In John 10:14-16, Jesus says,

I am the good shepherd; I know my own and my own know me, as the Father knows me and I know the Father; and I lay down my life for the sheep. And I have other sheep, that are not of this fold; I must bring them also, and they will heed my voice. So there shall be one flock, one shepherd.

Catholics and Protestants tend to interpret this passage in very different ways, and it makes a world of difference.

I. The Anti-Church Interpretation

One popular Protestant interpretation is that, since the sheep hear the Shepherd’s voice, we have no need for the Church or any other authority.

Of course, the argument’s not generally presented this explicitly. Often, it’s painted in terms of this passage’s alleged support for the self-authentication of Scripture, the idea that Scripture proves itself to be true, and therefore requires no other authority. As an individual believer, I can know that the Bible is the word of God, because I’m a sheep who hears the Good Shepherd’s voice. So, for example, Dr. Joe Mizzi refers to this verse in answering the question “How do you know that the books of Scripture are inspired?“:

Ultimately, I came to the full assurance that the Bible is the Word of God by the work of the Holy Spirit in my heart; for I, blinded by sin, could not perceive the light of the glory of Christ revealed in Scripture. He opened my eyes that I might see the beauty of His Word. Being one of His sheep, I hear the voice of my Shepherd. Or, if you like, being a child of the Father, I recognize my Father’s voice.

So Dr. Mizzi is a Christian, and therefore, he can read the Bible and know that it’s inspired. And not just that it’s inspired, but which Books belong in the Bible, and which don’t. C. Matthew McMahon explains the implications of this doctrine in Volume 2 of The Reformed Apprentice:

Self-authentication is something that Christians can witness over and against non-Christians. It goes back to, “my sheep hear my voice.” What that means is non-Christians cannot in and of themselves hear the Shepherd’s voice and therefore cannot be the rule by which the canon of the Bible is determined. Instead, the Bible is authenticated by itself and recognized by the Christians that read it. In our study so far, the Reformed Apprentice must recognize that being a believer is necessary to having the tools by which a self-authenticating scriptural document is recognized.

John Piper and numerous other Protestant pastors lean on this verse to make it say that Scripture teaches that Scripture is Scripture… even though in context, Jesus isn’t speaking about Scripture at all.

What are the implications of this interpretation?

To avoid acknowledging the Church’s infallibility, this invents individual infallibility. In other words, you can’t trust the Catholic Church to get the canon of Scripture right, because the Church is fallible. But you can trust me to get the canon of Scripture right, because I’m a sheep who hears the Shepherd’s voice. And every other true believer is equally infallible. It means that anyone who gets the canon of Scripture wrong isn’t a true believer. As McMahon writes, “the Bible is authenticated by itself and recognized by the Christians that read it,” while “non-Christians cannot in and of themselves hear the Shepherd’s voice.” As Christ said in John 10:26, “you do not believe, because you do not belong to my sheep.” So if your Bible has a different number of books in it than mine does, then you must not be a Christian.If you’re using the “I’m a sheep” argument to justify your canon of Scripture, you can’t disagree with this point, because it would require admitting that someone could be saved, could earnestly seek the truth, and still get the canon of Scripture wrong… the very conclusion this argument tries to avoid. If you’re going to say that all Christians can know the canon from hearing the voice of Jesus, then it follows that all those who don’t agree with your canon (or who agree with your canon, but without hearing the voice of Jesus) aren’t Christians. But this forces you into arguing that Catholics and Orthodox aren’t real Christians, since if we were, we would have the 66-book canon. And, of course, it’s not just modern believers that you’ll have to excommunicate… This standard disqualifies every Christian before the Reformation. The 66-book Protestant Bible didn’t exist before the Reformation. Even those Christians who thought that it should be the canon, like St. Jerome and Rufinus, (a) didn’t actually have a 66-book canon, and (b) didn’t base their argument off of this “I’m a sheep” line of argumentation. Rather, they based their arguments off of things like the Jewish canon at the time, and a mystical interpretation of the 22 books in the Hebrew Bible and the 22 letters of the Hebrew alphabet. But Protestants employing this “I’m a sheep” argument can’t accept these arguments, since “non-Christians cannot in and of themselves hear the Shepherd’s voice and therefore cannot be the rule by which the canon of the Bible is determined.”So you can’t just excommunicate modern Catholics and Orthodox. You’ve also got to toss out the Christians who defined the Trinitarian doctrines, the New Testament canon, who solved the Christological controversies for you, etc. Apparently, they weren’t Christians, and so you can’t trust their judgment. Oh, and while you’re at it, make sure to throw out Luther and Calvin, since neither of them believed in the 66-book Protestant canon, either. This blasphemes Christ. Many Catholics respond to these arguments that Catholics aren’t Christians by pointing out how rude and uncharitable it is. I hate that response, because it doesn’t address the truth or falsity of the thing. If someone is a member of a non-Christian group presenting itself as Christian, the most charitable thing you can do is draw them back to Christ.No, the problem with this whole “Catholics aren’t Christians” argument is that it’s blasphemous. All “total apostasy” claims are. In Luke 15:1-7, Jesus again compares Himself to a shepherd with a hundred sheep. When one goes missing, He leaves the ninety-nine to go after the lost one until He finds it. He then “lays it on his shoulders, rejoicing. And when he comes home, he calls together his friends and his neighbors, saying to them, ‘Rejoice with me, for I have found my sheep which was lost.’” (Lk. 15:5-6).Total apostasy theories, in contrast, say that Christ lost His whole flock , that all 100 went astray and that He failed (or declined) to bring any of them back. That’s not just an indictment of the errant flock; it’s an attack on the Shepherd. As Christ tells us, a shepherd who sees the wolf coming, and lets him snatch and scatter the sheep is unworthy to even be called a shepherd (John 10:12). To say that the entire Church disappeared, that the entire flock of Christ was lost, is to say that the Good Shepherd ceased to be Shepherd, or was never anything more than a hireling.

II. The Pro-Church Interpretation

A better interpretation of John 10 is that Christ isn’t promising this clarity to every individual sheep, but to the sheep collectively… and through the Church. It’s true that He promises that the sheep will hear His voice, but He also sends out the 72 saying that “He who hears you hears me, and he who rejects you rejects me, and he who rejects me rejects him who sent me.” So when we listen to the Church, we listen to Christ. And that’s the mark of being a faithful sheep: our fidelity to our earthly shepherds, the ones that Christ promised us in Jeremiah 3:15 (“And I will give you shepherds after my own heart, who will feed you with knowledge and understanding”).

Let’s return to Christ’s words in John 10:16, “I have other sheep, that are not of this fold; I must bring them also, and they will heed my voice. So there shall be one flock, one shepherd.” His meaning here is clear. When He speaks of “this [sheep]fold,” He means Israel. When He speaks of His “other sheep,” He means the faithful Gentiles. And when He promises to incorporate them into a single flock, He’s speaking of the Church.

In doing so, He’s repudiating the Protestant vision of an “invisible Church.” That’s the idea that all Christians are one simply by virtue of shared faith in Christ, and so corporate reunion is neither necessary nor possible (nor, in some views, even advisable). So we’re “one Church,” but we aren’t one ecclesial body, and we preach contradictory creeds. The Eucharist is either Jesus Christ or idolatry. Marian veneration is either the respect due our Mother, or idolatry. The priesthood and Sacraments are either critical for our salvation or un-Christian accretions.

But of course, that isn’t what Jesus was speaking of. The faithful Jews, Samaritans, and Gentiles already had that kind of union: a union in which you disagree with each other, and sometimes hate each other’s guts, but are still seeking the same God. So any vision of Church that subs Catholics and Orthodox and Protestants as modern-day Jews and Samaritans and Gentiles is a Biblically-weak vision of the Church. Christ promises us more: that we won’t just have one shepherd, but that we’ll actually become one flock. Later in John’s Gospel, He’ll go even further, praying that we may have the radical communion found within the Trinity Itself (John 17:20-23). At a bare minimum, this means a single, unified visible Church with a single Creed, “of one heart and soul,” like the early Church (Acts 4:32).

This is a ringing endorsement of the Catholic Church, and of her necessity. And this gives us a great rubric for our own spiritual journey. If you find yourself breaking off from the other 99 sheep, it’s because you’re the one who is lost. And this same logic applies whether it’s 33 A.D., or 1517, or 2015, or some point in the far distant future. You can’t both break off from the Church and follow the Shepherd’s will for your life. Hear in this the voice of our common Shepherd calling you to rejoin the flock.