Often when I’m talking to a couple who are planning to get married, they will say something to me along the lines of ‘we complete each other’. Or ‘there was something missing in my life until I found her’. And when I hear that I sometimes tell them that the Bible agrees with them. Right in the second chapter of Genesis – a remarkable book actually, Genesis, it has all the good stuff about love and sex and jealousy and the struggle for integrity and what it means to be human – anyone who thinks the Old Testament is dull or that it doesn’t have anything useful to say to 21st century life should read Genesis from cover to cover. Right in the second chapter we read the story of Adam, the human creature of the earth whose body is opened to create the first man and woman – when they awaken the man looks at the woman and calls her, ‘bone of my bone and flesh of my flesh’. The man and woman are incomplete until they are completed in one another. Incidentally, did you notice I didn’t say that the woman was made from the man? – the Bible in its original Hebrew doesn’t actually call the original human creature a man until after the nocturnal surgery but that maybe is a topic for another time.

So human beings need one another. In our own time we have come to understand that God’s purposes for human flourishing may also be fulfilled in same sex marriage and more generally in loving friendship – the covenant love between David and Jonathon in 1 Samuel is a good model for this. So much of who we know ourselves to be as human persons is formed by the relationships that give us life, and that sustain our lives. Our mothers who carried us in their wombs, our fathers who held us and made us safe, siblings whose love and rivalry taught us about intimacy and competitiveness, friends and teachers who expanded our horizons and taught us our limits, lovers who opened our hearts to the incandescence of desire. We are earth creatures whose lives are inextricably entangled and who can only grow into the fullness of our God-given identity through the ache and joy of relationship. We can’t be complete on our own because to be human is to exist within a dynamic flow of give and take.

And this is what draws us into the experience of God as Trinity. It explains some other stuff about God as well, like Jesus telling us as he has been these last few weeks in St John’s gospel, ‘abide in my love – love one another just as I have loved you, and I will abide with you’, or the most succinct ever definition of God that we get in the first epistle of John, ‘God is love’. Not, ‘God loves a lot’, or ‘God is loveable’, but the actual essence of what God is, ‘God is love’. And that’s the basic truth of God, God’s love that spills over in the act of creation, God’s love for human beings made in God’s own image, and God’s desire to be intimately involved in the life of creation. This is what we see in the Incarnation, in fact – God’s yearning to be bone of our bone and flesh of our flesh. God’s love and God’s desire for us, in fact, is the central and most important theme of holy scripture. Theologians sometimes make it sound more complicated than that.

And so I think that the ancient belief in God as a Trinity is most importantly a statement about the experience of God as love. We need to understand God as relationship, because it’s in relationship that we come to understand what love is about. So belief in the holy Trinity of Creator, Redeemer and Spirit is a claim that God has created us in God’s own image, as creatures both of earth and of heaven, and has given us the breath of life. Trinitarian belief is also the confidence that God loves us enough to share the reality of our lives, both the joy and the suffering of human life, so that we can be joined together in love forever. And it’s also the belief and experience that God loves us enough to be the Spirit at work in us disturbing our complacency, inspiring our creativity, igniting our love and illuminating our lives.

We come across the doctrine of the Trinity in all the ancient creeds of the Church, but I must admit I particularly like the Creed of St Athanasius, that mouthful up at the very end of the Prayer Book that refers to, ‘the Father incomprehensible, the Son incomprehensible, and the Holy Ghost incomprehensible’. To which theologian Dorothy Sayers added, ‘the whole darn thing, incomprehensible’. Of course theologians have grappled with the concept down through the ages – some creatively and helpfully, others less so. But I think the basic gist of Trinitarian faith is not an academic exercise at all, it belongs just as much to all of us who have ever tried to work out what it means to belong, to be loved, to be welcome. What it means to abide in love in the community of the Father and the Son and the Holy Spirit is exactly what the starry-eyed young wedding couple are trying to tell me, despite their naivety in assuming that they are the first humans ever to have worked it out. To stand up in church, as we do every week, and say, ‘I believe in God the Father, God the Son and God the Holy Spirit’, is the same thing as saying, ‘God is love. God loves the world that God has created. God loves everyone, everywhere, no matter what, and welcomes us into the flow of God’s own life’. To think of God as Father/Creator, as Redeemer and as Spirit reminds us that God above all, is a God of relationship, that God’s own self is relational, that God is known to us most fully in relationship.

God is not static and remote, but intimately interconnected and breathing with the life of all creation. And that means God is not only in relationship with us but is present to and moving within our relationships with one another. This is a formative relationship, it makes us who we are, the reality of God’s own life experienced and interwoven into our family, personal and human relationships, but more than that the creative reality of God’s life breathing within the breath of every living thing and interwoven into the stuff of creation itself.

The belief and description of God as Trinity means something deep and profound in our own lives - but it also means something deep and profound in the life and mission of the Church. Because when we see God as a community of love – as Father, Son and Spirit – then we begin to understand the whole purpose of the Church is to incarnate that love – to give it a concrete, human shape - and to proclaim the welcome to that love ... to everyone, everywhere, and always. The understanding of God as a Trinity of persons reminds the Church that loving relationship is both at the heart of God and at the heart of the identity and call of the Body of Christ.

In our Gospel reading this morning, Jesus himself articulates the call and mission given by the God who is a Trinity of loving relationship. "Go, teach, proclaim, baptise..." These are the action-oriented ‘Trinity verbs’ found at the end of the Gospel according to St. Matthew. They grow directly out of our experience of God’s love that we have seen fleshed out in Jesus, and they suggest – to me, at any rate - that the whole purpose of us being the church is to announce that love broadly and hopefully – not just in what we say about it, but in how we enact it, how we give it flesh and blood.

In my first parish, at Belmont, my sister in law Chris used to come fairly regularly with all six of her children – my little nephew Peter who was just going on nine used to sit as still as he possibly could whenever he had to sit through one of his uncle’s sermons but clearly thought there were better ways of spending a Sunday morning. So I was a bit surprised once when Chris told me she had asked Peter what I had talked about that morning. ‘Oh, the same thing he always talks about’, Peter told his mum. ‘He just goes, blah, blah, bah, blah, God loves you, so you’ve got to love each other’.

And that’s about it, really.