But those who deplore the hijacking of religion by willfully ignorant and dangerously self-righteous fanatics will find Ghobash’s book a drink of cool water. In it, he struggles to rescue the essence of Islam from the distortions of it promulgated by Islamists by cogently identifying and firmly calling out the less-than-holy motives and confusions that prompt their jihads.

About halfway through my reading of Letters, it struck me that some of Ghobash’s explanations of how zealots have distorted Islam uncomfortably parallel the motives and means by which American Christianity has been hijacked by our own jihadists. I’m quite certain that Ghobash’s intention isn’t to lecture American Christians on our faith, although God knows we could use a good talking to. Nonetheless, those of us concerned about American Christianity’s malformation by zealots who mistake obduracy for purity, judgmentalism for righteousness, and political partisanship for faith can learn from Letters.

Perhaps the most obvious parallel that emerges from Ghobash’s book is the binary moral thinking common to both Islamists and Christian zealots, the insistence that the moral universe is “divided clearly into that which [is] permitted and not permitted.” This puritanical absence of moral imagination either will not or cannot acknowledge what most sensible people learn early in life: that lockstep adherence to rigid moral principles isn’t the same thing as a morally principled life.

There’s no finesse, no gradation of virtues or vices, no gray moral zone, no room for compassion or letting-live, in either the Islamist or Christian zealot world. In the Islamist’s eyes, for example, all non-Muslims are unrighteous kafirs good only for enslavement and killing, and westernization is carte blanche satanic. When it comes to the two moral flashpoints for the Christian zealot, abortion and same-sex marriage, the same rigidity applies. All abortion, regardless of the trimester, is equally wicked. All marriage unions except heterosexual ones, identically displeasing to God.

The Islamist, argues Ghobash, draws two corollaries from his mercilessly absolutist ethical code. The first is that true moral rectitude requires a scorched earth renunciation of our corrupt age and a no-exceptions return to the religiously “pure” past of Muslim hegemony in the 7th and 8th centuries. The second is that merciless warriors of faith, strong and determined enough to push back against the current culture of wickedness, are essential if purity is to be regained. They are to the Islamist what the vanguard of the proletariat was to Lenin.

From a practical perspective, these corollaries mean doing whatever’s necessary, with true warrior ruthlessness, to reinstate the caliphate. Never mind that the purity of the Muslim empire—or any empire, for that matter—is mythical, or that lobbing off heads, raping girls and women, and enslaving people fall short of any reasonable person’s notion of rectitude. In the Islamist black-and-white moral universe, such reservations are inessential. Even the slightest deviation from the binary code opens the floodgate of license. As Ghobash puts it, Islamist moral logic goes like this: “Freedom is license, and license means anything goes.”

An accurate understanding of history is no more important to the Christian zealot than to his Islamist counterpart. The biblical fundamentalism central to the zealot’s position isn’t, as he claims, a return to a pure “ol’ time religion” that will save contemporary Christianity. His brand of fundamentalism is a 20th-century invention that would’ve baffled both ancient rabbis and early Christians. Moreover, the zealot’s total condemnation of abortion flies in the face of centuries of Christian moral teaching that termination of pregnancy is morally acceptable up to the point of “quickening,” or movement of the fetus. Finally, the Christian zealot, like his Islamist cousins, believes that the flood waters of moral chaos will sweep away everything if deviation from absolutist moral standards is allowed. This paranoia automatically excludes serious consideration of any serious scholarship about, for example, the nature of human sexuality, that might point to the need for moral reexamination.

Because Islamist distortions of Islam and Christian zealot distortions of Christianity see moral corruption and imminent disaster everywhere, the faith warrior’s primary obligation is to ferret out, renounce, and punish all those who stray from the strait and narrow. As Ghobash points out, Islamists are great at handing down fatwahs. Their moral radar bleeps crazily at perceived vice, but rarely at virtue. This almost voyeuristic penchant for relentlessly ferreting out and loudly condemning perceived sin is also characteristic of American Christian zealots, who seem never to miss opportunities, even if they have to create them, to pound pulpits and shout jeremiads.

Ghobash urges his fellow Muslims to pay less heed to firebrand clerics who claim “unerring authority” when it comes to morality and more attention to the dictates of common decency they discover when they examine their conscience. These are words we American Christians should take to heart as well. Evangelical celebrities whose reputations and fortunes are made by spewing hatred and preaching jihad are as baleful to Christianity as their Islamist imam counterparts are to Islam.

At the end of the day, Ghobash tells his son in this remarkable book, it is the duty of Muslims—and, I would add, Christians—to honor God by cultivating a genuinely holy dignity, individuality, and independence of mind, and by encouraging the same in others. Binary moral thinking, especially when it’s wrapped in the sheep’s clothing of religious fanaticism, closes the door to that. Let us hope that Ghobash’s Letters to a Young Muslim will nudge Muslims and Christians alike a bit closer to this truth.