Recently, two Protestants (on my Facebook page) vigorously and vociferously condemned this doctrine (or more specifically, particularly objected to any Christian saying that their own church was the one true Church). Their objections flow logically from Protestant first principles. They are simply consistently and sincerely following their own system, which does not allow this belief to be included. I shall explain how and why I think that is.

Sola Scriptura (the Protestant rule of faith) is the belief that there is one and only one final, infallible authority in Christianity: Holy Scripture. It follows by necessary logical exclusion that sacred tradition and the Church are not infallible; therefore, neither the Catholic Church, nor Orthodoxy, nor any Protestant sect can be considered “the one true Church.” Such a category is ultimately meaningless in Protestant ecclesiology.

It all came about historically when Martin Luther decided to dissent from many (not all) Catholic teachings. Once he took that path, he had no choice but to arbitrarily adopt sola Scriptura, since by definition, the Church and councils (one form of tradition) could not err on basic Christian doctrines.

Therefore, he had to reject the infallible authority of the Catholic Church; otherwise, he would have no case for his so-called “Reformation” of said Church, constructed on a vastly different rule of faith. Previously, the rule of faith in Christianity had been the “three-legged stool”: Bible-Tradition-Church.

It came to a head in 1519 in the Leipzig Disputation between Luther and Johann Eck. Protestant Luther biographer Roland Bainton described the climactic scene of the debate:

“Let me talk German,” demanded Luther. “I am being misunderstood by the people. I assert that a council has sometimes erred and may sometimes err. Nor has a council authority to establish new articles of faith. A council cannot make divine right out of that which by nature is not divine right. Councils have contradicted each other, . . . A simple layman armed with Scripture is to be believed above a pope or a council without it. As for the pope’s decretal on indulgences I say that neither the Church nor the pope can establish articles of faith. These must come from Scripture. For the sake of Scripture we should reject pope and councils.”

(Here I Stand, New York: Mentor, 1950, 90)

It was the contra-Catholic mentality (some things never change) that compelled Luther to dissent against the received rule of faith. By logical and/or practical necessity, in order to advance his agenda, and backed into a corner in this debate, he had to reject ecclesial infallibility. Once that was ejected from ecclesiology, then the default or fall-back position was sola Sciptura: a thing that is neither taught in the Bible anywhere, nor by any major Church father. The three-legged stool, on the other hand, is all over Scripture. For example:

1. In the prerogatives of Peter: the leader of the apostles, commissioned by Jesus to head the Church.

2. In apostolic succession (particularly, the election of Matthias to succeed Judas).

3. In episcopal government (bishops and hierarchy).

4. In frequent and solemn biblical condemnations of denominations and sects and assertions of one Church, one faith, one truth, etc.

5. In the Jerusalem Council, which issued a binding decree, guided by the Holy Spirit, which Paul then proclaimed for observance (Acts 16:4) throughout Asia Minor and elsewhere.

6. In the implications of 1 Timothy 3:15 (Church as the pillar and foundation of the truth).

7. In how the Bible describes the nature of the Church.

8. In Jesus' expressed opinions on tradition; e.g., concerning Moses' Seat.

9. In the biblical espousal of positive, apostolic tradition.

10. The “problem” of the determination of the biblical canon: to which Protestants have no coherent solution.

Once sola Scriptura is firmly in place, any final or authoritative notion of a visible, institutional Church bolstered by apostolic succession, whose teachings are authoritative and binding, has to go. And we see that in a document like The Westminster Confession:

I. The catholic or universal Church, which is invisible, consists of the whole number of the elect, that have been, are, or shall be gathered into one, under Christ the Head thereof; and is the spouse, the body, the fulness of Him that fills all in all.

II. The visible Church, which is also catholic or universal under the Gospel (not confined to one nation, as before under the law), consists of all those throughout the world that profess the true religion; and of their children: and is the kingdom of the Lord Jesus Christ, the house and family of God, out of which there is no ordinary possibility of salvation. . . .

V. The purest Churches under heaven are subject both to mixture and error; and some have so degenerated, as to become no Churches of Christ, but synagogues of Satan. Nevertheless, there shall be always a Church on earth to worship God according to His will.

(Chapter XXV: Of the Church)

Thus, we see that Protestants today consistently follow these unbiblical and arbitrary traditions of men. They're perfectly sincere and well-intentioned. The problem lies not in character or some supposed serious moral defect. Rather, it is in the adoption of false premises, and lack of understanding as to how they began, and how hostile they were to all of previous Christian history and to the Bible.

This is why Protestants not infrequently say that it is “condescending” or unecumenical (most “intolerant”!) for anyone to believe in one true Church. It's because their arbitrary category restrictions do not allow these categories at all.

In fact, Catholics are simply following biblical, apostolic, and patristic teaching in a consistent fashion. If one believes in an identifiable, demonstrable one true Church, it is their duty to proclaim this to others, so that they can share in the fullness and joy and contentment of such a view (i.e., so they can join such a Church and partake of its unique benefits).