The Key to the Trinity: Making a Start

Let’s call the destination we are headed toward in this series the Happy Land of the Trinity.[1] It is a beautiful place to be, a place in the believer’s life where one is biblically convinced that the doctrine of the Trinity is true, and is therefore free to enjoy relationship with the Father, Son, and Spirit, to the full.

Let’s pretend that it is also a place at which you have not yet arrived, and that you have a long journey to go, and blocking your path are many locked gates. Consider these articles a recurring reminder that you hold a key to unlock the gates – and that key is Christ.

Yes, there are many obstacles to face when studying the Trinity. In this article and the next we will confront four of them. That will leave us with one remaining obstacle, a gate so obstinate (for some people) that we will need the rest of the series to open all its locks. But in every case, the key for getting through is Christ.

“But I lack the desire.”

Look at this first gate blocking our way. It’s the lack of desire we may have to study the Trinity doctrine seriously. We intuit that the subject matter is complex, that the effort required will be too great, and so we give up before making a start.

Perhaps you feel this now. You are as unmotivated by this study as I am by the age of the earth debate. You think: Here is my opportunity. A series of articles – I’ll only need to read one a month. I can work through the Scripture references slowly and prayerfully, and maybe the Lord will enable me to embrace this doctrine with my whole mind and heart. But it will require a great deal of thinking, and if I’m honest, I lack the desire to sort it all out.

How will you unlock this barrier? By using the key. I used to have no interest in sorting out family relationships. My eyes would glaze over when Grandma tried to explain how so-and-so was cousin to one of my dad’s aunts. Or was it on the uncle’s side? But then I met my future wife. And soon I was to marry her! Suddenly one family’s relations became important to me. How did my wife relate to so-and-so? No explanation was too technical. Having a love-interest made all the difference.

So it is with studying the Trinity. We are to marry Christ! (Eph 5:32; Rev 19:7). If we dream long enough about spending eternity with Him, we will soon find ourselves asking: How does He relate to God?[2] And to the Spirit? How do they relate to Him? The more we love Christ, the more willing we’ll be to research His eternal relations, even if such research gets quite technical at times. We’re to be married to Him, after all. Studying the Trinity becomes a way of expressing our love for Christ.

“But will it make any difference?”

The Lord Jesus Himself, then, is the motive for pursuing this study. But now a second locked gate obstructs our way: no matter how much we learn about His trinitarian relationships, what difference will it make? The thief on the cross didn’t know much about the Trinity and yet he still went to paradise. What’s the point in proceeding if it doesn’t make a difference?

Again, Christ is the key to this barrier. Let’s find a simple gospel verse that’s only about the Lord Jesus. The apostle John has a good one for us, and we’ll include the verse preceding it for context: “Now Jesus did many other signs in the presence of the disciples, which are not written in this book; but these are written so that you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in his name” (Joh 20:30-31 ESV).

Unlike other verses,[3] there is no trinitarian formula here. This verse tells us plainly who the Lord Jesus is. He is “the Christ, the Son of God,” and to believe in Him is to receive eternal life. But notice how looking exclusively at Christ pulls us in a trinitarian direction. When we consider who Jesus is (the Son), we soon find ourselves grappling with how He relates to God (the Son of God), and with who God is, for our Lord’s identity as the eternal Son of God means that God is eternally a Father. Does it not make a world of difference to pilgrims on their way to heaven to know that the heaven they are journeying toward is the home of a Father loving His Son from before the foundations of the world? (Joh 17:24).

There is a glorious interdependency at play. The Father cannot be who He is (the Father) apart from the Son; the Son cannot be who He is (the Son) without the Father. Each finds His distinct identity in His relation to the other. They are inseparable. And in addition to being “the Son of God,” the Lord Jesus is also “the Christ,” the One anointed with the Holy Spirit. Here we are, looking at a simple gospel verse calling us to faith in Jesus Christ, the Son of God, and yet the faith we’re being summoned to is inherently trinitarian. As Michael Reeves puts it, “When you start with the Jesus of the Bible, it is a triune God that you get.”[4]

The Lord Jesus is indeed the key to the Trinity. The God He reveals is a Father, loving His Son in the joy of the Holy Spirit (Mat 3:16-17).[5] This is the fundamental reality of the universe we live in (1Jn 4:8). What could be more relevant?

[1] This phrase comes from Fred Sanders, The Deep Things of God: How the Trinity Changes Everything (Wheaton, IL: Crossway, 2010), 62. But I am using it differently.

[2] See David Gooding, Part 1 – The Trinity, The Trinity (2007) (Ceryyduff, Belfast, 2007),

[3] E.g., Matthew 28:19 and 2 Corinthians 13:14.

[4] Michael Reeves, Delighting in the Trinity: An Introduction to the Christian Faith (Downers Grove, IL: IVP Academic, 2012), 37.

[5] Reeves, 29.