The Immaculate Conception of Mary
The Immaculate Conception is one of the most Catholic, most mysterious, and most misunderstood Catholic dogmas. The Immaculate Conception has nothing to with how Jesus was conceived; it has to do with Mary’s birth instead.
In the eyes of the Church, Adam and Eve’s sin, called original sin, is transmitted to every subsequent generation. So just as you inherit the color of your eyes and hair from your parents, you also spiritually inherit original sin. When you’re baptized, original sin is replaced with sanctifying grace.
Catholics believe that from the first moment of her conception in the womb of her mother, St. Ann, Mary was kept free from original sin by the power of divine grace. So the Immaculate Conception is about Mary’s conception in her mother’s womb.
Because Jesus had no human father, his only human parent was Mary. She gave him his human nature, whereas he — as God — always possessed his divine nature. In order to give Jesus a completely untainted, spotless, and immaculate human nature, Mary had to be kept free from original sin. She couldn’t do so on her own, because she was a mere mortal. But God gave Mary the singular grace and privilege of the Immaculate Conception to prevent original sin from being transmitted to Jesus, so she was literally full of grace.
When the Archangel Gabriel addressed Mary in the first chapter of Luke’s Gospel, he said, Hail Mary, full of grace. She was full of grace because of the Immaculate Conception, a divine gift to her from God so that she could provide a worthy, spotless, and pure human nature for Jesus.
In all 2,000 years of Church history, only two papal ex cathedra statements have been made. These ex cathedra statements come directly from God — a pope is infallible when he makes an ex cathedra statement. The first of these statements was made in 1854 when Pope Pius IX confirmed the Immaculate Conception. The other ex cathedra statement was made in 1950; Pope Pius XII defined the dogma of the Assumption of Mary, body and soul, into heaven.