The post-Islamic State proponents of a Muslim homeland range from activists hardened by the dead-end outcome of the Arab Spring uprisings to Twitter’s group of caliphate nostalgia bros, who themselves range from staunch Islamists to history aficionados who miss the sepia-tinted grace and security that they believe caliphate rule once offered. One Twitter user, @dimashqee, for instance, argues for “an enlightened and ethical state” that would offer Muslims “social harmony” — “a polity which creates a high culture on the basis of the Arabic language and a neo-Ummayad frontier military aesthetic.”

Others, like @gleamingrazor, look ahead practically to how things can be done differently in the future. The Islamic State experience, he notes, has made it clear that “a state cannot be declared amid the fog of war and uncertainty.” Mr. Baghdadi demanded that millions emigrate to his “state” but couldn’t offer them security or employment. Next time, any leader presuming to declare statehood would need to control territory with industry and scientific research facilities; he would need an economic policy, the ability to conduct trade and commerce, and control over an electricity grid. Mr. Baghdadi’s caliphate was a “disgrace,” but it “imbued in us a renewed sense of hope and longing.” It also demonstrated that any feasible Islamic state would require the taking over of an existing state. “Maybe, just maybe, a Muslim general somewhere would be inspired.”

Perhaps to be expected, the emotional commitment to a caliphate holds strong among those who joined the Islamic State, only to be devastated by the outcome. One woman from Tunisia I met in a refugee camp outside Raqqa this past summer, who fled with her children and was later detained by Syrian Defense Forces, said: “If the Islamic State was real, I would not have left it. I would prefer to have died there than leave it.” Instead, she said, it turned out to be a band of vicious men intent on collecting cars and women. The Tunisian woman wanted to go home, but most of the Islamic State women detained alongside her didn’t. They wanted to live in Turkey, the closest thing to an Islamic state they felt was on offer today.

Caliphate intellectuals are united in reviling the Islamic State, but beyond that, their projections of the future vary widely. Would an idealized Muslim community be a conventional state, but governed by the Shariah? Would it be a federation of Muslim-majority countries under the banner of Islam, a proto-Islamic bloc like the European Union? Would it be a caliphate in the classical, historical form, a sort of empire in God’s name with a modern commitment to Islamic banking? Would it be sectarian? There are no solid contours yet to what form all these inchoate yearnings would take, but the sentiments are there, as real and inescapable a part of the modern landscape of the Muslim world as celebrity imams and Nike hijabs.

As we survey the husks of the cities the Islamic State controlled and speculate about the future, it is worth remembering: The Islamic State caliphate grew out of Syria’s civil war, but it was also made possible by thousands of Muslims from across the world — not just the Arab world, but Europe, the United States, Indonesia, Russia — boarding planes, leaving their countries behind, in pursuit of the dream of a Muslim homeland.

The discussion about the post-Islamic State world purports to be about security, but it fundamentally neglects the fact that what the Islamic State claimed to represent — the idea of a caliphate — remains squarely in the minds of Muslims, even if many forces conspire to keep those sentiments from the public view. The majority who long for an Islamic state are not jihadist-minded, nor do they advocate the murder of civilians. But these views are banned from the public sphere across most of the Arab Middle East; such thoughts are not permissible in civil society or on mainstream media platforms. You are much more likely to see a buffoon conservative on television (like the Egyptian figure who recently called the rape of women wearing skinny jeans a national duty) rather than the razor-sharp Islamist lawyer in Tunis.

The question that captivated Western audiences as the Islamic State gained ground was how Islamic it was. Perhaps a better query might have been why what it claimed to represent appealed to so many. As we struggle to formulate better questions looking forward, we should think about why the idea of a Muslim homeland bubbles up as needed — an old notion that has never had, in living memory, such depths beneath it.