Dear Brothers and Sisters in Christ,
This week the Holy Father has offered the universal Church a powerful call to unity and conviction in faith with his new Apostolic Letter “In Unitate Fidei” — “In the Unity of Faith.” Promulgated on 23 November 2025, the Solemnity of Our Lord Jesus Christ the King, the letter commemorates the 1,700th anniversary of the First Council of Nicaea (325 AD), at which the foundational profession of Christian faith — the Nicene Creed — was first solemnly formulated.
Pope Leo writes not as a theologian issuing new dogma, but as a shepherd inviting the entire flock to rediscover the Creed as “a living profession of faith,” one that calls us to personal conversion, communal witness, and renewed commitment to unity in Christ.
At the core of “In Unitate Fidei” lies, the affirmation that the Creed formulated at Nicaea remains the “common heritage of Christians” everywhere — a heritage handed down through centuries, across liturgies, confessions, and cultures. The Creed’s declaration — “I believe in one Lord Jesus Christ, the Only Begotten Son of God … for our salvation he came down from heaven” — is at once simple and profound. Pope Leo reminds us that this is “the heart of the Christian faith,” the central truth around which all else revolves.
Through Jesus Christ — God made flesh, Word become incarnate — the living God draws near to humanity. In the Incarnation, God becomes our neighbor, identifies with the poor and suffering, and calls us to respond with compassion and justice. The letter draws out this truth in biblical and traditional imagery: Jesus as “light of the world,” the Word made flesh, reconciler, Redeemer — the source of true human dignity, community, and hope.
This is not abstract theology, but faith meant to shape lives — our worship, our common prayer, our interior conversion, and our witness in the world. The Creed, which we often recite almost reflexively in the the Sunday Eucharist, must influence how we think, act, love, and live in solidarity with others.
The timing of this document is deeply significant. The Church will soon mark the anniversary of Nicaea with a pilgrimage to the ancient city of Nicaea (modern İznik, Turkey) — a symbolic journey to the roots of Christian unity. Pope Leo’s visit to Türkiye (and also Lebanon) underscores the broader ecumenical dimension of the letter: a call to remember what unites Christians rather than what divides them.
In a world torn apart by war, violence, injustice, inequality, and spiritual indifference, Pope Leo reminds us that the Creed can — and should — be a source of hope. He invites Christians everywhere to rediscover the Creed not as a relic of the past, but as a living, unifying confession of faith. Through that confession, we are called to witness to the love and justice of God, to care for the poor, creation, and neighbors in need — thereby incarnating the Gospel in concrete acts of mercy.
Moreover, the letter appeals not only to Catholics, but implicitly to all Christians — Orthodox, Protestant, and others — affirming that the Nicene-Constantinopolitan Creed is, for all of us, a common foundation. The Pope encourages ecumenical dialogue grounded on shared baptism and this common confession of faith.
Pope Leo’s letter does not call for triumphalism. Rather, he issues a sober challenge to examine our hearts: Are the words we profess each Sunday — “I believe …” — truly alive in us? Do they shape our attitudes, decisions, and actions? Do we treat God’s creation and our neighbor with reverence and solidarity?
In many societies, “God” has become a distant, abstract notion — or worse, an idol we manipulate according to our convenience. The Pope warns against reducing God to a philosophical or ideological concept; the Creed attests to a living God who draws near, redeems, and transforms. Our calling as Christians is to bear witness to that living God by living out the creed.
Through this interior conversion and outward solidarity, the Church can become a credible sign of unity, hope, reconciliation, and peace in our divided world. As Pope Leo says, “what unites us is much greater than what divides us.”