The Ante-Nicene Fathers affirmed Christ’s deity and spoke of “Father, Son and Holy Spirit”, even though their language is not that of the traditional doctrine as formalised in the fourth century. Trinitarians view these as elements of the codified doctrine.[21] Ignatius of Antioch provides early support for the Trinity around 110,[22] exhorting obedience to “Christ, and to the Father, and to the Spirit”.[23] Justin Martyr (AD 100–c. 165) also writes, “in the name of God, the Father and Lord of the universe, and of our Saviour Jesus Christ, and of the Holy Spirit”.[24] The first of the early church fathers to be recorded using the word “Trinity” was Theophilus of Antioch writing in the late 2nd century. He defines the Trinity as God, His Word (Logos) and His Wisdom (Sophia)[25] in the context of a discussion of the first three days of creation. The first defence of the doctrine of the Trinity was in the early 3rd century by the early church father Tertullian. He explicitly defined the Trinity as Father, Son, and Holy Spirit and defended the Trinitarian theology against the “Praxean” heresy.[26]
Although there is much debate as to whether the beliefs of the Apostles were merely articulated and explained in the Trinitarian Creeds,[27] or were corrupted and replaced with new beliefs,[28][29] all scholars recognize that the Creeds themselves were created in reaction to disagreements over the nature of the Father, Son, and Holy Spirit. These controversies, however, were great and many, and took some centuries to be resolved.
Of these controversies, the most significant developments were articulated in the first four centuries by the Church Fathers[27] in reaction to Adoptionism, Sabellianism, and Arianism. Adoptionism was the belief that Jesus was an ordinary man, born of Joseph and Mary, who became the Christ and Son of God at his baptism. In 269, the Synods of Antioch condemned Paul of Samosata for his Adoptionist theology, and also condemned the term homoousios (ὁμοούσιος, “of the same being”) in the sense he used it.[30]
Sabellianism taught that the Father, the Son, and the Holy Spirit are essentially one and the same, the difference being simply verbal, describing different aspects or roles of a single being.[31] For this view Sabellius was excommunicated for heresy in Rome c. 220.
In the fourth century, Arianism, as traditionally understood,[note 1] taught that the Father existed prior to the Son who was not, by nature, God but rather a changeable creature who was granted the dignity of becoming “Son of God”.[32] In 325, the Council of Nicaea adopted the Nicene Creed which described Christ as “God of God, Light of Light, very God of very God, begotten, not made, being of one substance with the Father”. The creed used the term homoousios (of one substance) to define the relationship between the Father and the Son. After more than fifty years of debate, homoousios was recognised as the hallmark of orthodoxy, and was further developed into the formula of “three persons, one being”.
Athanasius, who was present at the Council as one of the Bishop of Alexandria’s assistants, stated that the bishops were forced to use this terminology, which is not found in Scripture, because the biblical phrases that they would have preferred to use were claimed by the Arians to be capable of being interpreted in what the bishops considered to be a heretical sense.[33] Moreover, the meanings of “ousia” and “hypostasis” overlapped then, so that “hypostasis” for some meant “essence” and for others “person”. Athanasius of Alexandria (293–373) helped to separate the terms.[34]
The Confession of the Council of Nicaea said little about the Holy Spirit.[35] The doctrine of the divinity and personality of the Holy Spirit was developed by Athanasius in the last decades of his life.[36] He defended and refined the Nicene formula.[35] By the end of the 4th century, under the leadership of Basil of Caesarea, Gregory of Nyssa, and Gregory of Nazianzus (the Cappadocian Fathers), the doctrine had reached substantially its current form.[35]