In Pontius Pilate (1961), a Borges-like fiction by the French literary theorist and former surrealist Roger Caillois, the Roman governor of Judea who ordered the death by crucifixion of Jesus instead releases him under the protection of imperial legionaries. The charismatic Jewish prophet carries on preaching and dies at a great age. He leaves a reputation for holiness, and pilgrimages are made to his grave. But because of Pilate’s decision, made after a night of sleepless wavering, there is no Christianity.

If Tom Holland is right, there would be no modern secular civilisation either. The liberal West is a creation of the Christian religion, and continues to assert that its values are universal even though it has rejected the faith that inspired them:

Christianity, it seemed, had no need of actual Christians for its assumptions still to flourish… The trace elements of Christianity continued to infuse people’s morals and presumptions so utterly that many failed even to detect their presence. Like dust particles so fine as to be invisible to the naked eye, they were breathed in equally by everyone: believers, atheists and those who never paused to think about religion.

Secular liberals dismiss Christianity as a fairy tale, but their values and their view of history remain essentially Christian. The Christian story tells of the son of God being put to death on a cross. In the Roman world, this was the fate of criminals and those who challenged imperial power. Christianity brought with it a moral revolution. The powerless came to be seen as God’s children, and therefore deserving of respect as much as the highest in society. History was a drama of sin and redemption in which God – acting through his son – was on the side of the weak.

Modern progressive movements have renewed this sacred history, though it is no longer God but “humanity” – or its self-appointed representatives – that speaks for the powerless. In many ways, the West today is more fiercely self-righteous than it was when it was professedly Christian. The social justice warriors who denounce Western civilisation and demand that its sins be confessed and repented would not exist without the moral inheritance of Christianity. As Tom Holland writes, “Had it been otherwise, then no one would ever have got woke.”

He tells us his view of Christianity changed as a result of his study of the ancient world. As a teenager, he was like many others in seeing the biblical God as “the po-faced enemy of liberty and fun”. When he read Edward Gibbon’s Decline and Fall of the Roman Empire (1776), he was happy to accept that the triumph of Christianity meant “an ‘age of superstition and credulity’”. Unlike many, Holland did not stay stuck in a posture of adolescent scorn for the religion in which he had been reared. Twenty years of reading and writing about classical antiquity wore away his youthful admiration for pagan culture.

Caesar killed a million Gauls and enslaved a million more. Across the Roman world, wailing infants could be found on the roadside, on rubbish heaps or in drains, left there to perish. Female infants who were rescued would be raised as slaves or sold to brothels. It wasn’t simply Roman callousness that Holland was repelled by. It was “the complete lack of any sense that the poor or the weak might have the slightest intrinsic value”. His values were not those of classical civilisation, he realised, still less of “human nature”. They were the values of the modern West’s Christian past.

Dominion represents the culmination of Holland’s work to date. His Rubicon: The Triumph and Tragedy of the Roman Republic (2003) and Persian Fire: The First World Empire and the Battle for the West (2005) won distinguished prizes. His Millennium: The End of the World and the Forging of Christendom (2008); In the Shadow of the Sword: The Battle for Global Empire and the End of the Ancient World (2012); and Dynasty: The Rise and Fall of the House of Caesar (2015) established him as one of our most accomplished popular historians. A masterpiece of scholarship and storytelling, Dominion surpasses Holland’s earlier books in its sweeping ambition and gripping presentation.

As Holland shows, the triumph of Christianity was a rupture in Western civilisation. There is nothing at all self-evident about the equal intrinsic worth of all human beings or the inherent preciousness of individual persons. These values – which secular thinkers nowadays take for granted – were placed at the heart of the Western world by Christianity. (Holland says comparatively little about how they developed within Judaism.) In the final analysis, liberal humanism is a footnote to the Bible.

Holland focuses on the story of Jesus’s crucifixion, which by showing God in the form of a broken and tormented human being upended the pagan worship of vitality and beauty. But if anything, this may understate the moral revolution that Christianity accomplished. The nature of morality itself changed. There is nothing in Aristotle about humility or brotherly love. In the Ethics he celebrates the “great-souled man” contemplating the universe and admiring his own magnificence. Altruism – nowadays commonly viewed as the heart of morality – was not much prized in the ancient world. Followers of Stoicism were encouraged to perform public duties, and Epicureans instructed others in how to be happy. But helping suffering human beings through acts of self-sacrifice was not required by morality, or especially admired. The fact that Christians were ready to be martyred for their faith marked them out to the Roman authorities as practitioners of a strange and sinister cult.

Holland is less illuminating on the relationship between Jesus and the religion he is supposed to have founded. “Nothing was remotely as uncanny as the character of Jesus himself,” he writes. But how does he know Jesus was so unusual? There were many other Jewish prophets active in Roman Judea and surrounding areas when Jesus preached, and it may be no more than a fluke that he has been remembered and the rest forgotten. The received Christian picture of Jesus and his teachings may have only a passing resemblance to the historical actuality. In texts that have emerged since the discovery of the Dead Sea scrolls, he is shown in a variety of guises. The religion that came to be called Christianity was mostly an invention of Paul and Augustine and would likely have been unrecognisable to Jesus himself.

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Holland comes into his own when he shows how Christianity created the values of the modern Western world. Not all Christians accepted the idea of original sin. Pelagius (AD 360-418) believed the only reason human beings act badly is that they have been accustomed to doing wrong from childhood – a view repeated in modern times by generations of liberals who have never heard of the early British theologian. Holland goes on to tell how the medieval French scholastic Peter Abelard (1079-1142) was accused of heresy for his assertion that God’s world was rational and governed by laws that humans could understand, only for this belief to inspire the founding of universities all over Christendom. As much as any Enlightenment thinker, it was Abelard who infused the European mind with the spirit of progress.

In later sections of the book, Holland tells of the horror of the conquistadores when they realised the scale of the Mexican practice of human sacrifice, and of a 16th-century experiment in theocratic communism in the German city of Münster. He examines the remorseless exploration of the predatory moral consequences of mechanistic materialism by the Marquis de Sade – an Enlightenment thinker who really did reject Christian values. He examines the anti-Christianity of Lenin and Hitler and the anti-Nazi Christianity of JRR Tolkien, the Christian character of John Lennon’s atheism and the role of Christianity in shaping the moral culture that gave birth to the #MeToo movement. There are many, many more brilliant insights and vignettes.

Dominion presents a rich and compelling history of Christendom. What makes the book riveting, though, is the devastating demolition job it does on the sacred history of secular humanism. Holland summarises this intellectual folk tale:

The triumph of the Church had been an abortion of everything that made for a humane and civilised society. Darkness had descended on Europe. For a millennium and more, popes and inquisitors had laboured to snuff out any spark of curiosity, or inquiry, or reason… That nothing in this narrative was true did not prevent it from becoming wildly popular.

It is a tediously familiar mythology that no amount of historical evidence is likely to dislodge. It was Christian bishops and theologians, as Holland points out, who opposed the enslavement of indigenous peoples in Latin America, and Aristotle who was invoked to defend it. Secular liberals will immediately point out that slavery was practised throughout Christendom during much of its history. Of course this is so, but the fact does not alter Holland’s central point. Even if Christianity in power sanctioned all manner of evils, it set a standard of goodness that simply did not exist in the pagan world.

At the same time Christianity brought with it a new evil of its own. The very universality of the Christian message, its insistence that all human beings are equal in the sight of God, inspired a ferocious assault on other faiths. Christians made a claim to unique possession of the truth with no parallel in pagan religion, and the result was an unprecedented type of repression. As Holland writes: “A Church that proclaimed itself universal had, it seemed, no response to those who rejected it save persecution.” The rise of Christianity spelt the end for pagan toleration.

To be sure, the pagan world did not practise toleration in a modern sense. As the death of Socrates showed, there was no recognition of freedom of thought as any kind of human right. Yet Greco-Roman polytheism recognised that human beings need a variety of faiths, myths and illusions. Christianity destroyed this ancient tolerance, and in doing so inaugurated the modern world.

“Christianity spreads in two ways: through conversion and through secularisation.” This incisive observation, cited by Holland as coming from an unnamed Indian historian, encapsulates much of the argument of Dominion. Secular modernity is not the negation of Christendom but its continuation in another form. Bien-pensant atheists who bang on about how much more civilised we would be if only Christianity had not existed have not asked where their conception of civilisation came from. Nietzsche was closer to the truth. If you regret the rise of Christianity, you must regret the rise of liberalism, human rights and belief in progress as well.

Holland leaves the reader with a question. If the religion on which liberal values were based is dying out in the West, what future can these values have? He writes:

If secular humanism derives not from reason or from science, but from the distinctive course of Christianity’s evolution – a course that, in the opinion of growing numbers in Europe and America, has left God dead – then

how are its values anything more

than the shadow of a corpse? What

are the foundations of its morality, if

not a myth?

Holland seems to be suggesting that liberal values cannot survive the collapse of their Christian foundations. This is not a view confined to Christian believers. The nihilistic French author Michel Houellebecq appears to be thinking along similar lines, as are some atheists and agnostics. Yet I think this misreads our situation.

It may well be that liberal values as they were understood in the past are on the way out. But the source of their decline is more paradoxical than the mere loss of Christian belief. Beyond the West, Christianity is undergoing a revival. In post-communist Russia, for example, the Orthodox Church has re-emerged strongly. But the distinctive pattern of development through which Christianity generated liberal values in western Europe was not replicated in eastern Orthodoxy, and there is nothing liberal about resurgent Christianity in Russia. The same is true, for different reasons, in Africa. In the West, liberalism is not fading away with Christian belief but becoming more zealous and dogmatic. Ironically, today’s ultra-liberals have more than a little in common with the Christians who destroyed the pluralistic tolerance of the ancient world. Policing opinion, shutting down debate and bent on extirpating any beliefs and values other than their own, they are like the early Christians in seeing themselves as actors in an unfolding story of sin and redemption.

Roger Caillois’s fiction suggests a truer view of history. The rise of Christianity was an accident, and the liberal West a spin-off. Of course the hand of God can be seen in the decision Pontius Pilate made to have Jesus crucified. In recognition of Pilate’s pivotal role in the Christian story, he is canonised as a saint in the Coptic and Ethiopian churches. But unless these and later events were providentially ordered, the triumph of Christianity was fortuitous. If any one of an uncountable number of contingencies had not occurred, Europe might still be shaped by a mix of polytheistic cults and classical philosophy and Christianity would never have spread across the globe.

Such a world might be better, in some respects, than the one that actually exists; but it would lack the vision of human equality and moral progress that formed the modern West. If they read Dominion, as they certainly should, secular liberals might pause to reflect that they acquired their deepest values by chance from a religion they despise.

John Gray’s most recent book is “Seven Types of Atheism” (Allen Lane)

Dominion: The Making of the Western Mind

Tom Holland

Little, Brown & Co, 624pp, £25