The following is the full text of remarks given June 7, 2025, by Pope Leo XIV at a conference marking the 1,700th anniversary of the Council of Nicaea.
Peace be with you!
Your Eminence,
Your Excellencies,
Distinguished Professors,
Dear Brothers and Sisters in Christ,
I offer a warm welcome to all of you, who are taking part in the Symposium “Nicaea and the Church of the Third Millennium: Towards Catholic-Orthodox Unity,” jointly organized by Œcumenicum – the Institute for Ecumenical Studies of the Angelicum – and the International Orthodox Theological Association. In a special way, my greeting goes to the representatives of the Orthodox and Oriental Orthodox Churches, many of whom honored me by their presence at the Mass inaugurating my Pontificate.
Before I continue my formal remarks, I would just like to apologize for being a little late, and also ask for your patience with me. I am not yet one month into the new job, so there are a lot of learning experiences. But I am very happy to be with you this morning.
I am pleased to see that the Symposium is resolutely oriented toward the future. 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. The First Ecumenical Council is foundational for the common journey that Catholics and Orthodox have undertaken together since the Second Vatican Council. For the Eastern Churches, which commemorate its celebration in their liturgical calendar, the Council of Nicaea is not simply one Council among others or the first in a series, but the Council par excellence, which promulgated the norm of the Christian faith, the confession of faith of the “318 Fathers.”
The three themes of your Symposium are especially relevant for our ecumenical journey. First, the faith of Nicaea. As the International Theological Commission observed in its recent Document for the 1700th anniversary of Nicaea, the year 2025 represents “an invaluable opportunity to emphasize that, what we have in common is much stronger, quantitatively and qualitatively, than what divides us. Together, we believe in the Triune God, in Christ as truly human and truly God, and in salvation through Jesus Christ, according to the Scriptures read in the Church and under the guidance of the Holy Spirit. Together, we believe in the Church, baptism, the resurrection of the dead, and eternal life.” (Jesus Christ, Son of God, Savior, n. 43). I am convinced that by returning to the Council of Nicaea and drawing together from this common source, we will be able to see in a different light the points that still separate us. Through theological dialogue and with the help of God, we will gain a better understanding of the mystery that unites us. By celebrating together this Nicene faith and by proclaiming it together, we will also advance towards the restoration of full communion among us.
The second theme of your Symposium is synodality. The Council of Nicaea inaugurated a synodal path for the Church to follow in dealing with theological and canonical questions at the universal level. The contribution of fraternal delegates from the Churches and ecclesial communities of East and West to the recent Synod on Synodality held here in the Vatican was a valuable stimulus to greater reflection on the nature and practice of synodality. The Synod’s Final Document noted that “ecumenical dialogue is fundamental for developing our understanding of synodality and the unity of the Church” and it went on to encourage the development of “ecumenical synodal practices, including forms of consultation and discernment on questions of shared and urgent interest” (For a Synodal Church: Communion, Participation, Mission, n. 138). It is my hope that the preparation and joint commemoration of the 1700th anniversary of the Council of Nicaea will be a providential occasion “to deepen and confess together our faith in Christ and to put into practice forms of synodality among Christians of all traditions” (cf. ibid., n. 139).
The Symposium has a third theme related to the date of Easter. As we know, one of the objectives of the Council of Nicaea was to establish a common date for Easter in order to express the unity of the Church throughout the oikoumene. Sadly, differences in their calendars no longer allow Christians to celebrate together the most important feast of the liturgical year, causing pastoral problems within communities, dividing families and weakening the credibility of our witness to the Gospel. Several concrete solutions have been proposed that, while respecting the principle of Nicaea, would allow Christians to celebrate together the “Feast of Feasts”. In this year, when all Christians have celebrated Easter on the same day, I would reaffirm the openness of the Catholic Church to the pursuit of an ecumenical solution favoring a common celebration of the Lord’s resurrection and thus giving greater missionary force to our preaching of “the name of Jesus and the salvation born of faith in the saving truth of the Gospel” (Address to Pontifical Mission Societies, 22 May 2025).
Brothers and sisters, on this eve of Pentecost, let us remember that the unity for which Christians long will not be primarily the fruit of our own efforts, nor will it be realized through any preconceived model or blueprint. Rather, unity will be a gift received “as Christ wills and by the means that he wills” (Prayer for Unity of Father Paul Couturier), by the working of the Holy Spirit. And so, at this time, I would invite you all to stand so we can pray together to implore the Spirit’s gift of unity. The prayer which I will recite implores the Spirit’s unity in a prayer which is drawn from the Eastern tradition:
“O Heavenly King, the Comforter, the Spirit of Truth,
Who art everywhere and fillest all things;
Treasury of Blessings, and Giver of Life,
Come and abide in us, and cleanse us from every impurity,
and save our souls, O Good One.” Amen.
The Lord be with you. The blessing of Almighty God, the Father, the Son, and the Holy Spirit come upon you and remain with you forever. Amen. Thank you very much.
