Since the Church is “the Israel of God”, Christianity has supplanted Judaism – just as Jacob supplanted Esau and gained his birthright.  So ran a vein of Christian theology – which became part of the narrative of anti-semitism in Europe that, within living memory, caused the Holocaust and the murder of six million innocents.

Twenty years after the liberation of Auschwitz, the Roman Catholic Church excommunicated, so to speak, that misreading of scripture and tradition.  At the Second Vatican Council, it promulgated Nostra Aetate, a “declaration on the relation of the church with non-Christian religions”, which decried anti-semitism, declared that “the Jews should not be presented as rejected or accursed by God” and went back to the the roots of Christianity, in order to to rediscover the authentic teaching of the Church.  “Theirs is the sonship and the glory and the covenants and the law and the worship and the promises,” the document said, quoting St Paul.

Over the centuries, Islam has a better record than Christianity in relation to the Jewish people – but not today.  ISIS, Al Qaeda and violent Islamism are all on the march.  St Paul relied on word and letter to spread a gospel of redemption through faith.  ISIS has swifter means of pumping out its message of salvation through terror – YouTube, Twitter, and all the rest of the apparatus of social media.

But Jews are not the main victims of ISIS – of its assassinations, beheadings, crucifixions, burnings-alive and murder of children: far from it.  Christians are literally in the firing line.  No wonder the faith they follow is vanishing from the Middle East.  A century ago, Christians made up 20 per cent of its population.  Today, that figure is four per cent.

However, the main victims of ISIS are not Jews or even Christians, but Muslims themselves – which makes it perverse that three sisters from Bradford, together with their nine children, should apparently be seeking to join ISIS or other extremists in Syria.  Their representative has bemoaned a claimed lack of police support.  Earlier this year, the parents of three “jihadi brides” made the same complaint.

In today’s Daily Mail, Manzoor Mughal writes: “We Muslims must stop blaming others for the way our young are radicalised.”  It is one of those comment pieces in which the paper specialises (“Why I, as a talking badger, support King Miraz”), and none the worse for it.  The main point that the author makes is right: too many British Muslims blame Mossad or the CIA or whoever for the crisis in modern Islam.

None the less, many of them don’t take refuge in conspiracy theories, and most of them don’t support ISIS. Week after week in British mosques each Friday, there is a mass of local condemnations of extremism and calls for moderation.  Nor is Islamist extremism the only form in town.  There is Jewish extremism on the West Bank and Christian extremism in the United States.

Furthermore, the West has undoubtedly made foreign policy mistakes which have fed the flames.  But for all this, the fact remains that the main driver of ISIS isn’t western error but the poisonous combination of historical failure – the number of books translated into Arabic during the thousand years since the ninth century is less than those translated in Spain in a single year – and Islamist doctrine.

After the bombing of Glasgow airport in 2008, two futures could be glimpsed.  The first saw Britain engulfed in terror attacks.  The second envisaged a public rejection of extremism by British Muslims, as they poured on to the streets to protest against it.  Neither have happened.  There have, mercifully, been no successful mass terror attacks on our soil for the best part of ten years (though not for a want of trying).  But that mass movement for moderation hasn’t come about, either.  There is Quilliam.  There are initiatives that have fizzled out – the Sufi Muslim Council, the British Muslim Forum, and so on.  The anniversary of 7/7 is approaching.  It is hard to assess what has changes since that atrocity took place.

“We denounce and condemn extremism, radicalism and fanaticism today, just as our forefathers tirelessly denounced and opposed them throughout Islamic history,” declared the Amman Message – a recent document issued by over 200 Muslim scholars, under the patronage of King Abdullah of Jordan.  The message is an attempt to speak truth with authority to “the Muslim Street”.

It is thus a recognition that Islam needs its own Nostra Aetate moment – that’s to say, a reaffirmation of Jews and Christians as “peoples of the book” and a theology of backing for liberal democracy that has real force and projection.  But does anyone have the standing to make it stick, given the decentralised nature of Islam?  Does anyone’s writ run wider than that of the YouTube jihadis?