What is the Trinity? Part II

History behind the doctrine:

The doctrine of the Trinity was formally developed in the early church in reaction to errant teaching on the nature of God as found in Arianism. Arianism attempted to protect monotheism (the belief in one God) by denying the full deity of Jesus, a belief most Christians held at this time. Arianism taught that Jesus was divine, but that he was a lesser deity than the Father. To affirm the Church’s stance on the nature of God, the Trinity was formally stated in the Nicene Creed (325 A.D.) and the later Athanasian Creed. As a result of these early ecumenical creeds, any departure from the Christian doctrine of the Trinity was considered heresy. These creeds affirm the early Christian conviction that Jesus was God. Arianism caused the church to dogmatically affirm what was already believed and inherent to the earliest of Christian theology.

The term “Trinity”, is not found in the Bible. Theophilus of Antioch around 180 A.D. first used the Greek term trias (a set of three) in reference to God, his Word, and his Wisdom. However,Tertullian in 215 A.D. was the first one to state this doctrine using the Latin term, Trinitas (Trinity), referring to the Father, Son, and Holy Spirit

W. Fulton in the Encyclopedia of Religion and Ethics.