I always thought the phrase “immaculate conception” referred to the virgin birth of Jesus. I was, accordingly, shocked the other day when my wife — a Catholic convert — mentioned in conversation that immaculate conception properly refers to Jesus’ mother and the doctrine that Mary was free of original sin from the moment of her conception.
There’s a kind of rebirth when you discover a whole category of knowledge you didn’t know about. The immaculate conception of Mary is such an event for me, because I was wrong in my assumptions and because the doctrine makes perfect sense. Of course the mother of the Son of God had to be uniquely exempt from the original sin of Adam and Eve.