When I was a kid in the seventies, we often sang a song at church events and camps with this lyric:

We are one in the Spirit;
We are one in the Lord.
And we pray that all unity will one day be restored;
And they’ll know we are Christians by our love.

I remember thinking it was a bit corny; then as a teenager, I blew it off as clichéd as well as stylistically dated. But looking back now, I can see this lyric is actually quite profound, reflecting in simple words the sophisticated theology of Christian unity.

It’s a strange logic: in Christ, we’re already one, but we’re not yet one, so we must strive to achieve, maintain, or restore our oneness, until we finally attain our perfect, eternal oneness.

Strange Logic of Heaven

What makes this unity logic strange is that it begins with the assertion that we’re already one — otherwise, it follows a natural logical progression. But that’s just the thing: this logic is not natural; it’s supernatural. It’s the logic of heaven.

And it isn’t applied only to unity. We see this logic throughout the New Testament. The kingdom of God has come (Luke 17:20–21), and at the same time the kingdom of God is in the process of coming (Matthew 16:28). Christians have “been saved” (Ephesians 2:8), and at the same time we are in the process of “being saved” (1 Corinthians 1:18). Christians “have been sanctified” (Hebrews 10:10), and at the same time we are in the process of “being sanctified” (Hebrews 10:14).

“In this era, our status as redeemed saints is complete, but our experience of redemption is partial.”

So, when it comes to Christian unity, it shouldn’t surprise us that we’re told we “are all one in Christ” (Galatians 3:28), while at the same time becoming one (Ephesians 4:13). This logic reflects the nature of this awkward age between the inauguration and the consummation of Christ’s kingdom, which Christian theologians call the era of the already–not yet. In this era, our status as redeemed saints is complete, but our experience of redemption is partial. We are becoming what we are.

But as strange as this heavenly logic might sound, it makes very practical sense in our day-to-day lives as Christians. Here’s how.

‘Already’ Fuels ‘Not Yet’

God’s inexpressible gift of salvation in Christ is something we inherit from our Father as his adopted children (Ephesians 1:5, 11). But this inherited gift has a participatory dimension:

• Our justification (Romans 3:23–25) and the faith to receive it are given to us by God as a free (inherited) gift of his grace, and
• the evidence that this grace-gift is at work in us comes through our (participatory) “obedience of faith” (Romans 1:5).

It’s the participatory dimension of our inherited gift of salvation (and countless facets of this gift, like Christian unity) that explains the New Testament’s teaching on grace and works. The New Testament teaches that we are saved by God’s grace alone (Ephesians 2:8–9), and that works are necessary to our salvation (James 2:24). This can sound like a contradiction, but it’s not. Our works are not necessary in the causal sense — we don’t merit salvation by our works. Our works are necessary in the evidential sense — the fruit of works organically grows on branches that by faith abide in the “true vine” (John 15:1, 5).

This is the new-covenant reality of “by grace through faith” (Ephesians 2:8). We are saved by grace alone through the gift of faith alone, and the observable evidence that we are heirs of God’s gracious gift of salvation is manifest through our “work[s] of faith and labor[s] of love” (1 Thessalonians 1:3) — our obedience of faith. That’s what Jesus was getting at when he said, “If you love me, you will keep my commandments” (John 14:15). And it’s what his brother, James, was getting at when he said, “I will show you my faith by my works” (James 2:18).

Now, here’s how heaven’s already–not yet logic works as it pertains to our inherited oneness as Christians. Believing that we’re already one fuels our faith in God’s promise that, ultimately, we will be perfectly one. And it fuels our hope that all the obedient works of faith and labors of love to achieve, maintain, or restore our unity in this partial age — as discouraging and futile as they might appear to us at times — are not in vain in the Lord (1 Corinthians 15:58).

Our Duty: Tenacious Grace

Paul employs this heavenly logic when he urges the Ephesians (and us) to pursue unity in the opening verses of Ephesians 4:

I therefore, a prisoner for the Lord, urge you to walk in a manner worthy of the calling to which you have been called, with all humility and gentleness, with patience, bearing with one another in love, eager to maintain the unity of the Spirit in the bond of peace. There is one body and one Spirit — just as you were called to the one hope that belongs to your call. (Ephesians 4:1–4)

Christian unity is part of the inherited gift we receive when God, by his free, sovereign choice in election (Ephesians 1:4–6), calls us into the body of Christ. But it is also our participatory duty to “maintain the unity of the Spirit” as part of this gift of God’s calling.

To get some idea of the demanding nature of this duty, this obedience of faith, we just need to consider the little word all in Ephesians 4:2. We must bear with one another “with all humility and gentleness.” When was the last time you truly felt eager to maintain unity in a situation that required you to exercise all humility or all gentleness — in other words, in the middle of a significant, frustrating disagreement? Yeah, me too.

“This is love with rebar in its resolve; this is love with a spine of steel.”

This is nothing less than a call to tenacious grace and Calvary love. What happened on Calvary? Death. Voluntary death. Voluntary death for the sake of love. Voluntary death for the sake of love on behalf of those who don’t deserve that kind of love. This is love with rebar in its resolve; this is love with a spine of steel.

When Jesus commanded us to love one another just as he has loved us (John 13:34), this was the kind of love he was talking about.

By Our Love

That old chorus we used to sing fifty years ago ended on a convicting refrain: “And they’ll know we are Christians by our love.” It’s a close paraphrase of Jesus’s words in John 13:35: “By this all people will know that you are my disciples, if you have love for one another.” This might be a good time to bring that old chorus back.

Repeat that refrain a few times together as a church and, if the Spirit moves among us, it will provoke some hard questions. Especially when we think of how Jesus longed and prayed for our unity:

I do not ask for these only, but also for those who will believe in me through their word, that they may all be one, just as you, Father, are in me, and I in you, that they also may be in us, so that the world may believe that you have sent me. (John 17:20–21)

It requires the self-sacrificial love of tenacious grace to die to our own remaining sin and graciously bear with the remaining sin in other saints. But it’s this love that bears witness that we are followers of the One who laid his life down for his friends (John 15:13).

This unity is our inheritance in Christ. We are already one. Believing this fuels our faith in God’s promise that, ultimately, we will be perfectly one. And it will fuel all the obedient works of faith and labors of love that achieve, maintain, or restore our unity in this partial age. But we can’t do it alone. We need the Helper (John 14:26). For the love it requires to maintain the unity of the Spirit comes from the Spirit of unity himself.