May the words of my mouth and the meditations of all of our hearts be acceptable to you, O Lord, our strength and our redeemer. Amen

Now I thought we might start this morning with some mental gymnastics to ensure that you are all bright eyed and bushy tailed and to allow you to stun your fellow worshippers with your encyclopaedic knowledge and incisive analytical skills. Yes? No? Maybe you'd prefer to spend the next 10 minutes with brains in neutral, idling until you hear me utter the magic word ‘Amen' s that you know the sermon's finished? Well, sorry, not an option this morning – I need you alert!

Here we go, then. Let's start with something easy to get you warmed up. Could anyone tell me the chemical element in the periodic table with an atomic number of 85? No? I'll give you a clue – it's a halogen. Still no? Never mind – it's Astatine. Atomic number 85, atomic mass 211 and symbol At.

OK – maybe chemistry was a bad place to start – how about geography? The Marianas trench is the lowest region on the surface of the earth, the deepest part of the ocean floor. But – can you tell me how deep? I'll take feet or metres – I'm not proud. No? Well it is in fact 36,201 feet deep 11, 034 metres. Pretty amazing isn't it – that's actually a lot taller than Everest at 29,000 feet.

OK, one more – let's try something artistic this time. Japanese art. Would anyone like to hazard a guess as to what dates the Edo period of Japanese art covered? No? Maybe I'm confusing you, it was also known as the Tokugawa period? Any help? No? Well it was in fact 1615 to 1867.

All right I'll stop now and limit your suffering. It must be wonderful to have the sort of brain that could span knowledge like that – a brain that had in depth understanding of science, of art, of music, of the natural world. I've always looked on in awe at quizzes like University Challenge where the contestants are required to display the widest of understanding – much more impressive than the specialist section of Mastermind.

So what if you can answer everything that could possibly be asked about British steam locomotives manufactured in Crewe between 1850 and 1912. Anyone can bone up – but it takes real intelligence to know the stars that make up the constellations and recognise the theme from the second movement of Bruch's violin concerto.

You see very few people with brains like that. People with a natural intelligence unconfined by a specific discipline. Peter Ustinov, who died recently always struck me as one, Jonathon Millar, the playwright is another.

This Sunday is Trinity Sunday and the popular wisdom is that you need this breadth of intelligence to have any chance of understanding the concept of the Trinity. Never mind the depth of the Marianas Trench, this stuff is really complicated – this is degree level theology so how can we hope to understand it in a few minutes on a Sunday morning. How can our God be three persons and yet still be just one God. It defies our logic and our rational thought processes.

Well, let's see if we can explode the myth and make the Trinity understandable. The popular way to do that is through the use of analogy. The most famous analogy was, of course St Patrick who is reputed to have used the humble shamrock as his visual aid to show how the three leaves of the plant, whilst clearly distinct from one another are still a part of one plant. St Patrick's three leaves, each representing God the Father, Christ the Son and the Holy Spirit are all still part of one plant, one God.

This is fine, as far as it goes, but it has its limitations. We're still at GCSE stage with St Patrick. Sara Maitland, the essayist summed this up fairly elegantly and gives us another analogy, which you may find most useful in understanding the Trinity. She puts it like this.

“Although many of us have grown up gratefully with St Patrick's shamrock image of the Trinity – three leaves making up one leaf, there is always room for some new imagery as well. My favourite model of the Trinity is that it is like a child's pigtail. If the Trinity is seen as a plait, three equal strands, smoothly interrelated, there are some advantages

Firstly, you can tear one of the leaves off a shamrock threesome and leave the other two still related, but if you pull one of the strands out of a plait, the whole thing collapses. This threefold revelation of God makes perfect sense and obviously the same thing applies. You cannot have any of the two sources of God without the third because the whole concept falls apart.

At times, when plaiting, it is important to look at the whole pigtail and check that the hair has been accurately divided into three. Both the orthodox churches of the East and many charismatic churches in the West would claim that our Western Christian tradition has become too Christ centred, that our emphasis on the second person of the Trinity has made the pigtail somewhat lopsided. In the same way, I would suggest that perhaps we have allowed the strand of revelation in Creation get too skinny; that God's role as Creator and sustainer of the universe needs fleshing out, some extra weight.”

So, hopefully Sarah Maitland's analogy gives us yet another insight into our detection of the Trinity. Maybe we've progressed from GCSE to A Level but for me, there is only one theologian who can move us beyond that to a more in depth understanding and that is C S Lewis.

Most people are very familiar with the name of C S Lewis – usually because they have read one of his wonderful children's books, most likely, the Lion, the Witch and the Wardrobe. Fewer people realise that Lewis was a committed Christian and that he wrote and broadcast extensively on theology and Christian life throughout the 1940's and 50's.

If you are searching for answers and struggling to understand the world of Christianity then I would urge you to read C S Lewis. He is, simply, wonderful. He writes on the most complex issues of our faith with simplicity, with humour and with a deep and abiding spirituality. Mere Christianity is a collection of three short books that started out as broadcasts ad are thus lucid and clear. If you read no other book on Christianity, read this book. It will change your life.

So, in looking for an explanation of the Trinity, I turned to my well worn copy of Mere Christianity and, specifically to the last of the three short books that make it up; Beyond Personality. Here is how Lewis expands on the subject of the Trinity.

You know that in space you can move in three ways – to left or right, backwards or forwards, up or down. Every direction is either one f these or a compromise between them. They are called the three dimensions. Now notice this. If you are using only one dimension, you could draw only a straight line. If you are using two, you could draw a figure, say a square. A square is made up of 4 straight lines. Now a step further. If you have three dimensions, you can then build what we call a solid body; say a cube – a thing like a dice or a lump of sugar. And a cube is made up of six squares.

Do you see the point? World of one dimension would be a straight line. In a two dimensional world, you still get straight lines, but many lines make up one figure. In a three dimensional world, you still get figures but many figures make up on solid body. In other words, as you advance to more real and more complicated levels, you do not leave behind you the things you found on the simpler levels; you still have them, but combined in new ways – in ways you could not imagine if you knew only the simpler levels.

Now the Christian account of God involves just the same principle. The human level is a simple and rather empty level. On the human level, one person is one being and any two persons are two separate beings – just as in two dimensions (say on a flat sheet of paper) one square is one figure and any two squares are two separate figures. On the Divine level, you still find personalities, but up there you find them combined in new ways which we, who do not live on that level, cannot imagine.

In God's dimension, so to speak, you find a being who is three persons while remaining one being, just as a cube is six squares while remaining one cube. Of course, we cannot fully conceive a being like that: just as, if we were so made that we perceived only two dimensions in space we could never properly imagine a cube. But we can get a sort of faint notion of it. And when we do, we are them, for the first time in our lives, getting some positive idea, however faint, of something super personal – something more than a person. It is something we could never have guessed, and yet, once we have been told, one almost feels one ought to have been able to guess it because it fits in so well with all the things we know already.

You may ask, “If we cannot imagine a three personal being, what is the good of talking about Him?” Well, there isn't any good talking about Him. The thing that matters is being actually drawn into that three personal life, and that may begin anytime – this morning if you like.

What I mean is this. An ordinary simple Christian kneels down to pray. He is trying to get in 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 room where an ordinary man is saying his prayers.

The grace of our Lord Jesus Christ and the Love of God and the fellowship of the Holy Spirit be with us all ever more. Amen

Tom Crotty