Is this claim justified? The barbarism perpetrated by atheistic regimes in the 20th century indicates that it is. So too does the French Revolution itself. Maximilien Robespierre makes only a brief appearance in Perreau-Saussine's study, but a new biography, Robespierre: A Revolutionary Life (Yale University Press, £25), by Peter McPhee provides plenty of evidence to support Perreau-Saussine's argument. Doubtless McPhee would be offended by this conclusion. As he sees it, "the comparatively limited loss of life" during the Reign of Terror makes preposterous the parallel between Robespierre and Mao or Pol Pot. His Robespierre is a poor provincial boy from Arras with a strong will to succeed, who made his way to Paris and found himself a young revolutionary remaking a world against massive odds. McPhee's is a tale well told — particularly fascinating is the revelation that Robespierre had many female admirers — but it is hard to accept his conclusion that both Robespierre's greatness and his tragedy derived from his unwillingness to compromise the principles of 1789 in the interests of stability. 

Not surprisingly, Robespierre was a supporter of the Civil Constitution of the Clergy, seeing priests simply as elected officials and public functionaries. According to McPhee, he had no sympathy for the idea that the Church should be self-governing. At first, Robespierre expressed public sympathy for religion and saw no advantage in needlessly alienating the Church but, as the Revolution gathered pace, he came ever more to see the need for a new civic culture to replace Christian ritual and superstition. What Robespierre now envisaged was the complete regeneration of the people through an educational programme involving the compulsory removal of children from their parents. The Cult of a beneficent Supreme Being would replace the cruel God of the Catholic Church.

Yet, as McPhee vividly recounts, Robespierre's mental universe was one of unrelenting and imaginary conspiracies. The Revolution was to be a war to the death and the enemies of the people were to be exterminated. Political morality was reduced to terror as "prompt, severe, inflexible justice", with terror cast as virtue's necessary companion. In the end Robespierre could not distinguish dissent from treason. No one was safe. This included 14 nuns and lay sisters from a former Carmelite convent accused of living in a religious community. On  July 17, 1794 they were guillotined at what is now the Place de la Nation in Paris.

Much of the focus of Perreau-Saussine's study falls upon the consequences for the Church of this bloody and humiliating experience. For counter-revolutionary writers such as Joseph de Maistre, the Revolution of 1789 was both a satanic event and a Protestant plot. It was also an example of divine chastisement. Catholicism was again aligned with monarchy and against democracy. More importantly, many of the faithful came to see the so-called liberties of the Gallican Church as a form of slavery. Unable to identify themselves with either the revolutionary or Napoleonic state, they turned in ever greater numbers to Rome and a sovereign papacy as a guarantee of their spiritual autonomy. Catholics, in short, became ultramontanes, advocates of supreme papal authority in matters of faith. The First Vatican Council and its proclamation of papal infallibility was an answer to their prayers.