Yesterday was Christmas. Christmas is, of course, the Christian religious holiday that commemorates the birth of Christ, which may have to do with why this particular religious misunderstanding just happened to pop into my mind.

Or it might have popped into my mind because I heard the term “Immaculate Conception” misused, as if it were a synonym for “Virgin Birth,” on TV just the other night. (I think it was while watching a recent holiday episode of Family Guy.)

It’s a very common mistake, confusing one term with the other. And it isn’t just satirical TV writers and irreverent icons of pop culture who get the two terms mixed up; college students, for instance, often do the same thing. I’ve actually had students in my community college world religions classes argue this point with me, insisting that I must be wrong when I mention the fact that the Immaculate Conception and the Virgin Birth actually have to do with two completely different and unrelated matters.

Some of them honestly think I’m nuts for maintaining that the Immaculate Conception and the Virgin Birth are not just two different ways of referring to the same thing, but actually refer to two entirely different things altogether.

I have found that this particular little factoid comes as news to a fairly substantial number of people (including believing Christians). And so, since the entire point of this ongoing blog is to help erode rampant religious illiteracy — factoid by factoid, and misconception by misconception, if necessary — it’s worth clearing up this very common misunderstanding here and now.

The term “Virgin Birth” refers to the general Christian belief that Jesus’s mother Mary was a virgin when she miraculously conceived (and subsequently bore) her son Jesus, without any genetic fertilization by a human father.

However, the term “Immaculate Conception” is a specifically Catholic belief that Jesus’s mother Mary was herself miraculously conceived and born without the stain of Original Sin, a kind of spiritual birth defect otherwise universally inherited by all other human beings since the Fall, due to Adam and Eve’s primordial sinning in Eden when they ate the forbidden fruit (which, by the way, the Bible never says was an apple).

So, the Virgin Birth refers to one thing (Jesus having been miraculously born of a virgin mother), whereas the Immaculate Conception actually refers to something else altogether (Mary having been miraculously conceived completely unstained and untainted by Original Sin).

Just to be very clear, the Immaculate Conception doesn’t mean that Mary’s mother also experienced a virgin birth, or anything like that; it just means that when Mary was conceived in her mother’s womb, she was miraculously spared from inheriting that inborn and otherwise-universal taint of Original Sin. (And again, only Catholics affirm this particular belief about Mary.)

So, there you have it. Now, the next time you overhear someone referring to the Virgin Birth as an “Immaculate Conception” (or vice versa), you’ll be ready to cheerfully disabuse them of their erroneous but quite common misunderstanding of what these very different terms actually refer to.

Of course, they might not believe you, at first. They might even insist that you’re wrong. If so, then you may wish to invite them to look it up for themselves — just have them Google it, or whatever. They may be in for quite a surprise.

But they shouldn’t feel too badly; this one is a particularly widespread and deeply ingrained misconception indeed.