Critics of the piece, which generated a seemingly endless conversation online, claim it downplayed the extent to which the Isis jihadists exist outside the pale of established Islamic jurisprudence.
Others insisted that the organisation should still be seen as a deeply "modern" entity, a product of 20th century wars and 21st century networks.
A smart article on the War on the Rocks blog takes up the analysis of Isis as a "religious, millenarian group". Isis' "obsession with 'purity' and the apocalyptic prophecy it stakes its claim on" may be startling, but it's not unique, writes Eleanor Beevor, a researcher at the Quillam Foundation, a counter-extremism think tank based in London, and a PhD candidate at Oxford University.
In fact, as Beevor explores, echoes of its creed can be found in a militant group that's decidedly non-Islamic: the Lord's Resistance Army, an outfit formed two decades ago by the notorious Ugandan warlord Joseph Kony.
What distinguishes the LRA from a host of other militias operating in Central Africa is Kony's religiosity - and the grotesque slaughters, rapes and the abduction of tens of thousands of people conducted in his name.
The movement had emerged in the 1980s, led by a woman named Alice who claimed to be channelling the Holy Spirit. Kony, believed to be her cousin, eventually took over, as Beevor narrates: "Kony convinced a band of followers of his own conviction that he had inherited possession of Alice's holy spirit, and would take up her mantle.
"He pledged to overthrow [President Yoweri] Museveni's new Government and lead Uganda according to the Ten Commandments. These claims juxtaposed absurdly with the actions of his Lord's Resistance Army, famous for abducting children and mutilating and massacring the Acholi people they claimed to be fighting for. Not unlike [Isis], it was incredulously asked who could ever follow a preacher of such religious perversion."
And, yet decades later, the LRA and Kony endure, albeit in a far diminished state. He and a number of other LRA leaders are wanted by the International Criminal Court. No one dwells much on the seriousness with which they embrace their own apocalyptic Christian creed; there are far more immediate things to be concerned about.
Of course, Isis is a world away from the LRA, and has an ability to project power and inflict terror on a far wider scale.
But when we consider its already long litany of atrocities - its enslaving of Yazidi women, destruction of ancient art, beheading of hostages - there is a common thread with some of the grisly practices of the LRA, writes Beevor.
Kony's militia built itself through brutalising its initiates, particularly abducted children, and in turn made many of them do brutish things. At the same time, it created a unique cult of authority around its leader.
The tactical, almost ritual use of violence has a sustaining logic for religious extremists of all stripes, as Beevor explains: "These spectacles of violence are strategic, and crucial to the survival of cults that shroud power grabs in religion, rather than moral justification.
"This is a complex concept. To some extent religion is moral justification, because it invokes the unquestionable authority of God. Yet because cult leaders must appear divinely sanctioned, they find themselves in a game of salesmanship, having to convince their followers that they possess unique cosmological control. And in a grim contradiction to most religious teachings, the best way to demonstrate this is through shocking violence."
Isis is creating its caliphate through violence in the same way the LRA strengthened its own ranks. Isis wants "what every millenarian cult does: power, but power above and beyond what humanity can bestow", writes Beevor. "[Isis] and the LRA both need religion to sanction their claims, and no religion has a monopoly on the power-hungry."
