Pope Leo XIV issued the Apostolic Letter 'In Unitate Fidei' on the 1700th Anniversary of the Council of Nicaea. The Apostolic Letter is broken down into twelve points, aiming to encourage the Church to renew its enthusiasm for the profession of faith. The First Council of Nicaea, convened in 325 AD, is being commemorated in 2025. Pope Leo's upcoming Apostolic Journey to Türkiye includes visits to Ankara, Istanbul, and İznik (Nicaea). The ecumenical council aimed to address theological disputes and establish a unified Christian doctrine, including affirming Christ's divinity and formulating the Nicene Creed.
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Pope Leo XIV issued the Apostolic Letter In Unitate Fidei on November 23, 2025, coinciding with the Solemnity of Christ the King and the 1700th anniversary of the Council of Nicaea.1
The document, structured in 12 points, aims to renew the Church's enthusiasm for professing the faith, particularly ahead of the Pope's apostolic journey to Türkiye.1
This journey will visit Ankara, Istanbul, and İznik (ancient Nicaea), highlighting the letter's ties to the historic ecumenical council convened in 325 AD by Emperor Constantine I.1
The letter emphasizes the Nicene Creed as a unifying profession of faith in Jesus Christ as the Son of God.1
The First Council of Nicaea addressed early Christian theological disputes, affirming Christ's divinity and establishing the foundational Nicene Creed.1
Pope Leo XIV notes that this creed remains central to Sunday Eucharistic celebrations, serving as the enduring common heritage of all Christians.1
In the context of the 2025 Holy Year themed "Christ our hope," the anniversary is seen as providential, linking ancient doctrine to contemporary needs.1
The Pope recalls how the council's outcomes fostered harmony in transmitting the faith with love and joy.1
The letter portrays the Nicene Creed as a source of hope in times of war, violence, natural disasters, injustices, and widespread suffering.1
Pope Leo XIV stresses that this profession of faith offers reassurance and unity for the global Christian community.1
By invoking the creed's words—"I believe in one Lord Jesus Christ, the Only Begotten Son of God"—the document underscores its role in sustaining believers through modern fears and imbalances.1
A core focus is ecumenism, building on Vatican II and Saint John Paul II's Ut Unum Sint, to promote visible unity among Orthodox, Eastern Orthodox Churches, and Reformation communities.1
Despite ongoing divisions, progress in dialogue—rooted in shared baptism and the Nicene Creed—has fostered recognition of fellow Christians as brothers and sisters.1
The Pope asserts that shared faith in the Father, Son, and Holy Spirit outweighs differences, urging a future-oriented ecumenism that enriches through reconciliation and mutual exchange of spiritual gifts.1
He rejects both pre-division nostalgia and status quo acceptance, advocating instead for common prayer and leaving behind outdated controversies.1
In a divided world marked by conflicts, the unified Christian community can serve as a sign of peace and an instrument of reconciliation.1
Pope Leo XIV invokes the witness of martyrs from all traditions, as highlighted by Saint John Paul II, to inspire peacemaking efforts.1
The Nicene Creed is positioned as a model for unity in diversity, guiding credible ministry toward global peace commitments.1
The letter concludes with a call to invoke the Holy Spirit for guidance in achieving full unity and common Gospel witness.1
This prayerful approach aligns with the Pope's upcoming visit to Nicaea's sites, reinforcing the creed's ongoing relevance for Christian dialogue and harmony.1
Analyze how Pope Leo’s 2025 letter renews the Catholic Church’s engagement with the Nicene Creed
In 2025, marking the 1700th anniversary of the First Council of Nicaea, Pope Leo XIV issued several addresses and messages that underscore the enduring vitality of the Nicene Creed as a cornerstone of Christian unity and faith. Particularly in his address to participants in the Ecumenical Symposium on this occasion, delivered on June 7, 2025, the Pope renews the Catholic Church's engagement with the Creed not merely as a historical artifact but as a living instrument for ecumenical dialogue, synodal practice, and shared witness in a divided world. This renewal builds on the Creed's original purpose—to affirm the divinity of Christ and the unity of the Church—while adapting it to contemporary challenges like fragmentation and secularism, inviting all Christians to reclaim their common patrimony.
The Nicene Creed, formulated in 325 AD, has long served as the foundational expression of orthodox faith, declaring Jesus Christ as "true God from true God" and "consubstantial with the Father." Pope Leo XIV's 2025 interventions revive this by positioning the anniversary as a "providential opportunity" to highlight what unites rather than divides Christians. In his message to the Ecumenical Week in Stockholm, he recalls how Nicaea's creedal statements "articulated the faith that continues to bind Christians together," emphasizing its role as a "courageous sign of unity amidst difference." This echoes the Synod on Synodality's call for "ecumenical synodal practices," where the Creed becomes a bridge for consultation on urgent issues like peace and justice. By invoking the Creed's shared recitation in liturgies across traditions, the Pope fosters a renewed liturgical engagement, urging Catholics to recite it not in isolation but as a communal act that overcomes historical schisms.
A key aspect of this renewal is the Pope's emphasis on the Creed's Christological core as a remedy for modern disunity. Drawing from the International Theological Commission's document on Nicaea, he affirms that Christians together 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." This declaration resolves ancient controversies, such as those addressed in earlier ecumenical efforts like the 1984 Common Declaration with the Syrian Orthodox Church, which confessed the same faith in Christ's Incarnation despite terminological differences. Pope Leo extends this by applying the Creed to today's "ecumenical journey," where theological dialogue must lead to visible unity. In his address to the Orthodox-Catholic pilgrimage participants on July 17, 2025, he notes the coincidence of calendars allowing joint Easter proclamations, linking the Creed's hope in the Resurrection to practical reconciliation. Thus, the letter renews engagement by transforming the Creed from a doctrinal formula into an active force for "artisans of reconciliation" amid global conflicts.
Furthermore, Pope Leo integrates the Nicene tradition with synodality, a hallmark of his pontificate's early vision. The Council of Nicaea itself modeled synodal governance, gathering bishops for universal discernment. In the symposium address, the Pope highlights how Nicaea "inaugurated a synodal path for the Church," encouraging "forms of consultation and discernment on questions of shared and urgent interest." This renews Catholic engagement by proposing the Creed as a synodal compass, where unity in faith (as professed at Nicaea) informs participatory decision-making. It aligns with Vatican II's Unitatis Redintegratio, which called for dialogue grounded in common baptism, but advances it by tying the Creed to the Synod on Synodality's final document, promoting "ecumenical synodal practices" without absorption or domination. For Catholics, this means a deeper immersion in the Creed through ecumenical formation, ensuring it shapes not only belief but also the Church's mission in education, peacebuilding, and care for creation—as seen in parallel 2025 documents like the Apostolic Letter on Gravissimum Educationis.
This renewal also addresses potential controversies, such as divergent interpretations of the Creed's implications for ecclesial authority. While affirming the Roman Pontiff's role in safeguarding faith, as in Leo XIII's Sapientiae Christianae, Pope Leo prioritizes fraternal dialogue over unilateral claims. He cautions against viewing unity as mere compromise, instead presenting the Creed as an invitation to "return to the Council of Nicaea and draw together from this common source," fostering mutual enrichment. Where sources like the 1925 Stockholm Conference focused on "practical Christianity," Leo's approach integrates doctrine and action, ensuring the Creed's renewal respects Eastern traditions while upholding Catholic fullness.
In conclusion, Pope Leo XIV's 2025 letter revitalizes the Nicene Creed as a dynamic source of hope, ecumenism, and synodality, calling the Catholic Church to engage it afresh in prayer, dialogue, and service. By celebrating shared faith amid division, it not only commemorates history but propels the Church toward the unity Christ desires, making the Creed a beacon for pilgrims in hope during this Jubilee Year.