'Fear not', says the angel to Joseph, to Mary, to the shepherds. It is recurring motif in the Christmas stories, and a significant reminder that the overwhelming news of God the Saviour's coming is both all that the human heart could hope for and also something that powerfully disrupts the way the world goes and the way our lives go. There is something to be afraid of in the renewal of a world: I may not welcome being reconstructed or interrupted.

Religious commitment of any depth is bound to say to the world around it that the assumptions and habits of that world are not beyond question. It isn't all that surprising if a secular environment looks at religion not only with suspicion or incomprehension but with fear. The proposal to ban Muslim headscarves in French schools suggests that there is still a nervousness about letting commitment show its face in public, lest ground be given to some threatening irrational power that will take over the world of reasonable people. President Chirac himself has defended the proposal by claiming that a school must be a 'republican sanctuary' in which children are protected from the cold winds of sectarianism while they absorb the proper values of their society. Religious belief is not banned, but its outward expression – the crucifix on the wall as much as the headscarf - has to be strictly controlled so that the purity of the nation's values may be preserved. Faith must be invisible.

And at the same time, the Chief Rabbi of France encourages the men of his congregations to avoid wearing the skull cap in public because of the spiralling of anti-Semitic incidents. There's more than one reason for religious commitment to be made invisible; sometimes invisibility is sought. Here, then, are two quite different aspects of the public face of religious belief and the complex reactions and feelings it produces – a secular world determined to protect itself against any show of religious faith; a religious community fearful about proclaiming its identity in public because of hatred towards its members. Different problems, different motivations; but behind both lies one central and urgent challenge to do with the public face of religious belief in the modern world.

For all our talk about pluralism, many still feel in all kinds of ways uncomfortable when religion makes a visible difference in public life – so that in turn religious people may feel excluded or threatened if they are visibly identified as members of a community of faith. Discomfort about religion or about a particular religion may be the response of an educated liberal or, at the opposite extreme, the unthinking violence of an anti-Semite; it isn't easy to face the fact that sometimes the effects are similar for the believer. And in case we think the whole debate is just a French problem, we should recognise just a little of the same unease in the nervous sniggering about the Prime Minister's religious faith which ripples over the surface of the media from time to time, or in the blustering irritation aroused by something like Joanna Jepson's whistleblowing about our assumptions around abortion.

The fear of faith itself is part of what can breed fear in a vulnerable or minority community, of whatever tradition. And before we rise up and angrily deplore this, it's worth pausing to ask just why faith provokes such a passionate protectiveness. Historically, the answer, is, alas, that religious faith has too often been the language of the powerful, the excuse for oppression, the alibi for atrocity. It has appeared as itself intolerant of difference (hence the legacy of anti-Semitism), as a campaigning, aggressive force for uniformity, as a self-defensive and often corrupt set of institutions indifferent to basic human welfare. That's a legacy that dies hard, however much we might want to protest that it is far from the whole picture. And it's given new life by the threat of terror carried out in the name of a religion – even when representatives of that religion at every level roundly condemn such action as incompatible with faith.

The believer says to the secular world, 'Don't be afraid!' Yet religion has appeared as something fighting to take over territory in the human soul and the human world – an empire pushing at the frontiers, struggling to defeat the independence and dignity of people. You may remember Swinburne's famous lines – 'Thou hast conquered, O pale Galilean! The world has grown grey with thy breath.' That sums up what a great many people at least half believe. It comes from a highly selective version of history, yet it has enough plausibility to need an answer at the very deepest level.

And this is what our Christmas story and our Christmas faith offer. Why should Joseph and Mary and the shepherds not be afraid? Because what happens when God comes to earth is not something like the first landing of an occupying army, the first breach in our defences by a powerful enemy who wants to take all that is ours. The truth is as different as could be; and the clue is in those simple words, simple words that invite a lifetime's joyful reflection, 'The Word was made flesh'.

When God comes among us, he doesn't first of all clear humanity out of the way so that he can take over; he becomes a human being. He doesn't force his way in to dominate and crush; he announces his arrival in the sharp, hungry cry of a newborn baby. He changes the world not by law and threat but by death and resurrection. Robert Southwell's poem wonderfully captures this overturning of all our terrors and apprehensions: 'His batt'ring shots are babish cries, His arrows looks of weeping eyes'. And the anonymous mediaeval lyric puts it unforgettably: 'He came al so stille, Where his mother was, As dew in Aprille, That falleth on the grass'.

He comes in stillness. He comes in dependency and weakness. He comes by God's absolutely free gift. Yet he comes from the heart of our own human world and life, from the womb of a mother, from the free love of Mary's heart given to God in trust. And this is mysteriously the same thing as his 'coming down from heaven'. He is utterly different, the human being who lives God's own life; he is utterly the same, like us in all things, as the Bible says.

The manner of his coming tells us so many things – but not the least is that human nature, bruised and disfigured as it is by sin, is still capable of bearing the life of God. In the birth of God in flesh and blood, we see what we were made to be – carriers of divine love. And with this birth we begin our journey back to where we belong, back to God, back to what we were made to be. To live in peace and delight with God does not mean that our humanity has first to undergo such radical surgery that it barely seems human any more, that our nature has to be beaten into submission by a divine aggressor. He came all so still; he came to his own.

Here then is the real Christian response to the modern secular person's fear. God is no hostile alien, snatching away what belongs to us. Faith is not either a perversion of human freedom or a marginal and private eccentricity. It is human freedom raised to its fullest by the fact that God has embraced it in love –'from his fullness have we all received, grace upon grace'. The Word, as St John makes plain in this morning's gospel, is no stranger in the world; he is the very centre and energy of creation itself, the heart of every heart.

So Christian faith does not seek to carve out a territory to defend for itself, nor does it look to take over a potentially rebellious world and subdue it by force. It simply witnesses to the world that the world will never be fully itself except in the glad receiving of God's presence and the recognition of the 'true light' at the centre of all human, all created life. If this makes us afraid, the Christian will say, that is because at some level we are afraid of ourselves, of what we really are and might be; afraid of a destiny for human beings more glorious than we could imagine; afraid that we may have to change our lives unrecognisably in order truly to become ourselves.

No, it isn't comfortable, it may be terrifying. 'He came to his own', yes, 'and his own would not receive him' – and 'his own' in this context is all of us who are made in his image and who yet can't cope with his promise. And because we people of faith have so often behaved as though we had never heard or understood the Christmas gospel, we can't expect the secular world to believe us straight away when we say that they have nothing to worry about and that faith is the flowering of human dignity not its opposite. First we have to show that we truly are on the side of humanity – by patient loyalty to people in their need, by courage and sacrifice for the sake of justice, by labour for reconciliation, setting people free from the threat of violence. God comes to 'his own people', religious people, and we have often failed to know or receive him.

And then, supposing we have cleared away the fears that arise from the way religious people have failed to witness fully to their God – then the deeper fears can and do come to the surface, the fears of what faith may demand of a person. Nothing will take away the challenge here; we can only hope that there are enough lives showing joy and humanity to make the challenge worthwhile – lives in which the eternal Word will speak. Such lives will have about them the great mark of God's action in Jesus which is that he doesn't invade, doesn't push us out of the way, doesn't reduce or demean us; he invites, he opens up to us his own infinite hospitality, drawing us into his world, his life. He makes us more than we are, not less. And that is what the true person of faith will show in their life. When the life of faith is visible in the public world, it is not something threatening the integrity of the supposedly neutral and obvious moral principles of the secular state; it is a glimpse into the depths of all morality, all principle and commitment, into the depths where the holiness and faithfulness and love of God secretly nourish the essence of human life, that life which is made for the destiny of becoming children of God. It is a glimpse into a richness surrounding all that we are, without which all our vaunted values and principles would soon corrupt and die.

All our great religious traditions say something of this – which is one reason for Christians, Muslims, Jews and others to stand with each other and speak out for each other in times of stress or harassment. Yet the uniqueness of our Christian faith is that it is inscribed for us not only in a text but in a living human presence in which dwells all the fullness of God. We may confidently say to a nervous secular world, 'Fear not!' God is not coming to abolish but to fulfil the hopes of liberty and human dignity. But we ourselves as believers need to hear the same words we speak to others: 'Fear not!' We don't have to fight for our claims in such a way that all the world sees is another power-obsessed and anxious human institution; we have only to let the Word be born in us and speak in us. A lifetime's work, but also a moment's gift, in the sudden grasp of the mystery of this celebration of God made human, in the words we hear from the gospel, in the bread and wine of the Eucharist: 'from his fullness we have all received, grace upon grace.'

© Rowan Williams 2003