"I wanted to learn Islam from the inside, not the outside." That is how Mohammed, born Nathan, tells me how he's gone from a New York electronic repair shop to Mecca, studying with the Imam of the Kaaba, Islam’s holiest place.

We share U.S.-based friends, are around the same age and both have Jewish mothers from Queens. (He’s not the only one of our circle to have turned religiously ultra-conservative and moved to the Middle East - another who ended up a hippie-style Hasid in northern Israel.) But that's where our biographical convergence ends.

With three wives, three children and countless hours of study of Sharia and Islam under his belt, it's safe to say Nathan knows more about Islam than any other Jew alive - and perhaps ever. He's still engaged to some degree with his Jewish background, but don't expect him to speak out about anti-Semitism in the Arab world. Even to share his story, I've had to alter some names for their continued well-being.

Nathan/Mohammed's journey effectively began in the 1970s, when a pair of Russian Jewish immigrants took an enterprising Palestinian under their wing: Ashraf (known as Mike) was to become their son-in-law. Their daughter, Barbara, was just as taken by Ashraf's warm and boisterous Syrian-Palestinian family as Nathan himself later was, as an adolescent.

The intertwining between Muslims and Jews had long been the cultural default in Ashraf’s family.

In the pre-state area around Haifa, his Palestinian paternal grandfather’s first wife was a tall red-headed Jew named Sara. Learning she was infertile, she helped him find an additional wife with whom to have children: he ultimately had eight. Ashraf's father was born in Haifa in 1942 and fled the violence of 1947/8 for Syria, much like his maternal Jewish grandparents fled Russia from anti-Semitism and the build-up to WWI in 1913/4.

His Uncle Reza found a way out of the Palestinian refugee camps working at the post office and as a translator in central Damascus. He then opened a dance studio near the Jewish Quarter, where Eddy, as he was known by his many Jewish female patrons, cut quite the figure.

A generation later, Nathan’s own first great love, which blossomed right at the time he became fascinated with Islam, was with the daughter of a Moroccan Jewish Hebrew High School principal embarking on a similar spiritual quest toward Islam. Rather than proactively rejecting Judaism, Nathan is in many ways continuing his family's tradition.

How does Nathan relate to his father's Palestinian identity? Nathan points out that the term "Palestinian" for his family is rather fungible. His paternal grandparents, despite being post-1948 refugees, didn’t identify as Palestinian: "That wasn’t their issue," he suggests. His great-grandfather had been a deputy to the Ottoman Vizier within the region of Sham (Greater Syria) and hardly even spoke Arabic.

Growing up in an insular, if largely secular, Jewish neighborhood, Nathan’s cultural Judaism didn’t go much beyond his grandmother bringing out the shopworn "old country" recipes around holiday time. And his Syrian-Palestinian family were hardly strict practitioners of Islam; if anything, they were shaped by a Damascus of the sixties and seventies that was even more secular than New York.

He credits his Jewish grandmother, along with his parents, for pushing him to become the best student in his school and getting him into an elite magnet prep school. And though his relationship with his mother is strained (in which his conversion to Islam is no doubt one key factor), he still travels back to New York to visit family on a regular basis. His Muslim family greeted the move to Mecca with amazement and respect: "No Muslim would say anything but congratulations," he adds.

To hear him tell it, his embrace of Islam might be the most Jewish thing he’s ever done, and his understanding of Islam is one, it seems, that only a Jew could have. The Koran, he relates, addresses the "children of Israel" more than any other named group, 41 times in fact. He is highly conscious of the children of Israel's special role in the "final revelation" of Islam. "Primitive tribes are not addressed, neither are the Chinese: the Jews are in the center of the world and bear the ancestry of the prophets," he relates.

The "Go forth" command and promise to Abraham, so well-known to all Jews, in its Koranic telling crucially includes Mecca. People will come from every distant place there, it is prophesized, and the poor will be fed and provided for. The plunge of faith into the desert, desolate and forbidding, is every bit as central to Islam as Judaism.

For Nathan/Mohammed, the resemblance doesn’t stop at how the faiths began. His complex heritage gives him extras prisms with which to examine the roots of Islam.

Open gallery view Muslim pilgrims take a selfie at Mount Al-Noor, in the holy city of Mecca, Saudi Arabia August 28, 2017 Credit: SUHAIB SALEM/REUTERS

The key narratives in both the Torah and Quran are the experience of oppression and deliverance. The warnings they receive from God, to not abuse their newfound status and their divine covenant, are similarly heeded only fitfully and partially. Nathan/Mohammed observes that the same questions need to be posed in terms of the ethical choices made in contemporary times by Israel and Saudi Arabia.

Nathan/Mohammed today doesn’t "read" any different than countless youngish New York Jews of the outer boroughs: the obligatory fluency in hip-hop, the quick-witted, slang-inflected dialect and the genial mix of menace and humor. But he chose to leave the capital of 21st century American materialism for the desert.

But even Mecca has changed underneath his feet, unrecognizably so, in his two decades there. "I don’t feel I belong anywhere in the world now," he says. The new construction of hotels, car parks and a massive clock tower that overshadows the Kaaba, suggests to him what life was like before Islam, when materialism held sway.

He believes that this is a universal challenge for people of faith: "To be spiritual is to go against the stream, the Kaaba is in the valley, inside the pressure cooker." He finds respite on the nearby Mountain of Noor (Light) where the prophet Mohammed, according to Muslim tradition, received his first revelation.

All his spiritual work has brought him to a space beyond labels, he says: "I just don’t identify, I feel like an alien wherever I go." He passes over all other "isms" for the same reason, Christianity chief amongst them, in which he charges people identify with creations rather than the Creator. To be Jewish, in his eyes, is an ideology about a specific group, one based on ethnicity.

His outsider status and conversion story have prepped him for a role on the front line of current online debates about Islam – and have made him something of a proselytizing master. About a year and half ago one of Saudi Arabia's most influential imams invited him to join an NGO called "Edialogue," an internet chat platform on Islam.

He sees what looks like straightforward missionizing as "interfaith work," though the site highlights the number of "new Muslims" it's produced (42,000 and counting).

All kinds come to the chat room - from aggressive trolls and Islamophobes (whom he claims are part of a concerted, Western government-funded effort to undermine it) to those ready to take the leap of faith. During his own shifts, he says, those converts who have proclaimed the Shahada have climbed into the triple digits. Nathan apparently knows how to talk to all of them: he's open about being a convert and his Jewish background: "Sometimes they ask me or I bring it up occasionally."

Although Saudi Arabia had an established Jewish community before the coming of Islam it's not quite accurate to call him Mecca's "last Jew," hanging on in inhospitable climes. Nathan/Mohammed might instead be the first "new Jew" in Saudi Arabia, a throwback to the cultural and familial coexistence and intimacy between Muslims and Jews in parts of the Arab world that once was and perhaps could be again.

But we're not there yet. It's only because of Mohammed's wholehearted conversion to Islam that he's even allowed to step foot in Mecca; his older, Jewish alter-ego, Nathan, wouldn't even be allowed to enter.

Adam J Sacks holds an MA and PhD in history from Brown University and an MS in education from the City College of the City University of New York. He currently lives in Philadelphia