Irenaeus and Nicene Language
The Council of Nicaea’s debate and solution regarding the nature of Christ and the problem of the Trinity was not a novel discussion for the church. From as early as the mid to late 2nd century, heretical groups had already begun to espouse new teachings regarding the Godhead and the person of Christ. These false teachings required a response from church leaders as to what the apostolic teaching on these matters were. The response of these church leaders to the heretics helped provide a framework for the leaders at Nicaea to formulate their creed as to the orthodox teaching of the Godhead and the nature of Christ. One of the major leaders that helped provide the language used by the council was Irenaeus. A pupil of the Apostolic Father Polycarp and influenced by Justin Martyr, Irenaeus serves as a bridge between early Greek theology and Western Latin theology which is usually traced back to his contemporary, Tertullian. Irenaeus, in his magnum opus, Against Heresies, sought to undermine the Gnostics. Though there was a vast variance of belief within Gnostic thinking, prominent and universal views among them included: 1) The God of the Old Testament was evil, 2) a denial of the incarnation of Christ, 3) a belief that all material was evil, and 4) that ultimate salvation was to liberate the good immaterial from the evil material through a special knowledge (gnosis). In his work, Irenaeus refuted the Gnostic teaching by putting forth a “Rule of Faith,” which he taught had been the consistent teaching handed down from the Apostles and preserved by the church, much of his teaching would not only serve as the basis of the Apostle’s Creed, but also the Nicene Creed. Irenaeus, taught that there was one God, “Father and almighty Maker of heaven and earth, and one Christ Jesus who was made flesh for our salvation.” Irenaeus’ recapitulation theory which expounded on the nature of Christ served as a great basis for Nicene teaching. Irenaeus taught that Jesus, the preexistent Word, was truly God and truly man, and summed up in himself the whole sequence of mankind, sanctifying it and inaugurating a new, redeemed human race which he would serve the new head over. Irenaeus’ teaching on Christ and the Godhead was vital in developing Nicene language, but he was not the sole influence on Nicaea.
The Role of Tertullian, Origen, and Philosophical Language
Tertullian, the father of Latin theology was another important voice that contributed to Nicene language. Tertullian’s pre-Nicene Trinitarian thinking was, like Irenaeus, the response to false teaching that was creeping into the church. Tertullian’s Trinitarian thinking arose against the teaching of Monarchianism. This teaching was basically a form of adoptionism that was Unitarian and taught that Christ was only a mere man who had had the Spirit of God descend upon him. Tertullian sought to show the Monarchians that the unity of God was compatible with the threeness of the economy of the God. Tertullian was the first to use the Latin Trinitas, in Christian literature. The teachings of Tertullian were vital for the Nicene language of homoousia against Arias’ homoiousia. Tertullian taught that the Father, Son, and Spirit are one in substance (substantia), and that the threeness involved only grade or aspect of these persons (persona) of the one substance. 
Origen was another theologian who utilized language that was key in outlining the Nicene position. Origen building on Tertullian, was able to aptly utilize philosophical language and categories to help describe the triune nature of God. Origen held God to be transcendent in a manner combining both Platonic and Aristotelian philosophy. Unlike Irenaeus and Tertullian, Origen believed that though Orthodoxy is established and grounded in the apostolic teaching, informed Christians could go further through the use of philosophical thinking. Origen taught that God was separate from his creation, and was pure Spirit. The Son who was the eternal Logos, was begotten by God not in an act of time or as an event, rather Origin taught that this begetting of the Son is an eternal constant by the Father, and though he eternally flows from the Father (eternal generation), the Son exists as a distinct being (hypostasis) from the Father. Though Origen primarily focused on the Son and the Father, he also taught the deity and separate personality of the Spirit, as the one who inspired all prophetic and apostolic revelation. This teaching on the Spirit is echoed in the Nicene Creed as the “one who spoke through the prophets.” Origen’s use of philosophical categories to describe the difference between being and becoming were vital in outlining the eternal and coexisting nature of the Trinity.
It is clear to see from just these examples noted above that the teaching of the Trinity and the divine nature of Christ were not novel to Nicaea. A framework of teaching had already begun to be articulated from early fathers like Irenaeus through Tertullian on to Origen, Gregory of Nazianzus, and then clearly outlined in the Nicene Creed. Philosophy played a part in Tertullian’s thinking regarding categories of substance and persons, while ultimately its use was heightened even more with Origen and his distinction between being and becoming. Nevertheless, the most important source for the church father’s understanding of the godhead and the nature of Christ was the final rule of faith, the apostolic teaching, the Holy Scriptures. Though none of the men noted provided a fully developed teaching of the Godhead, their teachings provided a framework and the language necessary for the Nicene council to fully articulate.
 Tony, Lane, A Concise History of Christian Thought, revised ed., (Grand Rapids, MI: Baker Academic, 2006), 12.
 Roger E. Olsen, The Story of Christian Theology: Twenty Centuries of Tradition & Reform, (Downers Grove, IL: Intervarsity Press, 1999), 69.
 Irenaeus, Against Heresies 1.10.1
 Leo Donald Davis, The First Seven Ecumenical Councils (325-787): Their History and Theology, (Collegeville, MN: The Liturgical Press, 1983), 39.
 William G. Rusch, ed., The Trinitarian Controversy, (Philadelphia, PA: Fortress Press, 1980), 8.
 Rusch, 10.
 Stuart G. Hall, Doctrine and Practice in the Early Church, (Grand Rapids, MI: Eerdman’s, 1991), 105.
 Lane, 23.
 Hall, 105-106.