What is the role for denominations? What is the role for broad parachurch ministries or organizations? How should we understand confessional identity? If we are to have unity in essentials, what are those essentials? Where should Christians agree to disagree? Where should churches agree to disagree? What are the right doctrinal boundaries for churches, for denominations, for movements, for institutions, for friends?

If there are any aspiring doctoral students out there looking for a profitable subject for research and writing, may I suggest to you the subject of church unity. For the past hundred years, church unity has largely been a liberal concern. At times the concern has been an admirable reminder, or a necessary rebuke, that our unity cannot be merely “spiritual.” At other times, unity has been a blunt instrument with which to bludgeon conservatives who don’t share the same doctrinal latitudinarianism and ecumenical pipe dreams. “Unity” has become a byword among evangelicals, especially those in mixed denominations who can be shamed into silence by the mere whisper of the word.

But no matter the abuse, we must conclude from Scripture that the union and happy communion of the saints are precious to God.

Just as importantly, it’s easy to see how problems of “unity,” even among Bible-believing Christians, continue to baffle and confuse. Can Baptists partner with Presbyterians? Can we associate with those who associate with those we wouldn’t associate with? What is the role for denominations? What is the role for broad parachurch ministries or organizations? How should we understand confessional identity? If we are to have unity in essentials, what are those essentials? Where should Christians agree to disagree? Where should churches agree to disagree? What are the right doctrinal boundaries for churches, for denominations, for movements, for institutions, for friends?

I have a lot of questions racing through my mind about church unity. I started writing a book on the topic once, but it seemed too difficult and required a level of scholarship I wouldn’t have time for. The issues are complicated and tremendously important. Thinking through church unity is not a luxury, but required theological homework for any pastor, especially those belonging to imperfect denominations (all of them!) and working with various networks and broader coalitions.

So in an effort to get going on some of that homework, let me offer several points that can be drawn from Ephesians 4:1-16. This is the classic text on church unity (along with John 17) and the most practical for day to day church life. Make sure you read the sixteen verses before reading the following points I glean from the text:

1. Unity is a relational good we are called to maintain where true spiritual unity is already present. Having just finished explaining how the mystery of the gospel brings together Jews and Gentiles, Paul exhorts the Ephesians to “maintain the unity of the Spirit in the bond of peace” (v. 3). The assumption is that the Jews and Gentiles in Ephesus already share the most important things in common. The goal now is to be patient with each other and bear with one another in love (v. 2). The call to unity is the summons to show in relational practice what is already true in spiritual reality.

2. The spiritual reality on which relational unity is based is described in seven parts: one body, one Spirit, one hope, one Lord, one faith, one baptism, one God and Father of all. Paul wants the Jews and Gentile Christians in Ephesus to get along because, despite their historic, ethnic, and cultural differences, they have these deep spiritual realities in common.

3. Presumably, then, Paul is not exhorting everyone willy-nilly to maintain the unity of the Spirit. Indeed, there is no unity of the Spirit to maintain without, for example, a shared allegiance to our one Lord Jesus Christ and a shared commitment to our one faith. That Paul is thinking of an objective standard of faith in verse 5 (ala Jude 3) is confirmed by his use of “faith” in verse 13. This is an absolutely critical point. Church unity is dependent upon a common set of doctrinal beliefs. If we do not share “one faith” with Mormons or liberals or Unitarians, then we have no unity to maintain. Of course, this begs the question: what core doctrines constitute “the faith”? The ecumenical creeds are a start. A shared understanding of Scripture, justification, the resurrection, the atonement, basic Christian morality, the Trinity, and the person of Christ are certainly some of the non-negotiables. But however “the faith” is defined, the important point from Ephesians 4 is that it can be defined and circumscribes our shared unity.

4. Paul celebrates diversity in the midst of this unity, but the diversity is not theological. He expects an ethnic diversity (Jew-Gentile) and a diverse array of gifts and offices all working toward the same end (vv. 7-13)

5. Unity is something we have; something we maintain; and something we grow into (v. 13). While Paul expects there to be a common faith, he also allows that we will have to mature and grow into this unity of faith.

I believe the previous five points suggest a few other points by way of application.

1. There is no command to have unity with those who do not share the same basic elements of our faith.

2. If the command to “maintain the Spirit of unity in the bond of peace” is mainly a call to relational oneness in view of spiritual oneness, there is nothing in Ephesians 4 to suggest that Baptists and Presbyterians (for example) must necessarily be in breach of this command because they do not belong to the same ecclesiastical institution.

3. The “not yet” of verse 13 may, in fact, be our allowance (though not our desire) for some difference of opinion here on earth. Hopefully as we love and listen to those who are truly are brothers and sisters, we can increase in our knowledge of the faith and some of our disagreements can be minimized, even if we don’t completely attain the unity of the faith.

Like I said at the beginning, we need some of our best pastors, theologians, and historians to help the church understand what it means (and doesn’t mean) to be one. I’m only sketching a few bullet points. There are too many important issues at stake, and too many opportunities to bring God glory (or bring him dishonor), to ignore the biblical command to maintain the unity of the Spirit.

Kevin De Young has been the Senior Pastor at University Reformed Church (RCA) in East Lansing, Michigan since 2004.  Kevin blogs at the Gospel Coalition and this article is reprinted with his permission.