Clash by night.

Earthly Powers: The Clash of Religion and Politics in Europe from the French Revolution to the Great War, by Michael Burleigh (HarperCollins, 544 pp., $29.95)

ANYONE who thinks that American political life has been poisoned and polarized beyond any hope of cure should try to guess what nightmare of Napoleonic tyranny the French priest Felicite de Lamennais had in mind when he declared, following the Bourbon Restoration: "I have no hesitation in saying that, of all Bonaparte's conceptions, [this is] the most appalling to every considering man, the most profoundly anti-social, in a word the most characteristic of its author.... When the tyrant thought he had made sure by so many horrible laws of the misery of the present generation, he raised this monstrous edifice as a monument to his hatred for future generations; it was as though he wanted to rob the human race even of hope."

The "monstrous edifice" in question was none other than the Sorbonne University--and by the standards of 19th-century political rhetoric, Lamennais's vituperation was relatively tame. Indeed, his is among the more temperate voices echoing through Michael Burleigh's sweeping new book, Earthly Powers. An ultramontanist Catholic who spent the 1820s and '30s trying to reconcile the papacy to republican government, Lamennais was one of the few figures in that era who approached politics as something other than the extension of war by other means. His hopes were dashed: His intended rapprochement between Catholics and liberals foundered on the intolerance of both, and he died disappointed in 1854, leaving the stage to more uncompromising figures.

There is a tendency to view the European 19th century as a period of vanished tranquility--a hundred years of peace, optimism, and progress between the chaos of the French Revolution and the charnel house of World War I. Burleigh's book is an antidote to such nostalgia, and a reminder that the 1800s were the period when the ideas unleashed in 1789--the enthronement of political religion, in particular, and the deification of the nation and the state--worked themselves deep into the soil of continental politics, whence the poisoned fruit of 20th-century totalitarianism would spring.

Beginning with the political religion of revolutionary France, and carrying the story through the radicalization of the Russian intelligentsia, Italy's Risorgimento, Bismarck's Kulturkampf, and France's various convulsions, Burleigh paints a vivid portrait of secular utopianism's advance, and the struggle of the Christian churches to hold their newfound enemy at bay. The book contains perhaps too many multitudes: What began as an account of civic cults and nationalist rituals among Jacobins, Bolsheviks, and Nazis grew in the telling, Burleigh notes in his introduction, and the result is usually fascinating but often scattershot. But while the story tends to wander, leaping unexpectedly from theme to theme and nation to nation, the narrative voice never falters: Burleigh's tone is at once perceptive and dyspeptic, impatient with cant and weary of utopianism--perfect for a tale that has many extremists but few heroes.

His fiercest scorn is reserved for the political religions and their missionaries: The chapter on the Jacobins is entitled "Puritans Thinking They Are Spartans Run Amok in Eighteenth-Century Paris," and he dismisses the idealized "new man" beloved of Russian radicals as "a tyro of enormous will, a little poorly digested utilitarian knowledge, no capacity for self-doubt, and blinkered singularity of purpose." He is withering on various icons of Victorian thought, from Auguste Comte--whose ideology "was cosmic, as well as comic, in ambition," and whose "obsession with numbers, systems, and order was not unrelated to the squalor of his private life and his intermittent bouts of madness"--to Charles Fourier, whose work displayed "an extraordinary mixture of fitful insights into human nature and fantasies that suggest advanced megalomaniacal derangement."

Burleigh has a keen eye, as well, for how smoothly the various apostles of reason lapsed into credulity and superstition. Robert Owen, the English industrialist and social reformer, spent his twilight years visiting mediums and "attempting to commune with the spirit world"--which, Burleigh notes, was "an eccentric fate for the founder of a Rational Society." Comte's "religion of humanity" owed a significant debt to his sexual obsession, frustrated by impotence, with a much younger woman named Clothilde de Vaux: She was the type for a cult of womanhood that figured prominently in his proposed faith, and after her death he made her memory the focus of a monkish regimen, with her last love letter substituting for the Monastic Breviary. And outright silliness intruded, frequently, into the quest for progress and national self-determination: The sixth of Garibaldi's ten "patriotic commandments," issued during the unification of the Italian peninsula, announced that "Thou shalt not fornicate, unless it be to harm the enemies of Italy."

But if the political religions of the era were often little more than spilt Christianity, as intolerant in their way as the old order they replaced, Burleigh also makes it clear that, in the struggle for the European soul, the Christian churches rarely missed an opportunity to miss an opportunity. Though he is partial to Catholicism, and goes out of his way to distinguish between the failings of the Church and the sins of its members, reading Earthly Powers will make any Catholic thankful for the likes of Benedict XVI and John Paul II--as opposed to the succession of 19th-century Popes who clung, hopelessly but doggedly, to temporal power and a throne-and-altar world gone by. With the honorable exception of Leo XIII, who did much to reconcile the Church to the realities of democracy and the industrial age, the occupants of the see of Peter were either pious incompetents like Gregory XVI--"motionless in the thick darkness that surrounds him," Lamennais wrote, "he weeps and prays"--or stiff-necked blunderers like Pius IX, who lost the Papal States and penned the Syllabus of Errors, a document whose prescient warnings about nationalism were lost amid a cascade of venom. ("Rhetorical moderation, sensitivity, and subtlety were alien to him," Burleigh remarks.)

Many of the Protestant churches were, if anything, even worse--less nostalgic than the Holy See for a vanished age of absolutism, but more vulnerable to the siren song of ideologies that promised heaven on earth, or substituted the nationstate for God. In Germany, in particular, the Protestant willingness to uncritically embrace Teutonic nationalism anticipated the tragedies of the following century. The "Hegelian strain in liberal Protestant theology," Burleigh points out, "in which whatever one felt powerfully enough was indicative of the developing presence of God," lent itself easily to the deification of nationalist enthusiasms--culminating in August 1914, when a German pastor could argue unselfconsciously that "God is what the god-inspired people do."

The churches come off a little better when Burleigh considers their response to the dislocations of the Industrial Revolution: Leo XIII's encyclical Rerum Novarum steered Catholicism neatly, if somewhat glibly, between the Scylla of unfettered capitalism and the Charybdis of statism, and Catholics and Protestants alike carried out missionary work in the worst industrial slums, devoting their lives to people many secular utopians seemed to care for only in the abstract. But here, too, there is a sense of opportunities lost: With the exception of England, where the absence of both despotism and revolution cleared the stage for common sense, the Christian response to industrial poverty was too often overshadowed by the squabbles between church and state--and many Christians' eagerness to lift up the working class was matched only by a zeal to blame their plight on the rapacity of the Jews.

Indeed, Earthly Powers presents the whole of the 19th century as a lost opportunity for European Christianity, which adapted too slowly to a changing world, while either losing ground to the new political religions or tailoring its teachings to suit the spirit of the age. And though Burleigh ends his tale in 1914, leaving the "strange gods" of Communism and National Socialism to a future book, the past he depicts is prologue to our present--in which Europe lies fallow and spiritually exhausted, and Christianity is perceived to be just as discredited as the various faiths that sought to supplant it.

Secularization, Burleigh writes, was "not the ever receding tide imagined by Matthew Arnold in his poem 'Dover Beach,' but a movement of complex currents washing over a craggy shore, where the rock pools have been constantly replenished." But we are at an ebb tide now: The only water rushing into Europe's coves and tidepools comes from the south and east, and two centuries of war between Christianity and political religion seem to have ended with the evaporation of both, leaving a desert behind that some call peace.

Mr. Douthat is an associate editor at The Atlantic Monthly, and author of Privilege: Harvard and the Education of the Ruling Class.