How did the Nicene Creed come about?
In AD 325, 12 years after Christianity had become a “tolerated religion” in the Roman Empire, Emperor Constantine convoked and presided over the First Council of Nicaea (modern-day Izmir, Turkey). The council addressed several urgent issues, especially the need to clarify the relationship of Jesus Christ to God the Father. In answer to a teaching of an Egyptian priest named Arius, an existing creed was adapted to proclaim Jesus as homoousios (“consubstantial” or “sharing the same substance”) with God the Father. This established a principle that the Church would use later: A doctrinal teaching can employ non-scriptural terms when legitimate authority judges them needed and consistent with the faith.
At the First Council of Constantinople in AD 381, the last section about the Holy Spirit was added. Five centuries later, the Church in the West added the term filioque (and of the Son) to describe the procession of the Holy Spirit from God the Father and God the Son. This was not accepted in the East, not so much because it was not believed but because Christians there said the West had no authority to unilaterally change the Nicene Creed. At the Mass/Divine Liturgy referenced in the question and answer above, the filioque was not part of the Nicene Creed proclaimed there.
The first pastoral journey of Pope Leo XIV will be to Turkey to mark the 1,700th anniversary of the Nicene Creed. On June 7, 2025, when he addressed the symposium “Nicaea and the Church of the Third Millennium: Towards Catholic-Orthodox Unity,” Pope Leo XIV said: “The Council of Nicaea is not merely an event of the past but a compass that must continue to guide us towards the full visible unity of Christians. . . . [It is] not simply one council among the others but the first in a series, the council par excellence, which promulgated the norm of the Christian faith, the confession of faith of the 318 Fathers.”
On July 17, Pope Leo addressed an Orthodox-Catholic ecumenical pilgrimage from the United States, saying, “Your pilgrimage is one of the abundant fruits of the ecumenical movement aimed at restoring full unity among all Christ’s disciples in accordance with the Lord’s prayer at the Last Supper, when Jesus said ‘that they may be one’ (Jn 17:21).” The pilgrimage group went on to visit Patriarch Batholomew in Istanbul.
