Perhaps we have talked so much about our civilisation's potential to destroy the planet that we have forgotten that the planet also has an untamed ability to destroy civilisation too. Whatever else it has achieved, the Indian Ocean tsunami has at least reminded mankind of its enduring vulnerability in the face of nature. The scale of suffering that it has wreaked - 20,000 deaths and counting - shows that we share such dangers with our ancestors more fully than most of us realised.

An entirely understandable reaction to such an event is to set one's face against any large questions that it may raise. But this week provides an unsought opportunity to consider the largest of all human implications of any major earthquake: its challenge to religion.

A few days after the 9/11 attacks on New York, I had dinner with the Guardian's late columnist Hugo Young. We were still so close to the event itself that only one topic of conversation was possible. At one stage I asked Hugo how his Catholicism allowed him to explain such a terrible act. I'm afraid that's an easy one, he replied.

We are all fallen beings, Hugo declared, and our life in this world is a vale of tears. So some human beings will always kill one another. The attack on New York should therefore be seen not as an act of God, but as an act of fallen humanity. Then he paused, and added: "But I admit I have much more difficulty with earthquakes."

Earthquakes and the belief in the judgment of God are, indeed, very hard to reconcile. However, no religion that offers an explanation of the world can avoid making some kind of an attempt to fit the two together. And an immense earthquake like the one that took place off Sumatra on Sunday inevitably poses that challenge afresh in dramatic terms.

There is, after all, only one big question to ask about an event of such destructive power as the one that has taken place this week: why did it happen?

As with previous earthquakes, any explanation of this latest one poses us a sharp intellectual choice. Either there is an entirely natural explanation for it, or there is some other kind. Even the natural one is by no means easy to imagine, but it is at least wholly coherent.

The tsunami took place, say the seismologists, because a massive tectonic rupture on the sea bed generated tremors through the ocean. These unimaginable forces sent their energy coursing across thousands of miles of water, resulting in death and destruction in a vast arc from Somalia to Indonesia.

But what do world views that do not allow scientists undisputed authority have to say about such phenomena? Where do the creationists stand, for example? Such world views are more widespread, even now, than a secularised society such as ours sometimes prefers to think.

For most of human history people have tried to explain earthquakes as acts of divine intervention and displeasure. Even as the churches collapsed around them in 1755, Lisbon's priests insisted on salvaging crucifixes and religious icons with which to ward off the catastrophe that would kill more than 50,000 of their fellow citizens.

Others, though, began to draw different conclusions. Voltaire asked what kind of God could permit such a thing to occur. Did Lisbon really have so many more vices than London or Paris, he asked, that it should be punished in such a appalling and indiscriminate manner? Immanuel Kant was so amazed by what happened to Lisbon that he wrote three separate treatises on the problem of earthquakes.

Our own society seems to be more squeamish about such things. The need for mutual respect between peoples and traditions of which the Queen spoke in her Christmas broadcast seems to require that we must all respect religions in equal measure, too. The government, indeed, is legislating to prevent expressions of religious hatred in ways that could put a cordon around the critical discussion of religion itself.

Yet it is hard to think of any event in modern times that requires a more serious explanation from the forces of religion than this week's earthquake. Voltaire's 18th-century question to Christians - why Lisbon? - ought to generate a whole series of 21st-century equivalents for all the religions of the world.

Certainly the giant waves generated by the quake made no attempt to differentiate between the religions of those whom it made its victims. Hindus were swept away in India, Muslims were carried off in Indonesia, Buddhists in Thailand. Visiting Christians and Jews received no special treatment either. This poses no problem for the scientific belief system. Here, it says, was a mindless natural event, which destroyed Muslim and Hindu alike.

A non-scientific belief system, especially one that is based on any kind of notion of a divine order, has some explaining to do, however. What God sanctions an earthquake? What God protects against it? Why does the quake strike these places and these peoples and not others? What kind of order is it that decrees that a person who went to sleep by the edge of the ocean on Christmas night should wake up the next morning engulfed by the waves, struggling for life?

From at least the time of Aristotle, intelligent people have struggled to make some sense of earthquakes. Earthquakes do not merely kill and destroy. They challenge human beings to explain the world order in which such apparently indiscriminate acts can occur. Europe in the 18th century had the intellectual curiosity and independence to ask and answer such questions. But can we say the same of 21st-century Europe? Or are we too cowed now to even ask if the God can exist that can do such things?