A week after the horrific killings of the schoolchildren of Sandy Hook in Connecticut, most of us are still struggling to get our minds around such a nightmare. And how do we say and sing the words of this joyful season while we think of lives cut so brutally short and of the unimaginable loss and trauma suffered by parents?

Nearly 6,000 children and teenagers were killed by firearms in the USA in just two years. And we’d better not be complacent about the issues of gun and knife crime affecting young people in our own cities here. In the UK, the question is how we push back against gang culture by giving young people the acceptance and respect they deserve, so that they don’t look for it in destructive places. In the US, the question is, of course, about gun laws, one of the most polarising issues in American politics.

And there is one thing often said by defenders of the American gun laws that ought to make us think about wider questions. ‘It’s not guns that kill, it’s people.’ Well, yes, in a sense. But it makes a difference to people what weapons are at hand for them to use – and, even more, what happens to people in a climate where fear is rampant and the default response to frightening or unsettling situations or personal tensions is violence and the threat of violence. If all you have is a hammer, it’s sometimes said, everything looks like a nail. If all you have is a gun, everything looks like a target.

People use guns. But in a sense guns use people, too. When we have the technology for violence easily to hand, our choices are skewed and we are more vulnerable to being manipulated into violent action.

Perhaps that’s why, in a passage often heard in church around this time of year, the Bible imagines a world where swords are beaten into ploughshares. In the new world which the newborn child of Christmas brings into being, weapons are not left to hang on the wall, suggesting all the time that the right thing to do might after all be to use them. They are decommissioned, knocked out of shape, put to work for something totally different.

Control of the arms trade, whether for individuals or for nations, won’t in itself stop the impulse to violence and slaughter. But it’s a start in changing what’s taken for granted. The good news of Christmas is that the atmosphere of fear and hostility isn’t the natural climate for human beings, and it can be changed.

If all you have is a gun, everything looks like a target. But if all you have is the child’s openness and willingness to be loved, everything looks like a promise. Control of the weapons trade is a start. But what will really make the difference is dealing with fear and the pressure to release our anxiety and tension at the expense of others. A new heart, a new spirit, as the Bible says; so that peace on earth won’t be an empty hope.

This article is reproduced with grateful acknowledgements to Lambeth Palace (http://www.archbishopofcanterbury.org/) and BBC Radio 4 'Thought for the Day'. The MP3 audio recording can be listened to here: http://www.archbishopofcanterbury.org/canterbury//data/files/resources/2...

© Rowan Williams is Archbishop of Canterbury.