Surely she sinned.
And what is this way around, His grace stopped her from sinning? What does
that even mean? [MY NOTE: His grace did not "stop her" from sinning; she was free to sin; see below]
No. That would have been quite significant. Surely there would have been
more mention of her if this had been so.
All have sinned!
I have been in a long correspondence with this reader, a true lover of Christ who feels drawn to the Catholic Church, but confused by many of her teachings, this one most especially. I have helped him along the way the best I could, all in private emails (for the most part) - but this one requires a bit more work.
Let me see what I can do to address this concern on one of the most controversial teachings of the Catholic Church, which is not only the Immaculate Conception of Mary, but also her lifelong sinlessness.
First let me say that concerns about Mary never played a role in my conversion. I don't know why.
I suppose it's because one is faced with some choices early on when considering the claims of the Catholic Church.
1. First, once you accept that God exists and that Jesus Christ was God incarnate - well, that's the big one. If what the New Testament tells us about Christ is true, then it's not only possible that He established a Church that continues to act with His authority (a Church St. Paul over and over again calls The Body of Christ) - it's not only possible that Christ established an ongoing visible and corporeal presence of Himself on earth, but actually quite likely, for it's not possible to imagine how the Faith can be effectively promulgated without this ongoing divine presence. Therefore, once you begin to have faith in the Holy Trinity, and especially in the Holy Spirit, belief in His willingness and ability to guide believers in matters of Faith and Morals follows almost as a necessity.
2. Next, if this authority (the Church) can decide what books constitute Sacred Scripture, and if the Church, which is "the pillar and bulwark of the truth" (1 Tim. 3:15) encourages us to "stand firm and hold to the teachings we passed on to you, whether by word of mouth or by letter." (2 Thes. 2:15), then the Bible is rightly seen as a part of the Deposit of Faith, and not as the source of it, for the teachings have been passed down both "by letter" and "by word of mouth".
3. The question then becomes, if this Church teaches things that are not expressly stated in Scripture, are these things necessarily wrong? Of course not, for the Gospel, like Salvation History itself, is written in large letters across all of creation, and is not confined to the books of the Bible. As St. John tells us, "Jesus did many other things as well. If every one of them were written down, I suppose that even the whole world would not have room for the books that would be written." (John 21:25) Divine Revelation, therefore, can include truths not taught expressly in Scripture.
Now when it comes to Mary, we seem to have an example of something in Divine Revelation that is not included in Scripture, but worse than that - it's a teaching that seems to be contradicted by Scripture. Indeed, as my reader points out, "all have sinned and fall short of the glory of God" (Rom. 3:23), and "There is none who does good, not even one." (Ps. 14:2-3)
Of course already we have a problem, for my reader is using Catholic doctrine to contradict Catholic doctrine. How do we know Holy Scripture is infallible? Because the Church tells us. How do we know that these above quoted Bible verses support the dogma that all men, since Adam, are stained by original sin? Because the Church tells us - the Catholic Church (whose authority we have already decided to accept - see #1 and #2 above). For "original sin" as such is not expressly stated in Scripture, but is a teaching - like the dogma of the Trinity- that is implied in the Bible, but only understood outside of the Bible.
At any rate, even if you accept Church authority on these matters, you're still left with a problem.
If the Church teaches that all men are sinners, and if Scripture affirms this, then how is Mary an exception? Is the Church not contradicting herself in teaching that Mary, alone of all humans (other than Jesus) did not sin?
Well, "other than Jesus" - that's important. When Paul says, "All have sinned and fall short of the glory of God", we know that his "all" does not include Jesus Christ, who "has been tempted in every way, just as we are—yet he did not sin." (Heb. 4:15) Therefore Paul does not mean literally "all".
Still, it's a stretch to believe that Mary was conceived free from the stain of original sin and to believe that she never actually sinned, isn't it? Even if Paul's "all have sinned" means "all who are neither God incarnate nor His mother, filled with all grace", it's still a stretch.
Except when you start thinking about other things, which are both within Scripture and within Sacred Tradition.
The Church tells us Mary is the New Eve, the one from whom would come the One who would crush the serpent's head (Gen. 3:15). Certainly, the woman of Revelation 12 is an echo of the woman whose seed would crush the serpent. If this is true, and if Mary is the New Eve (for Christ is clearly the New Adam - see 1 Cor. 15), then she, like Eve, would have to be free from the stain of original sin from her conception on, as was Eve. How does God do this? Well, God can do anything, but the Church teaches that Mary was sanctified at the moment her life began by the sacrifice Christ would later make for her and all of us on the cross, gracing working backwards through time - "prevenient grace".
Now even in this kind of miraculous act of "cloning" (so to speak), this great experiment of creating a fresh start for humanity with the New Eve, the new "mother of all living", there's still a big risk. The first Eve began her life without the stain of original sin - the first Eve was (as the Church teaches Mary was) immaculate. But what did the first Eve do? Even though she was not compelled by the effects of original sin to sin - she sinned anyway! Free will is like that. Even when our will is not damaged or compromised, we can still use it to do wrong. The fallen angels prove that in spades. See C. S. Lewis' Perelandra for an imaginary treatment of the question - what would happen if Eve didn't sin? Well, Mary answered that question 2,000 years before Lewis did.
For Eve was free either to sin or not to sin. The Church teaches so was Mary. It was a fresh start. A fresh start in Christ.
Unlike the rest of us lugs, Mary had a clean slate - so that she could serve both as a fitting model for us of the perfect Christian and the most holy of saints, and also so that she could serve as the only fitting mother of the Man Who was God. And she simply did what Eve didn't do, but could have. She simply kept her slate clean, allowing God to write on it as He saw fit - "Be it done unto me according to thy word" (Luke 1:38).
But Mary was only able to avoid Paul's observation that "all have sinned" because of her Immaculate Conception, because she was conceived without the stain of or the effects of original sin. Mary's lifelong holiness would not have been possible had she not been immaculately conceived.
Now why is all this so important?
Well, for one big reason.
Jesus Christ could not be born from sin. He could bear all sin - as He did on the cross - but he could not be born from sin, or from a sinful woman. Holiness does not come from sin, but from grace - and grace - like the Immaculate Conception itself - is always and everywhere a miracle.
We cannot give birth to Christ in our hearts or in our lives through sin. And the more attached we are to sin - even venial sin - the less able are we to bear Him into the world.
And if you doubt this, look at the saints who bear Him forth so well.
Look especially at Mary.
By the way, my friend Mark Shea has written a trilogy of books on Mary, which are well worth reading. And it takes a trilogy, for I have only scratched the surface here.