Why was Mary free from original sin?

A:

Saint Augustine of Hippo (354-430) introduced the notion of original sin to the western half of the Christian Church, although it was never accepted in the Greek-speaking east and has been largely abandoned by many of the Protestant Churches. He said that original sin resulted directly from the disobedience of Adam and Eve, and believed that it could only be removed by baptism, so without baptism, souls could not go to heaven.

Because the Catholic Church could not accept the notion of Mary, mother of Jesus, being born with original sin, it developed the doctrine called The Immaculate Conception. Pope Pius IX solemnly defined it in his constitution Ineffabilis Deus on December 8th, 1854.

Cardinal George Pell recently stated that the story of Adam and Eve is a myth, describing it as a religious story told for religious purposes. Without their existence, it will be hard to sustain the belief that Christians are born with original sin as a consequence of the sin of Adam and Eve, or that without baptism all are condemned to hell. However, without Adam and Eve, and without a reason for original sin to exist, the doctrine of the Immaculate Conception becomes an anachronism.  

Roman Catholic Answer

This is covered in questions 490-494 in the Catechism. The bottom line answer is that was necessary for the greater glory of God, that the woman who would give birth to Him be untouched by sin or evil. The doctrine is developed from the first moment when Our Blessed Lord is conceived and the Archangel Gabriel greets her with the salutation "full of grace". Thus Mary was redeemed from the moment of her conception. This "splendor of an entirely unique holiness" by which Mary is "enriched from the first instant of her conception" comes wholly from Christ: she is "redeemed, in a more exalted fashion, by reason of the merits of her Son." (see Lumen Gentium 53, 56) 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. (Luke 1:28-38; cf. Rom 1:5) By the grace of God Mary remained free of every personal sin her whole life long. extracted from The Catechism of the Catholic Church, second edition, English translation 1994
 

Answer

In Catholic belief, Mary was born free from original sin because of her supposed immaculate conception. The Protestant Churches dispute this belief, while the Orthodox Churches never adopted the Augustine concept of original sin.

Answer #2

This is one issue where where Protestants and Catholics disagree. Protestants believe all but Jesus are free from original sin, while Catholics believe in the sanctity of the Blessed Virgin and the immaculateness of her conception to which Mary was conceived without sin. All Christians believe Jesus was without sin but the issue with Mary is controversial.