If you found out tomorrow that your beloved youth pastor had become a staunch modalist—he now insists the Father, Son, and Spirit are actually one person in three manifestations instead of three distinct persons—would your church excommunicate him? Or would that seem like splitting hairs? Is the Athanasian Creed really right to say, “Whoever wishes to be saved must think thus of the Trinity. And whoever rejects this faith will perish everlastingly”? Or is that the overstatement of the millennium?

How much does the Trinity matter to you? If you found out tomorrow that God is actually only one person instead of three, would your relationship with God feel any different? Would it require a drastic overhaul in the way you think or witness or pray? How much does the Trinity matter to you personally?

How much does the Trinity matter to your church? If you found out tomorrow that your beloved youth pastor had become a staunch modalist—he now insists the Father, Son, and Spirit are actually one person in three manifestations instead of three distinct persons—would your church excommunicate him? Or would that seem like splitting hairs? Is the Athanasian Creed really right to say, “Whoever wishes to be saved must think thus of the Trinity. And whoever rejects this faith will perish everlastingly”? Or is that the overstatement of the millennium?

Judging by the church’s historic creeds, Christians used to think the Trinity is really important. Judging by the honest answers likely given to the questions above, many modern Christians have lost the sense of why it’s so important, even if they’ve retained it in their doctrinal statements. But judging by a growing number of voices, there’s a renewed sense we’ve lost something precious that needs to be recovered.

Most of us have retained a formal belief in the Trinity. What we need to recover is an understanding and a felt sense of why it matters so much. To help us do that, here are two reasons why the Trinity matters.

1. The Trinity Matters because the Gospel Matters

The Trinity isn’t some complicated distraction from the simple gospel—it’s actually part of the gospel. Now, as Fred Sanders once quipped, this doesn’t mean you should begin every witnessing encounter, “God loves you and has a wonderful Trinity for you to understand.” You don’t have to unpack the Trinity in every gospel presentation (although you might, especially if you’re talking to a Muslim).

Nevertheless, I would maintain that the Holy Trinity is right below the surface in even the simplest gospel presentation (and it may poke its head up now and then).

If you don’t believe me—if you still think the Trinity is just advanced theology for the experts—consider John 3:16, one of the most famous and simple gospel statements in the whole New Testament. And think carefully about what it says: “For God so loved the world that he gave his only begotten Son, that whoever believes in him should not perish, but have eternal life.”

Did you ever notice that even in John 3:16 you’re already wading into trinitarian waters? Don’t get me wrong—I’m not saying that the whole doctrine is here full-blown (you’ll need the rest of John’s Gospel to get the Holy Spirit, including a few verses earlier in 3:5). But just think about all the Trinity-related truths stated or implied in this one simple verse. I can think of at least six:

1. Two of the three persons are explicitly mentioned: God and his only begotten Son.
2. The fact that God has a Son tells us that he’s a Father. It also suggests that when Scripture speaks simply of “God,” it’s often referring specifically to the Father.
3. The fact that the Father gave his Son tells us they’re distinct persons. The Father can’t be the Son if he gave the Son.
4. It says something about how the Father loves his Son that giving him would be the ultimate demonstration of his fatherly love.
5. The fact that Jesus is referred to as God’s only Son suggests there’s something unique about Jesus’s sonship. After all, Scripture teaches that God has other sons (Job 2:1; Heb. 2:10). In fact, John has already told us in 1:13 that when we believe in Jesus, we become God’s children. So how can he say that Jesus is God’s only Son? Answer: because while we are sons by grace, he is Son by nature. We become God’s sons by adoption and regeneration, but he doesn’t become God’s Son—he simply is God’s Son, begotten from the Father before all worlds, God from God, light from light, begotten and not made.
6. John 3:16 tells us that this is how we receive eternal life—by the Father giving his Son. Salvation is trinitarian. The Father has an only, eternally begotten Son, and in his love for sinners he sends that Son for us. The Son of God becomes a Son of Man, so that the sons of men might become sons of God. And then, the Father and Son send their Spirit to to dwell in us so we can experience this new life as sons (John 3:5, 7:37–39, 15:26, 16:12–15).

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