We don't know when this guy was born, and we don't know when he died. Apparently, before Hallmark existed, people didn’t pay as much attention to birthdays, but we do know when he lived—or when he flourished. You'll see the abbreviation Fl. around dates sometimes. That stands for flourished; as in the time when the figure in question flourished. So, our guy flourished around 200. His name is Tertullian, and we have a lot to be thankful for regarding Tertullian's flourishing.
First, Tertullian was the first one to coin the term Old and New Testaments in reference to the 39 books comprising the Old Testament, and the 27 books comprising the New. In the Gospels, we see a reference to the law, prophets, and writings, what we shorthand refer to as the Tanakh, or the Hebrew Bible. Paul and the other New Testament Epistle writers often speak of the Old and New Covenant, which refers to the Mosaic covenant in Old Testament times, and the New Covenant from Jeremiah and referring to the new epoch brought about by the life, death, resurrection and ascension of Christ.
But it was Tertullian who gave us the designations of Old and New testaments. We simply take them for granted, but we should be thankful to Tertullian for his work. There is another term we also take for granted. In fact, I don't know how you can have biblical, orthodox Christianity without it. It's the term Trinity.
One of the books I had a lot of fun with was a book I did for kids with a friend of mine, Ned Bustard. We called it The Church History ABCs: Augustine and 25 Other Heroes of the Faith. It was quite convenient for us because both Tertullian and Trinity start with "T." Now, I think I know what you're thinking. "What kind of a kid's book is this?" First, it tries to have them say the name Tertullian. Next, it's teaching kids the word Trinity.
That word Trinity, and what it represents, baffles theologians and scholars. How can we expect kids to understand it? Well, let's answer that question.
First, let's go back to Tertullian. Tertullian gave us the word, but he certainly did not give us the teaching, or the concept. That, we can chalk up to Scripture. From the very beginnings of Scripture, the first pages of the Old Testament, we get a sense of the oneness of God, but also of a complexity within that oneness. We see it in the creation account as the Spirit of God hovered over the waters. God reveals Himself, and His way of salvation over time. Theologians call this "progressive revelation." Over the course of progressive revelation, from the Old to the New Testament, we see that unity and complexity of God come to full expression. God is One in essence, yet three distinct persons. The Father is God; Jesus is God; the Holy Spirit is God. And at the same time, the Father is not the Son, and the Son is not the Spirit, and the Spirit is not the Father. Need a diagram? How about a concise and clear definition?Tertullian's definition: God is one substance, or essence, and God is three persons. God is one substance in three persons. The word "essence" comes right from the Greek. The word is ousia. The word substance comes directly from the Latin, substantia. Even the word person is Latin, its persona.
What Tertullian did for us when he gave us this theological term, is what theologians do for the church. At their best, theologians summarize the broad and vast, and sometimes even complex teaching of Scripture for us. Many times, we take the work of these theologians for granted. We take the work of these folks from church history for granted. Reminds me of the Scripture text that informs us that we are "drinking from wells" we did not dig. We should realize that there were those who went before us who did work we should appreciate, and work that helps us understand what it means to be a Christian.
Well, now back to the kids book and our letter "T." Should we teach our kids the word Trinity? Absolutely. The Christian God is the triune God. Or to put it another way, you can't have Christianity without the Trinity. Thank you, Tertullian.