Not in God's Name by Jonathan Sacks, book review: Unpicking the danger of 'them and us'

These are difficult times for Jews. Not only, or even especially, for them, of course. It's not a good time to be an Iraqi Christian or a Yazidi in Syria either. But, shade in the areas on a map of the world where simply looking like a Jew is a high or growing risk, and the area is expanding. Parts of some European cities have become danger zones in the space of only a few years. As for most of the Middle East, forget it. It seems incredible now that Baghdad was once home to 140,000 Jews.

Muslim intolerance of Jews, a separate phenomenon from the older Christian Jew-phobia, is not the "ancestral hatred" that many assume it to be, however. It is a recent import. Jews once preferred Muslim to Christian rule, which is why so many of them sought sanctuary in the Ottoman Empire in the later Middle Ages, fleeing the hostility to which "Christ killers" were exposed in Europe. That feeling of trust was mutual. When the Ottomans conquered Belgrade and Buda in the 16th century, they kicked out most of the Christians and encouraged Jews to settle in their place.

A slew of books has sought to explain the root causes of the new strain of fundamentalism in Islam – many inspired by a desire to rescue the reputation of God from being devalued as a result of the actions of his most violent followers. Jonathan Sacks' contribution complements these works well, because whereas most writers on religious violence, such as Karen Armstrong, come from the Christian tradition, the former chief rabbi provides a different, specifically Jewish, perspective.

Sacks could have filled a book with a frightening litany of recent murders, attacks on synagogues and desecrations of cemeteries. There is a lot to cover here, starting with the killings at a Jewish school in Toulouse in 2012, at the Jewish Museum in Brussels in 2014, at a kosher supermarket in Paris this January and at a synagogue in Copenhagen in February. Instead, after referring to these horrors, he focuses on unpacking the theological DNA of the new religious-inspired violence.

Sacks sees modern fundamentalism, Muslim-on-Jewish violence specifically, as rooted in a peculiarly vicious form of sibling rivalry, and at least in part in a false and theologically illiterate variant of dualism. The three Abrahamic faiths of Judaism, Christianity and Islam, he notes, are all monotheistic cousin religions. At first glance, monotheism solves one religious dilemma wonderfully – a bit like applying "clearing your clutter" to gods. Why make offerings to lots of squabbling deities when you can just deal with one Jehovah? But Sacks says monotheism is hard to take on board at a deeper level because its moral implications are far-reaching. If there is only one creator, there is only one creation; we are all in this together. Sacks says this unifying view of the cosmos runs up against a contrary human instinct. Something in our DNA has hard-wired us to see the world not as one big "us" but as an innocent "us" versus a guilty "them".

This kind of bastardised, often unconscious, theological dualism periodically re-asserts itself within the framework of the monotheistic faiths, says Sacks. It is like an ineradicable virus. In the past, it expressed itself in such offshoots as the Essenes in Judaism and in a raft of supposedly heretical cults in Christianity. For the most part, these sects were isolationist and passive. They wanted only to be left alone by a world that they rejected, so it didn't matter that much if they considered 99 per cent of humanity as evil.

Disaster only strikes when this kind of instinctive dualism becomes more universal in its ambitions, when this leap of imagination combines with a great leap forward in technology, such as the invention of the internet – and when all of this occurs in the context of a broad societal crisis. Sacks sees this as the case in much of the Arab world, where he fears that older, more dialogue-based forms of Islam have become discredited and compromised by association with failed states and corrupt regimes. The new fundamentalist approach to religious texts, which utterly rejects the ancient tradition of interpretation, complements this breakdown.

Sacks sees this rejection of interpretation as – obviously – extremely dangerous because the Koran, like the Hebrew and Christian bibles, contains passages that can easily be used to whip up hatred and violence. He also sees this as theologically wrong-headed; the canonical texts of the three faiths constantly have been, and should continue to be, reinterpreted, he writes: "That is what makes fundamentalism – texts without interpretation – an act of violence against tradition."

This book is more about diagnosis than cure – perhaps because there isn't one – although the author makes the point that if your average anti-Semite spent a little time as a Jew, he or she would think differently. He quotes the true but bizarre story of the far-right Hungarian politician Csanad Szegedi whose discovery that his grandmother had been a Holocaust survivor prompted a radical about-turn in his thinking. I was only disappointed that Sacks failed to mention an obvious counter-example, which is that the average Israeli might benefit from spending a couple of days as a Palestinian. Wouldn't he or she then see the whole problem of the West Bank with a different eye?

That apart, this book makes interesting and valuable points. The rise of violent Islamists has emboldened secularists to restate the case against religion per se, and they have every right to do so. But Sacks reminds us that it is wrong to casually conflate conservative or "orthodox" believers with armchair fundamentalists – with people who would quite like to kill unbelievers but who can't be bothered to act on their beliefs. The two approaches to faith are not only different but opposed to one another, he says. It is a case well put, and worth hearing.

Marcus Tanner is the author of 'Ireland's Holy Wars, the Struggle for a Nation's Soul' (Yale University Press)