflicts caused both by the Great Persecution and by Imperial interventions into the Church.

What Arius and his allies initially asserted against Alexander and his allies can be most simply summed up in the thesis that "there was when the Son was not." In other words, the Son did not exist eternally in the manner required of the highest divinity in both the Platonic and Christian traditions. 

As to what the Son was, though, and when he came into existence, things got considerably more complex. 

A common misconception, even among educated people, is that Arius regarded Christ as a mere human being. Arius would have regarded it as clear 'Ebionite' heresy to assert such a thing. For him, as much as for Alexander, the human being Jesus of Nazareth was identified with a pre-existent divine being, a member of the Holy Trinity, the Son or Word of God.

It is also commonly said, with more justification, that Arius did not believe that Jesus was God. This is in a sense true, but in literal terms false. Arius emphatically regarded the Son as a being that could and must be referred to and worshipped as God. It is, on the other hand, quite true that Arius did not regard the Son as God in the common theistic sense of a metaphysically ultimate being. The Son was not a part of the cosmos, or a creation like any other, but an absolutely unique entity whose role, broadly speaking, was to mediate between the one God and creation, to take the place of God and act on his behalf in all divine acts, including creation and salvation. 

A common misconception, ultimately traceable to a single popular scholarly text, is that the primary import of Arianism was found in Arius' conception of salvation, in which the Son, as a quasi-divine entity capable of sin and change like us, exemplified the virtues and acts which we must practice in order to return to God. As a matter of fact, as scholars have pointed out, soteriology has no place in any of Arius' surviving writings, which instead seem primarily focused on metaphysics, on the issues of how to reconcile divine simplicity and freedom and unchangeableness with both the act of creation and the Incarnation of Christ.

That being said, the account produced by Arius and his allies of God and the Son was remarkably sophisticated both Scripturally and metaphysically. Allies of Arius, especially Eusebius of Nicomedia, Eusebius of Caesarea, and Asterius, were particularly adept at producing metaphysical and linguistic means by which nearly all divine attributes and terminology could be ascribed to the Son in less than absolute terms. The Son, for instance, could be described as unchangeable to Arius inasmuch as he, though not absolutely changeless like God, nevertheless participated to the greatest degree possible in God's unchangeableness; though in his basic nature capable of sin, from the first moment of his existence he received impeccability through grace; and so on and so forth.

There was never a single theological account produced by Arius' opponents, who were much more disparate and united largely by opposition to what they saw as a few malefactors. All rejected and condemned Arius' thesis that the Son was not an eternal being. Some, however, seem to have done so not based on a sophisticated theology of their own, but inasmuch as this explicit assertion was novel and not found in previous ecclesiastical tradition. This, indeed, appears to be true; for while very hierarchical accounts of the Trinitarian relations are reasonably common in 2nd and 3rd century sources, every surviving account to discuss the question explicitly treats the Son's begetting as eternal. Some, presumably, were chiefly opposed to the canonical violations involved in Eusebius' receiving of an excommunicated priest of Alexandria, or primarily swayed by the authority of the ancient, revered Churches of Alexandria, Antioch, and (eventually) Rome.

Alexander himself seems to have been a relative Alexandrian moderate, and hardly a firebrand; he was quite comfortable with the (Origenian) language of three hypostases, and quite comfortable with rather hierarchical accounts of the Trinity. He took his stand on the deceptively simple assertion that "God was always a Father." This meant not only that the Son had always existed (since to be an eternal Father God required an eternally existing son), but also that his existence was intrinsic to God and to divinity itself. As Alexander also argued, the idea of God existing not only without his Son but without his Word and Wisdom and Power (all Scriptural titles for the Son) was absolutely inconceivable.

While Alexander's theology seems to have been quite moderate, this was not the case for all of his close allies. Marcellus of Ancyra in particular possessed a much more monadic view of divinity, in such a way as (at least in his early theology) to seem to contradict Alexander's own belief in God's perpetual fatherhood. Over the course of the controversy, Alexander appears to have been more and more influenced by his secretary, Athanasius, who developed a much more sophisticated and radical theology of the Trinity that emphasized the unity of Father and Son in ousia or "substance." Athanasius seems to have ghost-written a number of Alexander's writings during this period, and also accompanied him to Nicaea.

These broad questions also involved thinkers on both sides in many detailed debates over theology, metaphysics, and Scriptural exegesis, which it would be impossible to cover in this format. While these debates may seem merely technical to us, they clearly were considered crucially important for contemporary bishops and Christians. Hence, this account should not be seen as exhausting the debate over Arius and his doctrines, which can be followed in more detail through the actual texts, or fragments thereof, produced by both sides.

How did Constantine participate in the Council of Nicaea?

If Constantine was not primarily responsible for the Council's existence and goals, there can be no question that his participation significantly altered the event.

At what point Constantine became involved in the controversy is unclear. During his reign in the West, he became associated with the Spanish bishop Hosius of Cordoba, though the extent and nature of this association is still debated. A year or two prior to the Council, Hosius travelled to the East, apparently at least in part as an envoy of Constantine. This visit took place most likely in parallel with the ongoing civil war between Constantine and Licinius, enabled by Licinius' loss of control of most of the East, and had as one of its purposes the marshaling of support for Constantine among Christian bishops in this region. According to later historians, it was Hosius who carried with him a letter from Constantine addressed to Alexander and Arius, which aimed to address and settle their conflict. This letter is quite famous. Its essential message was that the two men and their followers should agree to disagree, since the basis of their quarrel was "trifling" and they had a duty, as Christian clerics, to aid Constantine in his divinely-entrusted task of bringing unity in doctrine and government to the whole world.

As is well known, this letter was not successful in settling the quarrel. Besides the obvious, one additional reason this is so is likely that the message of the letter was actively undercut by its carrier. Hosius, for his part, clearly favored the more institutional anti-Arius side of the controversy, and did his best to assist it. He seems to have attended the Council of Antioch in 324 that interrogated and suspended most prominent pro-Arius bishops, and announced the forthcoming larger Council to be held at Ancyra.

It is unclear whether, at this point, Constantine was even aware of these plans for a Council of Ancyra. At what stage Constantine became involved in these plans is also unclear. Nevertheless, he eventually did become involved--to such an extent that his efforts might be characterized as "hijacking."

Among the results of Constantine's involvement was a significant increase in the number of participants at the Council, enabled by Constantine's funding of bishops' travel via the Imperial cursus. Similarly, Constantine's decision to personally attend the Council and endorsement of its decisions via official Imperial letters greatly increased public awareness of the Council. 

In the process, the Council assumed a much wider, external significance beyond merely internal Christian deliberation. In effect, it became a public showcase of Christianity and Constantine's endorsement of it to the people of the Empire at large, and especially to the people of the Eastern Empire. At the same time, the Council served as a means for Constantine to introduce himself in person to the bishops and faithful of Licinius' former domains, to cultivate their support for their new ruler, and to convey to them his own sense (as an unbaptized Imperial catechumen) of his relationship with the Church.

Constantine's involvement also appears to have changed both the location and agenda of the Council, as it was moved from Ancyra to its final location of Nicaea, and was held not in a Church, like previous Councils, but in the audience hall of the Imperial Palace in the city. While there are various possible reasons for the change of city, it is very likely that the move was intended as a show of tolerance or even support for the smaller, pro-Arius faction. Ancyra was the see of Marcellus of Ancyra, one of Arius' bitterest enemies; holding the Council there conveyed well the intention that had animated the efforts by the larger Eastern faction to hold a council, namely, to depose and excommunicate their opponents. Nicaea, on the other hand, was the see of one of Arius' closest episcopal supporters. Holding the Council there conveyed, at least, the intention to extend a broad welcome to Arius and his supporters, if not an overt signal that they had friends in powerful places.

In a letter written a few months after the Council, Constantine says that Eusebius of Nicomedia, the leader of the pro-Arius faction, had sent him envoys prior to the Council asking for "an alliance," and admits that he had in fact for a time lent him his support. There is every reason to believe, then, that Constantine went into the Council with the conscious intention of keeping Eusebius of Nicomedia and his allies from being deposed: though whether this was primarily inspired by a desire for tolerance and harmony in the Church, a will to maximize his support among different Christian factions, theological sympathy for Arius and his allies, or some mixture of the above, is debated. Whatever the motives, however, Constantine's participation likely altered the outcome of the Council significantly, as it appears that both Eusebius of Nicomedia and the bulk of Arius' episcopal supporters were in the end able to survive the Council with their sees intact. 

Even if Constantine had not participated in the Council, it is almost certain that the bishops would have eventually appealed to Constantine to enforce their sentences by requiring deposed bishops to hand over the cathedrals and Church properties of their dioceses to new holders. In the 3rd century, the Council of Antioch had appealed to the pagan Emperor Aurelian to enforce its sentence of deposition on the bishop of Antioch Paul of Samosata, and Aurelian had, in fact, done so. Whether Constantine would have similarly enforced depositions against Eusebius of Nicomedia and Eusebius of Caesarea made by a Council over which he had exercised no oversight is admittedly unclear. 

At the same time, it was Constantine who, apparently on his own initiative, chose to punish the few losers at the Council, at his own discretion, with the purely Imperial punishment of "exile" (or rather compulsory interment). This represented a significant novelty even in regards to Constantine's past dealings with Christian clergy, and would certainly never have taken place without Constantine's close participations in the proceedings.

It is possible that Constantine was also responsible for some of the additional items on the Council's final agenda, in particular the wish to create a new, unified date for Easter for the Church as a whole. While there had been longstanding efforts to create a unified practice--the most famous one being spearheaded by the bishop of Rome in the 3rd century--these efforts had never been entirely successful due to the prevalence of different traditions and the willingness of influential bishops to tolerate them. While it is possible that another such push for a unified date of Easter was already on the horizons of the Eastern bishops prior to Constantine's involvement, it seems likely that the intensity of the push for a universal, standardized practice ultimately stemmed from the Emperor's famous concern for unity within his domains. 

What were the proceedings of the Council like?

No full account of the Council's proceedings exist, unlike most later Ecumenical Councils, where official acta (transcripts) were created and maintained and have largely been passed down to us intact. A few people to attend the Council have left us fragmentary accounts, and similarly fragmentary accounts and traditions are found in writers and ecclesiastical historians from following decades. No universally-accepted scholarly reconstruction of the Council's events exists, and many aspects are still fervently debated by historians today. What follows, then, is my own, relatively uncontroversial, reconstruction.

The Council took a great deal of time to assemble, with bishops and laypeople and interested pagans pouring into the city for weeks if not months before the Council's opening in May of 325. It is clear that different factions of bishops met extensively, both in Nicaea and elsewhere, to plan their strategies and goals and probably even to agree on doctrinal formulations and arguments in advance.

At the same time, more public-facing events also took place in Nicaea during the lead-up to the Council. Besides no doubt many liturgies held by different bishops and groups of Christians, several accounts indicate that Christian bishops began holding public logical disputations in the forums of Nicaea, in the process attracting large crowds both of Christians and of pagans. The purpose of these disputations seems to have been twofold: they served as "practice rounds" and "warmups" for the debates to come at the Council, served to encourage and impress the Christian faithful with the learning and the newly exalted and protected public status of Christian clergy, and also acted as a means of evangelization for the pagan public. 

Such disputations and rhetorical and logical displays were a popular spectator activity in the ancient Roman world, and were usually conducted by pagan sophists and philosophers. Some accounts suggest that pagan rhetoricians and philosophers in fact participated in the disputations with the bishops before the Council, attracted likely more by their own desires for publicity than by any particular desire to refute or endorse Christianity. At the same time, from surviving accounts it seems these disputations, though engaged in by numerous prominent bishops, also attracted a certain amount of criticism from some Christian circles.

The Council opened in May in the audience chamber of the Imperial Palace of Nicaea. We have an eyewitness account of its first session from Eusebius of Caesarea. According to him, the bishops were arranged carefully according to status in the chamber, and arrived first to take their seats. Before Constantine's arrival, all stood, after which the Emperor processed into the center of the chamber preceded by some of his high officials. After a brief address, Constantine was the first to sit down, after which the bishops all sat in turn. A panegyric was offered to the Emperor for the occasion by one of the bishops present (in my opinion most likely Eustathius of Antioch, though others argue for Eusebius of Caesarea or Eusebius of Nicomedia).

Later accounts of the Council tell of a gesture made by Constantine either before or on the first day of the Council, in which the Emperor showed the assembly written petitions which bishops had submitted to him against each other, and then burned these papyri in their presence. The significance of this gesture is debated. Some ecclesiastical historians as an indication of respect for episcopal status, while others have it as another signal of Constantine's unwillingness to become deeply involved in episcopal conflicts and a gesture in favor of reconciliation. Some modern scholars see it, in contrast, as an assertion of Constantine's autocratic power over bishops, underscoring his right to receive petitions and do what he wished with them. Others, perhaps more plausibly, see it primarily as yet another gesture designed to protect Eusebius of Nicomedia and the minority bishops from the censure of the majority. 

The Council's disputations, extending into July, seem to have been quite extensive and rather free-wheeling. There is some question who formally "presided" over the Council's proceedings. Most modern scholars argue for Hosius of Cordoba, though whether acting in his own name or as a delegate of Constantine and/or the bishop of Rome is unclear. His name appears first on at least some existing lists of signatories. Many ancient though not contemporary sources indicate that the legates of the bishop of Rome formally presided, in keeping with the practice at later Ecumenical Councils. At the Western Council of Serdica about two decades later, Hosius and Roman legates seem to have presided in tandem, and this may reflect the procedure at Nicaea.

Assuming the Council was run on the model of later Ecumenical Councils (based in turn on that used in Roman political assemblies, Senate meetings, and consistories) the "president" of the Council had as his responsibility the running of the Council's proceedings by proposing questions and votes and giving all individual bishops and groups of bishops time to speak according to their seniority. Reports of the Council, though, sometimes suggest more chaotic proceedings where dialogues and arguments were allowed to take place between bishops and groups of bishops relatively freely. It is likely that at certain points Arius and perhaps some bishops supporting him were brought before the assembly as defendants and given an opportunity to make their case and answer questions from the assembly. Despite popular accounts, however, it is extraordinarily unlikely that physical violence ever occurred during the proceedings, and no contemporary or near-contemporary source suggests any such thing.

Most reports suggest or directly portray a clear divide between a very small minority of clearly pro-Arius bishops and the overwhelming majority of the Council, and depict dialogues or arguments between these two factions. That the pro-Arius group was in fact a very small minority is suggested, among other things, by their apparent strategy at the Council. Apart from perhaps Arius himself, the pro-Arius clerics seem to have avoided directly arguing for the positions they had polemically asserted before the Council, and instead sought to present broad theological formulations that did not touch on controversial issues. Eusebius of Caesarea by his own account submitted a written creedal statement to the Council that was as anodyne as could be imagined in this context; and it is possible that Eusebius of Nicomedia also submitted a similar document. It is likely that the audience for this strategy was not primarily their fellow bishops, but rather the Emperor Constantine, who (as discussed above) had previously expressed his belief that the theological issues involved were unimportant and of less moment than overall unity, and who (also as discussed above) may even have previously offered his protection to these bishops. 

The main leaders of the anti-Arius group, in contrast, seem to have tried mostly to characterize their opponents' beliefs, catch them in equivocations, and insist on stricter and more explicit formulations to exclude them. The term "homoousios" ("the same in substance") in particular does not appear to have been in common theological usage prior to the Council, and was likely decided on by the Council not according to a clear, agreed-upon understanding of what the term signified, but as a polemical gesture against Arius' supporters. Indeed, according to one later account, the term was introduced by Eusebius of Nicomedia, who argued as a reductio ad absurdum that his opponents' beliefs were so radical that they would mean that Father and Son were "homoousious": in response to which the Council adopted the term as its own. According to Eusebius of Caesarea, however, the term was defended because it had appeared in letters of orthodox ancients, referring most likely to the letters of the bishop of Rome Dionysius treated above. It is also possible that the term originated with Athanasius of Alexandria, who unlike Alexander seems to have already begun to employ the term "ousia" (substance) extensively in his theology. 

One persistent scholarly idea (based on a misreading of a passage in Eusebius) is that the term came from Constantine, an idea that, as I have argued in my book, is totally without grounding and contradictory to all we know of Constantine's theology both before and after the Council. Constantine does seem to have participated in the Council's theological debates, however, speaking in Greek; and in particular is quoted by Eusebius as deprecating both the term "homoousios" and the term "hypostasis" and asserting the passionless nature of divinity, while also suggesting that God the Father could still be called a Father prior to the begetting of his Son. Taken together, this suggests that Constantine may have attempted at least broadly to defend the pro-Arius party at the Council.

While the Council also dealt with other issues--the date of Easter, settling the Meletian Schism in Egypt, and other practical disciplinary questions among them--we have virtually no accounts of how these questions were debated or discussed or decided on. This likely indicates that, for most of the bishops at the Council, the theological issues loomed largest.

What was the outcome of the Council of Nicaea?

In the end, a creedal statement was agreed upon by the Council and signed by at least the overwhelming majority of bishops present. This statement asserted that the Son was "true God from true God," "born not created," "from the substance of the Father," and "homoousios with the Father." To this creedal statement were appended the following anathemas:

"And those who say, 'There was when he was not,' and 'before his birth he was not,' and 'he came to be from nothing,' or those who pretend that the Son of God is 'of another subsistence or essence,' or 'created' or 'capable of change' or 'mutable,' the Catholic Church anathematizes."

It is unlikely, to say the least, that the bishops at the Council intended this theological statement to be a "creed" in the modern sense, let alone a text used by the whole Church for all time. Creeds at this time were widespread throughout the Church, but were not to our knowledge ever recited as part of the normal Sunday liturgy--a Byzantine innovation not prevalent in the Western Church until the 9th century. Creeds were used at this time for two purposes: as a text recited before baptism by adult converts, or as a text imposed upon heretics or suspected heretics to clear them of wrongdoing and/or receive them back into the Church. The Creed of Nicaea was not intended, clearly, as a baptismal creed, and local creeds continued to be used for this purpose. By all indications, the Creed was primarily intended as a polemical text intended to exclude "Arian" heretics from the life of the Church or clear suspected heretics. Even here, it is unclear that anyone intended the Creed to be utilized after or apart from the proceedings of the Council itself. 

That the Council had so clearly condemned Arius' position and attempted to target his specific beliefs and formulations was by all accounts seen as significant and intended to be authoritative and final by most bishops present. By this measure, the most common likely applied by bishops at the Council itself, the primary significance of the Council was that the pro-Arius faction of bishops had lost, and therefore their theology should not be tolerated in the Church any longer.

If the goal of the majority of the Council was to settle on a theological formulation unacceptable to the pro-Arius bishops, however, they do not seem to have been effective. It is clear that at least the majority of the pro-Arius bishops in the end signed the Creed of the Nicaea. It is equally clear, from the surviving account of Eusebius of Caesarea, that they did so without altering their own beliefs, but rather by interpreting the Creed in various tendentious manners highly contrary to the intention of most of its adopters and framers.

Why so many clearly pro-Arius bishops signed a document clearly designed to condemn their preferred beliefs may be seen as a relative mystery; but, as always, context is everything. In a Council called without Constantine's active participation, it is extraordinarily unlikely that the principal leaders of the pro-Arius agitation would have been given any opportunity to save themselves from deposition by signing a theological statement. At the same time, deposition by even a very large Council called without Constantine's involvement would not necessarily have resulted in these bishops actually losing their positions, as (particularly if the Council that deposed them had been smaller and they had not attended themselves) they could have continued to maintain support within their local Churches and networks along with control of local Church property. Constantine's decision to support the Council's actions with the additional Imperial punishment of exile raised the stakes even higher.

It is likely that it was specifically the combination of Constantine's higher degree of coercive pressure and his desire for peace and consensus that made most of Arius' episcopal allies abandon him and sign the Council's polemical anti-Arius creed. By doing so, they were able to not only preserve their positions, but also regain their reputations with at least some fellow bishops and curry favor with the Emperor--though it is clear that the bishops who had openly supported Arius continued to be regarded with hostility by at least the principal leaders of the anti-Arius network. Indeed, surviving fragments from Eustathius of Antioch and Marcellus of Ancyra show them enraged at the "trickery" by which the "Ariomaniacs" were able to maintain their positions despite the condemnation by the overwhelming majority of the Council of their theology and actions.

Even so, it is possible, though not certain, that a few bishops present at the Council were able to avoid signing at least some parts of the Creed and still escape punishment. A surviving letter from Eusebius of Nicomedia and Theognis of Nicaea states directly that they had refused to subscribe to the Council's "anathema"--which may mean either the anathemas appended to the Creed and/or the Councils' excommunication of Arius. At the same time, they indicate that they had agreed to at least most of the Creed, though using ambiguous language that may not indicate that they actually subscribed to it in writing. The account of the later, pro-Arian historian Philostorgius narrates that three bishops (the two above plus Maris of Chalcedon) had signed the Creed on tablets in which the term "homoousios" ("the same in substance") had been surreptitiously altered to "homoiousios" ("similar in substance")--a colorful account that is unlikely to be literally true, but suggests the kinds of reservations possible in such an environment. It is probable, then, that at least these three bishops were able to avoid subscribing to all of the Council's acts, and yet escape punishment, almost certainly due to Constantine's protection.

However, around three months after the Council, these three bishops appear to have been exiled by Constantine anyway on his own initiative. The reason for this change of heart is unclear: Constantine himself in justification blames Eusebius for deceiving him into assisting him at an earlier period, but does not indicate how he became undeceived. Philostorgius has the three bishops actively recanting their subscriptions in Constantine's personal presence, another colorful account unlikely to be literally true.

At the actual Council, however, Arius himself was anathematized by the bishops and exiled by the Emperor, accompanied by Euzoius, an Alexandrian deacon and close supporter, and most likely other supporters among the lower clergy. Two bishops, Theonas of Marmarica, and Secundus of Ptolemais, also refused to agree to the Council's decisions and were excommunicated by the Council and exiled by Constantine.

The Council's surviving letter announcing its results puts the theological quarrel first, but also mentions decisions taken to settle the Melitian Schism in Egypt. Though quite generous towards the Melitians, these measures were not successful at settling the conflict permanently. The Council also adopted a number of disciplinary "canons," most of which do not show a great deal of innovation, but (like the previous smaller Councils of the 4th century) seem aimed at reconstructing Church order after the Persecution and resulting disorders and schisms. All these canons are clearly directed at conditions and practices and specific problems in the Eastern provinces around Nicaea, and it is unlikely that they were intended to be applied directly to the whole Church; rather, they were intended to be specific and authoritative applications of what were taken as universal and agreed-upon canonical regulations and principles. Though frequently held up as authoritative in succeeding centuries, and hence foundational to later canon law, they were rarely followed when they conflicted with local or regional practice or later canonical rulings. 

Among the most significant canons, however, are those that affirm and reinforce the authority of the bishop of Alexandria and the bishop of Antioch over Egypt and Syria/Palestine, respectively, as well as the authority of Metropolitans over their provinces, and which mandated the practice, widespread already in the East, of holding regular provincial synods. A canon specifically forbade the practice of bishops being "translated" from see to see: most likely a measure specifically aimed at Eusebius of Nicomedia, though Eustathius of Antioch had transferred his see as well. The Council also called the city of Jerusalem by its ancient name (it had been known as Aelia Capitolina since the Bar Kochba revolt, and Jews forbidden from entering), and mandated that it receive the second degree of honor in its province after Caesarea; it did not, however, either raise Jerusalem to metropolitan status, or make it a "Patriarchate" (a profoundly anachronistic concept). 

The Council also was successful in gaining an agreement in principle on a common date for Easter for the whole Church; though even here, the results were less ambitious than they might at first appear. In particular, the Council forbade the minority Eastern practice--already attacked by the bishop of Rome in the 3rd century, and nearly the cause of a schism then--of celebrating Easter on the date of Jewish Passover, or in other words, not on Sunday every year, and mandated that Easter be celebrated according to the practice of the Church of Rome, which (along with the majority of Christians at this time) celebrated it always on a Sunday according to complex calculations designed to reconcile the lunar Jewish calendar with the prevailing solar Roman calendar.

This minority practice was not the only source of divergence for the date of Easter, however; while Churches closely networked with Rome or Alexandria or other major sees could derive their yearly dates for Easter simply by getting them by letter, dioceses and provinces did at times attempt to calculate their own dates. And since the Council did not actually mandate a particular method of calculation for Easter, let alone provide the lunar tables necessary to do so, dates continued to differ from time to time throughout the Church, varying largely based on the state of war and peace and communion and authority and communications across different churches. In the present day, the Latin Catholic Church (followed by nearly all Protestant Churches) celebrates Easter according to a different calculation from the Byzantine Catholic and Eastern Orthodox Churches, who in turn differ somewhat from the Church of the East's calculations.

The Council's principal results were announced, in keeping with typical synodal practice, in various letters by the bishops sent circular-style to important churches and regions: while these letters likely had larger circulation than previous letters due to the possible assistance of Constantine, it is highly unlikely they reached every bishop in the Empire. Constantine also sent circular letters in his own name announcing the results of the Council (as he understood them) to "the churches" and also, it seems, to individual churches as well.

Following the Council's close, Constantine invited the bishops present to join him in celebrations of the twentieth anniversary of his reign. Though clearly not all bishops did so, this appears to have involved banquets in the Palace at which the Emperor, in a break with previous practice, dined with small numbers of bishops personally, a gesture that appears to have particularly impressed Eusebius of Caesarea.

What was the aftermath of the Council like? How did Nicaea become so important?

Entire books have been written about this, including in large part my own. Suffice it to say that Nicaea was not immediately accepted by all as final and authoritative, either in broad strokes or in particulars. Though Arius and his doctrine had been condemned, the majority of his episcopal supporters continued to hold their offices and wield influence. Within about two years of the Council, Constantine recalled Arius himself and all his supporters, including Eusebius of Nicomedia, from exile, and publicly declared Arius orthodox. 

From this period on, Constantine appears to have supported Arius and his allies against their opponents. In particular, he sent threatening letters to successive bishops of Alexandria demanding they receive Arius back into communion, instigated the reception of Arius into communion by the many bishops at the Council of Jerusalem in 335, and participated in a series of depositions of the key leaders of the anti-Arius alliance, beginning with the bishop of Antioch Eustathius and extending through Athanasius the new bishop of Alexandria and a number of others. In the end, he was baptized on his deathbed by Eusebius of Nicomedia, a remarkable reversal. 

The Council of Nicaea's doctrinal definition may have first been attacked and condemned a matter of years after Nicaea by a Council held at Nicomedia, at which Constantine possibly attended, though our information on this event is very fragmentary and unclear. Under Constantine's son Constantius II, however, a sustained, Imperial-sponsored effort was made in the Eastern Empire to surmount the Creed of Nicaea with other creeds and definitions more amenable to the leading Eastern bishops, now predominantly key members of the initial pro-Arius alliance. This effort was led at first by Eusebius of Nicomedia himself, but upon his death was continued by later generations of theologians. This effort led at times to explicit condemnations by councils of Eastern bishops of the language used at Nicaea, as well as to the first large-scale schism between Eastern and Western bishops in 343.

Meanwhile, beginning in the 330s, bishops such as Athanasius, Marcellus, and Eustathius began appealing to the preeminent "ecumenical" authority of the Council of Nicaea to attack Eusebius of Nicomedia and other bishops controlling affairs in the East. The bishop of Rome Julius invoked Nicaea in condemning Eusebius and others as condemned "Arian heretics" and justifying his decision to receive exiles such as Athanasius into communion despite their deposition by Eastern Councils. However, all these appeals were mostly polemical rather than detailed and theological, and focused on the general condemnation of Arius and his supporters and theology, not the specific language or content of the Creed of Nicaea. 

It was not until the early 350s that Athanasius of Alexandria appears to have attempted to tie the specific language of Nicaea in with a sophisticated theological viewpoint. In the aftermath of Athanasius' repeated depositions by the Emperor Constantius II, Constantius attempted to force all bishops in the Western Empire and beyond to subscribe to the Creed of Sirmium and a condemnation of Athanasius on pain of deposition and exile. Around the same time, and likely in large part in response to the publicity generated by this unprecedented move, networks of "Nicene" bishops, led by the bishop of Rome Liberius, appear to have begun using subscription to the Creed of Nicaea as a theological litmus test. 

Negotiations between Eastern and Western bishops opposed to Constantius' increasingly heavy-handed attempts to enforce a substantially "Arian" orthodoxy more and more focused on how to understand the Creed of Nicaea and its use of the term "homoousios." This ultimately led to a consensus interpretation that allowed the vast majority of Eastern and Western bishops who refused to accept the new universal "homian" Creed promulgated by Constantius II via the Councils of Ariminum, Seleucia, and Constantinople to instead accept the Creed of Nicaea as an authoritative, episcopal and ecclesial rather than Imperial, and theologically anti-Constantian and anti-homoian alternative. 

This move was cemented by the decision of the bishop of Rome Liberius to make the Eastern bishops collectively subscribe to the Creed of Nicaea as a condition of admission to communion in 364: a successful negotiation that led to the bulk of Eastern and Western bishops entering into communion and explicit theological understanding with each other for the first time in decades. It was further reinforced by the sophisticated theological justification given to the Creed in Greek by the Cappadocian Fathers, as well as by the continuing attempts of the Emperor Valens to use force to maintain Constantius' alternative creed.

By the time Emperor Theodosius rose to power in the early 380s, there was a well-networked, entrenched Nicene Church that encompassed the vast majority of dioceses in both East and West and treated adherence to the Creed of Nicaea as an article of faith. It was this Church that was endorsed by him in the Edict of Thessalonika of 380 as that which the Emperors of Rome would treat as legitimate from thenceforth. Theodosius' rise to the position of senior Augustus of the whole Emperor permanently reinforced this position, which was never again seriously challenged within the Roman Empire or succeeding Byzantine Empire.

At the same time, however, a self-conscious "Arian" Christianity became the religion of the Goths and other Germanic peoples migrating into the Empire. The Germanic Kingdoms established in the 5th century in the former Western Empire all possessed state-mandated "Arian" Churches, even as the overwhelming majority of the population maintained adherence to a "Catholic Church" that continued to use the Creed of Nicaea as a principal test. With the downfall of some of these kingdoms and the conversion of Germanic elites throughout Western Europe from their own variety of Christianity to Catholicism, the overriding importance of the Council of Nicaea and its creed was further reinforced.