Christianity is what is called a monotheistic religion. That is, we believe in one God, as opposed to many gods, which is polytheism. Many of the religions that the ancient Israelites interacted with, and were tempted by, were polytheistic. Many regions would have their own tribal deity. We are all familiar with the ancient Roman and Greek pantheon, featured for example in Homer’s Iliad and Odyssey.
We are monotheists because Christianity grows out of the religion of Moses and the patriarchs. One of the main features of the religion of the Old Testament is its emphasis upon monotheism. The God who revealed himself to the patriarchs and the prophets is One: “Hear, O Israel, the LORD our God, the LORD is one” (Deut. 6:4). One of the recurring themes of the OT is the disheartening cycle of Israel forsaking the one true God for false idols, being punished, and then repenting and turning back to the true God, only to repeat the cycle again. The danger of the corrupting influence of polytheism is highlighted again and again.
Jesus was a Jew and all the first Christians were Jews. Every book of the NT, with the possible exception of Luke-Acts, was written by a Jew. So it should not surprise us that Christianity is also monotheistic. The apostle Paul, for example, wrote to the Corinthians, “For although there may be so-called gods in heaven or on earth – as indeed there are many ‘gods’ and many ‘lords’ – yet for us there is one God, the Father, from whom are all things and for whom we exist” (1 Cor. 8:5-6). Our Lord himself, when tempted by Satan to worship him, responded by quoting Deut. 6:13, “You shall worship the Lord your God, and him only shall you serve.” That is very clearly a monotheistic passage.
So why do we have a doctrine of the Trinity?
The short answer is that we have a doctrine of the Trinity because Jesus came. Another way to put this in terms of the season we are in is that we have the doctrine of the Trinity because of Christmas. I say doctrine, because the Trinity did not come into existence on Christmas day, but Christmas made the doctrine of the Trinity clearer than it had been under the old covenant, even though there are hints of a plurality in the unity of the Godhead even then. The incarnation of the Son of God confronted men and women with the reality that God the Father has a Son and that this Son is more than a man merely anointed and appointed by God, but someone who shares the very nature of God himself. It seems that this realization slowly dawned upon the apostles. They went from saying, “What sort of man is this?” (Mt. 8:27) to the exclamation of Thomas, “My Lord and my God!” (Jn. 20:28).
Very well, Jesus is God. But Jesus is not the Father. He is distinct from the Father, which can be seen in numerous places, like in our text, where the baptism of Jesus in the Jordan by John the Baptist is recorded, who “saw the Spirit of God descending like a dove and coming to rest on him [Jesus]; and behold, a voice from heaven said, ‘This is my beloved Son, with whom I am well pleased” (Mt. 3:16-17). The early church fathers would tell people who wanted to learn the doctrine of the Trinity, to go to the Jordan. In fact, here you have all three persons of the Trinity, Father, Son, and Holy Spirit, all three present at the same time, and all three clearly distinct from one another.
Thus the doctrine of the Trinity is implied by the Biblical teaching that Jesus – the Son of God – is God and the Father is God and the Spirit is God and Jesus is not the Father or the Spirit, the Father is not the Son or the Spirit, and the Spirit is neither the Son nor the Father. The question then becomes, how do you fit this into the other Biblical teaching that God is one? For if the Father is God, and Jesus is God, and the Spirit is God, then it would appear that God is three. How is it that God can be one and three at the same time?
Well, clearly, God cannot be one and three at the same time and in the same way. That would be irrational. And though we understand that there are limits to logic, this doesn’t give us the right to violate the laws of logic. So it must be that God is one in one sense and three in another sense.
But in what sense? It took the early church a while to iron out the details, but eventually they arrived at the following solution: God is one in substance or essence and three in person. Each person (Father, Son, and Spirit) shares the same substance. They are all equally God in the sense that they mutually indwell each other in terms of the essence of the Godhead. But they are also irreducibly distinct as persons sharing the same essence. This is the doctrine of the Trinity. Tertullian, who lived in the late second and early third centuries (A.D.), was probably the first theologian who used the words “Trinity” and “person” to describe the distinctions in the unity of the Godhead. A lot of people have a problem with this because the word “Trinity” is not found in the Bible at all. But what you have to understand is that Tertullian and those who followed him were using this kind of language, not to get around the Bible, or to invent something new, but instead to defend the truth of the Bible. The problem is that if heretics use Biblical language, the only way you are going to be able to distinguish the truth from error is to use words not found in the Bible to clarify what the Bible actually says. That is what Tertullian was doing.
You see, in his day, there were people who were advocating modalism, arguing that there is only one person in the Godhead who reveals himself in three different ways, like an actor wearing three different masks. From this came the doctrine of patripassianism, or the idea that the Father suffered on the cross, because the Son is the Father. One such a person who taught this was a Roman Christian named Praxeas, and Tertullian wrote a book to refute him around the year A.D. 210. Praxeas was doubly noxious to Tertullian, because he opposed the Montanists (an early charismatic Christian sect), of which Tertullian was an adherent, and advocated modalism: “By this,” Tertullian wrote, “Praxeas did a twofold service for the devil at Rome: he drove away prophesy, and he brought in heresy; he put to flight the Paraclete, and he crucified the Father.”
Tertullian described the doctrine of the Trinity in these words: “All are of One, by unity (that is) of substance; while the mystery of the dispensation is still guarded, which distributes the Unity into a Trinity, placing in their order the three Persons – the Father, the Son, and the Holy Ghost: three, however, not in condition, but in degree; not in substance, but in form; not in power, but in aspect; yet of one substance, and of one condition, and of one power, inasmuch as He is one God, from whom these degrees and forms and aspects are reckoned, under the name of the Father, and of the Son, and of the Holy Ghost.” There you have it: God is one in substance and three in person. It is the inevitable consequence of believing all that the Bible says about God: there is one God, and the Father, Son, and Spirit are God, and yet distinct from one another.
However, at this point, you might be thinking to yourself – okay, but what does it matter? It all seems very abstruse and abstract and difficult – and worthless. W.G.T. Shedd reports one theologian’s opinion that “as he that denies this fundamental article of the Christian religion may lose his soul, so he that much strives to understand it may lose his wits.” Well, we don’t want to lose our wits. And if that’s the way you view the doctrine of the Trinity, you are going to have a hard time seeing why you should bother much about it at all. Which brings us to the point of this message. I want you to understand not only that the doctrine of the Trinity is Biblical, but also why it is important for you to believe it. I don’t know about you, but for many years I embraced this doctrine without really understanding why it is so wonderful. Of course, I understood it is important as it was connected to the divinity of Christ, but for me it was more of a doctrine to be defended than a doctrine to be loved. A lot of people approach the doctrine of the Trinity like those awkward relatives we know we’re supposed to love but we’d really not rather sit by them at the table. For me, this stemmed from two basic mistakes: one, I failed to properly appreciate what the doctrine of the Trinity is really teaching; and two, I failed to see just how central it is to all of Christian life. My goal in this message and those following is to share with you how the Biblical teaching has corrected both these mistakes. I want you to love it and to see just how central and crucial it is for you to believe it.
Where do we start?
Let’s begin by thinking about this: what would you say is the fundamental truth of the Christian faith? Would you say it is the gospel? As important as that is, it is not the starting point of faith. Yes, we must believe it and we cannot be saved apart from faith in its message, and so the gospel is fundamental in that sense. But the gospel presupposes some things, and one of the things it presupposes is a certain view of God. If your view of God is the Islamic one, you will not believe the gospel. If your view of God is a pantheistic one, you will not believe in the gospel. So in that sense, what we believe about God is more fundamental than what we believe about the gospel (cf. Heb. 11:6).
Even the doctrine justification by faith, which Luther called the article of the standing or falling church, and which you might think is that which distinguishes Christianity not only from other religions, but also Protestantism from Catholicism and Orthodoxy, is not ultimately distinguishing, as I recently discovered to my surprise. Michael Reeves, in his book, Delighting in the Trinity,tells the story of a sect of Buddhism found in Japan in 1549 by the Roman Catholic missionary Francis Xavier, which believed in salvation by grace alone: “Simple trust in Amida, they held, instead of trust in self, was sufficient to achieve rebirth into the pure land. If we call on him, they taught, then despite our failings, all his achievements become ours.” In fact, Xavier identified this sect (Yodo Shin-Shu) with “the Lutheran heresy.” Of course there are still vast differences between this “justification by faith” and the Protestant doctrine, but what makes those differences is ultimately rooted in very different views of God.
The fundamental doctrine is our doctrine of God. It is the foundation of all other theological belief. And because God is a Trinity, that means that the doctrine of the Trinity is the foundation of all other belief. It is only as we get the doctrine of the Trinity right that we can with any justification say that we are Christian in any other point of faith and doctrine. As Reeves puts it, “The Trinity is the cockpit of all Christian thinking.”
And it is important to begin, not with an amorphous concept of “God” but with the very distinctive Christian God. One of the reasons we might have a problem with the doctrine of the Trinity, is that we don’t begin here. And when we don’t begin here, we usually end up with an idea of God that is very different from the Biblical vision of God. Have you ever noticed that the pagan gods of old looked just like the people who worshipped them? This is the problem with idolatry – it is remaking God in our own image. It is exchanging the creator God with a created thing. If we don’t begin with what God reveals himself to be, we inevitably end up with a God looking very much like ourselves. We have to begin with how God himself has revealed who and what he is, and since he has revealed himself to be a Trinity in Unity, this is where we have to start. We don’t start with an abstract idea of a single person God and then, as Reeves puts it, try to stuff two more persons into the Godhead. Rather, we start with the Trinity in Unity and go from there.
The Beauty of the Trinity
The idea of the Trinity is massively important for another reason. Did you notice the way the Father introduces the Son to the world at his baptism? “This is my beloved Son, with whom I am well-pleased.” This is immensely important. It is important for the following reason: love cannot exist in a vacuum of fellowship. And that means that love cannot exist apart from a plurality of persons. This means that if God is unipersonal, he could not be loving in himself. It would mean that love is something God would only have discovered once he created the world, but that before the world was created, he was loveless. And that would mean that God is not love, contradicting 1 Jn. 4:8. Because God is a Trinity, love is not something God discovered, it is something that he is. He didn’t develop it once he created other beings, he has always been loving from eternity.
Now think about what it would mean for the other attributes of God if God could not identify himself in terms of love. Think about sovereignty unattached from love, holiness and justice and power separate from love, and you get a God that is severe, untouchable, frightening, austere. It would be hard to love such a God; in fact, it would be impossible.
Of course, love requires more than a plurality of persons. You can have a room full of people who hate each other. Additionally, there must be a bond of fellowship that unites. And this is the way the Trinity is revealed to us; not just in terms of a plurality of persons but also in terms of a fellowship of mutual love. For the gospel tells us by the coming of Jesus Christ into the world, God identifies himself to us primarily as a loving Father, and from eternity he is a Father first and foremost to his Son. When he introduces his Son to us at his baptism, it is as “my beloved Son,” and you cannot have a Son without a Father. When Jesus teaches us to pray, it is to “our Father” (Mt. 6:9). In fact, one of the main points of the Sermon on the Mount is that we are to relate to God as Father. And though it is not as clear in the OT, God identifies himself as a Father there, too (see Ex. 4:22; Deut. 1:31; 8:5; Ps. 103:13; Is. 1:2; Jer. 31:9; Hos. 11:1).
But God did not begin to be a Father when the Son became incarnate. The Son is the eternal Son of the Father, for the Father sent the Son into the world; he did not send him to be the Son, but he sent him who already was the Son (Rom. 8:3). God the Father and God the Son have existed in an eternal fellowship of love. What was God doing before the foundation of the world? Jesus tells us: “And now, Father, glorify me in your presence with the glory that I had with you before the world existed” (Jn. 17:5). “Father, I desire that they also, whom you have given me, may be with me where I am, to see my glory that you have given me because you loved me before the foundation of the world” (Jn. 17:24). What was God the Father doing before the foundation of the world? He was loving the Son. They have always existed together in a holy fellowship of love and glory.
And the Spirit is the bond of that fellowship of love. You see it there at the baptism. How is it that the Father communicates his love to the Son? It is not only by declaring it, but also by sending the Spirit like a dove to rest upon his Son. Just as God communicates his love to us by the Spirit (Rom. 5:5), even so the Father communicates his love to the Son through the Holy Spirit: “In that same hour he [Jesus] rejoiced in the Holy Spirit, and said, ‘I thank you, Father, Lord of heaven and earth” (Lk 10:21). Thus the apostle speaks of “the grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit” (2 Cor. 13:14).
But this Spirit is not some impersonal force; rather he is a person in his own right: he can speak and send (Acts 13:2,4), choose (Acts 20:28), teach (Jn. 14:26), be lied to (Acts 5:3,9), resisted (Acts 7:51), grieved (Eph. 4:30), and blasphemed (Mt. 12:31). It is in the one Name that we are baptized; a name that is given by the Father and the Son and the Holy Spirit (Mt. 28:19).
So you see, God did not become loving. He has always been loving. God’s works in creation and providence and salvation are acts of love because that is what God is. God so loved the world that he gave his only begotten Son (Jn. 3:16; 1 Jn. 4:9-10). God overflows in love, first and foremost in the Trinity, and then outwards towards his creation. And we can know that God’s love is not some temporary blimp on the screen of his attributes because love is an eternal and necessary part of who God is. And it is important to see that it is the doctrine of the Trinity that guarantees this.
All this affects the way we relate to God. In Christ, we do not relate to God primarily as our Ruler, though he is that, nor as Almighty, though he is that. We relate to him primarily as our Father through the Son in the power of the Holy Spirit. The pattern in Scripture, the order, is this: by the Spirit, though the Son, we approach the Father. “For through him [Christ] we both have access in one Spirit to the Father” (Eph. 2:18; cf. Rom. 8:14-17). It’s important that we see this, because sometimes we can think of God as the One Essence and the Persons as somehow existing alongside “God.” Rather, the one God is the Holy Trinity. We don’t approach the “Unoriginate,” as Arius called God. After all, “With ‘The Unoriginate’ we are left scrambling for a dictionary in a philosophy lecture; with a Father things are familial. And if God is a Father, then he must be relational and life-giving, and that is the sort of God we could love.”
Now by saying that we relate to God primarily as Father, I’m not saying that we don’t believe that the Son or the Holy Spirit are lesser beings than God the Father – they are all properly God, equal in power and glory – yet there is an order in the Trinity. You will notice in the NT that almost always when “God” is used, the word refers to God the Father. This is not because the Son or the Spirit are not God. After all, John tells us that, “In the beginning was the Word and the Word was with God and the Word was God” (Jn. 1:1). In Acts 5, we learn that lying to the Holy Spirit is the same thing as lying to God. Rather, God almost always refers to the Father because there is a definite order in the Trinity. Paul mentions this order in 1 Cor. 11:3, when he writes, “But I want you to understand that the head of every man is Christ, the head of a wife is her husband, and the head of Christ is God.” The Father loves the Son, and this eternal fellowship of love overflows in the sending of the Son to love the Church. The Father sends the Son; it is never the other way round. The Spirit proceeds from the Father through the Son; it is never the Father or the Son proceeding from the Spirit. But what all this means for us is that the Son of God worked for us and the Spirit of God works in us in order that we might be able to approach God the Father as our Father. Thus Peter writes, “you call on him as Father” (1 Pet. 1:17). It’s why Jesus told Mary, “I am ascending to my Father and your Father, to my God and your God” (Jn. 20:17). It is precisely because of what Jesus has done for us that his Father becomes also our Father and this is a wonderful and amazing reality indeed.
Of course, some earthly fathers are mean and cruel. We must divorce all such notions from our minds when we think of God as Father. God is Father but he is not evil as we are (Mt. 6:11). He is good; the OT refrain remains true: “the steadfast love of the LORD endures forever.” The love that we are called to experience is the infinitely superior and pure love of the Trinity; it is not the selfish and overbearing and hurtful relationship that is sometimes expressed in broken and sinful families. It is the love that the Father has towards his own Son. There is nothing cruel or harsh or unkind or ugly about that love.
And it is this love that we are called to demonstrate in our lives. Why do you think that the first commandment is to love God and then to love our neighbor? It is because the only way you can relate to God is by love since he himself is love, and thus the only way we can imitate God is through love. The love that the Father has for the Son overflows in the Son’s love for the church, and that is to overflow in our hearts towards our spouses, our children, our friends and our neighbors. The Trinity is at the heart of everything; not only as an important doctrine but as the basis of our ethic as well, the foundation of all doctrine and duty.
So you should love the doctrine of the Trinity. But more than that, you should love the Trinity – Father, Son, and Spirit. For it is possible to love a doctrine and fail to love the God of the doctrine, and we don’t want to do that. We want to really love God; and to love God is to love the Father through the Son in the Spirit. It is to be included in the eternal fellowship of the holy Trinity through Christ our Savior. And there is no greater imaginable blessing than that.
 Many of the main ideas in this message are borrowed from this book. It is the best book I have read so far on the doctrine of the Trinity.
 This point is repeatedly made in Robert Letham’s very helpful book, The Holy Trinity.
 Delighting in the Trinity, location 253.
 Ibid., loc. 253.