What does the Catholic Church's Doctrine of the Immaculate Conception entail?
The Immaculate Conception, according to the teaching of the Catholic Church, was the conception of the Blessed Virgin Mary in the womb of her mother, Saint Anne, free from original sin by virtue of the foreseen merits of her son Jesus Christ. The Catholic Church teaches that Mary was conceived by normal biological means, but God acted upon her soul (keeping her "immaculate") at the time of her conception.
The Immaculate Conception is commonly and mistakenly taken to mean the conception of Mary's son Jesus Christ in her own womb, and the Virgin Birth of Jesus. These are covered by the Doctrine of Incarnation, while the Immaculate Conception deals with the conception of Mary herself, not that of her son.
Although the belief that Mary was sinless and conceived immaculate has been widely held since Late Antiquity, the doctrine was not dogmatically defined until 1854, by Pope Pius IX in his papal bull Ineffabilis Deus. The Catholic Church celebrates the Feast of the Immaculate Conception on December 8.