In the warped mind of Anders Breivik, his murderous rampages in Oslo and Utoya earlier this year were the first shots in a war in defence of Christian Europe. Not a religious war but a cultural one, to defend what Breivik called Europe's "cultural, social, identity and moral platform". Few but the most psychopathic can have any sympathy for Breivik's homicidal frenzy. Yet the idea that Christianity provides the foundations of Western civilisation, and of its political ideals and ethical values, and that Christian Europe is under threat, from Islam on the one side and "cultural Marxists" on the other, finds a widespread hearing. The erosion of Christianity, in this narrative, will lead inevitably to the erosion of Western civilisation and to the end of modern, liberal democracy.

The claims about the "Muslim takeover" of Europe, while widely held, have also been robustly challenged. The idea of Christianity as the cultural and moral foundation of Western civilisation is, however, accepted as almost self-evident – and not just by believers. The late Oriana Fallaci, the Italian writer who perhaps more than most promoted the notion of "Eurabia", described herself as a "Christian atheist", insisting that only Christianity provided Europe with a cultural and intellectual bulwark against Islam. The British historian Niall Ferguson calls himself "an incurable atheist" and yet is alarmed by the decline of Christianity which undermines "any religious resistance" to radical Islam. Melanie Phillips, a non-believing Jew, argues in her book The World Turned Upside Down that "Christianity is under direct and unremitting cultural assault from those who want to destroy the bedrock values of Western civilisation."

Christianity has certainly been the crucible within which the intellectual and political cultures of Western Europe have developed over the past two millennia. But the claim that Christianity embodies the "bedrock values of Western civilisation" and that the weakening of Christianity inevitably means the weakening of liberal democratic values greatly simplifies both the history of Christianity and the roots of modern democratic values – not to mention underplays the tensions that often exist between "Christian" and "liberal" values.

Christianity may have forged a distinct ethical tradition, but its key ideas, like those of most religions, were borrowed from the cultures out of which it developed. Early Christianity was a fusion of Ancient Greek thought and Judaism. Few of what are often thought of as uniquely Christian ideas are in fact so.

Take, for instance, the Sermon on the Mount, perhaps the most influential of all Christian ethical discourses. The moral landscape that Jesus sketched out in the sermon was already familiar. The Golden Rule – "do unto others as you would have others do unto you" – has a long history, an idea hinted at in Babylonian and Egyptian religious codes, before fully flowering in Greek and Judaic writing (having independently appeared in Confucianism too). The insistence on virtue as a good in itself, the resolve to turn the other cheek, the call to treat strangers as brothers, the claim that correct belief is at least as important as virtuous action – all were already important themes in the Greek Stoic tradition.

Conversely, perhaps the most profound contribution of Christianity to the Western tradition is also its most pernicious: the idea of Original Sin, the belief that all humans are tainted by Adam and Eve's disobedience of God in eating the fruit of the Tree of the Knowledge of Good and Evil. It was a doctrine that led to a bleak view of human nature; in the Christian tradition it is impossible for humans to do good on their own account, because the Fall has degraded both their moral capacity and their willpower.

The story of Adam and Eve was, of course, originally a Jewish fable. But Jews read that story differently to Christians. In Judaism, as in Islam, Adam and Eve's transgression creates a sin against their own souls, but does not condemn humanity as a whole. Adam and Eve were as children in the Garden of Eden. Having eaten of the Tree of Knowledge, they had to take responsibility for themselves, their decisions and their behaviour. In Judaism, this is seen not as a "fall" but as a "gift" – the gift of free will.

The story of Adam and Eve was initially, then, a fable about the attainment of free will and the embrace of moral responsibility. It became a tale about the corruption of free will and the constraints on moral responsibility. It was in this transformation in the meaning of Adam and Eve's transgression that Christianity perhaps secured its greatest influence, a bleak description of human nature that came to dominate Western ethical thinking as Christianity became the crucible in which that thinking took place. Not until the Enlightenment was the bleakness of that vision of human nature truly challenged.

Not only are the key ethical principles of the Christian tradition borrowed from pagan philosophies, but that tradition has been created as much despite the efforts of Christian churches as because of them. The collapse of the Roman Empire under the weight of the barbarian invasions of the fourth and fifth centuries left Christian clergy as the sole literate class in Western Europe and the Church as the lone patron of learning. But if the Church kept alive elements of a learned culture, Church leaders were ambiguous about the merits of pagan knowledge. "What is there in common between Athens and Jerusalem?" asked Tertullian, the first significant theologian to write in Latin. So preoccupied were devout Christians with the demands of the next world that to study nature or history or philosophy for its own sake seemed to them almost perverse. "Let Christians prefer the simplicity of our faith to the demonstrations of human reason," insisted Basil of Caesarea, an influential fourth-century theologian and monastic. "For to spend much time on research about the essence of things would not serve the edification of the church."

Christian Europe rediscovered the Greek heritage, and in particular Aristotle, in the 13th century, a rediscovery that helped transform European intellectual culture. It inspired the work of Thomas Aquinas, perhaps the greatest of all Christian theologians, and allowed reason to again take centre stage in European philosophy.

But how did Christian Europe rediscover the Greeks? Primarily through the Muslim Empire. As Christian Europe endured its "Dark Ages", an intellectual tradition flowered in the Islamic world as lustrous as that of Ancient Athens before or Renaissance Florence after. The discovery, and translation into Arabic, of Aristotle, Plato, Socrates and other Greek philosophers helped launch the golden age of Islamic scholarship.

Arab scholars revolutionised astronomy, invented algebra, helped develop the modern decimal number system and established the basis of optics. But perhaps more important than the science was the philosophy. The Rationalist tradition in Islamic thought, culminating in the work of Ibn Sina and Ibn Rushd, is today barely remembered in the West. Yet its importance and influence, not least on the Judeo-Christian tradition, is difficult to overstate. Ibn Rushd especially, the greatest Muslim interpreter of Aristotle, came to wield far more influence within Judaism and Christianity than within Islam. It was through Ibn Rushd (known in the West as Averroes) that western European scholars rediscovered their Aristotle, and his commentaries shaped the thinking of a galaxy of philosophers from Maimonides to Aquinas.

Christians of the time recognised the importance of Muslim philosophers. In The Divine Comedy Dante places Ibn Rushd with the great pagan philosophers whose spirits dwell not in Hell but in Limbo, "the place that favour owes to fame". One of Raphael's most famous paintings, "The School of Athens", is a fresco on the walls of the Apostolic Palace in the Vatican, depicting the world's great philosophers. And among the pantheon of celebrated Greek philosophers stands Ibn Rushd.

Today, however, that debt has been almost entirely forgotten. There is a tendency to think of Islam as walled-in, insular, hostile to reason and freethinking. Much of the Islamic world came to be that way. But the fact remains that the scholarship of the golden age of Islamic thinking helped lay the foundations for the European Renaissance and the Scientific Revolution. Neither happened in the Muslim world. But without the Muslim world, it is possible that neither may have happened.

If the story of the Renaissance and the Scientific Revolution has been rewritten in the interests of creating a mythical "Christian Europe", so too has the story of the relationship between reason and faith in the Enlightenment. What are now often called "Western values" – democracy, equality, toleration, freedom of speech and so on – are the products largely of the Enlightenment and of the post-Enlightenment world. Such values are, of course, not "Western" in any essential sense but are universal; they are Western only through an accident of geography and history.

A complex debate has arisen about the relationship between the Enlightenment and the Christian tradition. As the notion of the Christian tradition and of "Western civilisation" have become fused, and as the Enlightenment has come to be seen as embodying Western values, so some have tried to co-opt the Enlightenment into the Christian tradition. The Enlightenment ideas of tolerance, equality and universalism, they argue, derive from the reworking of notions already established within the Christian tradition. Others, more ambiguous about the legacy of the Enlightenment, argue that true liberal, democratic values are Christian and that the radicalism and secularism of the Enlightenment has only helped undermine such values.

Both views are wrong. For a start, the historic origins of many of these ideas lie, as we have seen, outside the Christian tradition. It is as apt to describe concepts such as equality or universalism as Greek as it is to describe them as Christian. In truth, though, the modern ideas of equality or universality are neither Greek nor Christian. Whatever their historical origins, they have become peculiarly modern concepts, the product of the specific social, political and intellectual currents of the modern world.

Moreover, the great figures of the Christian tradition would have been appalled at what we now call "Western" values. In his book Reflections on the Revolution in Europe, the American writer Christopher Caldwell argues that Muslim migration to Europe has been akin to a form of colonisation, threatening the very foundations of European civilisation. Yet Caldwell also acknowledges that "What secular Europeans call ŒIslam' is a set of values that Dante and Erasmus would recognise as theirs." At the same time, the modern, secular rights that now constitute "core European values" would "leave Dante and Erasmus bewildered". There is, in other words, no single set of European values that transcends history and binds together the Christian tradition in opposition to a single corpus of timeless set-in-stone Islamic values.

Not only are "Christian values" and "Islamic values" more complex and with a more convoluted history than contemporary narratives suggest, so too is the relationship between Enlightenment ideas and religious belief. There were, in fact, as the historian Jonathan Israel has pointed out, two Enlightenments. The mainstream Enlightenment of Kant, Locke, Voltaire and Hume is the one of which we know and which provides the public face of the movement. But it was the Radical Enlightenment, shaped by lesser-known figures such as d'Holbach, Diderot, Condorcet and, in particular, Spinoza, that provided the Enlightenment's heart and soul.

The two Enlightenments divided on the question of whether reason reigned supreme in human affairs, as the radicals insisted, or whether reason had to be limited by faith and tradition – the view of the mainstream. The attempt of the mainstream to hold on to elements of traditional beliefs constrained its critique of old social forms and beliefs. The radicals, on the other hand, were driven to pursue their ideas of equality and democracy to their logical conclusions because, having broken with traditional concepts of a God-ordained order, there was, as Israel puts it, no "meaningful alternative to grounding morality, political and social order on a systematic radical egalitarianism extending across all frontiers, class barriers and horizons".

The moderate mainstream Enlightenment was overwhelmingly dominant in terms of support, official approval and prestige. But in a deeper sense it proved less important than the radical strand. What Israel calls the "package of basic values" that defines modernity – toleration, personal freedom, democracy, racial equality, sexual emancipation and the universal right to knowledge – derive principally from the claims of the Radical Enlightenment. Most Enlightenment philosophes were believers (though not necessarily theists) and their Christian faith shaped their ideas. Yet what we now call "Western values" were honed arguably as much by thinkers who rejected the Christian tradition as by those who embraced it.

To challenge the myths and misconceptions about the Christian tradition is not to deny the distinctive character of that tradition (or traditions), nor its importance in incubating what we now call "Western" thought. But the Christian tradition, and Christian Europe, is far more a chimera than a pure-bred beast. The history of Christianity, its relationship to other ethical traditions and the relationship between Christian values and those of modern, liberal, secular society are far more complex than the trite "Western civilisation is collapsing" arguments acknowledge. The irony is that the defenders of Christendom are riffing on the same politics of identity as Islamists, multiculturalists and many of the other "-ists" that such defenders so loathe.

The reason to challenge the crass alarmism about the decline of Christianity is not simply to lay to rest the myths about the Christian tradition. It is also because that alarmism is itself undermining the very values – tolerance, equal treatment, universal rights – for the defence of which we supposedly need a Christian Europe. The erosion of Christianity will not necessarily lead to the erosion of such values. The crass defence of Christendom against the "barbarian hordes" may well do.

Published 2011-11-08

Original in English
First published in New Humanist 6/2011

Contributed by New Humanist
© Kenan Malik / New Humanist
© Eurozine