Today is Trinity Sunday, the day of the year when we dive deep into the most beautiful mystery of the heart of God. It’s a day that might sound as if it’s about obscure theology, most likely expressed in pretentiously incomprehensible Greek, but it’s actually a day that’s at the heart of what it means to be human. It’s also a day that draws me to fall in love again and again with God. For today we celebrate the dance of never-ending divine love, the continuous birth of never-ending beauty, today we listen again for the song of eternal creative joy.

Here is my favourite ever quote about the Trinity, from a 14th century German mystic Meister Eckhart. He wrote:
‘Do you want to know what goes on in the heart of the Trinity?
I’ll tell you.
At the heart of the Trinity
The Father laughs, and gives birth to the Son.
The Son then laughs back at the Father,
And gives birth to the Spirit.
Then the whole Trinity laughs,
And gives birth to us.’
Hold that in the centre of your being – that laughter and birth and relationship are at the heart of God and at the heart of how you were created. Remember that you are formed by the shared joyful laughter that echoes at the heart of God.

So I am a big fan of the doctrine of the Trinity. But not everyone feels the same way, especially those people who have a preference for down to earth action over hifalutin doctrine. They, you, may feel more inclined to agree with another German, the philosopher Immanuel Kant, who said: ‘From the doctrine of the Trinity, taken literally, nothing whatsoever can be gained for practical purposes’. But I believe Kant was wrong – that the doctrine of the Trinity isn’t just for those of us with our heads in the clouds but for those of us with our feet firmly on the ground too.

For what we see in God tells us something profound about who we are, as well as about who God is. We are the embodied image of God – each human being is this individually while the Church is this in community. When we ask ourselves who we should be as individuals, how we should be together, what our purpose and mission is all about, then we look to the one whose image we bear. To look to anything smaller is to short change our humanity.

And I think the most important thing we see in the Trinity is relationship and interconnection. Like all the monotheistic religions Christianity is very clear that there is only one God, no pantheon of divinities but one divine ground of all that is. There are no divine brothers, like Thor and Loki, constantly competing with each other, no divine marriages in which Zeus and Hera take out their frustrations on the human world. But, in Christianity that oneness is qualified – God’s very being is threefold, is relationship, is interconnection.

This is what creation sprang from. An overflowing of the love that was already present in the heart of God. An overspill of the delight that danced between the three persons of God – the Source of all being, the divine word, the eternal spirit; Creator, Wisdom, Breath; Mother, Daughter, Spirit; Father, Son and Holy Ghost. All different imperfect incomplete ways that we try to name that the heart of God is never passive, never static, never not creating, never not in relationship.

But I can hear Kant whispering in my ear – all very fine but this still isn’t exactly practical. How does believing that the heart of all reality is a trinity make any darn difference to how I spend my day, how I spend this one life I’ve been given to live on earth? And it’s a fair question.

And I want to answer this with a life rather than a theory. My uncle Bernard was in the Royal Air Force during the second world war. He flew in the bombers that left England at night to rain down destruction on the lands controlled by the Nazis. He was a teenager. He wrote to his favourite sister, my mother, about his training and his fears. But the fears he wrote about were not for his own life, nor even for his friends, though they all knew their life expectancy was terrifyingly short. Instead he wrote of his fears of what the war might make him become, of what he had to do, of the German lives he might cut short. Bernard’s plane was shot down over the channel in June 1941 when he was 19 and he died saving the lives of two others by putting them in the one fully operational life-raft.

Bernard was a young man of bone deep Trinitarian faith, truly formed by his understanding that the heart of reality, the heart of God, is relational. He feared losing that part of himself more than he feared death. He knew that we are called to be what we see in God – interconnected, rejoicing in relationship, overflowing with love even to our enemies. And that we are called to do what that directs us to – act out of love, for peace, in mutual respect – delighting in difference not fearing it. Being that love in action in the world we live in.

Belief in the Trinity does not make us perfect, or mean that we will live a perfect life. Bernard did bomb Germany, and probably ended innocent lives in the process. But it should always mean that, like him, we live examined lives, lives that are aimed at a purpose beyond our own material well-being, lives that are fully aware of our interconnectedness with others. To claim belief in the Trinitarian God and not to act like this is immorally hypocritical and a perversion of Christian faith.

This is what makes me so mad about some of the public faces of Christianity. That they can claim to love the God who is always in relationship, who rejoices in this inhabited world and delights in the human race, and yet show such disdain for other humans and for this planet. Those who condemn their siblings for their sexuality or their gender expression, those who are deaf to the cries of children held at detention centres, those who believe in white supremacy – these are not followers of the Triune God of love however much they claim the title Christian.

Those who love the God described as Father, Son and Holy Spirit must value in deed as well as in word the loving relationship that this Trinity reveals. This is the God who is beyond everything that can be known and said – utterly, mind-blowingly transcendent. This is the true and living God who walks beside her beloved every day, present in all those who share our journey. This is the God who breathes in and through us and all creation and who is embodied in our innermost being. This is the Triune God whose joyous laughter rings through the universe and who calls all to dance with her to the music of peace, justice and love.