In the wake of the second beheading of an American journalist by ISIS, the jihadist extremists in Iraq and Syria, President Barack Obama has sharpened his rhetoric. “Our objective is clear,” Mr. Obama said on Tuesday. He pledges to “degrade and destroy ISIL [an alternative acronym] so that it’s no longer a threat, not just to Iraq but also to the region and to the United States.” Vice President Joe Biden has even sharper words for ISIS: “We will follow them to the gates of Hell, until they are brought to justice,” he said in Portsmouth, New Hampshire, “because Hell is where they will reside!”

In the writings of Thomas Hobbes, the great 17th-century political theorist, we find a keen analysis of the danger ISIS poses to civilized life in the 21st century. I'll explore Hobbes's insights a few paragraphs down. But first, if you need a primer on ISIS—the group now calls itself simply the “Islamic State” (IS)—you might start by consulting these excellent info-packs by Zack Beauchamp at Vox. I’d also recommend watching the chilling, eye-opening video captured by a reporter from The Vice who spent three weeks embedded with the militants.

A Military Conundrum

The tough talk from the Obama administration over the past week is a notable change from Mr. Obama’s earlier admission that “we don’t have a strategy yet.” Yet harsh rhetoric and American military might cannot “destroy” ISIS, as the president pledged to do this week. As Mr. Beauchamp writes, it is simply implausible that the United States military, for all its force and firepower, can defeat ISIS. “There is no magic American bullet that could fix the ISIS problem,” Mr. Beauchamp claims. “Even an intensive, decades-long American ground effort—something that is politically not on the table, anyways—might only make the problem worse. The reason is that ISIS's presence in Iraq and Syria is fundamentally a political problem, not a military one.” As long as a significant proportion of Iraq’s Sunni population is on ISIS’s side, no amount of bombing will secure America's ultimate objective. And “a stepped-up US ground presence,” as Mr. Beauchamp writes, “might only further infuriate the Sunni population.”

Another myth Mr. Beauchamp dispels is the assumption that ISIS is “crazy and irrational.” While the militants adhere to “a violent medieval ideology,” and relish massacring minorities and slicing off innocent journalists’ heads, it would be a mistake to dismiss them as insane. For over a decade, ISIS has been motivated by ”one clear goal: to establish a caliphate governed by an extremist interpretation of Islamic law”:

ISIS developed strategies for accomplishing that goal—for instance, exploiting popular discontent among non-extremist Sunni Iraqis with their Shia-dominated government. Its tactics have evolved over the course of time in response to military defeats (as in 2008 in Iraq) and new opportunities (the Syrian civil war). As Yale political scientist Stathis Kalyvas explains, in pure strategic terms, ISIS is acting similarly to revolutionary militant groups around the world—not in an especially crazy or uniquely "Islamist" way.

This methodical, patient, well-organized approach has helped ISIS win and hold on to significant territory in Syria and Iraq, snatching American military equipment in the process and using it to fuel its campaign to take still more land.

A Caliphate Without Borders

Another aspect of ISIS that makes the organization so frightening is its particular mixture of religion and politics that has won the hearts and minds of tens of thousands. On June 29, ISIS declared its “caliphate” had been established, transforming it, in word at least, from an insurgency to a borderless political-religious state headed by a caliph, a leader with both temporal and spiritual authority over Muslims worldwide. Those who buy the notion that ISIS constitutes a caliphate believe they are living in the midst of a restoration of Muslim power like that which governed southwest Asia, North Africa and Spain from the 7th to the 13th centuries. It is a heady notion. Watching the Vice’s inside video on ISIS reveals how readily Muslims young and old embrace the concept and pledge their loyalty to Abu Bakr al-Baghdadi, the charismatic leader of the movement. This despite the condemnation of ISIS’s retrograde theology and brutal tactics by the vast majority of Muslim leaders around the world.

In Leviathan, Thomas Hobbes’ masterwork arguing that a ruler with absolute authority is the best prescription for social peace, the prospect of zealots with weapons was portrayed as one of the foremost dangers to overcome. Human beings seek out religion, Hobbes wrote, because they can’t make sense of the world. People are then drawn to the assumption “that there is some cause, whereof there is no former cause, but is eternal, which is what men call God.” This nascent religious belief gets the ball rolling in a dangerous direction. For once such a belief is established, people are willing to devote themselves to God out of fear and trick themselves into believing all kinds of ridiculous ideas, with birds, snakes and even “onions and leeks” taking on divine significance. That’s where scheming men with strange, even unfathomable, ideas enter the scene, according to Hobbes. And around the corner come figures like Abu Bakr al-Baghdadi, cunning would-be caliphs who draw followers into the palms of their hands. Hobbes might as well be blogging today:

“So easy are men to be drawn to believe anything from such men as have gotten credit with them and can with gentleness and dexterity take hold of their fear and ignorance.”’

These “authors of religion” try to take power and impose laws on people just as ISIS seeks to impose an unforgiving, medieval interpretation of Muslim Sharia law not only on their followers but on every “infidel and apostate” on the planet, with plans to raise the Islamic State flag in Istanbul, in Madrid and in Washington, DC. The harshness and inhumanity of their tactics, when coupled with the grandeur of their vision, take on the feel of a divine commandment. With every conquered city, with every battlefield victory, and yes, with every slickly recorded beheading of an infidel from the West, the movement takes on more power and becomes more attractive to the flock. And baiting America into air strikes just adds to the perceived legitimacy of the insurgency.

Hobbes was terrified by the tendency of human beings to be duped by murderous religious messages. But his fear of zealots did not lead to a position of secularism; far from it. Hobbes wanted sovereigns to maintain their own civil religion including a belief in God and public celebrations and affirmations of that faith. The key for Hobbes was reining everyone into a single public religious scheme and preventing dissenters from mucking up the works and threatening to rip apart the social bonds that make political society possible.

Leviathan shows how breathtakingly difficult it can be to defeat such visions for a pluralistic, freedom-loving republic.

In sum, ISIS is not likely to be defeated anytime soon—not on the battlefield and not in the forum of public opinion in the Middle East. President Obama may have no option but to talk tough and military options may seem increasingly inescapable, but the task, and the foe, are formidable.

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