In the second century A.D., it was the Christians who were denounced as “atheists.” JONATHAN BOROFSKY, “FOUR GODS” (1994)

Great portents and disasters turn some minds to God and others away from him. When an unusually bright and long-tailed comet was tracked through the sky in the last two months of 1680, posters and sermons called on Christians to repent. A hen in Rome seemed to confirm that the Day of Judgment was near. On December 2nd, it made an extraordinarily loud cackle and produced an exceptionally large egg, on which could be seen a likeness of the comet, or so it was said. This added to the religious panic. But the comet also sparked a small triumph for rationalism. In the next few years, as Armageddon somehow failed to arrive, a stream of pamphlets across Europe and America argued that heavenly displays were purely natural phenomena. The skeptics won the day. From the eighteenth century onward, no respectable intellectual saw comets as direct messages from God—though there were still some fears that one might eventually hit the earth.

The felling of the World Trade Center in New York, on September 11, 2001, brought its share of religion. Two populist preachers, Pat Robertson and Jerry Falwell, called it divine punishment (though both quickly withdrew their remarks), and not only the bereaved prayed for help. But September 11th and its aftershocks in Bali, Madrid, London, and elsewhere are more notable for causing an outbreak of militant atheism, at least on bookshelves. The terrorist attacks were carried out in the name of Islam, and they have been taken, by a string of best-selling books, to illustrate the fatal dangers of all religious faith.

The first of these books was “The End of Faith,” by Sam Harris, which was published in 2004 and was on the Times paperback best-seller list for thirty-three weeks. Then came “Breaking the Spell: Religion as a Natural Phenomenon,” by Daniel Dennett, a philosopher at Tufts University, who has written popular books on the science of consciousness and on Darwin. Next was “The God Delusion,” by Richard Dawkins, an evolutionary biologist and Britain’s preëminent science writer. Harris joined battle again last year with “Letter to a Christian Nation,” which renewed his attack on Christianity in particular. And now there is “God Is Not Great: How Religion Poisons Everything” (Twelve; $24.99), by Christopher Hitchens, which is both the most articulate and the angriest of the lot. Hitchens is a British-born writer who lives in Washington, D.C., and is a columnist for Vanity Fair and Slate. He thrives at the lectern, where his powers of rhetoric and recall enable him to entertain an audience, go too far, and almost get away with it. These gifts are amply reflected in “God Is Not Great.”

Hitchens is nothing if not provocative. Creationists are “yokels,” Pascal’s theology is “not far short of sordid,” the reasoning of the Christian writer C. S. Lewis is “so pathetic as to defy description,” Calvin was a “sadist and torturer and killer,” Buddhist sayings are “almost too easy to parody,” most Eastern spiritual discourse is “not even wrong,” Islam is “a rather obvious and ill-arranged set of plagiarisms,” Hanukkah is a “vapid and annoying holiday,” and the psalmist King David was an “unscrupulous bandit.”

It’s possible to wonder, indeed, where plain speaking ends and misanthropy begins: Hitchens says that the earth sometimes seems to him to be “a prison colony and lunatic asylum that is employed as a dumping ground by far-off and superior civilizations.” He certainly likes to adopt the tone of a bemused Martian envoy hammering out a report for headquarters. (We hear of “a showbiz woman bizarrely known as Madonna.”) In a curious rhetorical tic, Hitchens regularly refers to people whom he wishes to ridicule by their zoological class. Thus the followers of Muhammad are “mammals,” as is the prophet himself, and so are the seventeenth-century false messiah Sabbatai Zevi and St. Francis of Assisi; Japan’s wartime Emperor Hirohito is a “ridiculously overrated mammal,” and Kim Il Sung, the father of North Korea’s current dictator, is a “ludicrous mammal.” Hitchens is trying to say that these people are mere fallible mortals; but his way of saying it makes him come across as rather an odd fish.

He is also a fallible one. After rightly railing against female genital mutilation in Africa, which is an indigenous cultural practice with no very firm ties to any particular religion, Hitchens lunges at male circumcision. He claims that it is a medically dangerous procedure that has made countless lives miserable. This will come as news to the Jewish community, where male circumcision is universal, and where doctors, hypochondria, and overprotective mothers are not exactly unknown. Jews, Muslims, and others among the nearly one-third of the world’s male population who have been circumcised may be reassured by the World Health Organization’s recent announcement that it recommends male circumcision as a means of preventing the spread of AIDS.

Hitchens is on firmer ground as he traipses around the world on a tour of sectarian conflicts. He recounts how, a week before September 11th, a hypothetical question was put to him by Dennis Prager, an American talk-show host. Hitchens was asked to imagine himself in a foreign city at dusk, with a large group of men coming toward him. Would he feel safer, or less safe, if he were to learn that they were coming from a prayer meeting? With justified relish, the widely travelled Hitchens responds that he has had that experience in Belfast, Beirut, Bombay, Belgrade, Bethlehem, and Baghdad, and that, in each case, the answer would be a resounding “less safe.” He relates what he has seen or knows of warring factions of Protestants and Catholics in Ulster; Christians and Muslims in Beirut and in Bethlehem; Hindus and Muslims in Bombay; Roman Catholic Croatians, Orthodox Serbians, and Muslims in the former Yugoslavia; and Shiites, Sunnis, and Christians in Baghdad. In these cases and others, he argues, religion has exacerbated ethnic conflicts. As he puts it, “religion has been an enormous multiplier of tribal suspicion and hatred.”

That’s more plausible than what Sam Harris has to say on the subject. He maintains that religious belief not only aggravates such conflicts but is “the explicit cause” of them. He believes this even of Northern Ireland, where the Troubles between pro-British Unionists and pro-Irish Republicans began around 1610, when Britain confiscated Irish land and settled English and Scottish planters on it. As far as Harris is concerned, Islam brought down the Twin Towers, thanks in no small part to the incendiary language of the Koran; Middle East politics, history, and economics are irrelevant sideshows. This thesis suffers from a problem of timing: if he is right, why did Al Qaeda not arise, say, three hundred years ago, when the Koran said exactly what it says now?

One practical problem for antireligious writers is the diversity of religious views. However carefully a skeptic frames his attacks, he will be told that what people in fact believe is something different. For example, when Terry Eagleton, a British critic who has been a professor of English at Oxford, lambasted Dawkins’s “The God Delusion” in the London Review of Books, he wrote that “card-carrying rationalists” like Dawkins “invariably come up with vulgar caricatures of religious faith that would make a first-year theology student wince.” That is unfair, because millions of the faithful around the world believe things that would make a first-year theology student wince. A large survey in 2001 found that more than half of American Catholics, Episcopalians, Lutherans, Methodists, and Presbyterians believed that Jesus sinned—thus rejecting a central dogma of their own churches.