Theology is returning to the intellectual scene, says John Milbank, professor of religion, politics and ethics at the University of Nottingham. "That's why people like Richard Dawkins are so frightened, and why we're getting a more militant atheism."

He rattles off a list of renowned philosophers - Alasdair MacIntyre, Charles Taylor, Antonio Negri, Alain Badiou and Quentin Meillassoux - who are currently writing about Christianity. In The Monstrosity of Christ: Paradox or Dialectic?, due for publication next month, Milbank debates with Slavoj Zizek, Marxist theorist and international director of the Birkbeck Institute for the Humanities, about secularism, politics and the meaning of Christianity. The pair will also cross swords at an Institute of Contemporary Arts debate in mid-June.

"Forty years ago it would have been very unusual for a theologian to be in a public debate with a major intellectual. It's a sign of a shift," Milbank says. "Even Marxists take religion seriously. It's only the Anglo-Saxon left liberals that don't."

Militant atheism or "scientism" is expanding to fill the gap left by the "exhaustion" of secular ideologies such as capitalism, communism and humanism, he suggests. "What's left to turn into an ideology except for natural science itself?"

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The media are feeding this trend by setting up "lunatic" fundamentalist religion in opposition to "rational, scientific atheism", Milbank argues, leaving people feeling that the only way to be a religious liberal is to be "vaguely spiritual".

But it is not only philosophers who are refusing to buy this crude discourse, Milbank maintains. The religious revival is also occurring among reflective youth - "the sort of young person who might once have been Marxist".

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"They may have an influence out of proportion to their numbers in future because there's a vacuum; most people don't believe in anything very much," he says. "Over the years I've been surprised at the number of people who have said: 'I used to be a nihilist and I can't go back to humanism; I'm starting to take religion seriously.'"

In the 1970s, when Milbank began his theological career at Westcott House, the Church of England theological college in Cambridge, he says the field was dominated by liberal theology, which views the world as humanist and concentrates on fitting Christian beliefs around secular wisdom.

His teacher at Westcott House, Rowan Williams (now the Archbishop of Canterbury), questioned this approach and started his student on a road that led to Theology and Social Theory (1990), Milbank's most important book. It argues that instead of asking how theology may fit into the conclusions of secular social science, theology should challenge social scientists' assumptions.

"I argued that secular social science is traceable back to bad theology, or to reactions against it," he explains.

On reviewing the second edition of the book in 2006, Charles Taylor, emeritus professor of philosophy at McGill University, said: "When the first edition was published, the reaction was one of shock. Now, 15 years on, the shock has worn off; more and more people are questioning the universal competency of secular reason."

In 1999, Milbank broadened his thesis into a general challenge to secular dominance in Radical Orthodoxy, a collection of papers co-authored with Catherine Pickstock, reader in philosophy and theology at Emmanuel College, Cambridge, and Graham Ward, now professor of theology and ethics at the University of Manchester. "In a sense, we were going on the offensive against secularism," Milbank says.

Radical Orthodoxy argued for a return to Christianity's medieval roots, when "faith and reason were inseparable". It used creedal Christianity as a base from which to criticise modern society, culture, politics and philosophy.

The "radical orthodoxy" movement contends that modern philosophy traces its origins to a 13th-century scholar, John Duns Scotus.

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"Duns Scotus said that although finite reality was created by God, you can understand it in its own terms - you don't have to mention God to make sense of the world," Milbank says. The Franciscan theologian's stance ultimately led to the separation of the natural from the supernatural, and faith from reason, he adds.

"The modern idea that philosophy is not about becoming a better person, but is just an objective gaze on reality, is ironically the result of a kind of theology," Milbank observes.

The view of the early church fathers and St Thomas Aquinas that nothing in life is independent of God is just as rational as Duns Scotus' way of seeing the world, he adds. "It's just a road not taken."

Simon Oliver, senior lecturer in theology at the University of Wales, Lampeter, applied radical orthodoxy to Newtonian physics in Philosophy, God and Motion (2005). The book argued that the view of motion as the mere movement of mass through time is a limited description and should be expanded to encompass the medieval analysis, which saw moral movement, learning and growing as forms of motion.

Similarly, Milbank is exploring radical orthodoxy's application to evolution. "I argue that there are no absolute physical laws, but that physical reality tends to adopt certain habits. A lot of radical materialists are already saying that, although it sounds incredibly anarchic."

He points to the work on evolutionary convergence by Simon Conway Morris, professor of evolutionary palaeobiology at Cambridge, in which unrelated species develop biologically similar traits.

"My argument is that these habits or patterns are not accidental; they are the workings of a divine grace," says Milbank. "If you think ... of fixed laws, you see everything in terms of mechanics and efficient causality, but nature clearly works more creatively and randomly than that."

Immanentism, which explains reality by reference to natural laws, is "stuck in a kind of double bind", he argues, pointing to theories on the workings of the human mind.

One explanation for intelligence is that it is an epiphenomenon caused by the physical brain interacting with itself.

"This is saying that matter (the brain) has created a kind of mystery - it has become its own God. On the other hand, if you say the opposite, that nature is completely comprehensible, as Dawkins does, you come perilously close to a kind of idealism."

Habit is a "mediating category" between the purely material (the brain) and the purely mental, Milbank theorises. "When you ask yourself where that habit comes from, you either have to see it as random or as something that has established itself in response to something. Then you can start talking about God."

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From the outset, radical orthodoxy, whose members can belong to different churches, but tend to be Church of England or Roman Catholic, had ambitions to influence politics. Eugene McCarraher, assistant professor of humanities and history at Villanova University, wrote in the Roman Catholic journal Commonweal in 2001 that the movement "ought to get out into the world", arguing that it was "still too socially incubated in academia, too marinated in postmodern palaver".

He urged the movement's followers to "grasp the hands of labour unions, feminists, gay and lesbian activists", and warned that "if they remain content, as I fear some of them do, to carp and posture before gatherings of the anointed, then the movement will become at best a beloved clique and at worst another academic vaudeville show".

The groups mentioned may not want to shake Milbank's hand: he opposes gay marriage ("I don't want to get into the situation where we deny there is something special about being attracted to the opposite sex").

He says he is concerned about working-class women being left to raise children alone, "in part - alongside economic factors - because of the collapse of the male ethos of supporting the woman", and has written most stridently in opposition to in vitro fertilisation treatment for single women.

"By supporting the total disjuncture of sex and procreation, the Left is really supporting a new mode of fascism," Milbank says.

Radical orthodoxy is more liberal on some sex and gender issues than the Catholic Church, however, and Milbank speculates that the Vatican hierarchy may be wondering "whether we will provide them with a way of loosening up without selling out".

In his Commonweal article, McCarraher also noted that despite all its talk of "unprecedented boldness" and the "political nature of the Gospel", radical orthodoxy had displayed "little in the way of political acumen or imagination".

Milbank's answer was his 2004 essay "Liberality versus Liberalism", which argued that liberalism sprung from the idea that individuals need protecting from threats to themselves or their property. It therefore treats them as a potential source of danger to each other, which has led to the erosion of civil liberties.

"Liberal politics ... revolves around a supposed guarding against alien elements: the terrorist, the refugee, the person of another race ... if the ultimate thing to be respected is simply individual security and freedom of choice, then almost any suspensions of normal legality can tend to be legitimated in the name of these values," the essay states.

It argues that the democratic process offers no checks to this process, as it cannot operate outside a framework of "absolute good as grounded in something super-human". In a secular democracy, people can find out what they "should desire" only from themselves - the "general desires of the people" are their only cues. In other words, liberal democracy is based on populism and "the only justification for democracy is theological".

The result of liberal modernity's grip on the West is "mass poverty, inequality, erosion of (institutions) below the level of the state and ecological dereliction of the Earth ... it has abolished the rights and dignity of the worker, ensured that women are workplace as well as domestic and erotic slaves, and finally started to remove the ancient rights of the individual which long precede the creed of liberalism itself, such as habeas corpus".

The essay refers to gender equality as stemming from St Paul, an apostle seen by many feminists as a misogynist: his letters to the Corinthians include many references to man's authority over woman. Milbank's essay also advocates a "mixed government grounded in eternal law" alongside a "monarchic anarchy as clearly recommended by (J.R.R) Tolkien in The Lord of the Rings".

Confronted with this piece in the present day, Milbank admits: "It's a little polemical." However, the essay's argument that society should counteract the moral emptiness of capitalism by "subordinating contract to gift" has won support.

"Unlike most traditional societies, we have a sharp distinction between contract, which is public, fixed and definite, and the notion of gift, which is private, free and gratuitous," he says. An economy based on contract creates indifference in both parties: "It doesn't matter to me what happens to the person I'm doing a deal with."

On the other hand, a gift is reduced to an individual act of generosity, which does not create a bond or sense of reciprocity in either direction.

"We can't undo the concepts of money and contract, but we need to infuse them with the sense of gift exchange. Adam Smith suggests that you can't construct an economy on the basis of mutual sympathy. I think that may be too cynical - we're ignoring the fact that human economies have been constructed on that basis for hundreds of years," Milbank says.

In "Liberality versus Liberalism", he suggests favouring "local production ... of locally suitable things linked to local skills. We should import and export only what we have to."

The essay also highlights the Catholic notion of subsidiarity - the delegation of responsibility to the smallest or least centralised competent body - and the importance to civil society of institutions and other groupings.

"There is not first of all an aggregate of isolated individuals. On the contrary, people forever form micro-social bodies, and governments should treat people not according to formal abstraction, but as they are: in regions, metiers, local cultures and religious bodies."

Among Milbank's proteges is Philip Blond, head of Demos' progressive conservatism project and a former theology lecturer at the University of Cumbria. The ideas within "Liberality versus Liberalism" informed Blond's concept of "Red Toryism", which calls on the Conservatives to "take power from the market state and give it to the people ... to develop a full-blooded 'new localism' that works to empower communities and builds new, vibrant local economies".

Red Toryism represents radical orthodoxy's debut on the political stage, Milbank says. In a recent letter to The Guardian, he argues: "Now many of us are beginning to realise that old socialists should talk with traditionalist Tories. In the face of the secret alliance of cultural with economic liberalism, we need now to invent a new sort of politics that links egalitarianism to the pursuit of objective values and virtues ... after all, what counts as radical is not the new, but the good."

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