The guns of isis overlook Damascus. The Caliphate is triumphant, about to capture the besieged, shattered city. The first shells fall, people scream in fear, running for their lives. All except one man, who carries on preaching: Al-Masih, Arabic for Messiah. The skies darken and turn thick as a Biblical sandstorm thunders in. The Isis troops retreat, and Damascus is saved.

I’m enjoying Messiah, an intriguing new Netflix series set in an alternate reality. It stars, naturally, a slim and beautiful young man with long dark hair who wanders around the Middle East delivering miracles and moody epithets to his followers.

There are echoes, too, of Monty Python’s Life of Brian, which as well as being a brilliant satire was also a smart exploration of first-century Judea and its prophet-hunger. Al-Masih leads his followers to the Israeli border, then reappears in tornado-stricken Texas. He is captured and put on trial for border violations. None of this deters his followers, who grow and grow in number.

In an era that often seems to value image above all, she seems an unlikely icon.

Messiah obviously draws on the life of Jesus and other prophets. Netflix is keen to emphasise that Messiah is “not based on true events” (really?) but even so, in these censorious times, Messiah is brave and innovative television. But is Al-Masih really the Messiah or is he Al-Masih ad-Dajjal, the false Messiah of Islamic eschatology whose arrival marks the start of the end of days?

That dichotomy, between light and dark, good and evil, salvation and catastrophe, reaches back to the roots of our civilisation. The dualistic cosmology of Zoroastrianism, one of the world’s oldest but least-known religions, shaped Judaism, Christianity and Islam. It still influences our thinking today.

Nowadays, our fevered age demands prophets, but secular ones, please, who we can share on Instagram, such as Greta Thunberg. Lately I’ve been thinking a lot about Greta’s appeal.

In an era that often seems to value image above all, she seems an unlikely icon. She has written about her struggle with mental health issues and eating disorders, which may be why she is so small. She has a withering death stare and doesn’t seem much fun. Unlike Al-Massih, or even Monty Python’s Brian, Greta’s message is unrelentingly gloomy: politicians have stolen our future, almost nothing they do is do good enough to save us and if we don’t do what she says we are all doomed, she intones, like a modern-day Private Fraser of Dad’s Army.

She may be right, of course. Even if arsonists or lightning set off many of the fires now consuming much of Australia they would not have spread so far and fast without a three-year drought.

What Greta does offer is salvation from the coming apocalypse. She touches something deep within us: do what I say, follow me, and ye shall yet be saved. Yet that sense that we are dancing on the edge of disaster, that we will eventually be consumed in a fiery end, is also an essential part of her appeal.

Such primordial instincts are powerful. All three Abrahamic religions, Judaism, Christianity and Islam, believe in the end of days. But sometimes, watching Greta and the near-hysterical devotion she arouses among her acolytes, I am reminded most of all of Shabbetai Zvi, Judaism’s best-known false Messiah.

Zvi was born in Smyrna in 1626. A devotee of Kabbalah, Jewish mysticism, he moved to Thessalonica, where he lurched between asceticism and extreme self-indulgence, and declared himself to be the anointed one. At first, Thessalonica’s Jews simply shrugged. But these were dark and fevered times: in Ukraine, in 1648 and 1649, Bogdan Chmielnicki’s followers carried out savage pogroms against the Jews, slaughtering tens of thousands. To many it seemed the end of days had arrived.

At the same time, Kabbalah, once seen as dry and esoteric, was evolving. Lurianic Kabbalah, a new and populist doctrine, promised that through mystical prayer and ritual the Jewish people would redeem not only themselves but the very universe. Meanwhile, Zvi wandered across the Balkans and Middle East. He struggled with his mental health, lurching between manic elation and severe depression, before meeting Nathan of Gaza.

In 1665 Nathan proclaimed that Zvi was the Messiah. Zvi quickly went viral, his name and picture spreading across the Jewish world, cleaving communities in two between believers and sceptics. His adherents succumbed to a kind of mass hysteria, convinced of his and their righteousness. A year later, in Constantinople, Zvi was arrested for sedition. Offered a choice of death or conversion, he became a Muslim. Centuries later, scattered remnants of Zvi’s followers remain in Turkey.

The cult of Shabbetai Zvi was the greatest mass delusion in Jewish history. And it has lessons for us today. Climate change is real enough, but it’s complex. A teenage Swedish schoolgirl, no matter how strange and charismatic, is not Al-Masih.