'there is one God in three persons, the Father, the Son and the Holy Spirit.'

Giles Cattermole considers the trinity.

Isn't the trinity a bit odd? A theological abstraction that confuses and divides? Wouldn't it just be simpler to believe in a 'singular' god? Why is it the first statement in the doctrinal basis?

The trinity is what makes Christianity unique. Other religions and cults might believe in an almighty God, that Jesus was a great prophet (Islam), that he died for sins (Jehovah's Witnesses), or even that he is the Son of God (Mormons). But only Christians worship 'one God in trinity, and trinity in unity'. (1) Only Christians believe that God is both one and three; of one 'substance' in three persons, each eternal and equally God.

Part of our problem lies in what we think God is like. Pagan gods seemed more like mighty men with super-powers. A pantheist god is a force permeating all reality. The god of philosophy is a logical necessity, or an explanation of the design and fine-tuning of the universe. Pagans, pantheists and philosophers might see God as personal (but petty), around us (but without relationship), or powerful (but remote). Such a god might be a creator or ruler, but he's not the God of the Bible. And when we try to shoehorn the trinity onto one of those false understandings of God, it all becomes a bit of a mess.

The problem is that those false gods are based on what we think God is like. Instead, we need to hear what God says he is like. And he is radically different from what people imagine when they make God in their own image.

Jesus told his disciples 'I am the way and the truth and the life. No one comes to the Father except through me. If you really know me, you will know my Father as well. From now on, you do know him and have seen him.' (John 14:6-7) Read this again. It's not just that to know God we need to know Jesus (Hebrews 1:3), but that through Jesus we know the Father. God is revealed to us in this Father-Son relationship; in fact, the Father has always been the Father (John 17:24); the Son has always been the Son (Colossians 1:13-20).

This didn't begin in a stable in Bethlehem, it's part of the eternal nature of God. God is love (1 John 4:16), yesterday, today and forever (Hebrews 13:8). If God were primarily defined by being the creator or ruler, he'd be dependent on the world and his people for him to be what he is. If a 'singular' God were to be defined by his love, he would be similarly limited. But our God is trinity, in eternal love between the Father, Son and Spirit. The Father makes his love for the Son known through giving his Spirit (Matthew 3:16-17); the three persons of the trinity are bound together by love in the fellowship of the Holy Spirit (2 Corinthians 13:14).

This eternal, abundant, joyful love overflows in creation and salvation. God the Father both creates and saves by his Word, in the power of his Spirit (Genesis 1:1-2, Titus 3:4-7). Jesus is eternally loved by the Father, and creation is 'the extension of that love outwards so that it might be enjoyed by others.' (2) Because we rejected him, and because his love is so immense, God acted to save us in Jesus. God shares his love with, showers his love on, his people.

He now pours out this love by his Spirit (Romans 5:5). God doesn't just give us good things in salvation, he gives himself. He fills us with his Spirit, who points us to Jesus, who shows us the Father. This is the God we believe in, not some philosophical faceless force or petty tribal tyrant.

And this changes everything. Being a Christian is not about following rules or rituals, it's about the love that the persons of the trinity have for each other, and that they share with us. We are loved by God, filled by God, to love others. To love others in the way Jesus showed us on the cross (1 John 4:7-11). So trinity shapes our medicine because only in the trinity can we know who God really is and how he wants his people to live. He wants joyful, selfgiving service for the good of others. The compassion we are to show our patients should reflect the overflowing love of God. How could we be filled by the Spirit of love, and keep our knowledge or skills to ourselves? How could we not want to help the poor and vulnerable? When you're doing your umpteenth clerking in the middle of the night, if your view of God is 'singular', if he's just a big boss who tells you what to do, what motivates you other than duty and fear? But if your God has given his life for you, and given his life to you; if his over-flowing love for you has filled you in order for that love to overflow from you; what won't you do for others?

There's so much more we could say about the implications of trinity for medicine. At the heart of reality, within God himself, are personality and relationship, harmony and beauty, communication and knowledge, order and goodness. These things are real and eternal. If everything we see today came from a singularity (for example, of matterenergy) then these things would either be illusions, or contingent on something else that came later. But trinity means these things are of eternal reality and worth. It means ethics in medicine come from the character of a good and holy God. Our attempts to understand science make sense in the light of a God of order and revelation.

In the lab, in the lecture theatre, on the wards; trinity shapes our science, our ethics, and especially the compassion we show our patients. But most importantly of all, it is only because God is trinity that we can be saved. trinity is how God reveals himself in creation and salvation, and it is this God and this God alone who saves us, who redeems us through Jesus' death and resurrection, and who gives us new life in the Spirit.