On November 23rd, Pope Leo XIV announced the publication of an Apostolic Letter entitled "In unitate Fidei," dedicated to the commemoration of the Council of Nicaea. This document is part of the preparations for his trip to Türkiye and at Lebanonscheduled from November 27 to December 3, where he will take part in an ecumenical celebration commemorating this Council. Here is the official translation in French.
Apostolic Exhortation In unitate fidei Pope Leo XIV's statement on the commemoration of the Council of Nicaea
1. In the unity of faith, proclaimed since the origins of the Church, Christians are called to walk together, lovingly and joyfully preserving and passing on the gift received. This is expressed in the words of the Creed: “We believe in Jesus Christ, the only Son of God, who came down from heaven for our salvation,” formulated by the Council of Nicaea, the first ecumenical event in the history of the Christianity, 1700 years ago.
As I prepare to undertake my apostolic journey in TürkiyeThrough this Letter, I wish to encourage throughout the Church a renewed zeal in the profession of faith, the truth of which, for centuries, has constituted the common heritage of Christians and deserves to be confessed and explored in ever-new and relevant ways. In this regard, a valuable document from the International Theological Commission has been approved: Jesus Christ, Son of God, Savior. The 1700th anniversary of the Ecumenical Council of Nicaea. I refer to it because it offers useful perspectives for deepening the importance and relevance not only theological and ecclesial, but also cultural and social of the Council of Nicaea.
2. «The beginning of the gospel of Jesus Christ, the Son of God.» This is how Saint Mark titles his Gospel, thus summarizing his entire message under the sign of the divine sonship of Jesus Christ. In the same way, the Apostle Paul knows that he is called to proclaim the Gospel of God about his Son who died and rose again for us (cf. Rm 1, 9), which is God's definitive “yes” to the promises of the prophets (cf. 2 Co 1, 19-20). In Jesus Christ, the Word who was God before time and through whom all things were made – as the prologue of the Gospel of Saint John says – «became flesh and dwelt among us» (John 1, 14). In Him, God has become our neighbor, so that whatever we do to each of our brothers, we do to Him (cf. Mt 25, 40).
It is therefore a providential coincidence that, in this Holy Year dedicated to our hope in Christ, we also celebrate the 1700th anniversary of the First Ecumenical Council of Nicaea, which in 325 proclaimed the profession of faith in Jesus Christ, the Son of God. This is the heart of the Christian faith. Today, in the Sunday Eucharistic celebration, we still pronounce the Nicene-Constantinopolitan Creed, the profession of faith that unites all ChristiansThis gives us hope in the difficult times we are living through, amidst numerous fears and concerns, threats of war and violence, natural disasters, grave injustices and imbalances, of hunger and the misery suffered by millions of our brothers and sisters.
3. The times of the Council of Nicaea were no less troubled. When it reopened in 325, the wounds of the persecutions against Christians were still alive. The Edict of Milan (313), promulgated by the two emperors Constantine and Licinius, heralded the dawn of a new era of peace. However, disputes and conflicts quickly emerged within the Church following external threats.
Arius, a priest from Alexandria in Egypt, taught that Jesus was not truly the Son of God, although he was not merely a creature; he was an intermediary being between the inaccessible God and us. Furthermore, there was supposedly a time when the Son “did not exist.” This aligned with the prevailing mentality of the time and therefore seemed plausible.
But God does not abandon his Church; he always raises up courageous men and women, witnesses of the faith and pastors who guide his people and show them the way of the Gospel. Bishop Alexander of Alexandria realized that Arius's teachings were not at all in accordance with Holy Scripture. Since Arius was not conciliatory, Alexander convened the bishops of Egypt and Libya for a synod that condemned Arius's teachings; he then sent a letter to the other bishops of the East informing them in detail. In the West, Bishop Osio of Cordoba, Spain, who had already proven himself a fervent confessor of the faith during the persecution under Emperor Maximian and enjoyed the confidence of the Bishop of Rome, Pope Sylvester, mobilized.
But Arius's supporters also rallied to his side. This led to one of the greatest crises in the history of the Church in the first millennium. The reason for the dispute was not, in fact, a minor detail. It concerned the very heart of the Christian faith, namely, the answer to the crucial question that Jesus had posed to his disciples at Caesarea Philippi: "But who do you say I am?"Mt 16, 15).
4. As the controversy raged, Emperor Constantine realized that the unity of the Empire was threatened along with the unity of the Church. He therefore summoned all the bishops to an ecumenical, that is, universal, council in Nicaea to restore unity. The synod, known as the “Synod of the 318 Fathers,” was presided over by the emperor. The number of bishops assembled was unprecedented. Some of them still bore the marks of the tortures they had suffered during the persecution. The vast majority of them came from the East, while it appears that only five were from the West. Pope Sylvester confided in the theologically influential Bishop Osio of Cordoba, and he sent two Roman priests.
5. The Fathers of the Council bore witness to their fidelity to Sacred Scripture and to the Apostolic Tradition, as professed at baptism according to the mandate of Jesus: «Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit» (Mt 28, 19). In the West, several formulas existed, among them the Apostles' Creed.[1] In the East as well, there were many baptismal professions, similar in their structures. These were not learned and complicated languages, but rather – as will be said later – a simple language, understandable to the fishermen of the Sea of Galilee.
On this basis, the Nicene Creed began by professing: «We believe in only one God, Almighty Father, creator of all beings visible and invisible.[2] The Council Fathers thus expressed their faith in the one and only God. At the Council, there was no controversy on this point. However, a second article was discussed, which also used biblical language to profess faith in "« only one »Lord, Jesus Christ, Son of God.“ The debate stemmed from the need to address the question raised by Arius regarding the understanding of the expression ”Son of God“ and how it could be reconciled with biblical monotheism. The Council was thus called upon to define the correct meaning of faith in Jesus as ”the Son of God.”.
The Fathers confessed that Jesus is the Son of God insofar as he is "« of the substance (ousia) of the Father […] begotten, not created, of the same substance (homoousios) than the Father.» This definition radically rejected Arius’s thesis.[3] To express the truth of the faith, the Council used two words, «substance» (ousia) and "of the same substance" (homoousios), which are not found in Scripture. In doing so, he did not intend to replace biblical affirmations with Greek philosophy. On the contrary, the Council used these terms to clearly affirm the biblical faith, distinguishing it from the Hellenizing error of Arius. The accusation of Hellenization, therefore, does not apply to the Fathers of Nicaea, but to the false doctrine of Arius and his followers.
On a positive note, the Fathers of Nicaea sought to remain firmly faithful to biblical monotheism and the reality of the Incarnation. They wanted to reaffirm that the one true God is not distant from us, inaccessible, but on the contrary, that he has drawn near to us and come to meet us in Jesus Christ.
6. To express its message in the simple language of the Bible and the liturgy familiar to all the people of God, the Council takes up certain formulations from the baptismal profession: «God from God, light from light, true God from true God.» The Council then takes up the biblical metaphor of light: «God is light» (1 John 1, 5; cf. John 1, 4-5). Like the light that shines forth and communicates itself without weakening, so the Son is the reflection (apaugasma) of the glory of God and the image (character) of his being (ipostasi) (cf. Hey 1, 3 ; 2 Co 4, 4). The incarnate Son, Jesus, is therefore the light of the world and of life (cf. John 8, 12). Through baptism, the eyes of our heart are enlightened (cf. Ep 1, 18), so that we too may be light in the world (cf. Mt 5, 14).
Finally, the Creed affirms that the Son is "true God, born of true God." In several places, the Bible distinguishes dead idols from the true and living God. The true God is the God who speaks and acts in the history of salvation: the God of Abraham, Isaac, and Jacob, who revealed himself to Moses in the burning bush (cf. Ex 3, 14), the God who sees the misery of the people, listens to their cry, guides them and accompanies them through the desert with the pillar of fire (cf. Ex 13, 21), speaks to him in a thundering voice (cf. Dt 5, 26) and has compassion on him (cf. Bone 11, 8-9). The Christian is therefore called to convert from dead idols to the living and true God (cf. Ac 12, 25 ; 1 Th 1, 9). It was in this sense that Simon Peter confessed at Caesarea Philippi: "You are the Christ, the Son of the living God" (Mt 16, 16).
7. The Nicene Creed does not formulate a philosophical theory. It professes faith in God who redeemed us through Jesus Christ. This is the living God: He wants us to have life and to have it in abundance (cf. John 10, 10). This is why the Creed continues with the words of the baptismal profession: the Son of God, who «for us men and for our salvation came down, was incarnate and became man, died, rose again on the third day, ascended into heaven and will come to judge the living and the dead.» This clearly shows that the Christological affirmations of the Council are part of the history of salvation between God and his creatures.
Saint Athanasius, who had participated in the Council as a deacon to Bishop Alexander and succeeded him as Bishop of Alexandria in Egypt, repeatedly and forcefully emphasized the soteriological dimension expressed by the Nicene Creed. He wrote, in fact, that the Son, descending from heaven, «made us children of the Father and, becoming man himself, divinized men. He did not become God from the man he was, but from the God he was, he became man to divinize us.».[4] This is only possible if the Son is truly God: no mortal being can, in fact, conquer death and save us; only God can do this. It is He who has freed us in his Son made man so that we might be free (cf. Ga 5, 1).
It is important to emphasize, in the Nicene Creed, the verb descended, «he came down.» Saint Paul describes this movement with strong expressions: «[Christ] emptied himself, taking the form of a servant, and becoming like men» (Phil 2, 7). As the prologue to the Gospel of Saint John writes, "the Word became flesh and dwelt among us" (John 1, 14). That is why, teaches the Letter to the Hebrews“We do not have a high priest who is unable to sympathize with our weaknesses, but one who in every respect has been tempted in the same way, yet without sin” (Hey 4, 15). The day before his death, he humbled himself like a slave to wash the feet of his disciples (cf. John 13, 1-17). And it was only when he was able to put his fingers in the wound in the side of the risen Lord that the Apostle Thomas confessed: «My Lord and my God!» (John 20, 28).
It is precisely by virtue of his incarnation that we encounter the Lord in our brothers and sisters in need: "Truly I tell you, whatever you did for one of the least of these brothers and sisters of mine, you did for me" (Mt 25, 40). The Nicene Creed, therefore, does not speak to us of a distant, inaccessible, immobile God who rests in himself, but of a God close to us, who accompanies us on our journey along the paths of the world and in the darkest places on earth. His immensity is manifested in the fact that he makes himself small, that he divests himself of his infinite majesty to become our neighbor in the small and the poorThis fact revolutionized pagan and philosophical conceptions of God.
Another passage from the Nicene Creed is particularly revealing for us today. The biblical statement, “he took flesh,” is clarified by the addition of the word “man” after the word “incarnate.” Nicaea thus distances itself from the false doctrine that the Logos He would have taken a body only as an outer shell, but would not have taken the human soul endowed with intelligence and free will. On the contrary, he wants to affirm what the Council of Chalcedon (451) would explicitly declare: in Christ, God took and redeemed the whole human being, with body and soul. The Son of God became man – explains Saint Athanasius – so that we, human beings, might be divinized.[5] This luminous understanding of divine Revelation had been prepared by Saint Irenaeus of Lyons and Origen, and then developed with great richness in Eastern spirituality.
Divinization has nothing to do with the self-deification of man. On the contrary, divinization protects us from the primal temptation of wanting to be like God (cf. Gn 3, 5). What Christ is by nature, we become by grace. Through the work of redemption, God has not only restored our human dignity as the image of God, but He who created us in a marvelous way has made us partakers, in an even more admirable way, of his divine nature (cf. 2 P 1, 4).
Divinization is therefore true humanization. This is why human existence aims beyond itself, seeks beyond itself, desires beyond itself, and is restless until it finds rest in God.[6] Deus enim solus satiat, God alone satisfies man![7] Only God, in his infinity, can satisfy the infinite desire of the human heart; this is why the Son of God wanted to become our brother and our redeemer.
8. We have said that Nicaea clearly rejected the teachings of Arius. But Arius and his followers did not admit defeat. Emperor Constantine himself and his successors increasingly sided with the Arians. The term homoousios It became a bone of contention between the Nicene and anti-Nicene factions, thus triggering other serious conflicts. Saint Basil of Caesarea described the ensuing confusion with eloquent imagery, comparing it to a nighttime naval battle in a violent storm.,[8] while Saint Hilary testifies to the orthodoxy of the laity in relation to the Arianism of many bishops, recognizing that "the ears of the people are holier than the hearts of priests".[9]
The rock of the Nicene Creed was Saint Athanasius, irrepressible and steadfast in the faith. Although he was deposed and expelled from the episcopal see of Alexandria five times, he returned each time as bishop. Even in exile, he continued to guide God's people through his writings and letters. Like Moses, Athanasius would not be able to enter the promised land of peace ecclesial. This grace would be reserved for a new generation, known as the "Nicene Youth": in the East, the three Cappadocian Fathers, Saint Basil of Caesarea (c. 330-379), nicknamed "the Great," his brother Saint Gregory of Nyssa (335-394), and Basil's closest friend, Saint Gregory of Nazianzus (329/30-390). In the West, Saint Hilary of Poitiers (c. 315-367) and his disciple Saint Martin of Tours (c. 316-397) played an important role. Then, above all, Saint Ambrose of Milan (333-397) and Saint Augustine of Hippo (354-430).
The three Cappadocian Fathers, in particular, deserve credit for completing the formulation of the Nicene Creed, demonstrating that the Unity and Trinity in God are in no way contradictory. It was in this context that the article of faith concerning the Holy Spirit was formulated at the First Council of Constantinople in 381. Thus, the Creed, which has since been called the Nicene-Constantinopolitan Creed, states: «We believe in the Holy Spirit, the Lord, the giver of life, who proceeds from the Father. With the Father and the Son, he is worshiped and glorified, and he spoke through the prophets.».[10]
Since the Council of Chalcedon in 451, the Council of Constantinople has been recognized as ecumenical and the Nicene-Constantinopolitan Creed has been declared universally binding.[11] It therefore constitutes a link of unity between East and West. In the 16th century, the ecclesiastical communities stemming from the Reformation also preserved it. The Nicene-Constantinopolitan Creed is thus the common profession of all Christian traditions.
9. The path that led from Sacred Scripture to the Nicene Creed, then to its reception by Constantinople and Chalcedon, and even into the 16th and 21st centuries, has been long and linear. All of us, disciples of Jesus Christ, «in the name of the Father, and of the Son, and of the Holy Spirit,» are baptized, make the sign of the cross, and are blessed. We conclude each time the prayer of the psalms in the Liturgy of the Hours with «Glory to the Father, and to the Son, and to the Holy Spirit.» Liturgy and Christian life are thus firmly rooted in the Nicene-Constantinopolitan Creed: what we say with our mouths must come from the heart, to be witnessed in our lives. We must therefore ask ourselves: what is the state of the interior reception of the Creed today? Do we feel that it also applies to our current situation? Do we understand and live what we say every Sunday, and what does what we say mean for our lives?
10. The Nicene Creed begins by professing faith in God, the Almighty, Creator of heaven and earth. Today, for many, God and the question of God have almost no meaning in life. The Council Vatican He emphasized that Christians are at least partly responsible for this situation, because they do not bear witness to the true faith and hide the true face of God through lifestyles and actions far removed from the Gospel.[12] Wars have been waged, people have been killed, persecuted, and discriminated against in the name of God. Instead of proclaiming a merciful God, they spoke of a vengeful God who inspires terror and punishes.
The Nicene Creed thus invites us to an examination of conscience. What does God mean to me, and how do I bear witness to my faith in Him? Is the one and only God truly the Lord of life, or are there idols more important than God and His commandments? Is God for me the living God, close in every situation, the Father to whom I turn with filial trust? Is He the Creator to whom I owe all that I am and all that I have, the One whose traces I can find in every creature? Am I willing to share the earth's bounty, which belongs to all, justly and equitably? How do I treat creation, which is the work of His hands? Do I use it with reverence and gratitude, or do I exploit and destroy it, instead of preserving and cultivating it as the common home of humanity?[13]
11. At the heart of the Nicene-Constantinopolitan Creed is the profession of faith in Jesus Christ, our Lord and God. This is the core of our Christian life. That is why we commit ourselves to following Jesus as Master, companion, brother, and friend. But the Nicene Creed asks for more: it reminds us not to forget that Jesus Christ is Lord (Kyrios), the Son of the living God, who "for our salvation came down from heaven" and died "for us" on the cross, opening the way to a new life for us through his resurrection and ascension.
Indeed, the sequela The path of Jesus Christ is not a wide and comfortable path, but that path, often demanding, even painful, which always leads to life and salvation (cf. Mt 7, 13-14). The Acts of the Apostles talk about the new way (cf. Ac 19, 9.23; 22, 4.14-15.22), who is Jesus Christ (cf. John 14, 6): Following the Lord engages our steps on the way of the cross, which, through repentance, leads us to sanctification and divinization.[14]
If God loves us with all his being, then we must also love one another. We cannot love God whom we do not see, without also loving the brother and sister whom we do see (cf. 1 John 4, 20). Love of God without love of neighbor is hypocrisy; radical love for neighbor, especially love for enemies without love for God, is a heroism that overwhelms and oppresses us. Following Jesus, the ascent to God passes through descent and devotion to our brothers and sisters, especially the least, the poorest, the abandoned, and the marginalized. What we have done to the least of them, we have done to Christ (cf. Mt 25, 31-46). Faced with catastrophes, wars, and misery, we cannot bear witness to mercy God's mercy is shown to those who doubt Him only when they experience it through us. [15]
12. Finally, the Council of Nicaea remains relevant today because of its immense ecumenical value. In this respect, the achievement of the unity of all Christians was one of the main objectives of the last Council, Vatican II.[16] Exactly thirty years ago, Saint John Paul II continued and promoted the conciliar message in the encyclical Ut unum sint (May 25, 1995). Thus, with the great anniversary of the First Council of Nicaea, we also celebrate the anniversary of the first ecumenical encyclical. This can be considered a manifesto updating the ecumenical foundations laid by the Council of Nicaea.
Thank God, the ecumenical movement has achieved many results over the past sixty years. Even though full visible unity with the Orthodox and Oriental Orthodox Churches and with the ecclesial communities stemming from the Reformation has not yet been granted to us, ecumenical dialogue has led us, on the basis of the one baptism and the Nicene Creed
Constantinople, to recognize our brothers and sisters in Jesus Christ in the brothers and sisters of other Churches and ecclesial communities, and to rediscover the one and universal community of Christ's disciples throughout the world. Indeed, we share faith in one God, Father of all, we confess together the one Lord and true Son of God, Jesus Christ, and the one Holy Spirit, who inspires us and impels us toward full unity and a common witness to the Gospel. What unites us is truly far greater than what divides us![17] Thus, in a world divided and torn apart by numerous conflicts, the one universal Christian community can be a sign of peace and an instrument of reconciliation, contributing decisively to a global commitment to peace. Saint John Paul II reminded us in particular of the testimony of the many Christian martyrs coming from all Churches and ecclesial Communities: their memory unites us and encourages us to be witnesses and builders of peace in the world.
In order to carry out this ministry credibly, we must walk together to achieve unity and reconciliation among all ChristiansThe Nicene Creed can be the basis and benchmark for this journey. It offers us, in effect, a model of true unity within legitimate diversity. Unity in the Trinity, Trinity in Unity, because unity without multiplicity is tyranny, and multiplicity without unity is disintegration. The Trinitarian dynamic is not dualistic, like a au–au exclusive, but an engaging link, a and The Holy Spirit is the bond of unity that we worship with the Father and the Son. We must therefore leave behind theological controversies that have lost their purpose in order to acquire a common understanding and, even more importantly, a common prayer to the Holy Spirit, so that He may gather us all in one faith and one love.
This does not mean a return to the pre-division ecumenism, nor a mutual recognition of the status quo not the current diversity of Churches and ecclesial communities, but rather an ecumenism turned towards the future, of reconciliation through dialogue, of sharing our gifts and spiritual heritages. The restoration of unity between Christians It does not impoverish us; on the contrary, it enriches us. As in Nicaea, this goal will only be possible through a patient, long, and sometimes difficult path of listening and mutual acceptance. This is a theological challenge and, even more so, a spiritual one, requiring repentance and conversion from all. This is why we need a spiritual ecumenism of prayer, praise, and worship, as was the case in the Nicene-Constantinopolitan Creed.
Let us therefore invoke the Holy Spirit, so that he may accompany and guide us in this undertaking.
Holy Spirit of God, you guide believers on the path of history.
We thank you for inspiring the Symbols of Faith and for arousing them in our hearts joy to profess our salvation in Jesus Christ, Son of God, consubstantial with the Father. Without Him, we can do nothing.
You, eternal Spirit of God, from age to age, renew the faith of the Church. Help us to deepen it and always return to the essentials in order to proclaim it.
So that our witness in the world may not be inert, come, Holy Spirit, with your fire of grace, rekindle our faith, inflame us with hope, and set us ablaze with charity. Come, divine Comforter, you who are harmony, to unite the hearts and minds of believers. Come and grant us to taste the beauty of communion.
Come, Love of the Father and the Son, to gather us into the one flock of Christ. Show us the paths to follow, so that, through your wisdom, we may become once again what we are in Christ: one, so that the world may believe. Amen.
Of Vatican, November 23, 2025, Solemnity of Our Lord Jesus Christ King of the Universe.
LEO PP. XIV
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[1] LH Westra, The Apostles' Creed. Origin, History and Some Early Commentaries, Turnhout 2002 (= Instrumenta patristica and mediaevalia, 43).
[2] First Nicaea, Exposio fidei: CC COGD 1, Turnhout 2006, 196-8. [3] Saint Athanasius of Alexandria, Contra arianos, I, 9, 2 (ed. Metzler, Athanasius Werke, I/1,2, Berlin – New York 1998, 117-118). According to the statements of Saint Athanasius in the Contra Arianos I, 9, it is clear that homoousios does not mean "of the same substance," but "of the same substance" as the Father; therefore, it is not a question of equality of substance, but of an identity of substance between the Father and the Son. The Latin translation of homoousios Therefore, he rightly speaks of unius substantiae cum Patre. [4] Saint Athanasius of Alexandria, Contra arianos, I, 38, 7 – 39, 1: ed. Metzler, Athanasius Werke, I/1,2, 148-149.
[5]Cf. St. Athanasius of Alexandria, De incarnatione Verbi, 54, 3: SCh 199, Paris 2000, 458; id., Contra arianos, I, 39; 42; 45; II, 59ff.: ed. Metzler, Athanasius Werke, I/1,2, 149; 152, 154-155 and 235ff.
[6] Cf. St. Augustine, Confessions, I, 1: CCSL 27, Turnhout 1981, 1.
[7] St. Thomas Aquinas, In Symbolum Apostolorum, art. 12: ed. Spiazzi, Thomae Aquinatis, Opuscula theologica, II, Taurini – Romae 1954, 217.
[8] Cf. St. Basil of Caesarea, De Spiritu Sancto, 30, 76: SCh 17bis, Paris 20022, 520-522.
[9] Saint Hilary of Poitiers, Contra arianos seu contra Auxentium, 6: PL 10, 613. Remembering the voice of the Fathers, the learned theologian, then cardinal and now Saint and Doctor of the Church John Henry Newman (1801-1890) studied this controversy and concluded that the Nicene Creed was preserved primarily by the sensus fidei of God's people. Cf. On consulting the Faithful in Matters of Doctrine (1859).
[10] I, Constantinople, Exposio fideiCC, Conc. Oec. Gen. Decr. 1, 5720-24. The statement "and proceeds from the Father and the Son (Filioque) » is not found in the Constantinople text; it was inserted into the Latin Creed by the Pope Benedict VIII in 1014 and is the subject of an Orthodox-Catholic dialogue.
[11] Chalcedony, Definitio fideiCC, Conc. Oec. Gen. Decr. 1, 137393-138411. [12] Conc. Vat. II, Const. past. Gaudium et spes, 19 : AAS 58 (1966), 1039.
[13] Cf. François, Lett. enc. Laudato si'’ (May 24, 2015), 67; 78; 124: AAS 107 (2015), 873-874; 878; 897. [14] Cf. Id., Apostolic Exhortation. Gaudete et exsultate (March 19, 2018), 92: AAS 110 (2018), 1136.
[15] Cf. Id., Lett. enc. Fratelli tutti (Oct. 3, 2020), 67; 254: AAS 112 (2020), 992-993; 1059.
[16] Cf. Conc. Vat. II, Decr. Unitatis redintegratio, 1: AAS 57 (1965), 90-91.
[17] See S. John Paul II, Lett. enc. Ut unum sint (May 25, 1995), 20: AAS 87 (1995), 933.
