This is a talk Sr. Teresa Forcades i Vila gave about the Marian dogmas under the title "The Future of the Christian Experience". It is available on her Web site in its original Catalan and in a computer-assisted Spanish translation. Since I'm putting it on the blog, I have divided the text into four parts.
1. Introduction and Mary, Mother of God
2. Virgin Mary
3. Immaculate Mary
4. The Assumption of Mary, Conclusion and footnotes
3. Immaculate Mary, Pius IX, December 8, 1854
To state that Mary was conceived without original sin is not only equivalent to stating that sin is not part of our human nature such as it was created by God (i.e. it is possible to be fully human without having anything to do with sin and this is the case with Mary and Jesus), but also that God continues to guarantee – in spite of all the horrors of history past and present, in spite of the sadness of so many instances of injustice – that all of us without exception can one day come to live without sin, to be fully human, fully divine. Sin is never the fruit of freedom but only of the fear of freedom, the fear of loving as God loves. Therefore not only is it possible to be fully human without sin, the absence of sin (absence of fear) is the condition of possibility for this plenitude, it is the end towards which we are aiming. Mary and Jesus’ life without sin is the eschatological anticipation in history of what will be possible for all of us with the grace of God, that is, our full divinization which is the same as our full humanization.
Therefore, is there no basis at all for the difficulty in seeing in Mary a model of full humanity? Did that come out of nowhere? No. I don’t believe it came out of nowhere, but it is very important to specify that the difficulty is not born of Mary’s absence of sin (if it were thus, we would have the same difficulty with Jesus and then redemption itself – which is based on the full humanity of Jesus – would be empty), but rather the absence of temptation. The problem is in thinking that Mary was never “tempted”. And no dogma states that. Mary, like Jesus, was tempted. Mary, like Jesus and like ourselves, had to decide in every real moment in the space and time of her life, what loving is. That Mary was born without original sin does not imply that she could not sin. She could. Like Jesus, who also could (see the gospel passage on the temptations, Mark 1:13 and parallels).
Mary’s free and responsible answer made the advent of God into history possible, without which there would not have been Redemption. God could not have saved us without Mary’s free “YES”. That is why John Paul II proclaimed Mary Co-Redeemer. The dynamic of co-redemption, like that of co-creation, is unique in Mary but not exclusive to her, rather it is extended to all of us. Also in us is the truth that redemption cannot be accomplished without our free and responsible “YES”. God’s message is clear, and it was beautifully expressed by St. Augustine: “God created us without us: but he did not will to save us without us.”  This is our dignity, the dignity that belongs to our being in the image of God, to our freedom. Both for co-creation and for co-redemption Mary is the theological place in her fulfilled humanity that gave birth to the Light.
There is no dogma that says that Mary was not tempted. Jesus’ full and complete historicity is the same as that of Mary, to whom the old man Simeon announced that a sword would pierce her soul (the psyche). The sorrow that Mary suffered at the foot of the Cross and that artistic tradition has converted into one of the main representative motifs, is authentic in the same way that Jesus’ sorrow in Gethsemane is authentic. God’s ways are not ours. Mary, like Jesus, doesn’t understand everything, she is not protected from doubt or anxiety and she must decide for herself what it is to love at each moment, even at the foot of the Cross, when love seems to have been hopelessly vanquished.
At the beginning of Luke’s gospel we find a diptych that establishes a parallel and at the same time, a contrast between the scenes of the angel’s annunciation to Zechariah and to Mary. In both cases, the message of God seems impossible to accomplish since objectively the necessary conditions are not there. Both Zechariah and Mary express their perplexity: Zechariah says that his wife, Elizabeth, is long past the age of conceiving and Mary says that she has not known a man. And in spite of the strict parallel between the reactions of Zechariah and Mary, Zechariah is punished and remains mute, without being able to proclaim the Word of God or speak of what has been revealed to him, while Mary, on the other hand, is honored and joyfully goes to sing on the mountains the angel’s announcement. What happened? The difference between Zechariah and Mary is not that Zechariah doubts and Mary doesn’t, it is not that Zechariah thinks and reasons logically and Mary doesn’t, it is not that Zechariah has his own criteria and Mary doesn’t. The implicit difference in the story is that Zechariah absolutizes his own boundary of comprehension and Mary doesn’t. Mary, like Zechariah, expresses her objection but then, unlike him, gives witness with her fiat to her radical trust, which is the sine qua non condition of our relationship with God. Living in faith, like Mary and Jesus, prepares one to commit oneself out of love beyond one’s own ability to understand, and that attitude bases its reasonableness on the fact of having previously experienced that one’s own comprehension has limits that don’t correspond to objective reality.
The important point of the immaculate conception of Mary for the Christianity of the future is that any person is completely redeemable because his sin is not part of his essence and because the only thing that God asks of him is an act of trust that is always within his reach.