Of the teachings concerning Mary the most difficulty I have are with teachings of her Immaculate Conception and of her Assumption. If I remember correctly John Cardinal Newman had similar reservations concerning the same teachings. In the Roman Catholic Church today is the celebration of the Solemnity of the Immaculate Conception of the Blessed Virgin Mary. This day was pronounced by Pope Pius IX in the Constitution Ineffabilis Deus in 1854. (1854 is an easy year for me to remember for it is the year of the founding of St. Stephen Lutheran Church in Milwaukee.) Lutherans tend to either laugh or get angry upon hearing this and other teachings about Mary.
Below is an excerpt from the Catechism of the Catholic Church. Granted Lutherans cannot accept the sinlessness of Mary but they may be surprised that for the Catholic Church this is an exegetical question based on the Church's interpretation of "full of grace." Also, note below that this sinlessness from conception on and additional freedom from "all stain of original sin" is possible by "by a singular grace and privilege of almighty God and by virtue of the merits of Jesus Christ, Saviour of the human race . . ." (By whose merits(?) is always a question for Lutherans.)
Catechism of the Catholic Church
§ 490-493 – Copyright © Libreria Editrice Vaticana
"Hail, favored one!"
To become the mother of the Saviour, Mary "was enriched by God with gifts appropriate to such a role." (LG 56.) The angel Gabriel at the moment of the annunciation salutes her as "full of grace". In fact, in order for Mary to be able to give the free assent of her faith to the announcement of her vocation, it was necessary that she be wholly borne by God's grace.
Through the centuries the Church has become ever more aware that Mary, "full of grace" through God, was redeemed from the moment of her conception. That is what the dogma of the Immaculate Conception confesses, as Pope Pius IX proclaimed in 1854: "The most Blessed Virgin Mary was, from the first moment of her conception, by a singular grace and privilege of almighty God and by virtue of the merits of Jesus Christ, Saviour of the human race, preserved immune from all stain of original sin.
The "splendour of an entirely unique holiness" by which Mary is "enriched from the first instant of her conception"(LG 56.) comes wholly from Christ: she is "redeemed, in a more exalted fashion, by reason of the merits of her Son"(LG 53.). The Father blessed Mary more than any other created person "in Christ with every spiritual blessing in the heavenly places" and chose her "in Christ before the foundation of the world, to be holy and blameless before him in love" (Eph 1:3-4).
The Fathers of the Eastern tradition call the Mother of God "the All-Holy" (Panagia), and celebrate her as "free from any stain of sin, as though fashioned by the Holy Spirit and formed as a new creature". By the grace of God Mary remained free of every personal sin her whole life long.
So far the Catholic Catechism. For more commentary on this topic, including what Luther has to say, visit Weedon's blog.