A Wicked Company: The Forgotten Radicalism of the European Enlightenment. By Philipp Blom. Basic Books; 384 pages; $29.95. To be published in Britain in March by Weidenfeld & Nicolson as “Wicked Company: Freethinkers and Friendship in Pre-Revolutionary Paris”; £25. Buy from Amazon.com, buy from Amazon.co.uk

ATHEISM is a hot topic. In recent years writers from Richard Dawkins and Daniel Dennett to Christopher Hitchens and Sam Harris have penned popular tracts advancing the cause of godlessness. But, as the Bible reminds us, there is nothing new under the sun. Philipp Blom's latest book tells the story of a set of remarkable individuals on the radical fringes of the 18th-century European Enlightenment, whose determinedly atheistic and materialist philosophies denied the existence of God or the soul. Echoing ancient thinkers such as Democritus and Lucretius, they held ideas that were to prove too revolutionary even for a revolutionary age.

It is the story of the scandalous Paris salon run by Baron Paul Thierry d'Holbach, a philosophical playground for many of the greatest thinkers of the age. Its members included Denis Diderot (most famous as the editor of the original encyclopedia, but, Mr Blom argues, an important thinker in his own right), Jean-Jacques Rousseau, the father of romanticism, and the baron himself; even David Hume, a famous Scottish empiricist, paid the occasional visit.

A philosophy grew up around the baron's generously stocked table that denied religious revelation and shunned Christian morality, embracing instead the primal passions (the fundamental motives, said the philosophes, for human behaviour) and cool reason (which could direct the passions, but never stand against them). They dreamt of a Utopia built on pleasure-seeking, rationality and empathy. Their ideal nation would leave no room for what they saw as the twisted ethical code of Christianity, which they argued prized suffering and destructive self-repression.

Not only was their thinking radical, but expressing it was dangerous. Diderot was imprisoned for his writings, an experience, Mr Blom argues, that left him too scared to lay out his philosophy plainly, instead disguising it within numerous plays, novels and letters. Baron d'Holbach published most of his works under pseudonyms, which helped to keep him safe but also condemned him to centuries of philosophical obscurity (except in the officially godless Soviet Union). Even when the French revolution finally came, its self-appointed guardians had no place for the philosophy of the true radicals. For Maximilien Robespierre, chief architect of the reign of terror that followed the revolution, God and religion were far too useful in keeping the population in line.

Mr Blom's book is part biography and part polemic. He sketches the early lives of Diderot, Holbach, Rousseau and other players in the drama, and describes the philosophy they hammered out. It is also an iconoclastic rebuttal of what he describes as the “official” history of the Enlightenment, the sort of history that he finds “cut in stone” on a visit to the Paris Panthéon. There the bodies of Voltaire and Rousseau were laid to rest with the blessing of the French state. Neither deserved it, suggests Mr Blom.

Voltaire, he insists, was a milquetoast careerist, too concerned with his own reputation and his comfortable life to say anything truly unsettling. Rousseau he finds even worse. By denigrating reason, celebrating impulse and advocating repression and tyranny in the name of a loosely defined “general will”, Rousseau's thinking, argues Mr Blom, was actively maleficent (and, unsurprisingly, venerated by Robespierre). It is a tragedy of history, the author concludes, that Voltaire and Rousseau won the battle of ideas, whereas Diderot was reduced to the rank of editor of the encyclopedia, and Holbach was forgotten utterly.

Even today, and even in secular western Europe, the bald and confident atheism and materialism of Diderot and Holbach seems mildly shocking. We still cling stubbornly to the idea of an animating soul, a spiritual ghost in the biological machine. For Mr Blom, the modern, supposedly secular world has merely dressed up the “perverse” morality of Christianity in new and better camouflaged ways. We still hate our bodies, he says, still venerate suffering and distrust pleasure.

This is the message of Mr Blom's book, hinted at but left unstated until the closing chapters. He believes the Enlightenment is incomplete, betrayed by its self-appointed guardians. Despite all the scientific advances of the past two centuries, magical thinking and the cultural inheritance of Christianity remain endemic.