My madrassa classmate hated politics. Then he joined the Islamic State.

When we studied together at a madrassa, Rashid Moosagie had a very low opinion of my politics. I was disenchanted by the academic, abstract nature of our curriculum at the Deoband seminary, some 100 miles from New Delhi, where I was enrolled in 1978; I desperately wanted the wisdom of my faith to help shape the world, and I had begun to lose myself in the writings of political Islam.

Rashid had just arrived to apprentice under some scholars after completing his religious education elsewhere, and he thought my notion of “applied Islam” was nonsense. The ideas I loved offered heady rhetoric but little substance, he argued. And eventually I came to agree with him that the madrassa approach, focused on tradition and piety, along with an infusion of new knowledge, was the best way to revitalize Islam. By that time, Rashid had become a successful imam in his native South Africa.

So I was very confused to learn that, this year, Rashid immigrated to Syria and joined the Islamic State. He left Port Elizabeth with his wife, adult sons and daughter and parted with the circle of clerics in a city where he had served for more than 30 years. His brother Allie told a reporter that he is trying to persuade Rashid to return. In a letter he sent home and audio recordings I obtained from someone close to him who asked not to be named, Rashid claims it is theologically mandatory for a Muslim to migrate to a land where God’s law is applied. “I am very happy here,” he said. “Here I found what I missed all my life.”

It was a departure not just of place but also of mind. “The Islam that the Indian [scholars] taught us is totally, totally, away from Islam,” he said, renouncing our joint theological education. The madrassas had not taught him the rules for slavery, jihad or dealing with prisoners of war, he complained. “I have painfully realized that Indian Islam teaches you to become passive and submissive to infidel, secular laws, which is a kind of unbelief.” And this realization led him to trade the democracy founded by Nelson Mandela for the caliphate of Raqqa in Syria. He surrendered the orthodox commitment about which he had exhorted me and adopted the very idea he had mocked: a toxic version of political Islam on steroids.

How could this have happened? Islamic orthodoxy, which controls mosques and institutions worldwide, is out of step with the world in which the majority of Muslims live. In few places is orthodox Islam independent of the state; it is often a political tool used by authoritarian regimes, which explains why the Muslim intelligentsia does not respect it. Its hallmark is archaism in theology and ethics, and its reach covers most of the global community of faith. Once a robust intellectual tradition, today Islamic orthodoxy is in serious need of a makeover. Mainstream theologians who cater to the majority of lay Muslims, both Sunni and Shiite, are unable to address such critical moral and theological challenges as evolution, gender and sexuality, or the role and meaning of sharia in a modern nation. That’s because theological education is steeped in ancient texts with little attention to reinterpretation.

Groups like the Islamic State propound antiquated teachings still held to be true by many orthodox authorities. These include enslaving prisoners of war and taking female prisoners as concubines. Because mainstream Islam has not truly defused these theological hand grenades by explaining how they apply to the modern world, groups like the Islamic State and disaffected followers like Rashid can view these dangerous teachings as Islam’s true ideals. No wonder his parting message said that every Muslim must be loyal to the caliph, who decides what is in the best interest of the Muslim community. “From a sharia point of view,” he said in his audio message, “I cannot leave dawla [the Islamic State] . . . and if I did so I would be an apostate” — a crime punishable by death. He planned to settle in Raqqa and buy a house there for his family.

Rashid could theoretically have migrated to Afghanistan under the Taliban long before the birth of the Islamic State. But there is an important technical difference: The Taliban claimed to have established an autonomous emirate, not a sovereign caliphate. According to medieval Islamic law, only an Arab, a descendant of the prophet Muhammad, can hold the office of the caliph, a qualification the self-proclaimed Islamic State head, Abu Bakr al-Baghdadi, claims to meet.

My old friend’s new approach blends Salafism and millenarianism, a lethal combination. Salafism rejects any interpretation of scriptural sources. In this sense, Salafism is to sharia as formaldehyde is to a dead body. It prevents decomposition but also creates the illusion that the body is alive. But a sharia that truly lives would help Muslims adapt to a changing world.

Meanwhile, Rashid explains his millenarianism in his last message, which contends that the conflict in Syria is the last heroic war — the final standoff between Islam and its adversaries. This philosophy draws on Muslim apocalyptic literature that says Jesus will return to Syria to combat the forces of evil just before the end of the world.

There are few alternatives to this pressing challenge in Islamic thought because many among the guardians of orthodoxy, the ulama, believe too in the sharia-in-formaldehyde approach. Ordinary clerics are reluctant to replace the medieval rulings on blasphemy, apostasy and captives with new interpretations of Islamic law based on current realities. So a credible and sophisticated narrative of Islam remains out of the reach of most Muslims. In my view, a doctrinal overhaul is the best long-term antidote to the radicalism and senseless interpretations that masquerade as Islam.

Rashid’s final messages offer reasons to celebrate and to worry. First, he castigates some right-thinking orthodox Muslim authorities who believe slavery is an abominable legacy of the past. That means, thankfully, that some orthodox elements are prepared to rethink issues. Sadly, they are a minority.

Second, madrassa-hating Islamophobes will be disappointed to hear that Rashid believes that the madrassas are insufficiently radical.

Rashid also rebukes Sufism, or Islamic mysticism. For centuries Muslim theologians have blended the rigorist teachings of sharia with the insights of mysticism to allow the spirit, rather than the letter, of the law to shine. The Islamic State and similar groups insist upon the letter, which is why all kinds of obscenities — beheading, rape, slavery, forced conversion, war — are committed in the name of sharia. Rashid now denounces any human attempt at theological or legal deliberation as idolatry.

The Islamic State outlook does not threaten only groups like the Yazidis, Jews, Christians and Shiites. It poses an even greater threat to Islam. As long as mainstream Muslim authorities keep Islamic learning in formaldehyde, they make it easier for many more like Rashid to head for the violent apocalyptic theaters of the Islamic State in Iraq and Syria.

I don’t doubt Rashid’s sincere intention to live a pious life any more than I did when we studied together. But he was able to embrace the Islamic State as its lodestar only because Islamic orthodoxy has not offered a humane alternative.

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