Leading article: A papal visit laden with symbolism and danger

No one can deny that Benedict XVI is a brave man for even visiting Turkey at a time of such heightened unease between Muslim world and the West, and when many Turks are seething - to put it mildly - with the Pope personally and Europe in general. Each step the elderly Pontiff takes along the Hagia Sophia to the Blue Mosque will be watched and analysed; the Turks will be especially wary if he even looks like he is praying under the soaring dome of what until 1453, when Mehmet the Conqueror overran Constantinople, was the greatest church in Christendom.

The question, therefore, is not whether the papal visit will generate enormous attention - the riot police out on the streets of Istanbul are a sign this is guaranteed - but how he will use it. The whole world will be watching to see whether he will make a significant gesture to soothe Turkey's anger over its growing disputes with the West, or just make matter worse.

Turkey is a land that, for reasons of history and geography, is at the crux of so many of the most contentious issues facing the world, from fundamentalist Islam to its conflicts with free speech and liberal democracy, from immigration to nationalism, from the futures of both Europe and the Middle East to the disputes over Cyprus and the Kurdish region. Add to this volatile mix the inflammatory issue of the Armenian genocide, which the trial of the writer Orhan Pamuk, as well as a recent foolish vote by the French assembly, have helped bring back into the frame. Like it or not - and most Turks don't, as a rule - the ghosts of the Armenians slaughtered in the Ottoman Empire in the First World War have come back to haunt Turkey's application to join the European Union.

Whether the Pope, as head of a tiny European state as well as the Catholic faith, is the man to pour oil on troubled waters looks doubtful. The now notorious speech he delivered at the University of Regensburg on 12 September, citing with apparent approbation the strongly anti-Islamic sentiments of the 14th-century Byzantine emperor Manuel II, has forged a perception of him as an anti-Muslim crusader. While some maintained he was simply an elderly academic who had put his theological foot into it, others more credibly insisted he knew exactly what impact his remarks in Regensberg would make. They have also pointed out that at one time he was a vocal opponent of Turkey's application to join the European club.

No surprise, then, that Turkey's Prime Minister, Recep Tayyip Erdogan, nervous of his poll ratings, has decided he will not meet the Pope after all - unless they cross paths by accident at Istanbul airport, through which Mr Erdogan must pass on his way to a Nato summit. No surprise either that even before the Pope has arrived, crowds of angry Turks are gathering on the streets of Istanbul to give the Pope the kind of hostile reception none of his predecessors experienced.

This is a visit that drips with heavy symbolism. It is vital that neither the Pope nor his hosts allow the slightest gesture to fuel the widespread, if unwarranted, idea that a clash of civilisations between east and west is inevitable. The moderate majority of Turks must realise it will rebound to their great credit if they show magnanimity in the face of what they see as papal provocations. The Pope, for his part, must convince his hosts he has not come with a shopping list of demands on behalf of the local Christians but in a spirit of friendship.

As Turkey's official news agency put it yesterday: "Turkey will host the Pope despite its hurt. It's also our right to expect a gesture from the Pope." It could not have been put better.