AP

Rawalpindi (yet again) wonders why

THE list of causes and countries in which people are prepared to turn themselves, and those around them, into bloody piles of bone and gristle is long and growing. In Sri Lanka on February 3rd, a woman on a platform at Colombo's main railway station blew herself up, killing at least 15 people, including seven schoolboys and their sports coach. The next day, Israel saw its first suicide attack for more than a year: at a mall in Dimona, a Palestinian put an abrupt end to his own life, and that of an elderly Israeli woman. As rescuers tended to an unconscious youth who appeared to be a wounded victim, they noticed—just in time—that he too was wearing an explosives belt. Meanwhile in the Pakistani garrison town of Rawalpindi, where Benazir Bhutto was slain in December, a human bomb on a motorcycle rammed into a military bus, killing at least ten people.

There is almost always something mysterious about suicide: a gap between everything that was ever said by or known about the self-destroyer (even by his family), and the silence that remains. In the case of politically inspired suicide, the motives are at once more obvious and more elusive. Just why are terrorists, often promising young men (or increasingly, women) with much to live for, willing to kill themselves as well as others? It is exactly eight years since the first international conference on suicide terrorism was convened in Israel; since then, dozens of security pundits have been searching for new answers to the question.

At the time of that meeting in 2000, the secessionist Tamil Tigers, waging war in Sri Lanka, were the most prolific users of suicide tactics. Since then there has been a change. While Tamil nationalists are still at large, the locus of suicide-bombing has shifted to the Muslim world, and most perpetrators—whether they are fighting local wars, or a global campaign against America and its allies—have claimed to be acting in the name of Islam. The practice spread from the Hizbullah fighters of Lebanon to Hamas and other Palestinian groups—and thence to the killing fields of Iraq and Afghanistan. That prompts some Westerners to assert a link between Islam—especially Shia Islam, with its stress on martyrdom—and readiness for self-destruction.

But scholars who comb the available data about suicide attacks are often sceptical about religion's role. Robert Pape, of the University of Chicago, has identified three factors that make suicide terrorism probable. It is likely to occur when a community feels it is under occupation that must be resisted; when the “occupier” is a democratic society whose opinion can be swayed; and where there is a sectarian difference between the perpetrators' community and the target community. In his view, religious differences help to make suicide attacks conceivable, but they are not the main driver. Nichole Argo, a researcher at the Massachusetts Institute of Technology, agrees that religion's role is limited. What counts is a background of support for the idea of insurgency: a sense among self-annihilators that their peers will see them as heroes. Nor is religious indoctrination a big factor, Ms Argo insists; only a fraction of the alumni of hard-line madrassas in Pakistan and Indonesia engage in violence. Material deprivation is not decisive either; many suicide-bombers are from comfortable backgrounds.

Randall Collins, of the University of Pennsylvania, has made a good point about middle-class bombers: to do their job, human bombs need middle-class virtues like politeness and discretion—till the very moment of self-annihilation.