A few weeks ago, I took part in a discussion that involved a number of people working with children and young people who suffer from different forms of 'autism' – the kind of disorder that seems to cut people off from ordinary communication and shows itself in strange repetitive behaviours and sometimes in violent outbursts. We watched a video showing the work of one of the most experienced therapists in Britain, and then heard her talking about what she is trying to do with her methods.

The first thing we saw on the video was a young man, severely disturbed, beating his head against a wall, and then walking fast up and down the room, twisting and flicking a piece of string. The therapist's first response was strange: she began to twist and flick a piece of string as well. When the young man made a noise, so did she; when he began to do something different, like banging his hand on a table, she did the same.

The video showed what happened over two days. By the end of the two days, the boy had begun to smile at her and to respond when touched. A relation had been created. And what the therapist said about it was this. Autism arises when the brain senses too much material coming in, too much information. There is a feeling of panic; the mind has to regain control. And the best way of doing this is to close up on yourself and repeat actions that are familiar; do nothing new, and don't acknowledge anything coming from outside. But when the therapist gently echoes the actions and rhythms, the anxious and wounded mind of the autistic person sees that there is after all a link with the outside world that isn't threatening. Here is someone doing what I do; the world isn't just an unfamiliar place of terror and uncertainty. And when I do this, I can draw out an answer, an echo; I'm not powerless. And so relationship begins.

To see this sort of thing in action  is intensely moving. This is real mental and spiritual healing at work. But it gives us a powerful image of what it is we remember at Christmas. Human beings are wrapped up in themselves. Because of that great primitive betrayal that we call the Fall of humanity, we are all afraid of God and the world and our real selves in some degree. We can't cope with the light. As John's gospel says, those who don't want to respond to God fear and run away from the light. But God acts to heal us, to bring us out of our isolation – which is as bizarre and self-destructive as that young man beating his head against the wall. And he does this in a way that is just like the therapist in the video. He does what we do; he is born, he grows up, he lives for many years a life that is ordinary and prosaic like ours – he works, he eats, he sleeps. Here is ultimate love, complete holiness, made real in a back street in a small town. And when he begins to do new and shocking things, to proclaim the Kingdom, to heal, to forgive, to die and rise again – well, we shouldn't panic and run away because we have learned that we can trust him. We know he speaks our language, he has responded to our actions and our words, he has echoed to us what we are like.

Christ does not save the world just by his death on the cross; we respond to that death because we know that here is love in human flesh, here is the creator's power and life in a shape like ours. As we read the gospels, we should think of God watching us moment by moment, mirroring back to us our human actions – our fears and our joys and our struggles - until he can at last reach out in the great gestures of the healing ministry and the cross. And at last we let ourselves be touched and changed.

That's what begins at Christmas. Not a doctor coming  in with a needle or a surgeon with a knife, but a baby who has to learn how to be human by watching; only this baby is the eternal Word of God, who is watching and learning so that when he speaks God's transforming word we will be able to hear it in our own human language. He is God so that he has the freedom to heal, to be our 'therapist'. He is human so that he speaks in terms we can understand, in the suffering and delight of a humanity that he shares completely with us. And now we must let him touch us and tell us that there is a world outside our minds – our pride and fear and guilt. It is called the Kingdom of God.

May the blessing of Christ our incarnate King be with you all at this season.

+Rowan Cantuar