What does it mean to say that God is one? What does it mean to say that God is three? Is the doctrine of the Trinity logically coherent? Is it explainable? Where should I begin when it comes to presenting the doctrine of the Trinity to my non­-Christian friends or Jehovah’s Witness visitors? Is it important to try and under­stand the Trinity at all or should I just accept it as an impenetrable mystery?

The Trinity is indeed a mystery, so deep a mystery that at least 1500 years of enquiry by the greatest saints were unable to penetrate it; a mystery so profound that no one could have understood it except that God Himself has revealed it to us in the coming of His Son. But, like the mystery that is the gospel itself, God has revealed all we need to know about the Trinity. Further, it is helpful for us to think about it. Here are some things that we should know about the Trinity.

One of the biggest handicaps for modern Christians who want to understand and present the Trinity is an unfamiliarity with Trinity as three and one. We know that the Trinity is three and one at the same time but without grasping how they are three and one we are likely to think of the distinction as simply an inexplicable mystery or, worse, a contradiction.

We exacerbate this by our habit of referring to the Triune Being as “God” and “He”, which gives the impression that the Trinity is kind of fourth person over and above the three. It might come as some surprise to note that the Bible almost never talks like this. When the New Testament uses the word “God” it is almost always the Father who is in view; He is the “one God” we worship. To Paul in 1 Corinthians 8:6, the difference between Christianity and pagan religion is that “for us there is but one God, the Father, from whom all things came and for whom we live...”

Much later, the Nicene Creed faith­fully echoes the biblical pattern, beginning with an affirmation that,

 we believe in one God, the Father Almighty, Maker of heaven and earth, and of all things visible and invisible.

This is not, of course, to argue that Jesus is not equally “God”. But when the Bible calls him this it is using the word in a second sense to refer to the divine nature or being, not as a personal name. To adapt an analogy from D. Walter, it is as if we were to enter one of those old family-run businesses where the name on the door reads “Smith and Son”. In the sense that the sign uses the word, “Smith” refers to a single person beyond the door; namely, the older man who is the proprietor and owner of the establishment. Yet if we ask the young man at the counter, we learn that he too is “Smith” and that he is no less “Smith” than his father. In the personal sense the father alone is “Smith”; yet when the word refers to their family nature both are equally and fully “Smith”.

But Smith and his son are also different in another sense apart from their names. The older man is the “original” owner of both the Smith name and the Smith busi­ness. The son possesses both of these things simply because he shares his father’s nature and family and business. The Smith family and business passes from the father to the son. Here again there is a connection between human family relations and divine. Paul follows his description of the Father as “one God from whom are all things” by immediately adding that there is also “one Lord, Jesus Christ, through whom all things came and through whom we live”. Thus, while the Father is the “original” God, all that He is and does is eternally expressed in and through His Son.

Using a word like “original” should not, however, lead us to think that the Son’s generation begins in time as if God had begun to be a Father at some point.

“In the beginning was the Word. He was with God in the beginning,” says John in chapter one of his Gospel. “I am the Alpha and the Omega, the first and the last, the beginning and the end” says Jesus in Revelation 22, echoing the words of God the Father in verse 6 of the previous chapter.

The “begetting”, as the creeds put it, of the Son by the Father is a thing of eternity. The Father has always been the Father and the Son has always been the Son. The Nicene fathers were fond of using analo­gies such as sun and radiance or spring and river to express the inseparability of the two persons. Just as the sun cannot exist without its radiance, neither can the Father be who He is without His Son.

Yet, although this order or flow of nature from Father to Son is eternal, it also has an expression in what we see as salva­tion history. As we have already seen, Paul sees life and everything else coming from the Father and through the Son. In John 1, Jesus is the “Word” of the Father, the agent or instrument of his creative power through whom all things were made. In the important passage of John 5, Jesus spells out his relation to the Father as one of dependence, agency and equality. On one hand, Jesus affirms that he is unable to do anything by himself (v 19), yet on the other, he is the one through whom the Father does everything (vv 20-22), with the result “that all may honour the Son just as they honour the Father. He who does not honour the Son does not honour the Father, who sent him” (v 23).

This asymmetry and equality is some­thing fundamental to the biblical and orthodox understanding of the Trinity but it has also been under challenge in western, and especially Protestant, theol­ogy for centuries. From the time of Calvin we see an insistence that the Son be seen as autotheos or “God in his own right”. Warfield, criticising the vestiges of Trinitarian order left in Calvin’s theology, suggests that the Son and Father only act in an ordered way for the duration of sal­vation history. Most recently, Melbourne Anglican clergyman Kevin Giles has strongly insisted that the Son cannot be equal with the Father if this order extends beyond the boundaries of the incarnation.

The reason for this retreat is the com­mendable desire to say that the Son is equal to the Father in every way, yet the price paid for ignoring that this equality arises out of the priority of the Father is an inability to differentiate fatherhood from sonship and understand how the Trinity works. The more we abandon the order or “fromness” that attends the Father/Son relationship, the more the persons become superficial masks that conceal a singular triune being who now becomes the true “God”. This conception is either impossible to explain or smells suspiciously like the ancient heresy of modalism.

More seriously and sadly, if we insist that the Son and Father relationship is dif­ferent from what is revealed in salvation history, we will miss the connection between the Trinity and salvation history itself.

According to Colossians 1:16, the world was made not simply by the Son but for the Son. In Ephesians 1:10 we hear of the Father’s plan “to bring all things in heaven and on earth together under one head, even Christ”, while John 5:23 seems to point to the Father acting through His Son to bring honour to His Son. If the pattern we are seeing here is right, then salvation history is not fundamentally sal­vation history at all but Trinitarian history. The world is created by the Father to bring honour and glory to His Son through whom He creates and through whom the world is saved. Simultaneously the Son also honours the Father by sub­mitting to Him and faithfully expressing His will and character in the most costly way imaginable (eg John 10:17; 13:31; 17:4).

From this theocentric scheme salva­tion-history finds its proper and most glo­rious context. The salvation which the Son purchases at the behest of his Father becomes the central means by which the Son “inherits” the world in a distinctly new way (cf Rev 5).

To sharpen our vision at this point, it is worth observing that it is possible to imagine the Father working through the Son and yet the Son being transparent or invisible in the process. We can imagine it, first, because that is how things were in the Old Testament and, second, because that’s still the way things work with the Holy Spirit. Along with the Son we are told that there is a third person through whom the Father and Son work and are made known, but — though the Spirit is equally God, in the same way that the Son is God — his way of working is mostly invisible. “He’s like the wind” Jesus says in John 3 — you hear the effects of his passing but you can’t see him. If the Son is like the radiance of the Father’s glory, the Spirit is more like a lens that works invisibly to bring that light into focus and operation.

But the Father’s plan for the Son is that he be glorified in his own right. Although he was always the one through whom God worked invisibly, now in his incarna­tion, death, and resurrection God presents him to the universe so that he now possesses not simply his Father’s nature but a new glory. This glory belongs to him especially because he alone pays the blood-price for our sin. The Father’s sending of the Son fills the universe with a new song of praise:

And they sang a new song:

You are worthy to take the scroll and to open its seals, because you were slain, and with your blood you purchased men for God from every tribe and language and people and nation.

You have made them to be a kingdom and priests to serve our God, and they will reign on the earth.Revelation 5:9-10

The last lines of the verse above connect us to the most astonishing part in all this. It is one thing for the Son to be humiliated as a man and then be rewarded and praised in glory thereafter. Yet the Son remains a man forever. The earthy humanity which concealed his glory is transformed into a glorious spiritual humanity which he retains forever. Somehow humanity itself accommodates and frames his glory like a bezel fashioned for a jewel. Just as salvation is not first about us but the love of Father and Son, now we see that even our humanity is not about us but is an unfulfilled sign of the Son’s own destiny. In Jesus Christ, the Son made flesh, we learn that all the promises and glory of humanity were actually about him. The prophecies to David are really promises to Jesus, the promises to Abraham are really promises to Jesus, and the promises to Israel are again really promises to Him. Again God’s declaration that humans are rulers of his creation is really a promise to Jesus (Ps. 8, cf Heb. 2).

In us and through us God the Father speaks and makes promises to His beloved Son. But just because we turn out to be signs of and for Jesus doesn’t mean we are discarded when the fulfilment comes and he inherits his destiny. Instead he brings us with him into that destiny. The promises made to us which were really about him are now shared again with us in a mind-blowing new way!

So John tells us that,

now we are chil­dren of God, and what we will be has not yet been made known. But we know that when he appears, we shall be like him, for we shall see him as he is. 1 Jn 3:2

Jesus promises that whoever overcomes in the struggle against sin, “I will give the right to sit with me on my throne, just as I over­came and sat down with my Father on his throne” (Rev. 3:21). Paul writes that if we are believers in Christ we share everything that is his: sonship and inheritance (Rom. 8:16-17), exaltation (Eph. 2:6-7) or a res­urrected body just like his (1 Cor. 15).

The mystery of the Trinity is finally a secret that is revealed around and among us. It is the Father working through His Son to bring glory to the Son. It is the Son humbling himself and becoming human and then being raised as a glorious human by the will of the Father. It is the glory due to Jesus who not simply bears our sins but brings us into the Father’s embrace.