- from CatholicCulture.org
Mary as the Immaculate Conception, while not officially stated until the 19th century, is a concept that has existed since the early days of the Church. Although many people believe it refer to Jesus's conception, it actually refers to Mary's conception without the stain of original sin. This gift was given to the Blessed Mother in anticipation of her "Yes" to God's plan for the Incarnation. By preserving Mary from sin, God established her as the New Eve. Just as through Eve, all men and women fell from grace and the gates of heaven were locked, through Mary, all men and women would be saved and the gates of heaven opened. It is this great gift that we celebrate every December 8th.