If you are a playwright and you want to write a comedy, there is a standard device already much used by others. It consists in bringing about a confusion of identity between two or more characters in the play.

Oliver Goldsmith, did this in his play, She stoops to Conquer. Two young men, lost at night, are deliberately mis-directed, so they go to their true destination in the belief that it is an inn, instead of the home of the local squire, whose daughter they want to meet. Their rudeness to their host, because of their false belief, sets the scene for the escapades to follow.

Now you may wonder why I have begun in this way! What I want you to think about, is this: If we have a false notion about who someone is – we may be seriously led astray. And if that someone is God, we may fail to give him the honour, worship and obedience that is his due. And the result of that may be to our eternal loss. For Jesus himself said, "The Father... has entrusted all judgement to the Son, 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." (John 5:22,23) and, "If you do not believe that I am [the one I claim to be], you will die in your sins." (John 8:24)

When I last spoke here, it was to talk about Thomas, who made that wonderful confession to Jesus, "My Lord and my God." (John 20:28) Just as Thomas came to that realisation, so John in his Gospel is inviting each of us to do the same, aware that Jesus was both fully God, as well as fully human. That in itself is, of course, a deep mystery – but we are driven to believe it is so, because of the testimony of each of the Gospel writers – and of the rest of the New Testament – as well as of the experience of Christians down the years.

Daniel Webster, 19th-century American Senator and Secretary of State, was dining once in the company of literary men in Boston, when the conversation turned to Christianity, and he stated his beliefs. A Unitarian minister opposite him asked, "Mr Webster, can you comprehend how Jesus Christ could be both God and man?"

Webster replied, "No sir, I cannot comprehend it; and I would be ashamed to acknowledge him as my Saviour if I could comprehend it. If I could comprehend him, he would be no greater than myself, and such is my conviction of accountability to God, my sense of sinfulness before him, and my knowledge of my own incapacity to recover myself, that I feel I need a superhuman Saviour."

But, of course, the mystery doesn't end there – because Jesus obeyed God and prayed to him. He modelled for us the confident trust and the willing obedience a man or woman of faith should always have in God. He called God his Father – Abba, dear Father – whose all-embracing love he taught, and whose glory he always sought. (Mt 5:44; Lk 6:32ff;Jn 8:49;17:4)

And Jesus taught that after he had left his disciples, another Counsellor, another Helper, the Holy Spirit, would come as his deputy, to be with us for ever, and who would dwell in us and mediate the presence to us of both Father and Son. God doesn't hand us over to another, but in this other he keeps coming to us himself. (John 14:16-21,23-26)

The Father, the Son and the Holy Spirit, are spoken of together in many places in the New Testament, yet the Bible throughout maintains unequivocally that there are not three gods, but only one true, living God – in accordance with the constant teaching in the Old Testament.(Deut 6:4;4:35,39;Ne 9:6;Isa 44:6;Zc 14:9)

It is on the basis of this scriptural truth, and in response to deviations from it, that time after time tried to lead the Church astray, that the Church refined its understanding of God's nature – unfathomable mystery though that is. Or rather, it put up "No way!" signs at the parting of every false trail away from the New Testament teaching.

And those false trails are still very much in evidence today, for the human heart is still sinful, believes it knows better that Jesus himself – and prides itself that its reasoning is better than the understanding the Holy Spirit gave, as the Church wrestled with the New Testament data.

And what was the conclusion that the Church was led to? That God exists as three 'persons' in the unity of his being. That the Father, the Son, and the Holy Spirit are co-equal and co-eternal, uncreated and inseparable, undivided though distinguishable. We use the word 'person' here, not to convey the idea of separate individuals, but in the sense that each is aware of the others, speaks to the others, loves and honours the others. And this is how God is in himself, from eternity to eternity, and not just in his dealings with us.

Perhaps it will make things a little clearer, if I mention one or two of those false trails, where the Church has had put up "No way!" signs.

Some of you may recall the film, Dr Strangelove, in which the late Peter Sellers plays all the significant rτles. Some think God is like that – so that he became in turn the Father, the Son, and the Holy Spirit. But that makes nonsense of the clear distinction Jesus always made between himself and his Father.

Then there is the common idea that Jesus and the Spirit are not personally God, but God's two top creatures doing top jobs. The Jehovah's Witnesses believe that. That means, of course, that Jesus' death cannot have infinite value, to redeem all those who put their trust in him. Moreover, to worship Jesus and give him the commitment of our lives, which is what he calls us to do, (John 9:38;20:28; Matt 4:19;8:22; Mark 10:21,28) must be blasphemous, breaking the First Commandment given to his people by God.

An alternative idea is that the Father, the Son and the Holy Spirit are in fact three gods, whose solidarity in action masks the fact that they are not one in being. The Mormons think that, and do in fact believe in many gods.

So, we need the careful work done by those who, in the first centuries of the Christian era, thought long and hard about the biblical witness. To think aright about our God is not easy, but the Holy Spirit is given to every believer, so that as we ourselves read the Scriptures he caused to be written, he can lead us into the essential truth, and enable us to worship and serve God in the right way.

Let us then turn to that Gospel reading from John, chapter 3, which is not untypical of the way the New Testament, again and again, quietly demonstrates the way in which every person of the Godhead is involved in our salvation.

Let's remind ourselves about Nicodemus. A senior Jewish ruler and theologian, he was as eminent as an archbishop, a cardinal, or a distinguished professor is today. He came to meet Jesus, the novice preacher from the Galilean backwoods, for the first time in Jerusalem since his ministry began. Nicodemus speaks first, as the older man, and his words are kind, affirming and welcoming.

"Rabbi" [giving the young preacher a title of honour straight away] "we" [that is, 'my colleagues and I', Jerusalem's top people] "know you are a teacher who has come from God. For no-one could perform the miraculous signs you are doing if God were not with him." As if to say, I am sure, Jesus, you are wondering whether we of the religious establishment accept you and approve of what you are doing and regard you as one of us. Well now, I am here to tell you that we do, and we shall be happy to have you as a regular member of our discussion circle. Come and join us!

Do you see what Nicodemus was doing, under all that politeness? He was patronizing the Son of God! But Jesus never accepts patronage, then or now. It is for us to bow down before him, not the reverse, whoever we are. So Jesus doesn't thank Nicodemus for his kind words. He strikes a different note and tells his eminent visitor that, without being born again, one cannot see the kingdom of God.

Then he enlarges on this [in verse 5] in words I particularly want to draw to your attention. "I tell you the truth, no one can enter the kingdom of God, unless he is born of water and the Spirit." Natural and spiritual birth are two different things, Jesus explains, and goes on to say, "You" [plural – You, Nicodemus, and all those you represent] "must be born again!"

Notice that in verse 5 there are three persons mentioned. There is the 'I' of I tell you the truth – the speaker, Jesus himself – God's one and only Son, as John has already called him (1:14). There is God, the One whom Jesus called Father, whose kingdom Jesus is announcing. And there is the Holy Spirit, through whose power we must start life all over again, as a new creation, if we are ever to see and enter God's kingdom.

These three 'persons' of the Godhead are spoken of together at least ten times in this Gospel. And in Paul's letter to the Ephesians, from which our first reading was taken, they are spoken of together nine times – and, of course, many times more in the rest of the New Testament.

I ask you to notice that there are three successive steps in Jesus' discourse, which we may set out as follows:
(a) Do you want to see and enter the kingdom of God? Then you must be born again, of water and the Spirit. (v 3-10)

What is the kingdom of God? The whole New Testament makes it clear that this is not a territorial realm – but a personal relationship. The kingdom exists wherever God is made King, and Jesus the Saviour is acknowledged as Lord. And the only path to this relationship is new birth.

What is this new birth? What does it mean to be born of water and the Spirit? The water has been explained in various ways, but there is good reason to hold that here water and the Spirit speak of a single reality – God's cleansing and renewal of the human heart. I believe Jesus is referring to that promise God gave to Ezekiel, "I will sprinkle clean water on you... I will cleanse you from all your impurities and from all your idols. I will give you a new heart and put a new spirit in you... I will put my Spirit in you and move you to follow my decrees and be careful to keep my laws." (Ezek 36:25-27)

We sinners are naturally and habitually in rebellion against God, as were the Jews of Ezekiel's day. We need an inward cleansing and a change of heart that only God can bring about. Jesus calls it a new birth because it constitutes a totally fresh start to one's life.

How am I sure that Jesus was referring back to those words of Ezekiel? Because of the way Jesus chides Nicodemus, You are Israel's teacher – and do not understand these things? The rebuke only has point because it was set forth in the Jewish Scriptures.

This leads us to Jesus' second step in his flow of thought:
(b) Do you want to be born again? Then you must be willing to learn from Jesus Christ. (v 11-13)

By Nicodemus' own admission, the Jewish teachers did not know about the new birth. But, so far, they were not showing any willingness to accept these things from Jesus, the country preacher. But in reality Jesus was the Son of Man – the Messiah – come down from heaven, to make these things known!

Before we condemn these Jews we must ask ourselves – are we any wiser than they were? Do we let Jesus teach us? Of our own need of new birth? Of the way into God's kingdom?

Listen then to his final challenging words:
(c) Are you willing to learn from Jesus Christ? Then let him teach you to trust in him and in his cross for your salvation. (v 14-15)

Once more Jesus refers to the Old Testament – this time to the story in Numbers 21:6-9, which tells of how Israelites suffering snakebite were told to look at a brass snake that Moses, at God's command, had put up on a pole. Those that looked, lived. "Just as Moses lifted up the snake in the desert," says Jesus, "so the Son of Man must be lifted up, that everyone who believes in him may have eternal life."

The final message to Nicodemus, and to us, is this: Believe in Jesus – that is, trust him, rely on him, tell him he is your only hope, embrace him as your Saviour – and your sins will be forgiven, your spiritual sickness healed, your uncleanness before God washed away. Then you will know that you, too, have been born again.

Now this may be familiar ground – but no less vital for all that! – but this morning I want you to see that this conversation with Nicodemus presents us also with the profound teaching that each person of the Godhead is involved in our salvation.

Jesus, we learn, was sent by God the Father from heaven. "For God so loved the world that he gave his one and only Son..." (v16) Jesus is truly man, able to suffer and die on man's behalf. And he is truly God, so that his sacrifice is sufficient for all mankind – so it is God himself who redeems us from the dread consequence of his own broken law! With Paul, we should be able to say, "the Son of God.. loved me and gave himself for me!" (Gal 2:20) It was only by the cross that Jesus secures eternal life for us.

And that life comes to us through the work in our lives of God's Holy Spirit. We cannot ourselves bring about that change which Jesus described as new birth – only God the Holy Spirit can convince us of sin, of our guilt, and of judgement to come – (John 16:8)

Only he can bring us to repentance, enable us to trust in our Saviour (Eph 2:8,9) – and give us a new heart that loves and obeys God. Only he gives us eternal life, and the assurance that God is become our Father and that we have an eternal home with him for ever.(Gal 4:6; Eph 1:14)

Now, perhaps, you can see why Paul prays for his readers that they may know God better – the glorious Father, whose loving plan from all eternity was to redeem a people for himself (Eph 1:4,5;11,12) – the Lord Jesus Christ, "who, being in very nature God, did not consider equality with God something to use for his own advantageΉ, but ..taking the very nature of a servant... humbled himself and became obedient to death – even death on a cross!" (Phil 2:6-8) And the Holy Spirit of wisdom and revelation, who, in the words of Jesus, "will guide you into all truth.. taking what is mine and making it known to you." (John 16:13-15)

This is the gospel of God's sovereign grace set forth throughout the New Testament – but no less here, in Jesus' conversation with Nicodemus. And the truth of this gospel message and the truth about God himself are not two truths but one. The truth of salvation is the good news of the Father's giving us his Son to redeem us and his Spirit to renew us. And the truth about God is the good news of three divine persons in one God, working together to raise us to spiritual life and bring us to God's kingdom – for his glory alone.

What I have been trying to tell you, then, is that the doctrine of the Trinity is not something dull and obscure, a philosophical puzzle invented by men in their cleverness – but the very heart of our faith, rightly understood. If this teaching is rejected, by denying the deity of any of the three persons – our gospel falls.

Jehovah's Witnesses, Christadelphians, Mormons and those liberal Protestants for whom the personal deity of the Son or the Spirit is suspect – can never state the gospel correctly, because they think of the Godhead wrongly. Clear confession of the Trinity – the distinctive Christian name for God – is the essential foundation of our faith. May we know the reality of it in our lives!

For it is possible to confess Christ, yet not live in the power of the Holy Spirit, nor have confident trust in our Father, nor willing obedience towards him. May God send the Spirit of his Son into all our hearts, crying, Abba, Father! (Gal 4:6) And to him be all the Glory! Amen.

Ή This is the very best modern translation of the Greek word Paul uses.