Neoplatonism was a prevalent philosophy within the Roman Empire that Christian theologians used along with Aristotelianism to develop their understandings of the gospel. A key assumption of both philosophies was that the divine is immutable. As the divine was thought to be perfect it was understood to be unchangeable, existing in eternity beyond the fluctuations of history. This notion of divinity underlay what is known as the Arian controversy, named after Arius, whose teachings helped instigate it. Theologians on both sides of this controversy assumed God to be immutable. Arians argued that Jesus who suffered on the cross could not be fully divine because the divine was unchanging and so could not “become” something. The Word that became incarnate in Jesus was therefore a lesser god,44 created by a higher and greater divinity that was unchanging and fully divine. The Word mediated between this fully divine God and creation but did not share God’s nature.45 Athanasius’ contrary argument was based on the same premise but determined by soteriological concerns. Only God whose existence is unchanging and beyond the power of sin and death is able to save humanity from these. In order for Jesus to save he must share this divine nature. For Athanasius, only if human nature is assumed by the radically transcendent God through the Logos becoming incarnate in Jesus is humanity saved from sin and death. Therefore Jesus as the mediator of salvation could not be a lesser divinity, but must be fully divine, one with the God whom Jesus called “Father” in John’s Gospel, where the two are said to be one (John 10:30).
The New Testament could not be decisive in this debate because it was a source for both sides. Resolving this question of the nature of Jesus’ person and relationship to God involved developing doctrine that went beyond explicit statements of Scripture. The Arian debate was not about what the Bible said but about how its witness should be interpreted.46 This question became pressing partly because the notion of divine immutability was so deeply embedded in Hellenistic thought and culture.47 The biblical witness describes God as absolute and immutable. But it also describes God as living and, to a certain extent, internally related to creation.48 Understanding these two affirmations in a coherent way is one of the greatest challenges of Christian theology. In the Arian debate both sides were sure that God was absolute and unchanging. But if Jesus was fully divine, God also has to be understood as living and able to act in new ways. The way the church found to understand God as both living and absolute was the doctrine of the Trinity. It was the experience of salvation mediated through Jesus Christ and a sense of God’s radical transcendence that compelled the church to understand God in this way.
The Arian controversy that led to the council of Nicaea began about the year 318, when a priest named Arius objected to the teachings of his bishop Alexander that the Son was always with and eternally generated from the Father.49 At this time there was no consensus or explicit church teaching on what was orthodox in this regard. Arius’ dispute with his bishop “ignited a fire waiting to happen.”50 It began a wide-ranging controversy involving church polity as well as doctrine. Bishops lined up for or against Arius and his teaching. Lay people became caught up in the debate. In its later stages Gregory of Nyssa complained about the extent of this.
If you ask for change, the man launches into a theological discussion about begotten and unbegotten; if you enquire about the price of bread, the answer is given that the Father is greater and the Son subordinate; if you remark that the bath is nice the man pronounces that the Son is from non-existence.51
These were issues that moved church members and so concerned the Emperor.
In order to restore unity to the church Constantine convened the council of Nicaea in 325, which he paid for and presided over. Between 250 and 300 bishops attended, most from the Eastern church.52 The results of their meeting can be summarized as follows:
The council issued a creed which said that the Son was generated “from the essence of the Father” and was hence “homoousios” (the same thing or being or essence) with the Father. The creed also condemned anyone who said that the Son was from an ousia or hypostasis other than that of the Father. Arius was condemned and exiled.53
Arius himself soon ceased to be important to the controversy, which continued until shortly before the council of Constantinople in 381.54 Part of the reason it went on so long was that theologians were developing technical terms like hypostasis and homoousios to conceptualize Jesus’ relationship to God. In effect, they were developing a new understanding of God under the impact of Christology. The result was the doctrine of the Trinity affirmed at Nicaea, but only subsequently conceptualized more fully by the Cappadocians55 in the East and Augustine in the West.
The doctrine of the Trinity affirmed at Nicaea expresses the otherness and freedom of God in relation to creation.56 God is not an aspect of the universe or even its highest element. Rather, God is able to become present in history in a new way, and in so doing bring the promise of a future beyond the limits of created life as presently experienced. The doctrine as eventually worked out by Augustine and the Cappadocians affirms that God is one in nature (ousia) but exists in three persons (hypostasis). The affirmation that Jesus was of one nature, homoousios with the first person of the Trinity meant that the divine being was essentially and eternally Trinitarian. Tertullian and others had understood God as Trinitarian in terms of God’s relationship to history. But Nicaea pushed beyond this to affirm that God was Trinitarian in eternity, before and apart from creation. This remarkable innovation in church teaching57 led to the development of a distinction between the immanent Trinity, God in eternity apart from creation, and the economic Trinity, God as revealed and active in history.58 This problematic but important distinction helped the church understand how God could be living, involved in history, and radically transcendent to it. The affirmation of the Trinitarian nature of God at the council of Nicaea was in effect a new beginning that came to provide the framework for Christian understanding of God and Jesus Christ in centuries to come.59
From Nicaea to Chalcedon
The council of Nicaea did not end the Arian controversy. Decades of debate and polemic followed until roughly 360,60 although Arianism continued to be present in the church long afterwards and still is today. However, after 360 the focus of controversy shifted from Jesus’ relationship to God to the nature of Jesus’ person. The questions now became, given that Jesus was fully divine, was he also fully human and if so to what extent, and how were his human and divine natures related? Disputes over these questions led to the council of Chalcedon in 451 and continued afterwards.61
These issues first surfaced at the synod of Alexandria of 362 in connection with the Christology of Apollinaris.62