Ask any Protestant Christian what the Immaculate Conception is, and at least in my experience, they will will say it is the “conception of Jesus”. Which is exactly what I thought too, until I researched it.

On the way to synagogue every week, I pass by a Catholic church (Ok, since Covid-19 I haven’t been going in person, but…). On their sign, in the middle of December, it read “Come Celebrate The Feast of the Immaculate Conception,” and the math didn’t work out. If Jesus was conceived in December and born in December, the math didn’t work out. That is when I realized that the Immaculate Conception was not the conception of Jesus, but of Mary.

Which leads me to the question, why do Catholics believe that Mary was born of a virgin? Well, if the Pope says it, it is truth (obviously according to Catholics).

We declare, pronounce, and define that the doctrine which holds that the most Blessed Virgin Mary, in the first instance of her conception, by a singular grace and privilege granted by Almighty God, in view of the merits of Jesus Christ, the Saviour of the human race, was preserved free from all stain of original sin, is a doctrine revealed by God and therefore to be believed firmly and constantly by all the faithful.

Sheed 1958, p. 134-138.

There is nothing in the New Testament that teaches this. Somehow though, the Catholic Church also has traditions about Mary’s parents, Anne and Joachim, and conception without sexual intercourse. In fact, I have seen the place that the Church claims to be where Mary was born, in the middle of Jerusalem (which doesn’t really fit if they are from Nazereth), but it is very convenient for tourists to light a candel and donate a little money.

Also, it isn’t just Catholics that have extreme loyalty to Mary, even Martin Luther showed devotion to Mary, including the concept of leading a sinless life. (https://en.wikipedia.org/wiki/Immaculate_Conception#cite_note-73). Martin Luther took the Church head on and corrected quite a few teachings and traditions, but in my opinion, failed to complete the mission. I feel like he wiped out 1/3 of the errors of the Church, but still clung to the other 2/3.