8 Alister McGrath - Thinking about the Trinity

I often get asked to explain what Christians mean by the doctrine of the Trinity. When I was an atheist myself as a teenager, I saw the doctrine of the Trinity as confirming my view that religion was total nonsense. How can God be three and one? Yet many within Christianity also find it baffling. So let me explore why this doctrine makes sense, and why it’s so important.

The doctrine of the Trinity sets out to tell the full truth about God, no matter how hard it is for us to take this in. It aims to tell the full story, and paint the full picture. It might be easier to tell the story of God’s dealings with the world and humanity by leaving out some bits. The Christian panorama is that of God creating the world, redeeming it in Christ, and being present in the world and our lives through the Holy Spirit. That’s complicated, some will say. So what happens if we try to make it a lot simpler?

For Christians, God entered into this world in Jesus of Nazareth: “the Word became flesh and lived among us, and we have seen his glory”

Let’s pretend that God is simply someone up in heaven, who made the world. That’s the way many Greek philosophers thought about God. It’s not a difficult idea. So why don’t Christians just adopt this simple view of God? The reason is clear. This may be an easy idea to understand, but it is a totally inadequate view of God, from a Christian point of view. Why? Because this scaled-down God is the distant and far-removed creator of this world, who never becomes directly involved in its affairs. And Christians know that God just isn’t like that. For Christians, God entered into this world in Jesus of Nazareth: “the Word became flesh and lived among us, and we have seen his glory” (John 1:14). Good theology is about telling the full story, and enabling us to see the full picture. And that means weeding out inadequate ideas about God. We simply cannot do justice to the Christian experience and vision of God without using the traditional biblical and theological language of Father, Son, and Holy Spirit.

Now some will read these words, and rightly wish to raise an objection. Their faith is simple. They trust in God, and believe firmly that they’ve been redeemed through Christ. Why do they need to believe this complicated stuff about the Trinity? Isn’t their simple faith good enough? It’s a fair question, and needs to be answered properly.

No, you don’t need to believe in the Trinity. But when you start to reflect on your faith, you will find that – maybe without knowing it – you already do believe in the Trinity! It may not be something that you explicitly affirm. But it’s implicit in what you already believe. Let’s tease out this important point.

If you are holding a coin in your hand, and let it drop, it will fall to earth. If you are growing apples or pears in your garden, the fruit will drop off the tree when it is ripe. Those are very simple observations. We’re all familiar with them, and there’s nothing difficult about them. But what do these observations imply about our world? What is the bigger picture of which they are part, and which they disclose, to some extent?

Sir Isaac Newton, one of the leading figures of the Scientific Revolution of the seventeenth century, realised that these everyday observations pointed to the existence of something deeper – a force which he called “gravity”. Everyone already knew that apples fell off trees. What Newton did was to make clear what that implied. He was able to show that the same general principle that governed apples falling to the ground also applied to planets orbiting the sun.

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The same principle underlies the Christian doctrine of the Trinity. Christians believe that God is creator and lord. Christians pray and worship. They talk about being saved by Christ. They talk about being guided by the Holy Spirit. But what concept of God is implicit in these beliefs? The doctrine of the Trinity affirms the truth of these simple statements. But it goes further, and asks: what must be true about God if these simple statements of faith are true and reliable? What is the bigger picture of God, that holds these snapshots together?

Imagine that you come across a lake – perhaps on a country walk, or in an ornamental garden – in which water lilies are growing. Their great leaves and elegant flowers seem to float on the surface of the water, creating an impression of tranquility and harmony. But what we see on the surface is sustained by a complex root system. The water lilies grow on stalks that are rooted in the ground at the bottom of the pond. These roots provide both physical support and biological nourishment for the leaves and flowers. They’re part of a bigger picture, which is not fully seen from the perspective of the observer, who notices only the leaves and flowers floating on the pond.

The doctrine of the Trinity is like the part of the iceberg that is under the water. It’s there, and it needs to be there.

A “surface faith” is about what we see and experience. That means it’s about prayer and worship. It’s about affirming the articles of the creeds, and talking about Jesus of Nazareth as our saviour and Lord. But beneath this is a “deep faith” – a set of more profound beliefs that are implied by our “surface faith”. The doctrine of the Trinity is like the part of the iceberg that is under the water. It’s there, and it needs to be there. But for everyday purposes, you don’t need to worry about it. You can live out the Christian life without explicitly talking about the Trinity! But what you need to realise is that there is a deep Trinitarian logic to the language of our faith. When Christians declare that “Jesus is Lord!”, they imply that God is Trinity.

C. S. Lewis offers us a mental experiment that many people find helpful. Lewis asks us to imagine someone who is praying, and think through what this implies:

“An ordinary simple Christian kneels down to say his prayers. He is trying to get into touch with God. But if he is a Christian he knows that what is prompting him to pray is also God: God, so to speak, inside him. But he also knows that all his real knowledge of God comes through Christ, the Man who was God – that Christ is standing beside him, helping him to pray, praying for him. You see what is happening. God is the thing to which he is praying the goal he is trying to reach. God is also the thing inside him which is pushing him on – the motive power. God is also the road or bridge along which he is being pushed to that goal. So that the whole threefold life of the three-personal Being is actually going on in that ordinary little bedroom where an ordinary man is saying his prayers."

In the end, the Trinity is not really something that we can hope to understand. It’s an attempt to do justice to God – not a distant, absent God, but a God whose love and presence we can know here and now, in our ordinary lives.

Alister McGrath recently retired as Andreas Idreos Professor of Science and Religion at the University of Oxford. His latest book is What’s the Point of Theology? Wisdom, Wellbeing and Wonder, published recently by SPCK.