If you were to ask an impartial observer, “what do Christians believe about God?” his best answer would be a recitation of the Nicene Creed. And if you were to reduce the Nicene Creed to its essence, it would be the affirmation of God’s Trinitarian reality. This creedal affirmation of the Trinity is a point of unity for most Protestants, Anglicans, Orthodox believers, Assyrians, and Roman Catholics. It is therefore of central importance for all Christians.
While it’s named after the AD 325 Council of Nicaea, the creed as we know it today is actually a product of long historical development. Its propositions originate in the baptism rites of the Apostolic Era, in which the newly baptized affirmed their faith in the Father, the Son, and the Holy Spirit—the baptism formula itself of the Trinity. The act of baptism and the confession of the Trinity were therefore united. While belief in the Trinity is clear in these very early sources, the theology of the Trinity developed over time as Christians meditated upon the life of Christ and the nature of God.
In the late third century, an Alexandrian presbyter named Arius advanced a theory of the Trinity that suggested a Christ created by the Father. This theology was accepted by many as a possible solution to the seeming paradox of God’s three personalities. It was in response to Arianism that the Council of Nicaea was called in 325 and the first iteration of the creed agreed to. This formulation focused on the divine, uncreated nature of Christ, and it only briefly mentioned belief in the Holy Spirit. However, in 381 at the Council of Constantinople, the assembled fathers not only sought to confirm the condemnation of Arianism, but were forced to deal with a new heresy known as Macedonianism. The Macedonians denied the divine nature of the Holy Spirit. In response, the fathers emphasized Christ’s divinity and his humanity and added the propositions dealing with the Holy Spirit and his action in the world through the Church; with this development, the creed as it continues to be recited in the East was born.
In the West, however, the Nicene creed was not done developing. Arianism was alive and well among the Germanic tribes that had advanced into the crumbling Roman Empire. In response, orthodox theologians in the Latin church emphasized the common patristic doctrine that the Holy Spirit proceeded from the Father and the Son: ex Patre Filioque procedit. The clause was added to the Nicene Creed in 589 in Visigothic Spain, and Charlemagne, the emperor in the West after 800, adopted this form. It spread slowly through the Latin church—the filioque was not finally accepted in Rome until the eleventh century. With the addition of this clause, the Nicene Creed as it is generally known in the West came into its final form.
From beginning to end, the creed’s concern is the Trinitarian reality of God and the dual natures of Christ, and it is these doctrines that form the fundamental agreement between Christians. Christians’ shared assent to the Nicene Creed is a testament to its profound subtlety and insight. The Nicene Creed, the common patrimony of all Christians, is one of the most important creations of Church history. You can read more about this fascinating history in the Early Church Fathers series, Historic Creeds and Confessions, The Apostles’ Creed, and Creeds, Councils and Controversies.