Objection 3: Calling the Mother of Jesus, "Co-redemptrix" or her subsequent role as "Mediatrix" implies a role of mediation by someone other than Jesus Christ, but scripture plainly states in 1 Timothy 2:5 that "there is one God and one mediator between God and men, the man Christ Jesus," and therefore no creature can rightly be a mediator.
The definition of "mediator"—in Greek, mesitis, or "go-between"—is a person who intervenes between two other persons or parties for the goal of uniting or reconciling the parties. Applying this term to Jesus Christ, St. Paul indeed states that there is one mediator between the parties of God and humanity, namely the 'man Christ Jesus." No one therefore reaches God the Father except through the one, perfect mediation of Jesus Christ.
But the question still remains, does the one perfect mediation of Jesus Christ prevent or rather provide for others to subordinately participate in the one mediation of Jesus Christ? In other words, does the one exclusive mediation of Christ prevent any creature from participating in that one essential mediation? Or does its divine and human perfection allow others to share in his one mediation in a subordinate and secondary way?
Christian Scripture offers examples similar to this question of mediation where Christians are obliged to participate in something that is also "one," exclusive, and dependent entirely on the person of Jesus Christ.
The one Sonship of Jesus Christ. There is only one true Son of God, Jesus Christ, who was begotten from God the Father (1 Jn. 1-4). But all Christians are called to participate in the one true sonship of Jesus Christ by becoming "adopted sons" in Christ (cf. 2 Cor. 5:17; 1 Jn. 3:1; Gal. 2:20), as a true sharing in the one sonship of Christ through baptism which allows adopted sons and daughters to also share in the inheritance of the one Son, that of everlasting life.
Living in the One Christ. All Christians are called to share in the "one life" of Jesus Christ, for grace is to participate in the life and the love of Jesus Christ, and through him in the life and love of the Trinity. As St. Paul teaches, "it is not I, but Christ who lives in me" (Gal. 2:20) and 2 Peter 1:4 calls Christians to become "partakers of the divine nature," to live in the one Christ, and thus in the life of the Trinity.
The one Priesthood of Jesus Christ. All Christians are also called to share in different degrees in the one priesthood of Jesus Christ. The book of Hebrews identifies Jesus Christ as the one "high priest" (cf. Heb. 3:1; 4:14; 5:10) who offers the great spiritual sacrifice of himself on Calvary. And yet Scripture calls all Christians, albeit on different levels of participation, ministerial (cf. Acts 14:22) or royal (cf.1 Pet. 2:9), to participate in the one priesthood of Jesus Christ in offering "spiritual sacrifice." All Christians are instructed to "offer spiritual sacrifices acceptable to God" (1 Pet. 2:5, 2:9).
In all these cases, the New Testament calls Christians to share in that which is one and unique of Jesus Christ, the Alpha and Omega, in true though completely subordinate levels of participation. In reference, then, to Christ the one Mediator (1 Tim 2:5), we see the same Christian imperative for others to share or participate in the one mediation of Jesus Christ, but in a secondary mediation entirely dependent upon the one perfect mediation of Jesus Christ.
The pivotal christological question must then be asked: Does such subordinate sharing in the one mediation of Christ obscure the one mediation of Christ, or rather does it manifest the glory of his one mediation? This is easily answered by imagining a contemporary world without "adopted sons and daughters in Christ," without Christians today sharing in the one life of Jesus Christ in grace, or without any Christians offering spiritual sacrifices in the Christian priesthood. Such an absence of human participation would only result in obscuring the one Sonship, the one High Priesthood, and the very Life of grace in Jesus Christ.
The same principle is true regarding participation in the one mediation of Jesus Christ in a dependent and subordinate way: the more human participation in the one mediation of Christ, the more the perfection, power, and glory of the unique and necessary mediation of Jesus Christ is manifested to the world.
Christian Scripture moreover offers several examples of God-instituted human mediators who cooperated by divine initiative in uniting humanity with God. The great prophets of the Old Testament were God-ordained mediators between Yahweh and the people of Israel, oftentimes seeking to return the people of Israel to their fidelity to Yahweh (cf. Is. 1; Jer. 1: Ez. 2). The Old Testament patriarchs, Abraham, Isaac, Jacob, and Moses, etc., were at God's initiative the human mediators of the saving covenant between Yahweh and the people of Israel (cf. Gen 12:2; 15:18; Ex. 17:11). St. Paul identifies Moses' mediation of the law to the Israelites: " Why then the law? It was ordained by God through an intermediary" (Gal 3:19-20). And the angels, with hundreds of mediating acts spanning Old and New Testaments, are God's messengers, who mediate for reconciliation between God and the human family, both before and after the coming of Christ, the one Mediator (cf. Gen. 3:24; Lk. 1:26; Lk. 1:19).
Now regarding Mary, Christian Scripture also clearly reveals the secondary and subordinate participation of the Mother of Jesus in the one mediation of Jesus Christ. At the Annunciation, Mary's free and active "yes" to the invitation of the angel mediates to the world Jesus Christ, the Redeemer of the world and the Author of all graces (cf. Lk. 1:38). For this unique participation in giving to the Redeemer his body and mediating the Source of all graces to the world, Mary can rightly be called both "Co-redemptrix" and "Mediatrix of all graces" as one who uniquely shares in the one mediation of Jesus Christ.
This unique Marian participation in Christ's mediation, specific to the Redemption of Jesus Christ, is climaxed at Calvary. At the cross, her spiritual suffering united to the redemptive sacrifice of her Son, as the New Eve with the New Adam, leads to the universal spiritual fruits of the acquisition of the graces of redemption, which, in turn, leads to the gift of spiritual motherhood from the heart of the Crucified Christ to every human heart: "Behold your mother" (Jn. 19:27). The Redeemer's gift of his own mother as spiritual mother to all humanity leads to the spiritual nourishment by the Mother to her children in the order of grace. This constitutes the distribution of the graces of Calvary by Mary to her spiritual children as Mediatrix of all graces, which perpetually continues her unique sharing in the one saving mediation of Jesus Christ.
John Paul II explains the Catholic understanding of this unique Marian participation in the one mediation of Jesus Christ:
Mary entered, in a way all her own, into the one mediation "between God and men" which is the mediation of the man Christ Jesus.... We must say that through this fullness of grace and supernatural life, she was especially pre-disposed to cooperation with Christ, the one Mediator of human salvation. And such cooperation is precisely this mediation subordinated to the mediation of Christ.
In Mary's case, we have a special and exceptional mediation.
And in his commentary on 1 Timothy 2:5 and Mary's maternal mediation, John Paul II further states:
We recall that Mary's mediation is essentially defined by her divine motherhood. Recognition of her role as mediatrix is moreover implicit in the expression "our Mother," which presents the doctrine of Marian mediation by putting the accent on her motherhood...In proclaiming Christ the one mediator (cf. 1 Tim 2:5-6), the text of St. Paul's Letter to Timothy excludes any other parallel mediation, but not subordinate mediation. In fact, before emphasizing the one exclusive mediation of Christ, the author urges "that supplications, prayers, intercessions and thanksgivings be made for all men" (2:1). Are not prayers a form of mediation? Indeed, according to St. Paul, the unique mediation of Christ is meant to encourage other dependent, ministerial forms of mediation...In truth, what is Mary's maternal mediation if not the Father's gift to humanity?
Therefore we can see Mary's participation in the one mediation of Jesus Christ as unique and unparalleled by any other human or angelic participation, and yet entirely subordinate and dependent upon the one mediation of Jesus Christ. As such, Mary's motherly mediation manifests the true glory and power of Christ's mediation like no other. The Marian titles and roles of Co-redemptrix and Mediatrix of all graces (and Advocate as well) do not in any way violate the prohibition of 1 Tim. 2:5 against any parallel, autonomous, or rival mediation, but bespeak a unique and exceptional motherly participation in that one, perfect, and saving mediation of Jesus Christ.
In the words of Anglican Oxford scholar, Dr. John Macquarrie:
The matter (of Marian mediation) cannot be settled by pointing to the danger of exaggeration and abuse, or by appealing to isolated texts of scripture as the verse quoted above from 1 Timothy 2...or by the desire not to say anything that might offend one's partners in ecumenical dialogue. Unthinking enthusiasts may have elevated Mary's position to a virtual equality with Christ, but this aberration is not a necessary consequence of recognizing that there may be a truth striving for expression in words like Mediatrix and Co-redemptrix.
All responsible theologians would agree that Mary's co-redemptive role is subordinate and auxiliary to the central role of Christ. But if she does have such a role, the more clearly we understand it, the better. And like other doctrines concerning Mary, it is not only saying something about her, but something more general about the Church as a whole, and even humanity as a whole.