In Political Pilgrims, the sociologist Paul Hollander exposes and excoriates the mentality of a certain kind of Western intellectual, who, such is the depth of his estrangement or alienation from his own society, is predisposed to extend sympathy to virtually any opposing political system.

The book is about the travels of 20th-century Western intellectuals to the Soviet Union, China, and Cuba, and how these political travelers were able to find in such repressive countries a model of “the good society” in which they could invest their brightest hopes. Hollander documents in relentless and mortifying detail how this utopian impulse, driven by a deep discontent with their own societies, led them to deny or excuse the myriad moral defects of the places they visited.

But the significance of Political Pilgrims extends far beyond its immediate subject matter, and its insights may help to illuminate the mentality of that most recent and disconcerting set of pilgrims: namely, the Western migrants to the Islamic State, whose estrangement from their own societies can prime them to idealize the so-called Islamic State and overlook or justify its terrible human-rights abuses.

It is estimated that around 4,000 people have left their homes in the West to migrate to ISIS. Many have become jihadist fighters in the apparent hope of achieving martyrdom. A significant number—over 550 women—seem to have gone to become mothers and raise the next generation of jihadist “lions.” Some have left to put their medical expertise to use, and others to help in whatever capacity they can. Their motives are as mixed as their backgrounds. Indeed, the striking fact about these new pilgrims is that they don’t fit any single profile. They represent a broad spectrum of humanity, from former rappers and gangbangers to grandparents and gifted students.

On the face of it, they share little in common with the rarefied intellectuals of Political Pilgrims. Yet their estrangement from Western society and the force of their belief in an alternative system far superior to it, evidenced in interviews they have given and other forms of personal testimony, suggest that they share certain discontents and susceptibilities with the subjects of Hollander’s study.

Among the countless examples of folly cited by Hollander is Sidney and Beatrice Webb’s tome Soviet Communism: A New Civilization?, in which the Soviet penal system is praised for—wait for it—its progressive spirit. The second edition of this book, from which, as the historian Robert Conquest noted, “the question mark was triumphantly removed,” was published in 1937—“at precisely the time,” Conquest observed, that “the regime was in its worst phase of gloomy, all-embracing terror.”

How could the Webbs and others like them have gotten it so wrong? They were clearly foolish, but they were not stupid. Indeed, writes Hollander, many of the intellectuals in his survey were widely revered for their fierce intelligence and lively skepticism. Hollander contends instead that they wanted to be deceived about the failures and depredations of the societies they visited. And this, he theorizes, was in turn because, psychologically, they needed to believe in the existence of a perfect social system that not only exemplified their deepest ideals but also gave voice to their deepest misgivings about their own societies.

“Wishful thinking,” the sociologist Karl Mannheim wrote, “has always figured in human affairs. When the imagination finds no satisfaction in existing reality, it seeks refuge in wishfully constructed places and periods.” Hollander approvingly reproduces this quote in his introduction to Political Pilgrims, and one of the great merits of his book is the clarity and force with which it shows how desire can supersede and subvert critical thinking.

The recent migrations to ISIS, just like the political pilgrimages before them, are yet further testimony to the power of wishful thinking and how desire can trump reason.

Earlier this month, it was reported that a family of 12 from Luton, England—including, according to the BBC, “a baby and two grandparents”—had made the journey to Syria. It was the second family believed to have left the United Kingdom for the Islamic State since May. Was the family coerced or, as one relative has suggested, manipulated into going to Syria? Were they the victims of some collective psychosis? Not a chance, if a press release purportedly from the family is to be credited. The BBC acquired the statement from an individual claiming to be an Islamic State fighter, though the media organization could not verify its authenticity.

“None of us were forced against our will,” it said, describing a land “free from the corruption and oppression of man-made law ... in which a Muslim doesn’t feel oppression when practicing their religion. In which a parent doesn’t feel the worry of losing their child to the immorality of society. In which the sick and elderly do not wait in agony, tolerating the partiality of race or social class.” It also derisively alluded to the “so-called freedom and democracy” of Western states.

The statement, as the scholar Shiraz Maher pointed out, clearly serves a propagandistic purpose, and it could well be a fabrication. But it also accurately reflects the sentiments expressed by other Western migrants who have made the journey to Syria, and who in their social-media postings have mocked the notion that they have been “brainwashed” into joining ISIS. Furthermore, it distills two intimately connected themes that are essential for understanding the mentality of the Western migrants: estrangement and utopian hope.

ISIS’s caliphate project, because it offers a bracing utopian alternative to Western secular society, speaks directly to those who feel their lives are worthless, spiritually corrupted, empty, boring, or devoid of purpose and significance, and who see no value in their own societies. It promises, in short, salvation and ultimate meaning through total commitment to a sacred cause. “I don’t think there’s anything better than living in the land of Khilafah,” or caliphate, said one British jihadist in a video, “Eid Greetings from the Land of the Khilafah,” released last summer by ISIS’s media arm. “You’re not living under oppression. ... You’re not living under kuffar [unbelievers]. ... We don’t need any democracy. … All we need is shariah.”

Similar themes come out strongly in a recent report on female Western migrants. Based on the social-media postings of self-identified migrants apparently within ISIS-controlled territory, the authors found that estrangement from Western society and anger at perceived injustices against Muslims worldwide, together with a strong sense of religious calling and an unwavering faith in the rectitude of the newly emerging caliphate, form the basis for why these women journey to ISIS.

From this, it is clear that their departures owe as much to perceived corruption and oppression at home as to a desire to see in the Islamic State a utopian society free of any such secular perversions. This may also explain how, despite all the evidence, Western migrants to the caliphate can ignore or discount the mountain of incriminating evidence against ISIS, and risk everything to join it.

In Britain, where Prime Minister David Cameron just this week introduced a counterterrorism strategy as part of what he called “the struggle of our generation,” debate over ISIS and its recruitment methods has become unhelpfully polarized. On the one side are those, including British officials, who portray ISIS recruits as “vulnerable” or impressionable youth who, despite their murderous intentions or actions, are actually victims. On the other side are those, often academics and human-rights activists, who similarly argue that ISIS recruits are victims, but of oppressive government policies and actions rather than sinister jihadist groomers. The problem with both lines of argument is that they deny the agency of those who join ISIS, and obscure the religious idealism that motivates them.

One of the biggest challenges associated with countermessaging efforts against ISIS is how to prompt would-be migrants to rethink their favorable perceptions about the group and its self-proclaimed state. This is less a problem of finding the “right” narrative than of reconfiguring individual human desire, because it is possible that, at some deep psychological level, would-be migrants to ISIS want to be deceived about its widely reported depredations. As Christina Nemr, a former U.S. counterterrorism advisor, recently observed, people “push ‘threatening information’ away in favor of information that confirms their own beliefs.”

It is hard enough to sway those who have yet to make up their minds about ISIS— the so-called “fence-sitters.” But it is monumentally harder to sway those who, because of their idealism and estrangement from their own societies, want or need to see the best in ISIS.