For many modern Christians, the Council of Nicaea marks a basic decision of the church about its faith. After that crucial event, all who disagree with Nicaea's insistence that the Son is one in being (homoousios) with the Father could only be considered heretics.

But that is not how people saw it at the time. The idea that Nicaea was a fundamental turning point developed gradually over the decades that followed. Modern Christians should certainly accept the church's decision for Nicaea and the Trinitarian faith, but they should know that the Spirit only slowly led Christians to the true reading of Scripture.

There are two reasons Nicaea was not originally regarded as the decisive moment that many textbooks assume. First, the idea that a creed with fixed wording might serve as a universal standard of belief had not yet developed. The council made an ad hoc decision, and it stated its faith in terms that clearly differentiated its beliefs from Arius's. But nobody at Nicaea assumed that this particular wording would stand as the fundamental Christian confession for centuries to come. Local creeds continued to be used for teaching converts and children until the next century. (One of the best examples is the "Apostles' Creed," which originated as the local creed of the Roman church.) The Council of Nicaea was well known (because of its size and its association with Emperor Constantine), but no one regarded its confession as a universal marker of orthodoxy. At that point in history, no creed was treated that way.

Second, the controversy between Arius and his bishop Alexander was the product of wider tensions in the early fourth-century church. Nicaea was one battle in a much wider war between different ways of interpreting what the Scriptures said about the Father and the Son. The wider conflict continued for decades. Some popular books have also presented the fourth century as the period in which "Jesus became God." The idea that Christians did not previously consider Jesus divine is, however, unfounded nonsense. But it is clear that Christians differed considerably over what God meant. Many assumed that there could be degrees of God: Christ was God, but not the one God, the Father (such people often appealed to 1 Timothy 6:16).

A new cast of opponents

Arius played a key part in the events that led up to the Council of Nicaea, but he did not have a role in the controversies that raged between 325 and 381. After the council, Arius was readmitted to communion by many bishops after he placated them with a somewhat bland confession of faith. Then, in 337, he died.

Here are the main players in the controversy that erupted in the years after Nicaea:

Marcellus of Ancyra: one of the most important leaders of Nicaea itself, but one who had strongly unitarian tendencies [see p. 32].

Athanasius: bishop of Alexandria from 328. In 336 and 339 he was exiled for maladministration, including charges that he had been violent towards his opponents. Some who had also opposed his predecessor Alexander were delighted to be able to remove one of their theological opponents. Athanasius's exile was not purely a matter of theology, but he hoped to present the conflict that way. In a rhetorical masterstroke, he presented his enemies as "Arians" rather than "Christians." Many Western theologians accepted this terminology, and in the later decades so did some Easterners.

The Eusebians: a large group of Eastern bishops who stood in a broad tradition that encompassed both the church historian Eusebius of Caesarea and the slightly lesser-known Eusebius of Nicomedia. They insisted that there is a basic ontological distinction between Father and Son. But they insisted just as strongly that there is an ineffable closeness between Father and Son, such that the Son's being can be said to be from the Father in some indescribable sense, and that the Son is "the exact image of the Father's substance" (cf. Wisd. 7:25-26; Heb. 1:3). Such theologians found Athanasius's insistence that the Son is the "proper wisdom of the Father" too unitarian. Comparing the relationship between the Son and the Father to the relationship been a human person and his or her wisdom was too simplistic, they felt. In such a picture God was truly one, but was the Word of God really distinct from God the Father? Arius himself may be considered a slightly idiosyncratic "Eusebian," but the other members of this tradition were not in any way dependent on Arius, and they knew little of his particular theology.


During the 350s, the controversy shifted considerably. This was partly because of the emperor Constantius, and partly because new "Heterousian" theologies emerged.

Constantius was the most successful of Constantine's three sons, and during a complex civil war between 350-353, he came to control the whole empire. Constantius was a strong opponent of Athanasius, whom he considered a danger to the unity of his realm. He supported a group of "Eusebian" leaders who strongly opposed Marcellus's theology and distinguished clearly and hierarchically between Father and Son. Scholars now term this theology "Homoian." Homoians argued that the Son is "like" (homoios) the Father, although a distinct and inferior being. They also rejected any use of being or essence (ousia) terminology, saying it was unscriptural and implied that God was materially divided in generating the Son.

The most radical wing of this movement (represented by Aetius and his disciple Eunomius) insisted that Father and Son were unlike in being. Their teaching provoked a strong reaction and seems to have affected public perception of the Homoian movement. During the 370s and 380s, Eunomians or Heterousians (heteros = other; ousia = being) increasingly became a distinct church group. (In older accounts these are referred to as "extreme Arians" or "neo-Arians.") One of their Homoian associates, Eudoxius, became bishop of Antioch from 357 and promoted Aetius, to the disgust of many who would previously have been in broad agreement with a "Eusebian" theology.

One group who strongly opposed the Homoian radicals and the Homoian attempt to prevent the use of essence language focused for a while around Basil of Ancyra (who had replaced Marcellus in that bishopric). They described the Son as "like the Father according to essence" and were known as Homoiousians (homoios = like). Many people sympathized with their approach because they seemed to uphold "Eusebian" principles. They believed it was necessary to talk about essence or being in order to preserve and emphasize the unique closeness between Father and Son. Homoiousians taught that the Son was from the Father in a unique sense: His essence differed from the Father's only in not being unbegotten. The language of "likeness in essence" thus seemed to uphold the balance they desired in theology.

The Homoiousian approach was very different from that of the Heterousian theologians, who could describe the Son as a creation: unique indeed, but still a created product of the divine will. During the 350s, these tensions among the "Eusebians" could not be easily contained.

The Emperor strikes back

In 359 and 360 Constantius called two councils that, under pressure from him, promulgated a Homoian creed. This was of immense importance. Before Constantius's councils, the wording of the Nicene Creed was becoming an increasingly important point of reference for some, but there was still no history of a creed functioning as a universal marker of Christian identity. But by the councils of 359 and 360, Constantius and his advisors had come to see the logical end of the gradual rise in the use of creeds over the previous 20 years. Forcing provincial councils and individual bishops to agree to one creed seemed an obvious way to ensure uniformity.

In the face of this policy, only one creed—the Nicene—could stand as a clear alternative. Between 360 and 380, the policies of Constantius and the rise of Heterousian theologies prompted a variety of groups to coalesce around the Nicene Creed as a standard of faith. Scholars now call these theologians pro-Nicene. This coalescing of different groups was made possible in part by the death of Constantius in 361. His sudden death and the antipathy of his successor Julian "the Apostate" towards Christianity meant that the Homoian creed never had the chance to gain a firm foothold.

The mystery of Three in One

This rapprochement between these previously opposing groups involved a slow and often difficult negotiation towards a shared sense of the core faith for which they agreed Nicaea would be a symbol. The theologies of Basil of Caesarea, Gregory of Nyssa, and Gregory of Nazianzus are three key examples of pro-Nicene theologies. So are the western theologies of Ambrose of Milan and Augustine of Hippo, and the theologies of the later Athanasius, Didymus the Blind, and Cyril of Alexandria.

Two key themes united pro-Nicene theologians. First, and most important, pro-Nicenes agreed that God's being was not divided, and that the persons of the Godhead were truly distinct from each other. Pro-Nicenes were prepared to accept a wide variety of terms for unity and distinction in God: what mattered was that God was undividedly one and yet irreducibly three. How this was so was a mystery. In this context it seemed much more possible to say that Father and Son were of one "essence" or "being" without implying that God was material or that Father and Son were "parts" of God.

This sense of the incomprehensible divine unity and distinction provided the context in which to understand the earlier Nicene insistence that the Son was eternally begotten of the Father. It was also the context in which they understood what it meant for the Spirit to proceed eternally from the Father and Son. These decades saw pro-Nicenes clearly state that the Spirit was one with Father and Son against those who still maintained earlier beliefs that the Spirit was subordinate to Father and Son (often understood as the greatest of the angels).

An important corollary of the divine unity was the doctrine of inseparable operation: all three persons are present in each and every divine action. While we easily attribute particular roles to each person, calling the Spirit "sanctifier" or the Son "redeemer," Gregory of Nyssa and Augustine showed how Scripture encourages us to speak of the persons in this way because of the weakness of our human intellects: we must realize that Scripture also tells us that in the divine unity God, Word, and Spirit all sanctify.

Second, pro-Nicenes emphasized that human beings would always fail to comprehend God and that one could only make progress towards knowledge and love of God through discipline and practices that would reshape the imagination. Increasingly, pro-Nicenes emphasized the importance of the joint purification of the soul and the body as a precondition for attention to the divine mystery. The fallen mind had lost its natural attention to God and become obsessed with material imagery.

This sense that the human intellect needed to be purified was the context for their understanding of Scripture as a divinely revealed and always trustworthy resource for the Christian imagination. Scripture resulted from a divine act of love: God spoke in human words, but of realities that lie beyond our comprehension. Recognition and exploration of the mystery at the heart of Christian faith is at the heart of pro-Nicene theology.

To Constantinople and beyond

In 381 the rapprochement of the previous two decades resulted, through the help of the pro-Nicene emperor Theodosius, in the Council of Constantinople. This council promulgated a revised version of Nicaea's creed that is still used by Christians today. The council added clauses on the Spirit to insist that "with the Father and the Son He is worshipped and glorified." Groups of non-Nicene Christians continued to be a real force within the Christian world through the next century, but increasingly they became distinct and isolated ecclesial groups. "Homoian" theology survived among many of the German tribes who came to rule over the western half of the Roman Empire but over the centuries that followed, even they gradually came to accept the Nicene faith.

Christians believe that in Christ the Word of God who is eternally one with the Father was at work. They believe that the Spirit who is one with Father and Son filled the earliest Christian community at Pentecost. Christians should also never forget that the Spirit is the Spirit of truth who dwells in the Christian community, leading it into truth (John 14: 17, 26). The story of the fourth century is one of the most important examples of this leading. The emergence of classical Trinitarian theology was a slow and complex process, the culmination of Christian reflection and argument that had begun at Pentecost. But we should not hide from the messiness of this process: it is always real human beings that the Spirit leads. Thus the faith of Nicaea is the true faith of Christians, but it was drawn out of the community's reading of Scripture not only by human effort but by the inspiration of the Spirit shaping and guiding, leading a real human community into the truth.

Lewis Ayres is assistant professor of historical theology at Emory University. He is the author of Nicaea and its Legacy (Oxford, 2004) and co-editor of The Cambridge History of Early Christian Literature (Cambridge, 2004).