In The True Believer, published in 1951, the philosopher Eric Hoffer suggested that mass movements hold a special appeal to “sinners,” providing “a refuge from a guilty conscience.” “Mass movements,” he wrote, “are custom-made to fit the needs of the criminal—not only for the catharsis of his soul but also for the exercise of his inclinations and talents.”

This also applies to jihadist groups like ISIS, which promise would-be recruits not just action and violence, but also redemption.

In his 2005 study of al-Muhajiroun, a banned Islamist movement based in Britain with reputed connections to ISIS, Quintan Wiktorowicz detailed the multiple material and social costs attached to what he calls “high-risk Islamic activism.” He mentioned one al-Muhajiroun document in which members are sternly warned to refrain from behaviors ranging from “listening to music and radio” and “window shopping and spending hours in the market,” to “hanging out with friends” and “joking around and being sarcastic.” The organization’s activism, Wiktorowicz observed, is “fast-paced, demanding, and relentless.” It also bristles “against the mainstream,” generating a “kind of excitement often found in counterculture movements rebelling against the status quo.” Many members, he noted, “seem to enjoy their role as ‘outsiders.’”

But more crucially, Wiktorowicz argued, al-Muhajiroun promotes the idea of spiritual salvation—socializing its members to believe that their sacrifices in the here-and-now will be rewarded in the hereafter.

High-risk, high-intensity Islamist activism, in other words, seems tailor-made for the needs of criminals and ex-cons, providing them with a supportive community of fellow outsiders, a schedule of work, a positive identity, and the promise of cleansing away past sins.

Can the same be said for converts to Islam or born-again Muslims?

A common line of argument among scholars is that converts to Islam are insufficiently knowledgeable about their new faith and thus acutely vulnerable to extremist interpretations of Islam, which they lack the intellectual or theological resources to counter. While this explanation seems intuitively plausible, it assumes that converts to Islam know less about their newfound religion than Muslims who were born and raised into it. Yet the evidence for this claim is shaky, and at odds with studies showing just how engaged and well-versed many converts are in debates over matters of faith. The idea that converts, lacking in religious knowledge, are peculiarly susceptible to demagogic manipulation also carries the implication that those with a deep knowledge of Islam are unlikely to join jihadist groups. This, too, is a contentious point—and it’s unclear whether it could even be empirically established, given how contested Islamic knowledge is. More contentious still, this logic essentializes Islam as inherently pacifist, suggesting that some true or proper understanding of the faith would serve as a repellent against deviant jihadist interpretations. But what Islam is or isn’t is an open (and indeed volatile) question; there is not one “true” Islam, but a plurality of Islams, each competing for epistemological hegemony.