So, why kill the rabbi? There is a branch of apologetics - which I take crudely to be the belief that the crime is the fault of the victim - that assumes a milder form, and which I'll call explanetics. So the explanatists view of the Mumbai massacres last week is that the cause lies in what concretely has been done to, or in the vicinity of, the young, cool-looking men with the grenades and the machineguns.

On the day after the attacks began the Indian writer, campaigner and serial explanatist, Arundhati Roy, lambasted her own country on The World Tonight on Radio 4, for its rural poverty and its fluctuating support for Hindu nationalism. These, she seemed to suggest, were root causes of the terror. Elsewhere, analysts have pointed to the 60-year-old Kashmiri crisis as fuelling the jihad. More exotically the writer Misha Glenny now suggests that organised crime in the Pakistani city of Karachi is “the operational key” to such attacks (he has just written a book about international organised crime), but that the origins of last week's nightmare lie “in the deterioration in relations between Hindus and Muslims in Mumbai and India”. Well, these things are bad. Kashmir is bad. Hindu communalism is bad.

Poverty is bad. You can see the reasons for warfare in Kashmir, for riots in Hyderabad and for Maoist uprisings in the deep rural areas of India. But why kill the rabbi? Why invade the small headquarters of a small outreach sect of a small religion, which far from being even a big symbol of anything, you would almost certainly need a detailed map and inside knowledge even to find?

From what has been learnt from the one surviving attacker, the baby-faced and variously pre-named Mr Kasab, his group came largely from the rural southern Punjab in Pakistan. It is therefore unlikely that any of them had even encountered a Jew, or knew anyone else who had.

Yet last week, Nariman House was chosen for special murderous attention, alongside the Oberoi and Taj hotels, the railway station and the Leopold café. It reminded me of the 2003 Istanbul bombings when - post Iraq war - specifically British and American targets were augmented, for some reason, by the blowing up of the synagogues belonging to the much diminished Jewish population of that great city.

There is nothing more important about the life of a member of one race or religion than that of another. If the murders of the rabbi, his wife and the other Jewish people in Nariman House are horrific, they are no more horrific than the shooting, bombing and knifing of all the other victims, from the skipper of a hijacked Indian ship to the woman waiting for the night train to Patna. Two years ago, at round about the same time, late in the evening, I was one of two or three white faces in a tired sea of people at that same station. It is not a place to go to shoot Westerners, but there are rich rewards for a serial murderer of ordinary Indians, like the ones whose blood we saw in the photographs.

So the Chabad hostages in Nariman House aren't any more dead than the others. But they do give the lie to explanetics. The only possible reason for going to such lengths to seek out a few Jews (as opposed to having a grand Columbine-type shoot-up in the big city) is ideology. Is because someone has told you, and you have accepted, that these people are your particular enemies.

I was struck by a report at the weekend from the area that the murderers are reported to have come from near the towns of Multan and Bahawalpur. Two of the main terror-insurgent groups in Pakistan, Lashkar-e-Taiba and Jaish-e-Mohammed, recruit heavily in this area. It is also a place where religious schools adhering to the puritanical Deobandi stream of Islam predominate. Jason Burke, reporting last weekend for The Observer, recounted conversations with religious teachers from the local madrassas, one of whom was the brother-in-law of the British jihadi, Rashid Rauf, killed last week by an American drone near the Afghan border.

One such teacher, who, according to Burke, oversaw the education of 40,000 students, told him: “To fight in Afghanistan or Kashmir and to struggle against the forces who are against Islam is our religious duty.” Note how the two specific arenas of struggle are complemented by the third, far more general one, to struggle (ie, take up arms) “against the forces who are against Islam”. Just over a year ago The Times carried an article on the Deobandi influence in Britain's mosques. This highlighted the work of teachers such as Riyadh ul-Haq, a graduate of the Deobandi religious school near Bury. This school, according to our reporter, banned TV, art, chess, music and football. One of its graduates claimed in a sermon that music was part of a “satanic web” erected by Jews to pervert Muslim youth. Ul-Haq cautioned that Muslims were in danger of picking up the habits of unbelievers, who were an “evil influence”.

I'm sure there are plenty of Deobandi followers who are in no way violent or dangerous, but one sees here an ideology, a psychosis in search of a grievance, not an expression of an existing grievance. And it will always find a grievance.

It may seem unfashionably neoconservative to say it, but surely the underlying problem in southern Punjab is a failed society, within a failing state, in which a particular ideology begins to dominate. It is highly suggestive, I think, that the same area that gave birth to some of the Mumbai murderers has one of the highest levels of acid attacks on women anywhere in the world. In 2003 there were at least 74 of these disfiguring assaults in a southern Punjab - surely one of the most appalling manifestations of misogyny to be found anywhere on Earth.

“Sometimes,” according to Human Rights Watch, “the attacked women are seeking a divorce or the husband is seeking a second wife over the first's objections. Sometimes the triggering event can be as trivial as an argument over grocery money.” If readers get a chance I'd recommend the report by Nicholas Kristof, of the The New York Times, last weekend from Pakistan. Just don't look at the pictures.

That would be a real cause for terrorism, wouldn't it? But what arises instead is a political-religious movement of men espousing violent self-righteousness, impossible purity and hatred of human complexity. No wonder the target was cosmopolitan Mumbai, with its foreigners, minorities, its maddening mix of people and moralities, all of them diluting the one, true, narrow way.

The rabbi, in death, tells us this. There isn't anything - whatever the explanatists say - we can concede to the zealots of Faridkot that will persuade such people, once radicalised, not to try to kill us.

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