Then it was the Da Vinci Code. Renaissance artists knew more than first century apostles, it seemed: Jesus not only was not divine, he wasn't celibate either, but had a family and progeny whose identity was a closely guarded secret.
Now – to borrow the title of Peter Jones' analysis of the New Age movement – the Gnostic empire is striking back, and doing it with a vengeance.
Gnosticism (don't pronounce the 'g') comes from the Greek word 'gnosis' (still don't pronounce the 'g'), meaning 'knowledge' (pronounce the 'g'). We know about Gnosticism from the early Christian apologists, particularly Irenaeus, in the second century, because it was identified as one of the early departures from the faith against which the Fathers had to defend orthodoxy.
Information about the Gnostics, therefore, was rather scant, until the discovery of the Nag Hammadi library in Egypt in 1945. Like the discovery of the Dead Sea Scrolls, these parchments suddenly shed new light on movements that had all but gone into oblivion, and could only be known through their detractors.
For the early Church Fathers, Gnosticism was a departure from the truth, a heresy which was insidious precisely because it appealed to so many elements of the faith. Drawing on pagan mystery religions and not a little Greek philosophy, the Gnostics believed that inner knowledge of the divine was possible quite apart from written texts or creedal statements.
There was a certain attraction in this position. After all, hadn't Jesus himself taught that eternal life was a matter of 'knowing God'? Hadn't he stressed the importance of personal experience, of rebirth, of inner transformation?
Of course he had, but that was never to be at the expense of the written text of Scripture, argued the Fathers. So when the Gnostics wanted to divorce the God of the Old Testament from that of the new, and separate Jesus the Son from Christ the Redeemer, and teach that matter was bad while spirit was good, the early defenders of the faith reacted vehemently.
They argued that Gnosticism was a departure from what had been handed down by apostolic authority through the tradition of the church. This was not an attempt to give Scripture and tradition equal ultimacy; it was simply to recognize that the church had irreducible core commitments which faithfulness to Christ required that one generation pass on to the next.
However, the modern historians are doing with Gnosticism what Baigent and Leigh did with the Dead Sea Scrolls and what Dan Brown did with Da Vinci: using it to revise our whole idea of Christianity. It was not Gnosticism, argues historian Sean Martin, that was the early heresy, but Nicea!
According to Martin, when the bishops and leaders of the fourth century church convened at Nicea in 325, they created a 'monster' which would control the minds of men and women for two thousand years. The 'monster' was the doctrine that Jesus was God, the orthodox faith of the Christian church.
But we got it all wrong then, and, says Martin, we are still getting it wrong. The Gnostics were much closer to the teachings of Jesus than the orthodox believers were; Jesus preached the Sermon on the Mount, while Paul preached Christ crucified. There is a huge difference, says Martin; which led to Paul being the real inventor of Christianity.
This could be dismissed as yet another door for heresy – which, of course it is – were it not for the fact that it is not just in order to revise history that Gnosticism surfaces nowadays. The tragedy is that our ultra-technological age, with all its sophistication and independence of any higher being, has developed its own brands and versions of the Gnostic myth.
It is still the case that the gurus of inner light are selling the possibility of deep knowledge; our churches may be emptying, but only because our yoga clubs and our self-help groups and our personal therapy courses are raking in millions. For the Gnostics as well as for twenty-first century man and woman, the problem is outside, and healing lies within.
That is not how the early Fathers read the situation; nor, it seems to me, is it how Jesus saw the situation. For the early preachers of the Gospel the problem was not external but internal: the fundamental need of man lies in the direction of his relationship with God. And for that to be righted, as the first step to salvation, man needs to go outside of himself, not deeper into himself. The solution lies in another person altogether: the person we call Jesus.
Of course, the modern purveyors of inner peace are happy with the revisionists who want to say that the Church taught the deity of Christ only for her own love for power. It's a bit like those who argue that the Church in modern Lewis wants the Sabbath kept just to retain her own control of society.
The revision is nonsense, of course. The Church's formulations at Nicea and Chalcedon were only a reflection of the clear statements of the prophets and apostles, all of whom testified to a Jesus who is equal with God in deity and equal with us in humanity.
And against that backdrop Gnosticism was clearly heretical; for all its appeal to the Scriptures, and for all its attraction to many second century Christians, it flew in the face of the testimony of the Bible and was therefore unable to deliver what it promised.
Actually, every attempt to revise the story convinces me it must be true. Why the quest for so many alternatives to the truth? Just because the truth is true. We may revise it and ignore it all we like, but it comes back to confront us all the time, and to challenge us as we go chasing after the purveyors of self-help therapy instead of to the physician of Gilead.
And isn't it tragic that the only heresy left is to call something a heresy? Just because it works for you, doesn't make it God. Pronounce the 'G'.