Take away the places where resentment grows - make them museums, says Gwynne Dyer
There was an unpleasant incident in Cordoba cathedral last week.
It was the world's second-biggest mosque until the Spanish reconquest of the city in the 13th century, and a group of 120 Muslim tourists from Austria was visiting it.
Suddenly, half a dozen of them began to pray - and the security guards intervened and told them to stop.
They refused, so the police were called.
Two young men from the group still would not stop, there was a scuffle between them and the police, and they were arrested.
One security guard and one policeman, we are told, were "slightly injured", but one suspects that they did not need time off work to recover ("... and then the accused struck me right in the fist with his face, Your Honour, causing this cut on my ring finger").
The bishop's office offers a more lurid account of the incident, in which the tourists "provoked in a pre-planned fashion what was a deplorable episode of violence".
The spokeswoman for the National Police, Rosa Ortiz, who may have seen a bit more real violence than the bishop, said it was just a "shoving match" between the police and the two men, who were aged 19 and 23.
And that's all that happened. But you just know, given the delicate state of relations between Muslims and Christians in this time, that the blogs and websites that obsess about such things are going to make a big deal out of it.
Especially since the Catholic Bishop of Cordoba, Demetrio Fernandez, recently reaffirmed the ban on Muslims praying in the building.
What he actually said was: "The shared use of the cathedral by Catholics and Muslims would not contribute to the peaceful coexistence of the faiths."
It sounds very stuffy and old-fashioned, but I think he's right.
Because I keep thinking about what would happen if a bunch of Christian tourists went into the Ayasofya mosque in Istanbul and tried to perform some sort of Christian ceremony.
Ayasofya was known as Hagia Sofia Cathedral (and the city was known as Constantinople) until the Ottoman conquest in 1453.
For a thousand years it was the largest cathedral in the world, but Mehmet II, the Ottoman emperor who finally breached the city's walls, had it converted to a mosque.
The bells, altar and iconostasis were removed and replaced by a mihrab and minbar, the Christian mosaics were plastered over, and four minarets were added at the exterior corners.
That's how things were done in those days. The borders between Christendom and Islam moved back and forth a lot during the thousand-year struggle between the new faith and the slightly older one, and when either side gained new territory or recovered lost lands, it immediately put its stamp on them.
Since Islam's first wave of expansion almost exclusively involved the conquest of formerly Christian countries, many of the great mosques of the Arab world outside Arabia are built on the remains of Christian churches - except al-Aqsa in Jerusalem, of course, which is built on what remains of the Jewish Second Temple. (And under that are a few traces of Solomon's Temple, and under them, in all likelihood, are the foundations of some even older pagan temple.)
The great mosque that is now Cordoba cathedral was built on the ruins of an 8th-century Christian church, and you'd probably find some stones from an earlier Roman temple under that: people build their places of worship in the same places, over and over again.
But once they have changed hands, the only sensible thing to do is to accept it. There are too many fanatics around: we are not yet at the point where sharing makes sense.
It would be nice if history were over: if we were all grown-ups now, and we could share this church or that mosque without conflict.
But I know Christians who think that Islam is "the Devil's religion," and that it is trying to take over the world.
And I know many Muslims who cannot see that the Crusades and the Reconquista were Christian counter-offensives to recover lost lands, not unprovoked attacks on Islam.
So everybody is a victim in their own minds, and the historical resentments are only a millimetre below the skin in many people, and it would be a really bad idea to provide a place where those resentments could fester and grow.
If you allow Islamic religious services in Cordoba cathedral, for example, or Christian services in the Ayasofya mosque, you know exactly the sort of extremists and obsessives it would attract.
Except that Ayasofya isn't a mosque any more. In 1935 the government of the Turkish republic turned it into a museum where nobody is allowed to perform religious ceremonies, and you could certainly count on a "shoving match" with the security guards, if not something more, if you tried.
It was a cathedral for 1000 years, it was a mosque for 500, and now it's a museum. Full stop.
That, perhaps, is the best solution for Cordoba cathedral and a few other high-profile church-and-mosques as well.
Make them museums for everybody, not active places of worship for anybody, and the heat goes out of the situation: no more winners and losers.
But the Spaniards are probably not ready for that yet. They were an occupied country for 700 years.
* Gwynne Dyer is a widely published independent journalist based in London.There are too many fanatics around: we are not yet at the point where sharing makes sense.