Do you know anywhere 'thin'? In modern spiritual writing, people sometimes talking about journeying to 'thin' places. By that they don't mean a health farm, or a narrow gorge somewhere. They mean a place where the boundary between this physical world that we're part of, and the spiritual world, seems to be thinner than usual, and more people are more conscious there of God than they would be elsewhere. Some of that of course is because it's a place where a lot of people pray, like the isle of Iona in Scotland or Holy Island in Northumberland. But you too may have had an experience of feeling unusually aware of God or the spiritual world, even in the midst of everyday reality.

I'm not someone given to mystical experiences. But I still remember an occasion when Hilary and I went to see friends in South Africa and we were standing on a hill looking over a rocky landscape, and for a little while I saw the trees and bushes, not simply as great plants, and not simply with my physical eyes, but saw them as the life of God breaking through the crust of the earth and reaching up to heaven.

Such experiences change how you look at the world. And an understanding of modern physics can do much the same. Just looking around you it seems all solid and secure: but it's all an illusion – most of us and this cathedral is empty space with little atoms and electrons and particles whirling around in it, maybe underlaid by 10-dimensional vibrating bits of string. We build a dependable safe ordinary life in what's an unsafe and changing and incredible world – a world where everything is thin, and nothing is as it seems.

The common theme in today's bible readings is that of life beyond death – most obvious in the Thessalonians reading about Jesus coming back. Christian faith has had at its heart since it began the good news of the resurrected Jesus, with its insight that the world we see is not the world as it really is, and that we live now in order to prepare for eternity with God.

It's the rise of modern scientific culture that's caused a loss of nerve in Christian faith. Our society is concerned – and in many ways it's a right concern – with how life is to be lived now. Some Christians (usually the rich ones) used to say in effect that it's all right to have inequality and injustice now, because God will make it all right in the next life – which is why Karl Marx saw religion as the opiate of the people, keeping them compliant and submissive. True Christian faith proclaims God's demand on us to bring the justice and peace of the heavenly world into existence in the world here and now

But we also to regain the Christian critique of present culture in the name of the God of eternity: we need to hold on in faith to the promise of the resurrection – that, although death is a reality we must experience, there is life with God beyond death for ever. You can't prove it – and nor can you disprove it. It may indeed be that our faith in Christ is an illusion, although the quality of life it brings to the present moment makes it pretty powerful nonetheless. But the idea that you only live your own life, and what you see around you is all there is to it, is most certainly an illusion.

The ancient Jews believed in God, but they didn't believe in personal survival after death until later on in their history. The words we had read from the book of Job are not a confident affirmation of resurrection: but, as with other statements in the Old Testament, particularly in the psalms, they say that, if you have faith that God knows you and loves you, then why should you expect God's knowledge and love of you to stop when you die?

That's the punchline in Jesus' words to the Sadducees when they scoff at the idea of resurrection. Why believe in the resurrection, he says? Because God is the God of Abraham and your other dead ancestors: but he's not God of the dead but of the living, for to him all of them are alive. All are alive to God; and Jesus having passed through death is alive to us.

All the world is a thin place. What you see is not what you get: because God's world is just over your shoulder, and as Jesus tells us, eternal life with God begins now.

The choir is going to sing Roland Bainton's musical setting of almost the final words from the Bible, ch.21 of the book of Revelation: words about what lies beyond and behind what's called this vale of tears; words which may be for us, as we listen prayerfully to them, a twitching aside of the net curtain through which we may glimpse something of God's eternal life.