In John 17:22 Jesus prays that the disciples would be “one, as we are one.” And in John 17:23, He desires that they (and us) be “completely one” (NRSV), “perfect in one” (KJV, NKJV),   “perfectly one” (RSV, NEB, REB), or in “complete unity” (NIV), or “perfected in unity” (NASB).

Now, it is pretty difficult to maintain that this entails no doctrinal agreement (and “perfect” agreement at that). And, reflecting on John 17:22, I don't think the Father and the Son differ on how one is saved, on the true nature of the Eucharist or the Church, etc. So how can Protestants claim this “perfect” oneness, “as we [the Holy Trinity] are one”, or even any remote approximation?

Furthermore, if Paul and the other apostles are to be trusted, the Catholic view of a unified, institutional, visible, apostolic Church (with a head: the pope) would seem to be far and away exegetically the best. Paul commands: “mark them which cause divisions and offenses contrary to the doctrine ye have learned; and avoid them” (Rom 16:17). In 1 Corinthians 1:10, he desires “no dissensions,” and that Christians should be “united in the same mind and the same judgment." No one can say this is simply a “warm fuzzy” love and mutual recognition. Paul goes on to condemn mere “contentions” in 1:11, and asks in 1:13: “Is Christ divided?”

In 1 Corinthians 3:3, Paul says that whatever group has “strife and divisions” are “carnal, and walk as men.” In 1 Corinthians 11:18-19 he seems to equate “divisions” and “heresies.” He calls for “no schism” in 1 Corinthians 12:25, etc., etc. (cf. Rom 13:13; 2 Cor 12:20; Phil 2:2; Titus 3:9; Jas 3:16; 1 Tim 6:3-5; 2 Pet 2:1).

How much more biblical evidence is needed to convince all of us that denominationalism and sectarianism are sins?

Protestant scholar Marvin Vincent, in his Word Studies in the New Testament, comments on 2 Peter 2:1 as follows:

A heresy is, strictly, the choice of an opinion contrary to that usually received; thence transferred to the body of those who profess such opinions, and therefore a 'sect.' . . . commonly in this sense in the NT (Acts 5:17; 15:5; 28:22) . . . See Acts 24:14; 1 Cor 11:19; Gal 5:20. The rendering 'heretical doctrines' seems to agree better with the context; false teachers bringing in 'sects' is awkward. (vol. 1, 689)

Romans 16:17 mentions doctrine (didache). In 1 Corinthians 1:10 Paul calls for being “perfectly joined together in the same mind.” Galatians 5:20: “strife, seditions, heresies” (according to Vincent above). Etc., etc.

H. Richard Niebuhr (Lutheran) stated that:

Denominationalism . . . represents the accommodation of Christianity to the caste-system of human society. (The Social Sources of Denominationalism, New York: Meridian Books, 1929, 6, 21)

Donald Bloesch (evangelical Protestant) observed:

There will never be real evangelical unity, let alone Christian unity, until there is an awakening to the reality of the oneness and catholicity of the church. (The Future of Evangelical Christianity, Garden City, New York: Doubleday, 1983, 56-57, 65)

Nevertheless, even the generally brilliant and insightful scholar and apologist Norman Geisler repeats the cliche which is the common Protestant response to these considerations:

Orthodox Protestants differ largely over secondary issues, not primary (fundamental) doctrines, . . . Protestants seem to do about as well as Catholics on unanimity of essential doctrines.(Roman Catholics and Evangelicals, Grand Rapids, Michigan, Baker Book House, 1995, 193)

This is special pleading, in my humble opinion. Who's to decide what an “orthodox” Protestant is? And who's to decide what qualifies as a “secondary issue”?

All Protestants accept each other as brothers? No: not always. Of course, there are all the mutual anathemas of the “Reformers,” too, such as Luther regarding Zwingli as “damned” and Calvin calling Luther “half-papist” and an “idolater.” Many Calvinists (of a certain sort) pride themselves on being the true “Reformation” Protestants, while the rest of 'em are second-class Protestants, if at all.

I don't want to spend my whole life searching for the basic truths of Christianity. There is no “unity” in Protestantism in the biblical sense. I grant that there is (very broadly speaking) a “mere Christianity” type of unity, but why should anyone accept this “lowest common denominator” unity? I want all the truth and nothing but the truth.

Why should any Christian tolerate error, when all lies come from the father of lies (Satan)? We know for sure, from straightforward logic (the presence of numerous mutually contradictory positions) that error (falsehood) is rampant within Protestantism. Therefore, many millions are (by logical necessity) holding to numerous theological falsehoods.

The Catholic Church not a denomination, but rather, the original New Testament Church. Just because a bunch of sects claim to be another sort of “church” (invisible), doesn't negate the fact that only one has the historic pedigree all the way back (apostolic succession), whereas no other Christian communion does. This is called “triumphalism”? Whether it is that or not, it’s New Testament ecclesiology.

What Protestants in our time will dare take a stand for whatever brand of Christianity they espouse, as the real, true, Christian belief, which is superior to all others? At least the so-called “Reformers” believed strongly enough in each of their sects to anathematize the “dissidents” outside of them. In those days, John Calvin characterized Lutheranism as a whole, as “evil.” Today’s “post-Enlightenment” Protestants wink at differences and pretend that there is a unity in “essentials.” And as a result many of us have moved from Protestantism to Catholicism and found peace at last.

Protestants are free to believe and worship as they please, and we assuredly regard them as brothers in the faith and the Body of Christ, but we wish they would call a spade a spade and squarely face the glaring inadequacies of denominationalism. I'm happy to renounce much of what happened in the Inquisitions, Crusades, etc. Why can't Protestants renounce sinful sectarianism? But if they do, what is the plausible alternative? It’s Catholicism.