In Chapter 12 of Acts, St Peter suffers a brief period of imprisonment at the hands of King Herod, before being freed by a friendly guard. He rushes off to a safe house where he greets the assembled throng with "Tell James and the brothers". Read countless times during the Sunday morning lesson, this has scarcely prompted a raised eyebrow. James might be James the Apostle or one of the many followers of Peter littered in the text. Yet it has led Professor Eisenman of California State University to fashion a scenario which, if true, could empty the pews forever.
Simply put, it is that this line is the last remaining clue in the New Testament of the true history of Christianity. In this account, the Virgin Mary had three, perhaps four, sons. After Jesus, her eldest, was executed for political crimes, his brother James took over and led what was in essence a small, ultra-devout Jewish sect. Strictly vegetarian and obsessed with ritual purity and bathing, this family business saw its biggest asset - the memory of Jesus - stolen from under its nose by budding entrepreneurs like the Apostle Peter and St Paul, allegedly Herod's stooge and his distant relative. These two schemers then encouraged written accounts of Jesus's life that edited out what really happened in favour of, as Eisenman puts it, "Hellenistic romance and mythologising ... with a clear polemicising of dissembling intent".
Claiming Jesus for Judaism is fashionable at the moment. A N Wilson's newly-published account of St Paul does much the same, though with more panache. It is not, however, a new thought, and the same could be said of much of Eisenman's theory. The historical Jesus has long been a mystery, since the gospel accounts were written long after his death by authors with their own axes to grind. Mary's virginity came even later, dreamt up by the early church to separate Jesus from the messy business of sex. In his time as Bishop of Durham, David Jenkins reminded us of this salient fact in a soundbite a fraction of the length of Eisenman's tome.
To flesh out the single line in Acts, Eisenman turns to various surviving contemporary texts and fragments. In contrast to his harsh words for the gospels, he treats these "apocalypses" with exaggerated reverence, as if decades of careful and often damning analysis of their claims had not already taken place.
The problem is that while the Bible may indeed by historically unreliable, so too are most other sources on the period. Between the Old and New Testaments, for example, there is a gap of 200 years. It was filled by a whole host of apocryphal books, prompted by the national self-doubt of the Jews who, under Roman overlordship, began to question their status as God's chosen people. And at the same time as the New Testament, there was another wave of early Christian literature - gospels according to Mary of Bethany, Peter, Mary Magdalene, and so on.
Somewhat arbitrarily, later church leaders decided to exclude most of these from the authorised account, little imagining the confusion this might cause. For Eisenman, after showing scripturally illiterate church- goers the shortcomings of the gospels themselves, demands that parallel accounts - which have all the drawbacks of Matthew, Mark, Luke and John - be taken literally. He adds a dollop of passion to the mix in his outrage at the historical "injustice" that has befallen James.
His trump-card in all this is his knowledge of the Dead Sea Scrolls, a collection of texts and fragments found in 1948 in the Holy Land and dating from Christ's time. Eisenman has long campaigned for these to be more accessible to scholars. Yet the best he can manage in relation to James is that there are parallels between Jesus's would-be brother and the "righteous teacher" figure referred to in some of the scrolls.
The irony is that, 50 years after their discovery, the Dead Sea Scrolls have generated an industry in precisely the sort of populist speculation that, behind all the pseudo-academic jargon, lies at the core of Eisenman's book. Barbara Thiering's 1992 Jesus The Man was the most celebrated example. At the very least, the scrolls are as complex, contradictory and coded as any passage of the Bible. Amateurs should proceed with caution, and beware of selective quotation without reference to a context that is still little understood. And woven into the web of the scrolls' mystery has to be the question of why they were abandoned in a cave in the first place. It could conceivably have been because they were considered of no importance at the time.
Professor Eisenman would like to see himself as breaking the taboos of traditional biblical scholarship and bringing a new authenticity to the understanding of our Christian heritage. What he manages instead is a book that will mount a feeble challenge to Erich von Daniken's Chariots of the Gods and Michael Baigent et al's The Holy Blood and The Holy Grail, in the lucrative market in fascinating but fanciful investigations into religious "mysteries".
8 Peter Stanford's 'The Devil: A Biography' is published by Mandarin at pounds 7.99.