People of faith have long assumed that the Devil’s principal stratagem is to tempt his victims with thoughts of revenge, deceit, lust, pride, and other deadly sins. In his diabolical classic The Screwtape Letters, C. S. Lewis suggests a very different approach: “It is funny how mortals always picture us as putting things into their minds,” explains Screwtape, a senior demon advising his protégé. “In reality our best work is done by keeping things out.”

If true, this insight helps explain the radically divergent paths of the British-born author-brothers Christopher and Peter Hitchens. Both men rejected the Christianity of their youth and turned to Trotskyism and secularism. Christopher eventually abandoned Marxist ideology and transformed his atheism into a sideline of book publishing and public debates. A stint as a Moscow correspondent helped Peter shed his leftist illusions as well. Yet he eventually returned to the Anglican faith because he couldn’t keep certain ideas—provocative, chastening, awful ideas—out of his mind.

In The Rage Against God he delivers a spirited defense of Christianity that is a mix of memoir, cultural critique, and history lesson. He is well-positioned for the task: A columnist for the Mail on Sunday, Hitchens has reported from all over the world and in 2010 won the Orwell Prize for foreign reporting. He has written several books on the moral and political decline of Britain. His latest work, with its candor about the failings of Christianity there, may not endear him to members of the church establishment; nevertheless, his treatment of the social and spiritual threat of the new atheism—what he calls “the League of the Militant Godless”—should be required reading for people of all faiths.

There can be little doubt that Peter Hitchens’s rejection of Christianity was as thoroughgoing as that of his famous brother. While a teenager on the playing fields of his Cambridge boarding school, Hitchens burned his Bible in a “full, perfect, and complete rebellion against everything I had been brought up to believe.” Enlightened self-interest would function as his moral compass.

With an impressionistic style, he describes the loss of faith in England after the Second World War, a story that contrasts starkly with the American scene. In the triumphant, dynamic, postwar United States, American religion was booming: robust church attendance, the popular crusades of Billy Graham, Hollywood blockbusters such as Ben-Hur and The Ten Commandments. In Great Britain, by contrast, the decline of empire and a grim economy became linked in many minds to the bankruptcy of the Church of England. It was a season of severe disillusionment: “Those who fought so hard to defend Britain against its material enemies did so at a terrible spiritual cost,” Hitchens writes. “War does terrible harm to civilization, to morals, to families, and to innocence.”

His embrace of Soviet communism would prove even more disappointing. In Moscow he witnessed the degradations of an atheistic regime: its despotism, staggering inequities, coarseness, and everyday hopelessness. He recalls its victims being discovered in unmarked graves in parks near his Moscow residence. He saw a society “from which the whole apparatus of trust, civility, and peace has been stripped,” and it led him to ponder how these qualities could be preserved in the absence of religious conviction.

Although he commendably avoids personal attacks on his brother, he takes him to task on this point, particularly as it appears in his recent God Is Not Great: How Religion Poisons Everything. Christopher never fully confronts the innate malevolence of atheistic communism; he even seeks to blame Soviet savagery on religion itself. This is an intellectual deceit that Peter cannot abide, and his sketch of the Soviet Union’s assault on Christianity—its “institutional loathing for the teaching of religion”—is expertly drawn.

Peter Hitchens can be brutally frank about the problem of politicized religion; he abhors the corrupting influence of faith-based patriotism. Yet here he goes too far. He allows the excesses of the Allied effort against the Nazis, for example, to overshadow the central achievement of the Second World War: the preservation of a measure of justice and humanity that would have perished in the racist fury of Hitlerism. Is there no role for religion in inspiring the virtues required for fighting just wars? The bitterness of Hitchens’s youthful disenchantment with British patriotism seems to linger.

Nevertheless, there are greater dangers in play. Hitchens describes, as only an ex-Communist could, a new specter haunting the West: the specter of belligerent atheism. He points to various campaigns to defame Christian belief, to denounce the religious education of children as child abuse, and to exclude religious ideals from democratic life. “A new and intolerant utopianism,” he writes, “seeks to drive the remaining traces of Christianity from the laws and constitutions of Europe and North America.” It is a resuscitated version of the League of the Militant Godless, the name of a Soviet-era social movement to eradicate religion. The ultimate objective, he says, is man’s radical liberation from his Creator.

The burden of Rage is to insist that along this path lies the eclipse of freedom, personal and political, as the new elites consolidate control. And Hitchens’s alternative vision is anchored in history and in personal experience. Surrounded by secular and sophisticated colleagues all his life, he nonetheless couldn’t ignore “the old unsettling messages” of mortality and sin. In the 1990s, on a trip to Burgundy in search of fine wine, he took an artistic detour and found himself gazing at Rogier van der Weyden’s The Last Judgment. The depiction of individuals fleeing the pit of hell—naked, suffering, mournful, terrified—seized him.

I had a sudden, strong sense of religion being a thing of the present day, not imprisoned under thick layers of time. A large catalogue of misdeeds, ranging from the embarrassing to the appalling, replayed themselves rapidly in my head. I had absolutely no doubt that I was among the damned, if there were any damned.

Peter Hitchens’s lucid memoir of a prodigal son reminds us that these are not thoughts which, once allowed to enter the human mind, naturally serve the Devil’s purpose. Indeed, as C. S. Lewis suggested, such ideas can become a means of divine grace, for they help awaken a man’s reason, as well as his conscience. “And once it is awake,” asks Screwtape, “who can foresee the result?”

Joseph Loconte is a lecturer in politics at The King’s College in New York and a contributing editor to The American.