What is the Trinity?

Sermon 426 St. Martin’s 180 (Riverway) 5/31/26

The Trinity Debate

In the fourth century, a bishop described that the whole city of Constantinople was filled with lively discussions. He said, “If in this city you ask anyone for change, he will discuss with you whether God the Son is begotten or unbegotten. If you ask about the quality of bread, you will receive the answer that ‘God the Father is greater, [and] God the Son is less.’ If you suggest that a bath is desirable, you will be told that ‘there was nothing before God the Son was created.’”[i] 

Actually, that’s what my four-year-old said to me last night as she was trying to get out of bathtime.

But honestly, things have changed, haven’t they? We don’t live in a time in history when a restaurant waiter asks for our thoughts on Jesus’ divinity, nor will the lady scanning your groceries ask for our opinion on the role of the Holy Spirit within the Godhead.

But if someone came up to you and asked, “What is the Trinity?” What would you say? Where would you even start?

When I was in college, I became friends with a guy named Muhammad. He must have felt like a fish out of water because he worked as an athletic trainer…at a Christian college.

He was the lone Muslim on campus, but he and I had some deep conversations. And when we began talking about our faith, the very first question he asked me was, “What’s this about the Trinity? Seems to me you all believe in three gods.”

And that got me thinking. What is Christianity if we take away the Trinity? If we just decided to throw out this doctrine of the Holy Trinity, what would we have left of our faith?

It might be surprising to think that there are plenty of Christian books that could stay on the shelf even if we got rid of the Trinity. So many of them don’t reference it at all.

One of the greatest theologians of the twentieth century, known as the father of modern theology, Friedrich Schleiermacher, wrote a book titled The Christian Faith, and he didn’t even discuss the Trinity until the appendix.

How can you have the Christian faith without the Trinity? Apparently, it’s tempting even for theologians to just ignore the matter entirely.

And so, in honor of the Trinity, I want to spend the rest of our time considering three things the Trinity isn’t, three things the Trinity is, and how we are called into Trinitarian faith.

What the Trinity Isn’t...

1. The Trinity is not three gods.

This was the thing I had to try to explain to my friend Muhammad, because from the outside looking in, it sure looks a lot like polytheism. I’ll get into the nuts and bolts in a moment, but to start, it’s important to remember Christianity believes that Jesus of Nazareth fulfilled all that was foretold in the Law and the Prophets. He was the long-awaited Messiah who brought God’s kingdom to earth, and through his self-sacrifice atoned for the sins of the world.

Judaism's unique gift to the ancient world was its claim that there was only one God. That was a revolutionary idea. And the rallying cry for their monotheism, which they would say (and even Jesus would say) when he woke up, when he lay down to sleep, was the Shema: “Hear O Israel, the Lord our God, the Lord is one.”

There are no other gods. There isn’t a storm god; there aren’t specific gods of Egypt or Canaan. Yahweh is the Lord of all. He is one.

Christians are not divorced from that heritage, far from it. We affirm there is only one God of heaven and earth. But we would add that we are trinitarian monotheists. The God of Abraham, Isaac, and Jacob is the God we believe in. This God has revealed himself in three modes of being, or three persons, but this is the one true God who is Father, Son, and Holy Spirit.

2. The Trinity is not different in the Old and New Testaments.

A lot of folks will ask: “Why is the God of the Old Testament angry and violent while the God of the New Testament is so loving?” I will say it again: we are monotheists, there is only one God, and the God throughout the Bible is the same God, with the same mission for his creation.

There is no more loving act than creating us and the world around us—and that’s found on the first page of the Old Testament. There is nothing more caring than freeing people from slavery or bringing hope to an exiled community.

In the New Testament, we find God flipping tables and saying things like “if you want to gain your life, you must be willing to lose it. Take up your cross and follow me.” There is absolutely no difference in the God found in the two Testaments. The genres and circumstances may differ, but God is consistent at all times. He is the same yesterday, today, and tomorrow.

3. The Trinity is not a problem to be solved.

The Trinity is a mystery. The inner workings of the Godhead far exceed anything we could begin to comprehend. Now, you could say that because we cannot fully understand the Trinity, it must not be true. Anything that is real must be observable and verifiable.  

But just because something is hard to understand does not mean that it’s untrue. There is so much about ourselves and the universe we live in that we don’t fully understand, but that doesn’t stop us from contemplating those things and longing to learn more. No, scientists will talk about the mysteries surrounding dark matter, black holes, or spacetime itself as an invitation to deeper understanding.

The Trinity is not an equation to be figured out, to be mastered by us. Instead, it may be best to say that the Holy Trinity is infinitely knowable. We are never going to come to the end of this journey. We will never grasp who God is in totality. God is not a mystery that is unknown, but a mystery that is infinitely knowable.  

What the Trinity Is…

1. The Trinity shares the same ousia.

This means the Trinity has the same essence, the same substance, the same divinity. The Father, Son, and Holy Spirit are of one mind and will. God is not divided, and none of the persons of the Trinity is “less than” another because they share the same ousia (the same essence of divinity).

The debate over much of this is how we came to have the Nicene Creed, which is a fundamental statement of our Christian faith. Was Jesus God, or was he like God? Was he of the same substance or of similar substance to God?

All this may make our heads spin, but it helped us figure out if that was God on the cross or someone else. We concluded that it was indeed God on the cross. Jesus is of the same ousia as God, while also being fully human.

2. The Trinity is three persons.

“Persons” is such a strange word to use. It was an imperfect term used in the fourth century, and it remains lacking to this very day. Of course, two of the three members of the Trinity are not literal persons, but it is crazy to think that one of the three has a literal flesh-and-blood body, even now in heaven.

“Person” denotes a being who is personal, relational, and who has the ability to know and love. We usually think we apply the term person to God, but maybe it’s the other way around. God, who is personal within God’s very being, has bestowed upon us the gift of personhood. We are reminded, when using the term "person," that God is Someone rather than Something.[ii]

3. The Trinity is a communion of fellowship.

God is completely self-sufficient and lacks absolutely nothing. There was never a time when God was not, and there has never been a time when God needed anything the way you and I need things all the time. God is perfect.

And yet, God’s abundant love and creativity overflows from the Godhead to us. God creates, God sustains, God redeems, though none of it is forced upon him. He is completely free to do as he pleases, and God (for some unknown reason) has chosen to be for us, and to stay committed to the human project, though he has consistently failed him. He owes us nothing and yet continues to give of himself.

God created us (and all there is) through the Son and by the Spirit, and he has done it so that we might share in his love and delight. By the Cross of Christ and the indwelling of the Holy Spirit, we are invited into the Trinity’s fellowship. Not as an equal member, but as a beloved child of this Triune God.

Our longing for community and for one another is rooted in our longing for our God, who is the essence and genesis of community.  

Living Out Our Trinitarian Faith

And so, to go back to our original question: What is Christianity if we take away the Trinity? The truth is, the whole structure comes crumbling down without it.

Our understanding of God as one and yet three, who is equal yet communal, who is self-sufficient and yet self-giving, helps explain why we, as followers of this God, seek to model the same love, humility, generosity, and community we have found in God.

In reality, we discover something important about who we are, the more we contemplate who God is.

You and I are called to live out our Trinitarian faith through the values I just described, but we know that it can’t be done alone, and so we intentionally do something every time we are about to leave worship in this place and head back into the world.

You may have heard some familiar words in our reading from 2nd Corinthians 13 today. The very end of that reading is how we close each of our services here in Riverway. It’s a reminder that we are a trinitarian community whose fellowship is rooted in the grace and love of our Trinitarian God.

But it is a sending out moment that is meant to be said to one another, rather than just looking forward and reading it on a screen.

It’s an opportunity to look one another in the eye and say, “As you leave this place, may you be clothed in the grace of our Lord Jesus, may you be rooted in the love of God, and bound in the fellowship of the Holy Spirit, until we come here again.”

We do not know what is going on in the lives of those who sit around us at church, and Lord knows we have a lot going on, but this is an opportunity to bless our neighbor, our brothers and sisters in the Lord, in the name of the most Holy Trinity.

The best way to start living out a trinitarian faith is to lean into this incomprehensible mystery, this mystery that is infinitely knowable…and one that is revealed more deeply in community, in fellowship with one another…because, well, that seems to be the essence of the Trinity.   

[i] Gregory of Nyssa

[ii] God is a single consciousness who exists in three ways as Father, Son, and Holy Spirit.