By the Titular Archbishop of Selsey
From Co-Redemptrix to Mater Populi Fidelis: Pius XII and the New DDF Note
When Pope Pius XII wrote Mediator Dei in 1947, his purpose was to safeguard the integrity of Christian worship by reaffirming that all liturgical and devotional life flows from Christ the one Redeemer. Yet in that same encyclical, and later in Mystici Corporis and Ad Caeli Reginam, he articulated a luminous vision of Mary’s participation in redemption. She is the New Eve who offers her Son to the Father, uniting her maternal compassion to His sacrifice, and who continues to distribute the graces of that sacrifice to humanity. The Church therefore honoured her under the titles Co-Redemptrix and Mediatrix Omnium Gratiarum — not as rivals to Christ, but as signs of her unique cooperation with Him in the order of grace.⁶
The new doctrinal note of the Dicastery for the Doctrine of the Faith, Mater Populi Fidelis (4 November 2025), revisits these titles with a markedly different emphasis. It affirms Mary’s singular role in salvation history but declares the titles Corredentrice and Mediatrice di tutte le grazie “inopportune,” lest they “obscure the unique mediation of Christ.”⁷ Instead, it invites the faithful to contemplate her primarily as Mother of the Faithful People — a maternal symbol of accompaniment rather than a formal participant in redemption.
Doctrinal Continuity and the Change of Accent
Pius XII taught:
Ipsa cum Filio suo patienti doluit, ac pro nobis se obtulit, ac pro salute humani generis sua materna iura ac maternum amorem immolavit. — Mystici Corporis Christi, §106
“She suffered with her Son, offering Him for us and immolating her maternal rights and love for the salvation of mankind.”¹
In this conception, Mary’s cooperation is real, causal, and meritorious by divine association: she cooperates in the act of redemption, though wholly dependent on the Redeemer. Likewise, Mediator Dei insists that “Christ is the one and only Mediator between God and men,” yet acknowledges that “Mary’s mediation shares in His and draws all its efficacy from it.”²
By contrast, Mater Populi Fidelis states:
L’uso del titolo di Corredentrice è teologicamente improprio, poiché rischia di oscurare la singolare mediazione del Redentore.
“The use of the title Co-Redemptrix is theologically inappropriate, as it risks obscuring the unique mediation of the Redeemer.”³
The Note does not deny Mary’s cooperation but recasts it as discipleship and maternal empathy — a “participation of faith and love” rather than of redemptive causality. Its emphasis is relational, not metaphysical; experiential, not ontological.
From Participation to Accompaniment: A Disincarnate Shift
Here the issue runs deeper than terminology. The Incarnation itself is the divine charter of participation: Deus homo factus est ut homo fieret Deus — God became man that man might become God.⁸ By assuming our nature, the Son did not merely draw near to humanity; He redeemed through humanity. Every act of grace therefore presupposes human cooperation elevated by grace — not human passivity.
Mary’s role in the Incarnation reveals this mystery in its fullness. By freely giving her consent for God’s Son to take flesh in her womb, she became the living bridge between heaven and earth. Through her “yes,” the Word truly became man, and by sharing in His suffering and love, the human nature He took from her became the very instrument of our salvation.⁹ God chose not to save us apart from humanity, but through it — and Mary’s cooperation shows how human freedom, united with divine grace, becomes the means by which redemption enters the world.
Mary’s fiat and her suffering at Calvary embody this incarnational realism. Through her consent, the humanity the Word assumed is offered back to the Father. Pius XII’s vocabulary of Co-Redemptrix safeguarded that truth: God’s redemptive will operates through a human will perfectly conformed to His own.
Mater Populi Fidelis, by reducing cooperation to empathy, risks turning that mystery inside out. If Mary’s role is merely affective, then the human instrumentality of redemption is blurred. Grace becomes a gesture of divine proximity rather than a transformation of human nature. In place of metaphysical participation stands psychological association — Mary as companion, not co-operator. This subtle disincarnation endangers not only Mariology but Christology itself, for the whole meaning of the Incarnation is that the divine and human truly act together in one salvific economy.
St Leo the Great expressed the principle: Agit enim utraque forma cum alterius communione quod proprium est.⁴ “Each nature performs what is proper to it, in communion with the other.” The Incarnation therefore enshrines cooperation as the structure of salvation itself. To diminish Mary’s participation is to obscure how God’s work continues through His creatures — and how the Church herself is the prolongation of the Word made flesh.
Tradition and the Risk of Reduction
The Note rightly warns against confusion or exaggeration, yet it risks overcorrection. The faithful have long understood that Co-Redemptrix implies dependence, not equality — the cooperation of the New Eve with the New Adam. To silence that language is to weaken the incarnational principle: that divine grace truly employs human freedom as its instrument. The faithful cease to see that their sufferings and prayers can be united to Christ’s redemptive act; the Marian model becomes sentiment rather than sacrament.
The Church’s lex orandi has always proclaimed otherwise: Stabat Mater dolorosa, iuxta crucem lacrimosa, dum pendebat Filius. Devotion to Mary as Co-Redemptrix does not rival the Cross — it magnifies its fruit in the human heart.
Mary Between Doctrine and Diplomacy
The title Mater Populi Fidelis is pastorally tender but diplomatically safe. It mirrors the modern preference for inclusive imagery over metaphysical definition. Yet the Church cannot live by diplomacy alone. Doctrinal language is not a barrier to charity but its guardian. As Pius XII reminded the faithful, “The truths of faith are not obstacles to unity but its foundation.”⁵
To obscure Mary’s co-redemptive office is, indirectly, to weaken the Church’s understanding of her own share in Christ’s saving work. For as the Fathers taught, quod Maria cooperata est in carne, Ecclesia cooperatur in Spiritu — what Mary accomplished in the flesh, the Church continues in the Spirit.¹² The Dicastery’s caution is understandable; its pastoral intent is genuine. Yet beneath every pastoral formula lies a doctrinal reality. The Mother of the Faithful People remains, in the deeper order of grace, the Co-Redemptrix of mankind — not because she redeems with Christ as equal, but because she uniquely, surrendering her body and will – cooperated and allowed His redemption to materialise and be affected through her.
¹ Pius XII, Mystici Corporis Christi, §106 (29 June 1943).
² Pius XII, Mediator Dei, §84 (20 November 1947).
³ Dicastery for the Doctrine of the Faith, Mater Populi Fidelis (4 Nov 2025), §15 (Ital.).
⁴ Leo I, Sermo 28 De Nativitate Domini, §3.
⁵ Pius XII, Address to the Ecumenical Congress of Assisi (1955).
⁶ Pius XII, Ad Caeli Reginam, §§34–39 (11 October 1954).
⁷ Vatican Press Office, “Nota Dottrinale Mater Populi Fidelis,” (4 November 2025), press.vatican.va.
⁸ Athanasius, De Incarnatione Verbi Dei, §54.
⁹ Luke 1:38; cf. Lumen Gentium, §§56–57.
¹⁰ Pius XII, Allocution to the Marian Congress of Buenos Aires (1954).
¹¹ Sequence Stabat Mater, Missale Romanum (1570).
¹² Augustine, Sermo 25 de Sanctis, PL 46, 937.
