What Is the Church?

By | February 6, 2026

The Unity of the Church

What defines, or rather, what should define, the “one, holy, catholic, and apostolic” Church? In what does the unity of the Christian Church (chiefly) consist? One can find many different answers to this question depending on whom one asks, but most answers can be categorized under four main headings: (1) a specific institutional hierarchy, (2) a set of doctrines, (3) a set of practices, and (4) the Holy Spirit.

During the first century AD, while the original apostles were still alive, (1–4) largely coincided (Acts 2:42–47). There was one cohesive institution that was largely agreed on matters of doctrine and practice and that bore witness to the working of the Holy Spirit in its midst. Over time, however, (1) gradually took precedence. To be a “true” Christian you had to be connected to the “right” institutional body, which body in turn defined the “correct” doctrines and practices. It was only within those boundaries that unity in the Spirit was thought possible. This shift was partly political and partly apologetic. To protect the Church’s apostolic doctrine and practice from heretical infiltration and corruption by Gnostics and others, and drawing on apostolic precedent that placed bishops over presbyters (priests) (cf. Acts 21:18; Titus 1:5; 1 Tim. 5:17–22) there emerged the ideas of a monarchical episcopate (i.e., the idea that there should be only one bishop over a city or a region) and apostolic succession (i.e., the idea that there must be an unbroken chain of ordination from the original apostles to their episcopal successors to the priests). This monarchical structure enforced orthodoxy and orthopraxy by excommunication, exclusion from the Church community (Matt. 18:15-17; 1 Cor. 5). Over time excommunication became associated primarily with exclusion from the sacraments, particularly the sacrament of communion, that is, the Eucharist. To put “teeth” into the threat of sacramental exclusion there developed the twin doctrines of sacramental necessity (i.e., one must be baptized, partake of the Eucharist, etc. to be saved; see John 3:5 and John 6:53–54) and sacramental validity, i.e., the salvific efficacy of the sacraments depends on their being performed in the “right” sort of way (right intent, right matter, right form) and by the “right” sort of person (a priest ordained by a bishop in apostolic succession). These two doctrines gave bishops in the institutional Church monopoly control of the means of salvation. Hence, we have Cyprian of Carthage’s (c. 210–258) famous declaration that “there is no salvation outside the [institutional] Church” (extra ecclesiam nulla salus). This made excommunication a potent tool for suppressing not just heresy but any kind of dissent—you best not get on the bishop’s bad side ’cause he can send you to hell by kicking you out of the ecclesial “ark” of salvation.

Of course, there was still occasional infighting, especially when bishops disagreed with other bishops. And then, in 1054 AD, the “Great Schism” happened between East and West. There were now two independent institutional Churches—Roman Catholicism in the West and Eastern Orthodoxy in the East—with partially competing doctrines and practices. Yet both institutions claimed, and still claim, to be the one, holy, catholic, and apostolic Church. The natural result was not only a literal sundering of communion between Christian communities, but also to an exclusionist and triumphalist mindset. To be a “true” Christian one had to be a member in good standing with the “right” ecclesial institution—namely, us—because we’ve got “it factor” making us the true Church and not those other guys.

Things obviously didn’t stop there, however. With the Reformation schisms proliferated in the West. Some groups insisted on (2) as a fundamental ecclesiastical criterion. For them, to be a “true” Christian one had to affirm a “confession” endorsing specific doctrinal positions. The result was a highly intellectualized conception of the Church with tight doctrinal policing. Other groups emphasized (3)—to be a “true” Christian was primarily to engage in (or avoid) certain practices, whether liturgical or social. The result of this emphasis was a ritualistic and/or moralistic conception of the Church. Still other groups emphasized (4) and deprecated (1) and, to some extent also (2) and (3). To be a “true” Christian, on this conception, is to be united with Christ through the Holy Spirit. All of those so united were said to constitute an “invisible” Church, one which only partly overlapped with the variously institutionalized “visible” Church. The result of this emphasis was an individualistic ecclesiology, one focused on private spiritual experiences above all else.

In my view, a proper understanding of the Church needs to balance (1–4). It should neither exclude any of those criteria of Church unity nor allow any of those criteria to completely dominate the others. Institutional unity (1) is important insofar as the Church is intended to be a visible expression of Christ’s body (Matt. 5:13–16), but this has to be balanced by unity in the Spirit (4) if we are to avoid triumphalism and authoritarianism on the one hand and rampant individualism on the other. However highly we regard certain ecclesial institutions, it must be kept in mind that the Spirit moves as He wills (John 3:8). If the Spirit wills to raise up Christians outside the standard institutional protocols (cf. Matt. 3:9 and Acts 10:44–48), then He has that prerogative. Christ is the head of the Church (Eph. 5:23; Col. 1:18), not any institutional hierarchy. Established ecclesial institutions should not become inflexibly unable to receive the “new wine” that the Spirit pours out (Matt. 9:17). Conversely, independent movements of the Spirit should seek integration into established Christian institutions and not permanently splinter off, thereby forsaking the larger ecclesial assembly (Heb. 10:25) so that the Church may be one (John 17:20–23). The gifts of the Spirit are intended for the body of the Church, not merely for private individuals or isolated communities (1 Cor. 12:7). Complete integration may not be possible if the established institutions have become too inflexible, but better integration should always be sought to the extent that core doctrinal (2) and practical (3) differences allow. Note that in John 17 Jesus prays for the practical oneness of the Church. Metaphysically speaking, the unity of the Church is guaranteed by Christ’s headship. The totality of those actually connected to Christ by the Spirit constitute the one, true Church. But practical unity isn’t guaranteed by definition or spiritual metaphysics. Otherwise Jesus wouldn’t have needed to pray for it and encourage his disciples to strive for it.

Just as (1) and (4) help balance each other out, so do (2) and (3). Doctrinal unity (2) or orthodoxy (i.e., right teaching) reminds us that the Church has a tradition with core doctrinal commitments. “No creed but Christ” may sound nice as a slogan, but it’s a prescription for doctrinal and institutional chaos. The Church remains “apostolic” only if it holds fast to apostolic teaching (2 Thess. 2:15; 2 Tim. 1:13; Titus 1:9; Jude 1:3). When overemphasized, this can lead to over-intellectualism and “heresy hunting” inquisitions, but underemphasized it sends the message that doctrine and the practices those doctrines inform are unimportant. Without a doctrinal backbone, the Church will eventually collapse into spineless irrelevance. Conversely, practical unity (3) or orthopraxy (i.e., right practice) reminds us that the Church is not just or even primarily a doctrinal debate society but a training ground for righteousness and a hospital for wounded souls. People will know Christians by their love for one another (John 13:35) and by the mercy and practical assistance they extend to others (James 1:27; Gal. 6:10). When overemphasized this can lead to moralistic pride. When underemphasized, however, it leads to a Church that is “lukewarm” (Rev. 3:16) and “good for nothing” (Matt. 5:13).

In sum, the unity of the Church is multi-dimensional. Each of (1–4) should be valued and sought for. But objectively and metaphysically the ultimate ground of Church unity is the spiritual connection of individual believers to Christ. The Church consists of all of those, past and present, who by the Spirit are “joined” to Christ (1 Cor. 6:17; Eph. 2:18–22; Eph. 4:15–16).

Normative versus necessary

One thing the Bible is very clear about is that Christ, not any pope, patriarch, or pastor, is the head of the Church (Col. 1:18). To be part of the Church, therefore, is to be “in Christ” (Rom. 12:5). We should consider then the question “What does it take to become and remain united to Christ?”

Is it baptism? No. Baptism is a sacrament of initiation into the Church, but it is not necessary for one to be “in Christ.” This is evidenced both by Jesus’s words to the thief on the cross (Luke 23:43) and by the salvation of Cornelius and his household (Acts 10:44–48). The former passage might perhaps be sidelined by virtue of its taking place before the Resurrection and before Pentecost, but not the latter passage. Here we are clearly told that the Holy Spirit came upon Cornelius and his household and only then were they baptized. While this doesn’t undermine the normative function of baptism as a rite of initiation, it does show that baptism, whether by a duly ordained priest or even by the apostle Peter himself, is not necessary for being in Christ. What is necessary is union with Christ through the Holy Spirit. Indeed, if baptism were strictly necessary, then we should be baptizing babies as soon as they are born and new converts as soon as they sign up for catechism. Delay of any duration makes no sense if eternity is really on the line. That almost nobody does this shows that the vast majority of the Church does not believe in the necessity of baptism but only its normativity.

Is it right doctrine? To some extent, yes, though the necessary content is fairly minimal. Thus, Hebrews 11:6 says that “without faith it is impossible to please him, for whoever would draw near to God must believe that he exists and that he rewards those who seek him.” 1 John 5:1 adds that “everyone who believes that Jesus is the Christ has been born of God.” To believe that Jesus is the Christ, is to believe that Jesus is the Messiah, the unique mediator between God and man, the only “name under heaven given to mankind by which we must be saved” (Acts 4:12). This entails believing that Jesus is “the Son of God” (John 20:31; 1 John 5:5) and “the Lord” (Romans 10:9). And since Christ is the mediator between God and man, one must also believe that Christ has “come in the flesh” (1 John 4:2–3) and that “God raised him from the dead” (Romans 10:9). Now, this might seem like a lot, and there are certainly profound implications of these claims, implications that would take some centuries to fully unpack in later councils and creeds, but I would strongly caution against reading sophisticated conciliar theology into these belief requirements. After all, Jesus makes clear in all three synoptic gospels that the kingdom is accessible to young children: “Let the little children come to me, and do not hinder them, for the kingdom of heaven belongs to such as these.” (Matt. 19:14; cf. Mark 10:14; Luke 18:16). From our position in history it makes sense to uphold ecumenical doctrinal statements like the Nicene Creed as normative. But again, normative is not the same as necessary.

It is membership or active participation (Eucaristic or otherwise) in some particular ecclesial institution? No. Such participation is normative (Heb. 10:25) but not necessary, as again the Biblical examples of the thief on the cross (Luke 23:43) and Cornelius and his household (Acts 10:44–48) make clear. In both cases salvation comes independently of and prior to sacramental initiation into any particular ecclesial institution.

Is it good works and service to others? No. Such service is normative (James 1:27; Gal. 6:10) but it is not sufficient (1 Cor. 13:1–3) and not necessary because it is evident in Scripture that individuals, like young children, the thief on the cross, or the prodigal son (Luke 15:11–32) can become saved despite not (yet) having any works other than bare repentance to show for it.

Can we say anything specific and positive about what the one, holy, catholic, and apostolic Church should look like in practice? Yes, but again we need to distinguish between features that are sine qua non or necessary and features that, all other things equal, are really nice to have and perhaps even normative but that are not strictly essential or necessary.

Here’s a partial list of candidate features:

  1. Nicene / Chalcedonian theology
  2. Expository preaching
  3. Traditional liturgy
  4. Engaging worship – active parishioner participation in the liturgy
  5. Apostolic succession (i.e., an unbroken ordinational pedigree going back to the original apostles)
  6. Communion in both kinds (i.e., parishioners partake both bread and wine)
  7. Open practice of spiritual gifts
  8. Visible growth in the fruit of the Spirit
  9. Involvement in practical ministry (e.g., soup kitchens, prison ministry, crisis pregnancy centers, education, etc.)
  10. Active evangelism and missions
  11. Monastic orders

Obviously there are more things that could be added, and some of the above could be subdivided or differently nuanced, but I think it’s fair to say that all of the above are certainly “nice to haves.” All things equal, we’d like our theology to be in continuity with the early Church and early ecumenical councils. The traditional liturgies are beautiful, educational, and uplifting. Expository preaching and Bible teaching are obviously good. Apostolic succession is certainly a nice thing if you can have it. And so on. Of course, smaller, poorer, and more remote churches will generally be more limited in what they can manage.

Opinions will likely differ here, but in my view, broad continuity with the apostolic tradition in both theology and practice is as close to a necessity or sine qua non as we can find. That means having a robust, traditional liturgy and adhering to the central deliverances of the early ecumenical councils (e.g., the Nicene Creed). Maintaining an orthodox Christology is, I believe, quite essential to Christianity. That doesn’t mean that to be a Christian one has to fully understand and accept all the nuances of orthodox Christology, but the main position should be affirmed (Christ is one divine person, the Word or Logos, who is by nature both fully divine and fully human). I also believe that the Trinity is quite essential to Christianity. This doesn’t mean that one has to understand and accept all the nuances of, say, monarchial trinitarianism, or any other model of the Trinity, but the core position that God by nature eternally and essentially consists of three distinct divine persons, Father, Son, and Holy Spirit should be affirmed.

I also believe that some concern for practical ministry and evangelism/missions is necessary. Any church that doesn’t engage in such endeavors in accordance with their means is being disobedient to the Great Commission (Matt. 28:19–20) and to clear apostolic teaching (James 1:22–27).

I do not believe that apostolic succession is a “must have,” nor do I believe that there must be a unique, visible institutional Church, a status Eastern Orthodoxy and Roman Catholicism both claim for themselves. As I read the Scriptures, the kind of succession that most matters is adherence to apostolic teaching. Having an unbroken ordinational pedigree is certainly nice to have, but I see no reason to think that it’s necessary in order to have “valid” sacraments, i.e., sacraments capable of communicating God’s uncreated grace. Institutional unity is also obviously nice to have and something normatively to be sought after (John 17:20–23), but realistically at this point in history it’s not an immediately achievable reality. Unless one is prepared to say, quite implausibly, that huge numbers of sincere, devout Christians are not “in Christ” and thereby consign them to hell, we must accept that visible, institutional unity, while normative, is not necessary.

Of the remaining items on my list (monastic orders, communion in both kinds, spiritual gifts, the fruit of the Spirit, and engaging worship) I think the practice of spiritual gifts and growth in the fruit of the Spirit (Gal. 5:22–23) are “must haves.” The others, while arguably very important and even normative, are merely “nice to haves.” Since it is by the Spirit that Christians are joined to Christ, and since He gives gifts believers for the edification of the wider Church, we should expect to evidence of the Spirit’s working in the lives of true Christians and in every true Christian community.

In closing, I believe the unity of the Church is most fundamentally a unity in Christ by the Spirit. This is not an “invisible” unity, however. Because the Spirit is living and active in the lives of all true Christians, there must be visible evidence of this. But the visible is not equivalent to the institutional.

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