Pity the poor reviewer tasked to do justice to Karen Armstrong’s latest mighty offering. Armstrong is one of our most erudite expositors of religion, famously (or, perhaps, given the background to this book, notoriously) having surrendered the life of a nun to a lifetime’s attempt to make a comprehensive and unprejudiced study of world religions, their roots, practices, philosophy and place in a global culture. The oeuvre is extensive, bringing a rare mix of cool-headed scholarship and impassioned concern for humanity to bear on the vexed topic of religion. And increasingly vexed it is, as recent shocking events on the world stage have grimly demonstrated.

Armstrong nails her point of departure in the introduction to Fields of Blood. “In the West the idea that religion is inherently violent is now taken for granted and seems self-evident… Even those who admit that religion has not been responsible for all the violence and warfare of the human race still take its essential belligerence for granted… They cite the Crusades, the Inquisition and the wars of religion in the 16th and 17th centuries. They also point to the recent spate of terrorism committed in the name of religion to prove that Islam is particularly aggressive.” It is this, as she intimates, generally accepted take on religion, at least in the west, that this book aims to probe.

The probing process is detailed and often riveting. In the first part of the book she undertakes accounts of ancient religions from the Sumerians (immortalised in the marvellous Gilgamesh epic poem) through the Assyrians, the Egyptians, the Greeks, Zoroastrians, Vedic and Confucian and, foundation stone of western Christianity, the Jewish religions. Armstrong can be relied on to have done her homework and she has the anthropologist’s respect for the “otherness” of other cultures (a position that, if the behest of its founder were attended to at all, lies at the heart of the Christian ethic). A crucial strand in her thesis is that until recent times religion was inextricably bound up with the political and social life of a people. “The habit of separating religion and politics is now so routine in the West that it is difficult to appreciate how thoroughly the two cohered in the past… In the pre-modern world, religion permeated all aspects of life… a host of activities now considered mundane were experienced as deeply sacred: forest-clearing, hunting, football matches, dice games, astronomy, farming, state-building, tugs of war, town planning, strong drink, and, most particularly, warfare.” And, while she does not specially list this, science has also been inseparable from religion, the cosmic and divine orders, throughout most of human history, being perceived as one.

Because Armstrong’s range is so wide, and her representation of the different faces of religions so assiduous, it is sometimes tricky to trace the bones of her argument, which, if I have it right, boils down to this: violence is hard-wired in human nature, as is our more likable need to seek existential meaning. Therefore human psychology will naturally seek to attribute meaning to acts of violence and in doing so will tend to bestow on what is a universal human trait – often exercised actively in the service of economic or political supremacy, or, more metaphorically, in ritual acts of animal sacrifice – a religious significance. At least in cultures where religion has not been segregated from the rest of social and political life. This also gives rise to the many myths that codify violence in order to imbue it with meaning. The Assyrian king who is ritually slapped by the priest to reassert the inferiority of human power, or the ancient Aryan myth of the king who is sacrificed by his brother the priest for his people, and thus brings order into the world, finds many variants (and almost certainly – my view not Armstrong’s – is the basis for the much later Christian myth of Christ’s sacrifice).

The second part of the book attempts to explore the ways in which religion, while inseparable from its sociopolitical origins, may also evolve to oppose, or find sanctuary from, violence. Armstrong writes authoritatively about Jesus of Nazareth, that complex and misty figure, usefully pointing out on the way that contemporary inscriptions regularly referred to the Emperor Augustus as “Son of God”, “Lord” and “Saviour” and announced the “good news” of his birth.

Armstrong, rightly, judges Jesus’s mission to be political as much as spiritual, setting his doctrine of non-violent antinomianism against the often cruel oppression of the Roman rule, the observation of the letter rather than the spirit of Jewish law, and the imperviousness of the privileged among his own race to the plight of the homeless and poor. (This Christian radicalism has a respectable English lineage from Bunyan, through Blake, Ruskin and the last two archbishops of Canterbury.) The spiritual practice required to achieve the necessary state of mind was kenosis, an emptying of the self-interested, self-preserving demands of the ego, and here is where the condition of the literally poor and the “poor in spirit” (that is to say without self-aggrandisement) meet. To identify with the weak and oppressed requires a willingness to abandon the propensity to seek self-definition through the use of power, which, inevitably, involves violence. Armstrong, who is nothing if not democratic in her exposition, is at pains to say that this is not a position unique to Christianity. It is the essence of Buddhism and also the mystical branch of Islam, Sufism. And indeed humanists would argue that it is also the essence of humanism.

In part three Armstrong turns to modern times where she has to address the commonplace argument that atheism has never led to war while acts of extreme violence are today – we need look no further than the atrocities perpetrated by the misleadingly titled “Islamic State” – still performed under the alibi of obedience to divine authority. She makes her point, but here her very conscientiousness tells against her. For it takes real attention to see how, having evolved from a “martini society”, where the gin of religion is inextricable from the rest of the cocktail, religion has also provided a sobering antidote by which to counter the drunken effects of the cocktail. My own view is that if you take any human ideal – liberty, equality, justice, health, education, parenthood – you will find it being hideously distorted through the deployment of violent means to supposedly “good” ends. We have the French revolution, our own civil war, Stalin’s “purges”, the ducking stool, straitjackets, the whip, the strap, lobotomies, chemical castration – the list, if not endless, should be frightening. We should not blame the current craze (and it is a craze because ultimately it’s crazy) for the jihad on religion. It is a distorted search by the disaffected for meaning in a world that has lost touch with the means of finding deeper meaning, arguably through losing touch with the saner, more creative aspects of religion.

Salley Vickers’s latest collection of stories, The Boy Who Could See Death, will be published by Viking Penguin in April 2015.

Fields of Blood is published by Bodley Head (£25). Click here to buy it for £18.49 with free UK p&p