Pages from a copy of the Koran dated back to 1284 are displayed at an exhibition in the newly opened Museum of Islamic Art in Doha December 2, 2008. Fadi Al-Assaad / Reuters

In his Atlantic article on “What ISIS Really Wants” last March, Graeme Wood insisted that “the Islamic state is Islamic. Very Islamic.” Wood’s detractors have been similarly emphatic, arguing that ISIS is a perversion of the Islamic faith. For Wood’s critics, secular politics, far more than religion or religious ideology, is the key to understanding the existence and appeal of jihadist violence.

In the immediate aftermath of the Orlando massacre in June, the same arguments resurfaced. According to one line of thinking, the shooter Omar Mateen was a repressed homosexual and his actions are inexplicable without understanding the psycho-social—and hence fundamentally secular—roots of his hatred toward the LGBT community. Correspondingly, “radical Islam” had little to do with the massacre, and Mateen’s professed allegiance to ISIS was merely a smokescreen and a way of aggrandizing himself. This would suggest that the Orlando massacre was about secular hate, not religious terror, not radical Islam, not ISIS.

An alternative viewpoint is that Mateen was a lone-wolf terrorist, whose actions were inspired, if not directed, by ISIS, and who took to heart the Islamic State spokesman Abu Muhammad al-Adnani’s injunction to carry out attacks in the West during Ramadan. Moreover, according to this viewpoint, Mateen’s decision to target the LGBT community in particular, as opposed to unbelievers more broadly, is perfectly explicable in terms of ISIS’s murderous homophobia.

These discrepant positions—one emphasizing the secular origins of ISIS-related violence, the other emphasizing its theological roots in “radical Islam”—reflect a deeper difference over the role of ideology in social and political life.

In fact, the ongoing “is ISIS Islamic?” debate is, in effect, a debate between idealists and materialists, and it long predates the current controversies—or more recent ISIS-related atrocities in Bangladesh, Iraq, and elsewhere. In England in the Age of the American Revolution, published in 1930, the British historian Sir Lewis Namier warned about public figures who summon high moral principles to explain their own actions, and insisted that such professed ideals will be ex post facto rationalizations that have little or nothing to do with those individuals’ actual motives for acting. Indeed, for Namier, like the Marxist historians he claimed to despise, the ideals invoked by politicians were mere epiphenomena, deployed to conceal intentions of a very different and often inadmissible kind. Namier and his followers were castigated by less hard-headed historians for their cynicism. Hebert Butterfield, for example, argued that many public figures are “sincerely attached to the ideals” in whose name they proclaim to act.

The clash over the role of ideology in human affairs also formed a crucial sub-textual thread in the debate between Christopher Browning and Daniel Goldhagen over the nature and origins of the Holocaust. According to Goldhagen’s Hitler’s Willing Executioners, the “ordinary men” who shot and murdered Jews or else assisted in their deportation to the death camps did so because they had internalized “a Hitlerian view of Jews, and therefore believed the extermination to be just and necessary.” Against this, Browning, in Ordinary Men, argued that German soldiers killed Jews not because they were virulently anti-Semitic, but because there were powerful “situational factors” in operation that caused them to kill Jews. For Browning, far more important than ideology was conformity to the group or peer pressure: the desire for praise and career advancement, and the fear of being seen to be weak or cowardly for not killing. Commenting on the contrasting explanatory worldviews behind these two conflicting accounts, the philosopher Nick Zangwill wrote, “Goldhagen, in somewhat Hegelian style, thinks that ideology drove at least this segment of history; Browning, in somewhat Marxist style, thinks that ideology did not drive at least this segment of history.”

The same division can be seen today in arguments over ISIS, where one set of protagonists insists that ideology in the form of radical Islam is the key to understanding the group’s violence, whether directed, inspired or branded, and the other argues that materialist factors, like political grievance or political self-interest or social networks, override any ideological-religious dimension.

According to the Namierite reading of ISIS, the group’s rise to power is a story of political state failure in Iraq, where jihadists, in collaboration with ex-Baathists from the previous Saddam Hussein regime, were able to exploit Sunni disaffection and seize territory and resources. Ideology, according to this story, did not drive this historic advance, but rather was, like the territory itself, annexed and refashioned for ISIS’s own political purposes. Dalia Mogahed, for example, argued, contra Graeme Wood, that “a violent reading of the Quran is not leading to political violence. Political violence is leading to a violent reading of the Quran.” Or as The Atlantic’s Kathy Gilsinan paraphrased Mogahed: “It’s not ISIS’s interpretation of Islamic texts that drives its brutality—it’s the group’s desired brutality driving its interpretation of the texts.” In this view, ideology legitimizes ISIS’s violence, but it doesn’t cause it.

The Namierite reading also extends to the individuals who perpetrate violence in ISIS’s name. The British journalist Mehdi Hasan, for example, has pointed out that “it isn’t the most pious or devout of Muslims who embrace terrorism, or join groups such as ISIS.” Referring to two British men who purchased copies of Islam for Dummies and The Koran for Dummies prior to joining a jihadist group in Syria, Hasan wrote: “Religion plays little, if any, role in the radicalisation process.”

This view has gathered considerable traction since Wood’s article was published last year. Writing after the Brussels attacks in March, The Washington Post’s Ishaan Tharoor argued that “radicalization is driven less by religious fervor than by more local factors, and it is shaped also by ties to gangs and other criminal activity.” Although Tharoor referred to the “complexity” of the causes of jihadist radicalization, he declined to identify religion as a salient variable in the causal mix. Far more important, he suggested, quoting Cas Mudde, an associate professor at the School of Public and International Affairs at the University of Georgia, is the story of how Europe “has created the conditions for the resentment that drives the terrorists.”

On the other side of this argument are those who insist, in somewhat Hegelian style, to echo Zangwill, that there is direct relationship between belief and action, and that the former inexorably drives the latter. “Believe,” the atheist philosopher Sam Harris has written, “that you are a member of a chosen people, awash in the salacious exports of an evil culture that is turning your children away from God, believe that you will be rewarded with an eternity of unimaginable delights by dealing death to these infidels—and flying a plane into a building is only a matter of being asked to do it.” Ayaan Hirsi Ali, a former Muslim who is now among Islam’s more prominent critics, similarly contended that the “cause of [jihadist] terrorism” lies in “the ideology of radical Islam.” She also wrote contemptuously of the view that religion “is a mere smokescreen for underlying ‘real’ motivations, such as socio-economic grievances.”

But in their rush to either blame or exonerate Islam, participants on both sides of this debate have contrived to ignore what to non-politicized ears must sound like a thundering platitude: Namely, that people who engage in jihadist violence may have mixed motives for doing so, and that these may be both secular and religious in character. As Peter Bergen recently observed, summarizing his research on jihadist activism in the United States since September 11, 2001:

I found that the perpetrators were generally motivated by a mix of factors, including militant Islamist ideology; dislike of American foreign policy in the Muslim world; a need to attach themselves to an ideology or organization that gave them a sense of purpose; and a “cognitive opening” to militant Islam that often was precipitated by personal disappointment, like the death of a parent. For many, joining a jihadist group or carrying out an attack allowed them to become heroes of their own story. But in each case, the proportion of the motivations varied.

There is a further sense in which the division between the ideological (or religious) and the material (or secular) is artificial. Even if jihadists in the first instance are motivated by worldly goals, like fame or political grievance, they nevertheless seek to legitimize their violence through an appeal to a religious ideology that, as Graeme Wood has convincingly demonstrated, has a basis, however controversial and contested, in Islamic texts and history. If they did not have recourse to such an ideology, and if such an ideology found no support among a broader constituency, however small, their capacity for violently acting out would be restricted—or grafted on to another culturally available cause. As the intellectual historian Quentin Skinner has postulated, critiquing both Namier and his antagonists, “Any course of action will be inhibited to the degree that it cannot be legitimized.” Accordingly, Skinner argued, “any principle that helps to legitimize a course of action will therefore be among the enabling conditions of its occurrence.” More succinctly: Ideology is not a sole cause; but it is a cause, insofar as it legitimizes and hence facilitates any course of action.

Omar Mateen, whoever he was and whatever he wanted, needed the warrant of combative Islamic martyrdom, however shakily interpreted, to justify his act of suicidal mass slaughter. And in ISIS he found it. This warrant may not have given him the desire to kill. It may not have led him to kill when he did, who he did, and where he did. But it gave him the moral license, however hallucinatory, to do it, and thus directly facilitated his murderous plan. This is why ideological-religious motifs, as much as personal and political motives, must feature in any adequate attempt to fathom the conundrum of jihadist violence.​

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