Are you at peace with the doctrine of the Trinity? Have you come to terms with it? If someone pressed you – “Do you believe God is triune?” – and you said yes, would some doubt-ridden part inside of you wince?
This series is about helping Christians be at home with the doctrine of the Trinity. We’re trying to get to a place where such doubts no longer trouble us or threaten our enjoyment of the Father, Son and Holy Spirit. And the way we get there is through Christ, the key to understanding the Trinity. Only He can unlock the gates that bar us. Already He has helped us through the first two obstacles – our motivation shortage, and suspicions that the doctrine is irrelevant. Let’s see if He can help us with the third.
“I’m uncomfortable with the use of extrabiblical words.”
As mentioned in the first article, the terms “Trinity” and “God the Son” are not found in Scripture. When reading defenses of the Trinity doctrine, it can be frustrating and alarming to encounter many more extrabiblical terms, or terms that, if they do occur in the Bible, are used with a different meaning: Godhead, economic Trinity, ontological Trinity, Being and Persons, divine substance or nature. If the terms are foreign to Scripture, maybe the doctrine is too, we may wonder.
This is exactly what some argue. They insist that we should only use the Bible’s words. Phrases such as “God the Son” and “One God in three Persons” are human inventions that obstruct the simple teaching of Scripture. They urge us to abandon this man-made language completely.
This is a major obstacle for some people. Maybe it is for you. Turning to Christ, we see that He is the way through. First, our Lord warned against investing man-made commandments with divine authority (Mar 7:7). The insistence that we never use extrabiblical language is itself extrabiblical and is thus self-refuting. Second, in His teaching, the Lord Jesus didn’t just quote His text over and over as if no additional words were needed (e.g., Mat 19:3-12). His example shows us that to teach Scripture is not merely to parrot Scripture. We must use our own words to unpack the meaning of its words.
Third, the truth of Christ’s gospel illustrates the merit of using extrabiblical words. At the heart of this gospel is the wonderful truth that Christ died as a legal substitute in the place of sinners: “The Son of Man came not to be served but to serve, and to give his life as a ransom for many” (Mar 10:45 ESV). Some who call themselves Christians, however, deny penal substitution. They find it abhorrent. They believe texts like the one I just quoted mean something else entirely, not that Christ suffered the sinner’s punishment in his place, but that His death benefits people in some more general sense.
The point is this: how is an elder in the church to weed out such a teacher? It’s not enough to ask him if he believes that the Son of Man gave His life as a ransom for many. “Of course I believe that,” he’ll reply. But meanwhile his understanding of that verse (and the gospel) is utterly deficient. But if an elder asks if he believes in the penal substitutionary death of Christ, he’ll have used some extrabiblical words, but he’ll also have protected the people from unbiblical teaching.
I’ll speak frankly. It is the heretic who is the loudest in insisting that only Bible words be used. “The theologians of the Christian Church,” in contrast, “were slowly driven to a realization that the deepest questions which face Christianity cannot be answered in purely biblical language, because the questions are about the meaning of biblical language itself.” Extrabiblical language serves Bible words, not supplants them.
“I can’t believe in a logical contradiction.”
Think about what you already believe about Christ. If you’re a Christian, you already believe in the mystery of the Incarnation. You are convinced that the Word became flesh (Joh 1:14), that in one Person are two distinct natures: a divine nature and a human one. You believe that He was upholding the universe by the word of His power (Heb 1:3), even while He was on His mother’s breast. You already believe this!
I stress this because some people have a difficulty that goes as follows: “I can’t possibly believe in the Trinity doctrine. How can there be three Persons, each of them God, and yet only one God? I can’t bring myself to believe in a complete contradiction.”
My first reply is to assure you that you don’t need to believe in a contradiction. Let’s clarify right now, early on in this series, that Christians do not speak of the oneness of God and the “threeness” of God in the same way. We are not saying 1x = 3x (a mathematical impossibility). The doctrine of the Trinity is profoundly not that there is one God and yet three Gods, one Being and yet three Beings, one Person and yet three Persons. Rather, it is that there is one Being (God) in three Persons. One what and three who. This doctrine requires you to believe a mystery, not a mathematical absurdity.
And my second reply is that, because of Christ, you are already well-poised to believe this mystery. How so? Because, as we’ve just recalled, you already believe in the mystery of His Incarnation. The step from believing in that mystery to believing in the mystery of the Trinity is a small one. The crucial step is the one you’ve already taken. If Christ has convinced you of the mystery of the two in one, you are well on your way to embracing the mystery of the One in Three.
That’s not to say it’s an easy step. We still have one more gate to go, and it will take us the rest of these articles to get through it. Buckle up: this series is about to turn textual.
 I owe this point to my friend Joel Barnes.
 It gives us an inspiring example, or wins us back to Him by His love. Both are true, but on their own inadequate.
 R.P.C Hanson, The Search for the Christian Doctrine of God: The Arian Controversy 318-381 (Grand Rapids, MI: Baker Academic, 2007), xxi.
 See Vern S. Poythress, The Mystery of the Trinity: A Trinitarian Approach to the Attributes of God (Phillipsburg, NJ: P&R Publishing Company, 2020), 184–93, for more on the value (and limitations) of using extrabiblical words.