Anyone who believes that she was sinless, regardless of when one considers the grace had entered her fully, has to face this question. That includes the Orthodox. The question, by the way, is a product of a distinctly unorthodox theology of atonement as purchase. If there is no sin, the transactional heresy of atonement goes, there is nothing to redeem. But we know that the work of Christ was to give us eternal life. This is the life He gave the Blessed Mother also. Whether it was given at conception or at some later point is beside the point.
Are we to strive to attain some similitude to the Theotokos, to attain a "likeness" to the Theotokos rather than Christ, or in addition to Christ? Is this a sine qua non of theosis?
The Catholic Church does not teach that the Blessed Mother is a sine qua non of theosis, and it does teach that we are to emulate Christ. But your objection is without substance: as she is holy, and as we imitate Christ and become holy, so we imitate her, whether we do so while aware of the Immaculate conception or not. If you do not see a problem with imitating Christ who is all-holy directly, you should not have a problem with imitating Our Lady, who thanks to Him is all-holy.
The co-mediator theology comes from her saying "be it onto me"; with this she did for us collectively what we are to do individually. I do not see what is inorthodox about it; in fact, the article posted by Kawaii yesterday explains it better than any Catholic would:
2. The Virgin Mary's Significance in Our Salvation.If not Mary, who first received the salvation of the New Testament, not rejecting it but accepting it with faith? To whose faith are we obliged for our salvation? For whom did this faith of Mary's accept the Saviour? For whom is this faith of Mary's saving, if not for the whole race of man? The faith of each man saves him alone, yet his prayer of faith can help many; but is was a faith offered from all peoples and saving for all mankind which only Mary could offer and which could be offered only by her alone, as being the one who herself ministered at God's incarnation.
The Lord does not save us without our participation, nor does He do it by force. Having granted man freewill, He does not require him to submit to Himself, but He calls, He awaits his conversion, He seeks a voluntary acceptance of salvation. He stands at the door, knocks and waits, that one might hear His voice and open the door to Him, and only then does He enter (Rev. 3:10). Therefore even the very initial act of salvation, the incarnation of the Son of God, was achieved not by the forcible entry of the Holy Spirit and the power of the Most High into the Virgin, but rather through the salutation of the Virgin with the good tidings, through an appeal to her faith, and after she had expressed her voluntary agreement with it. Thus salvation and the incarnation were achieved not only by the fact that God alone desired this, but also by the fact that man himself, in the person of the Virgin Mary, had expressed his consent to this.
In her Christ first of all saved us. And she saves us all in Christ.
In this way, as the salvation of man directly depends on man's will, on the one hand we are obliged to the All-holy Virgin Mary for our salvation, and her significance in the work of our salvation is of the first order and enormous. At the Annunciation, when the Lord knocked, she heard His voice and opened the door for the salvation of all.
3. "All-holy Theotokos, save us." There is no one who served more in Christ in the good work of our salvation than the All-holy Virgin Mary. For this reason the prayerful address, "All-holy Theotokos, save us," always has only one meaning, which is implicit in it, and that is, "save us in Christ, for thou hast already done this, for in Christ thou hast already saved us." She, who has brought us to salvation in Christ, is alone more than worthy among all the saints, to receive the petition and prayerful supplication: "save us."
Because, on behalf of mankind, the Virgin offered everything to God for the salvation of man, so she is a support to man's efforts, and in human perception, which is granted us for our salvation, she is the closest associate in the work of our salvation. After her, through her and with her help, we are raised up to heaven. She is closer than all the saints to people, a mediatrix before God possessing the most praeter-perfect human nature, and one who, out of love for and compassion for people, and for the sake of their salvation, lent flesh and blood to God.
Chosen of all generations, blessed among women, uniquely from amongst all, as one who has obtained grace from God, as the elect bride of the All-holy Spirit, she possesses the most powerful faith among all the sons and daughters of man, and the deepest humility among all; she among all peoples was the most good hearted on account of her love and compassion.
And she dwells with God, living with all her feelings, virtues and powers, ready to help everyone that calls upon her.
At the moment of her Dormition, the All-holy Virgin not only lost nothing of her powers, or of all that she had received from God, but in the power of that supernatural faith, by which all is granted (for "all things are possible to him that believeth"—Mark 9:23), she is the most powerful helper and intercessor for the race of man.
Just as on earth, so also in the heavens the Lord works wonders for the good and salvation of people through the loving mediation of His mother. Neither the Lord, nor the All-holy Virgin lost anything of their capabilities or of their powers in being taken up into heaven from earth. Her mediation, and the miracles which He works through that mediation, can never be cut short.
We are her kinsfolk according to the flesh, her brothers, sisters and children according to the statement of her Son, and we are related to her according to our nature, and through her mediation for us with her Son. And on account of this, her love towards us is that of a kinswoman, close, heartfelt and tender. She feels this more than we do, for she is aware of it even though we are not and cannot comprehend it.
4. The Virgin Mary—an example of making salvation our own. Twice the Lord pointed out that only those blessed people, who like His mother heard the word of God, kept it and fulfilled it (Mark 3:35; Luke 11:28), could be His kinsmen and mothers. And the one, who "kept" all the words of the Lord, "laying" them "up in her heart" (Luke 2:19, 51), the one who "found grace with God" (Luke 1:30) in fulfilling the commandments regarding faith, obedience, humility, selflessness, and love, has been made manifest as an example of making the salvation, which the Lord offered for us, our own.
The making of the salvation of Christ our own begins on earth, actually it originates with the Virgin Mary, who, as Mother of the Saviour, served at His incarnation. From her first of all saving faith and every virtue were offered to God. She received Christ, just as everyone always should receive Him, in her soul, and in her virtues. She is an example of the building up of the human soul, so that it might be the temple and home of God, and she was the first to achieve this. Every soul is a bride of Christ, fore-ordained for its heavenly bridegroom, and like the first bride, the Virgin Mary, it must be well-appointed for the reception of God.
The Most Holy Virgin by faith and through the Holy Spirit received within herself the Word of God, and carried Him within herself and nourished Him. And every soul, called to salvation, receives within itself the word of God, and carries that which has been conceived from faith and through the Holy Spirit, and by the mind and will nourishing it, and by fulfilling it and keeping it, it incarnates Christ within itself and within all its life. Thus it gives birth to Christ in itself, often in the torments of the struggle with sin, it represents Him to itself, likening itself to Him, building itself on Christ. Just as the Church gives birth to every soul in Christ, so every soul gives birth to "an infant of the male sex" (Rev. 12:5), that is to Christ Jesus in itself, and both the one and the other, the soul and the Church, correspond to the Virgin. And in all, the soul gives birth in Christ by the Spirit of God.
The Virgin Mary is an example of bearing God, of communion with God in the moral sense, on account of her faith, humility and every virtue.
You know I agree that Catholic popular mariology too often muddles up these distinctions and invites certain unhealthy sentimentalism. But on the other hand, no one said that theological truths are easy, -- surely not this side of the Tiber.
ping
"Anyone who believes that she was sinless, regardless of when one considers the grace had entered her fully, has to face this question. That includes the Orthodox. The question, by the way, is a product of a distinctly unorthodox theology of atonement as purchase. If there is no sin, the transactional heresy of atonement goes, there is nothing to redeem. But we know that the work of Christ was to give us eternal life. This is the life He gave the Blessed Mother also. Whether it was given at conception or at some later point is beside the point."
In great haste I will respond now only to this as I am at the office. The whole theory of purchase/atonement is indeed a heresy and so far as I know, a Protestant innovation. Orthodoxy does not teach this at all. What Orthodoxy does teach is that because of the Sin of Adam's effects on us, no matter how good humans were, they were in bondage to death. The Righteous of the OT were bound up by death in hades, not in union with the uncreated Divine Energies. That bondage was broken by the death, descent to the dead and resurrection whereby death's hold was destroyed. The icon of the Resurrection graphically demonstrates this. Sinless or not, prior to the resurrection we were all stuck. That's what the Sacrifice of Christ wrought. It has nothing to do with a payback to some divine, blood thirsty monster, popular opinion to the contrary notwithstanding. In any event, that's why the Theotokos needed a savior, not because of any personal sin.
More later.