Around this time of year, I will often hear a Protestant Christian (or a non-Christian) refer to Jesus’s conception as the “immaculate conception.” This is incorrect. Many folks think that the phrase “immaculate” refers to the miraculous conception of Jesus, but it’s actually a Roman Catholic doctrine about the conception of his mother, Mary. And it didn’t become official doctrine for the Roman Catholic church until 1854.
The idea of immaculate conception was a way to answer a medieval theological problem: in order for Jesus to be sinless, he would need to be free of original sin. And since original sin was passed down through the generations by sexual reproduction (“fleshly union”), from Adam and Eve until the present day, the only way Jesus could be free of original sin was if his mother was also free from sin. It wasn’t enough that he didn’t have an earthly Father; his mother had to be made sinless, too. So, Mary’s original sin was taken away miraculously at the point of her conception, so that she could become the pure vessel for the incarnate God.
Of course, if God could take away original sin simply by willing it, it raises a bigger question about the atonement: why did Jesus have to die to take away sin?
As a Protestant, neither the doctrines of Mary’s immaculate conception nor her “perpetual virginity” form any part of my theology. I think they have led to some very unhelpful Christian ideas about both sin and sex. I also reject the theology that says Christianity is primarily about “sin management.”
But I do think these ideas about Mary filled a need for Christians to recognize the feminine side of the divine. In Roman Catholic theology, Jesus is not alone either in his sinlessness or his close relationship with the Father. He is less of a rugged individualist, because his mother paved the way for him, and was the model for his humble obedience. It even makes his grandma (Anne) relevant to the story. It reminds us that Jesus did not fall out of the sky, but had a family who nurtured him in both his physical life and his vocation, and that God was active in their lives, too, before he ever arrived on the scene.
You can read about the history of the doctrine of the Immaculate Conception here.
Prayer: Creator God, though you are the same yesterday, today, and forever, your mercies are new every day. Help us to see both the wisdom and folly of our theologies, which can only point to you, but never define.
—Rev. Dr. David Barnhart, Jr.
Dave Barnhart 
I wouldn’t expect a lot of Protestant Christians to know the meaning of the Immaculate Conception. What amazes me is the number of my Catholic neighbors who don’t know the meaning of it.
Several have argued with me about it, telling me I don’t know what I’m talking about.
From what I understand, the theologians were worried that Pius would name Mary as a co-redemptrix, effectively expanding the Trinity to four. Thanks for your articles! Advent Blessings.