One of the more intriguing trends in Jewish circles is growing interest in Jesus. The work of scholars such as Geza Vermes who have explored the Jewish background of the Christian messiah has filtered into the mainstream. Shmuley Boteach published his book Kosher Jesus last year; Naomi Alderman’s recent novel The Liar’s Gospel was an alternative version of the Jesus story. The American academic Amy-Jill Levine, author of the Jewish Annotated New Testament, found a ready audience at the Limmud conference in Warwick last winter.

There is now a greater willingness to reclaim Jesus as a radical rabbi who preached Jewish teachings to Jews. Christianity is explained as the creation of his followers who introduced into it pagan notions such as the rebirth of a dying god.

But a daring new book by one of the world’s leading Jewish scholars challenges this simple contrast. The Jewish Gospels is a short work aimed at general readers by Daniel Boyarin, a professor of Talmud at the University of California in Berkeley. In ancient times, the borders between what Judaism and Christianity were far more porous than we conceive today, he argues: it was not until the fourth century that the doctrinal differences were clarified, not least because of the desire of the Roman-backed church to put clear water between the spreading new faith and those it considered Jews.

His most explosive contention is that the concept of a divine messiah was not an alien import but part of the cauldron of ideas that bubbled in the volatile world of classical Judaism. “The basic underlying thoughts from which both the Trinity and the incarnation grew are there in the very world into which Jesus was born,” he writes.

Jesus could have plausibly claimed to be the “son of God”, or rather the “son of Man”, as was the more potent phrase, which goes back to the Book of Daniel. In his dreams, the prophet sees heavenly thrones — the plural is significant. On one sits the “Ancient of Days” whose hair is white as wool (Daniel 7:9): but emerging from the “clouds of heaven” is another apparition, who is likened to a “Son of Man”, whose “dominion is an everlasting dominion” and who is to be served by all peoples and nations (7:13-14).

Some interpreters may regard the Son of Man simply as the symbolic representation of a warrior-Messiah , who does not enjoy divine status, or of heroic Israel. But Boyarin suggests that Daniel’s vision reflected earlier traditions of a dual Father-Son godhead — which later rabbis successfully fought as heresy but which underlay the Gospels’ depiction of Jesus.

It is fair to say that the apocalyptic visions of Daniel are not familiar territory even to most shul-going Jews. Even less known are other texts on which Boyarin draws to bolster his argument that “Gospel Judaism” was a “Jewish messianic movement”.

The Similitudes of Enoch is an apocryphal work dated by scholars to the tumultuous first century CE — the same era as Jesus — and named after the mysterious character who appears briefly at the start of the Bible and is whisked to heaven.

In the Similitudes, the narrator Enoch recounts a heavenly vision of a figure with “a head of days” like “white wool”, accompanied by another “whose face was like the appearance of a man”. That “Son of Man” sits on “the throne of glory”: he will deliver judgment, vanquish the wicked and be worshipped on earth. Enoch comes to understand that the Son of Man is actually himself.

Another first century Jewish text, the Fourth Book of Ezra, depicts a redeemer “like the figure of a man”, flying with the clouds of heaven to initiate some kind of judgment day. “The forms of many people came to him, some of whom were joyful and some sorrowful; some of whom were bound and some were bringing others as offerings.”

Boyarin also shows how Daniel’s vision could be decoded to lend credence to the idea of suffering redeemer. The New Testament, he concludes, is “much more deeply embedded within Second Temple Jewish life and thought than many have imagined, even… in the very moments that we take to be most characteristically Christian as opposed to Jewish: the notion of a dual godhead with a Father and a Son, the notion of a Redeemer who himself will be both God and man, and the notion that this Redeemer would suffer and die as part of the salvational process.”

Of course, this is by no means a consensus view among scholars. PeterSchäfer, author of The Jewish Jesus, for example, believes that Boyarin overstates his case. But investigations of first-century Judaism are shaking old certainties. We all build our worldview on ideas about the past. The effect of works like Boyarin’s is to make the solid ground on which we think we stand seem more like ice that can melt into something more fluid.

The implications of such radicalism could extend beyond the halls of academia and theological exchange between Christians and Jews. If Boyarin is right, then messianic Jews whose belief in Jesus as messiah puts them currently beyond the Jewish pale might have more claim to be an offshoot of Judaism than we think.