From the beginning of his election as the successor to St. Peter, Pope Leo XIV has summoned the Church to a renewed faith in the one Savior. As he said emphatically in the opening Mass of his pontificate, in words he desired to address to the entire world: “Look to Christ! Come closer to him! Welcome his word that enlightens and consoles!”

This call to a vibrant profession of faith takes on a special meaning in light of the 1,700th anniversary of a key milestone in the Church’s journey: the Council of Nicaea, which took place from May to July of the year 325.

Each Sunday, in reciting the Nicene Creed, the Church echoes the decisive statement of belief made at Nicaea. While the cultural and theological circumstances have greatly changed, this first ecumenical council continues to serve as a point of reference for Christians as we seek to give expression to our faith in today’s world.

Recalling the history of this assembly can remind us of a principle which, by Divine Providence, has repeated itself throughout the life of the Church. That principle is that doctrinal errors can serve as an opportunity for the Church to articulate the truth more clearly and profoundly.

In this case, the originator of the error was a priest of the Church of Alexandria, Arius, who stirred great controversy in the Eastern portion of the Roman Empire with his teaching about Christ. The city of Alexandria was at the time an important center of Christian learning which witnessed the interaction of Greek philosophy, in particular Plato, with Christian revelation.

Such a coming together of classical learning and revealed truth was not a straightforward process. In the case of Arius, it led to a teaching that was deeply at odds with the teaching of the New Testament. In keeping with the theological bent of his city, Arius placed strong emphasis on the transcendence of God. For him, God would be God the Father, for whom he had a keen appreciation as the “unbegotten.” The New Testament signals clearly that God the Son, by contrast, has been begotten by Father (John 3:16).

For Arius, this distinct role of the Son would mean that he is less than God, or, as he wrote in a letter to Bishop Alexander of Alexandria, that the Word is “not eternal, nor co-eternal with the Father, nor uncreated like the Father … for it is from the Father that he has received life and being.”

The position has a certain appearance of logic and seems to protect the transcendence of God. The New Testament does indeed speak of a certain priority of the Father with regard to the Son. Such characteristics no doubt contributed to the immense popularity of Arius’ position, even long after it was condemned at Nicaea.

Nonetheless, Arius’ theological assertions went profoundly against a core teaching of the New Testament. Christ’s revelation challenges reason with the truth of the second divine person of the Trinity, who is indeed begotten of the Father and yet at the same time has existed in the divine life of the Trinity from all eternity (John 1:1-2).

St. Alexander soon came to recognize the problems of Arius’ thought. He summoned a council in the city that condemned Arius’ doctrine and excommunicated him and his followers. Arius, refusing to accept the judgment of his bishop, proceeded to spread his teaching throughout the Roman Empire and won support from several influential bishops.

In the face of such discord, Emperor Constantine summoned the Church to a general council at Nicaea — in present-day Turkey — with the aim of bringing peace and unity to his realm. While the assembly was open to bishops across the empire, almost all of the more than 300 bishops who attended were from the Eastern portion of Constantine’s domain. Hosius of Cordova, a Spanish bishop, presided at the council and is thought to have done so in the name of Pope St. Sylvester I, who also sent two Roman priests to represent him.

While some of the bishops desired to hold to strictly biblical language, the council would come to take the baptismal creed proposed by Eusebius of Caesarea as the basis for its doctrinal definition. This profession acknowledged Christ as “God of God, Light and Light.”

In the face of the Arian heresy, the council fathers felt that they needed to go still further, and they added the specific affirmation Christ is “true God from true God, begotten not made, ‘of one substance’ (Greek homoousios ) with the Father.” While the word homoousios used in relation to the Son was well known during the previous century, Nicaea would make the word a defining characteristic of authentic faith in Christ.

With this Greek term, Nicaea took a new step in the history of Christian teaching by expressing the revealed mystery of Jesus Christ in the language of Greek philosophy. Such a formulation did not imply a subordination of God’s revelation to human knowledge. Rather, at Nicaea the Church made use of reason in a bold new way to express the revealed mystery in the face of a very serious misunderstanding.

Nicaea’s use of the phrase “of one substance,” as Cardinal Joseph Ratzinger comments , “adds nothing to the New Testament,” but rather defends the “literal meaning” of what the word ‘Son’ means in relation to Christ.

The profession of faith made at Nicaea would by no means bring an end to the Arian crisis. Several decades would still pass before the Church could more precisely formulate its teaching about Jesus Christ and the Trinity. Nonetheless, the first Ecumenical Council opened up a path in the elaboration of doctrine which has become crucial in the course of history.

Over time, the Church has continued to state its belief in new ways and grow in its knowledge of revealed truth, making use of all the resources of human learning. At the same time, the Church also takes care to discern and at times purify human knowledge, so that it might more fully express supernatural truths.

In this process the bishops of the world, and in particular the Roman pontiff, play an authoritative role. The Council of Nicaea reminds us of the essential role that the bishops — the successors of the Apostles — carry out, in union with the bishop of Rome, in professing the Church’s faith in each moment of history.

Language, society and culture undergo transformation over time. Still, the People of God make use of such mutable elements to express the unchanging truth that Jesus Christ is perfect God and perfect man.

Looking back at Nicaea, 1,700 years later, can renew us in the confidence that the Holy Spirit will help us to continue to communicate the same truth in a way that resonates with men and women today, and which at the same remains faithful to the sublime mystery that God has revealed.