He is my favourite subject, academically and personally, but popular accounts of the "historical Jesus" are getting tedious, and some of them are giving history itself a bad name.

Hardly a month goes by without a media outlet announcing something "new" about Jesus. Some half-qualified scholar tells us how the original Jesus was, unsurprisingly, quite unlike the figure of the Gospels. He was married, he was gay, he was both, he never existed, he was peaceful, he was violent, and on and on it goes.

The most recent effort is Reza Aslan's Zealot: The Life and Times of Jesus of Nazareth . Typical of this genre, the author's principal credentials are not in ancient history, classics, New Testament or Jewish studies - the directly relevant disciplines. Instead, he has a PhD in the sociology of religion and is a "professor of creative writing," which explains both the riveting prose and eccentric content. The mismatch between Aslan's grandiose claims and his limited credentials in history is glaring on almost every page. The sizable bibliography and notes are no substitute for formal training - as is equally well-attested in the similarly blustering works of fundamentalist Christian apologetics.

Naturally, everyone is allowed to express a view on historical matters. All I am saying is that not everyone is allowed to claim the mantle of "expert" in what is a vast and highly specialized field of academic enquiry, in which Aslan has not contributed a single peer reviewed article, let alone monograph.

Aslan's new old thesis

The thesis of Aslan's book is as simple as it is fragile. Jesus was a nationalistic revolutionary - a "zealot" - with ambitions to oust the Romans from Palestine and establish himself as a temporal king. He got himself crucified because he and his followers posed, or claimed to pose, a violent threat to Rome. The "redeemer Jesus" who died and rose again and who taught us to love all-and-sundry was, predictably enough in this sort of literature, a later invention of none other than that biblical whipping boy, the Apostle Paul. We shouldn't miss the humour of Aslan's contention, though. Typically, popular writings argue that Paul distorted Christianity by making the message of Jesus narrower and meaner. Aslan effectively has Paul making Jesus much more open and friendly!

The best that can be said for Aslan's thesis, apart from the lovely writing, is that brilliant and qualified persons have argued it before, most notably the famous German professor of Near Eastern culture Herman Samuel Reimarus, in 1768, and the British priest-theologian Samuel Brandon who tried to revive the thesis in the 1950s and 60s.

Two-and-a-half centuries ago, Reimarus observed what is now Roman-East relations 101: some Jews didn't like the Romans in the Holy Land and occasionally tried to get rid of them through military means (Reimarus thought Jesus was one of them). There is debate about the extent of such rebel movements before the outbreak of the war with Rome in AD 66, but it cannot be doubted that some of Jesus's contemporaries were revolutionaries.

But that is where the good history stops. In order to move from the bleeding obvious (that some Jews were freedom-fighters) to the utterly implausible (that Jesus was one of them), Aslan takes several false steps, all of which involve as much creativity as history.

Exaggerating the historical context

First, there is the exaggerated depiction of Jesus's homeland as a place brimming with insurrection and crazed prophets of doom. Scholarship over the last four decades, ever since Martin Hengel's seminal work, has concluded that "zealotry" in Palestine was a limited, if contiguous, set of movements through the first half of the first century. More recent work, such as that of Martin Goodman and Geza Vermes of the University of Oxford, call into question any Sunday school notions that Jesus was pretty much the only peace-loving guy in a nation of Roman-haters. This same body of work undermines Aslan's inflated portrait of seething political unrest in first-century Judea and Galilee.

And what of these crazy prophets of doom we hear about? Were they popping up behind every fig tree and olive grove? As evidence, Aslan cites the ancient Greek intellectual Celsus who tells us of untold numbers of holy men in Jesus's day declaring:

"I am God, or the servant of God, or a divine spirit. But I am coming, for the world is already in the throes of destruction. And you will soon see me coming with the power of heaven."

This quotation appears on the first page of his book and has been quoted in at least two of Aslan's media appearances that I have seen. It seems to be important. As history, it is a crock.

For starters, Celsus is almost certainly exaggerating and very probably lying. No one thinks a Jewish prophet of this period (or any period) would declare "I am God" or "I am a divine spirit" - not even Jesus is quoted as saying that! But even if we imagined that Celsus spoke sincerely and accurately, his tract against the Christians, from which this quotation comes, was written around AD 180, one hundred and fifty years after Jesus.

How can this be trusted? Aslan invites suspicion about the Gospels, written 40-70 years after Jesus, and about Paul's letters, written 20-30 years after him. Here, he expects us to take seriously a piece of anti-Christian apologetic written outside of Palestine a century-and-a-half after the fact. Coming as it does on the first page, this quotation does not inspire confidence.

Misunderstanding crucifixion

A second plank of Aslan's theory is that crucifixion was a punishment reserved for political criminals - Jesus must therefore have been a revolutionary. This takes a half-truth and runs into fantasy. All scholars agree that, since the crucifixion of Jesus is beyond doubt, any historically plausible portrait of Jesus must present him as "crucifiable." But Aslan's problem is twofold.

First, it just isn't true that winding up on a Roman cross points directly (or indirectly) to insurrection. One only has to dip into the scholarship on crucifixion to discover that, while this particular form of capital punishment was generally considered the worst of all death penalties, it was not "reserved" for a particular set of crimes. Romans employed this grisly penalty to shame victims and their associates and to offer a public deterrent. It was thus used against disobedient slaves and robbers, as well as against insurrectionists and traitors of various kinds. The mere fact of Jesus's crucifixion cannot stand as evidence that he was a seditionist.

Indeed, thirty or so years after Jesus a large group of Christians was also crucified by Nero. The emperor accused them of lighting the great fire of Rome. To be sure, such an act of vandalism would have been seen as rebellion, but the point here is that no one (in ancient Rome or in modern scholarship) believed the Christians lit the fire or that they were insurrectionists in the political sense. By the AD 60s they were already well and truly under the influence of all that "love the enemy" stuff that Aslan imagines later Christians invented. Thus, even if Aslan is right that crucifixion was only used against those accused of formal sedition (which no one but Aslan believes), here is clear evidence that crucifixion cannot stand as evidence of actual rebellion.

Secondly, and more to the point, countless scholars from within the relevant disciplines are amply satisfied that there are straightforward explanations of the fact that Jesus of Nazareth ended up on a Roman cross. And none of them involves trampling on the range of evidence in our possession that Jesus eschewed violence on behalf of the kingdom of God.

Specialists as diverse as James Dunn from the University of Durham and Paula Fredriksen of Boston University (now at the Hebrew University of Jerusalem) agree that Jesus's public demonstration against the Temple, overturning the tables of the money-changers and calling the Jewish elite a "den of robbers," was the climactic cause of Jesus's execution. The temple authorities could easily argue to the Roman prefect Pontius Pilate that such a public demonstration was likely to excite the crowds and disturb the peace, especially during the enormous Passover festival.

Reza Aslan agrees that the Temple incident precipitated Jesus's arrest, but he interprets it in an almost Sunday school fashion, as an act of violence and a direct challenge to Rome. But a clear consensus of scholarship reads the temple incident not as an act of violence or an attack on Rome (or even the Temple) but as an "enacted parable" or "prophetic sign" in the tradition of Jewish prophets centuries before Jesus.

Hosea married "an adulterous wife" named Gomer - something that was unthinkable under normal circumstances - as a sign that Israel had betrayed her divine husband. The prophet Ezekiel built a miniature siege works in a public court and "attacked" it to signify Jerusalem's destruction. He ate bread cooked over excrement as a picture of the coming defilement.

All of this lies behind Jesus's prophetic symbol of overturning the tables of the money-changers. And the people of his day knew precisely what he was doing: he was not "attacking" anyone, but rather "enacting" God's displeasure against the Temple system. That Aslan doesn't bother to interact with the vast scholarship on this matter continues a disturbing pattern.

Other factors no doubt contributed to Jesus's execution as "King of the Jews" - including and especially his "royal" entry into Jerusalem riding on a donkey (something Fredriksen, among others, has articulated). But it was his "prophetic theatre" in the Temple courts that constituted his most dramatic challenge to authority - and the challenge, it is clear, was to the Jewish Temple elite not the Roman overlords. "The gun may already have been cocked," wrote Duke University's Ed Sanders, a leader in the field for several decades and no friend of orthodox Christianity, "but it was the temple demonstration which pulled the trigger." Aslan does not endeavour to overturn this near-consensus of historical Jesus studies. He simply offers his rebel thesis as a "solution" to a non-existent "problem."

Evidence and conspiracy theories

A third problem with Aslan's revival of Reimarus's thesis is that no one seems to have remembered it. There is not a scrap of real evidence that any Christian traditions - any traditions at all - recalled Jesus urging rebellion toward Rome. Where are the stray sayings of Jesus that imply insurrection? Where are the hints in Josephus or Tacitus? There is simply nothing.

Aslan thinks he finds a hint in Matthew 10:34, the opening quotation of the book: "Do not suppose that I have come to bring peace to the earth. I did not come to bring peace, but a sword." Quoted on its own and put on the lips of some other first-century figure, this might read like a call to arms. But I would wager my annual book allowance that 99.9% of specialists in the field would echo Ulrich Luz, perhaps the leading authority on the Gospel of Matthew today, that "our saying does not reveal a revolutionary Jesus. The immediate context, vv. 35-36, makes this interpretation impossible." In this passage, Jesus is speaking in classic Jewish imagery of the dividing lines his message will bring among families. This is exactly what the following verses go on to say. But by ignoring evidence that doesn't fit and stretching evidence so that it appears to fit, Aslan is able to make the "impossible" a reality: the sword statement, he assures us, is a relic of an earlier revolutionary Jesus.

All of the "love" sayings, by contrast, were either inventions of the Gospel writers or originally focused on the love of one's fellow disciple and collaborator against the powers. Aslan insists, "After the Jewish revolt and the destruction of Jerusalem (in AD 70) the early Christian church tried desperately to distance Jesus from the zealous nationalism that had led to that awful war." This is pure revisionism that gains its plausibility in the way doubts about the 1969 lunar landing do.

Aslan's thesis requires us to believe that the Gospel writers were crafty enough to invent a Jesus who regularly called for humility, service and the "love of enemies" but stupid enough to leave traces in their works of a Jesus who endorsed fighting Roman enemies. It's the stuff of conspiracy theorists: dismissing evidence that contradicts your theory as "manufactured," while simultaneously interpreting the massive lack of evidence as proof of suppression.

The discipline of history cannot work like this. Rarely can a theory be taken seriously that is not based on evidence attested across sources. Deleting, cherry-picking and imagining are no substitute for the even-handed sifting of evidence that characterizes historical enquiry. This is why almost no one followed Reimarus back in the eighteenth century and why Brandon's revival of the thesis in the mid-twentieth century is typically found today only in a footnote. I predict Aslan's work won't even find its way there.

Worse for Reza Aslan, there is overwhelming positive evidence that Jesus, far from being a closet zealot, directed his teaching against that tradition. That his message focused on love and, in particular, love of the unlovely and the enemy, is richly attested across the historical traditions left behind by those closest to him.

This is not a case of looking up Bible verses and choosing our favourite ones. The study of the historical Jesus is a fundamentally "secular" discipline, applying the same tests of historicity one finds in all historical investigation. A key criterion is known as multiple attestation, which affirms that when multiple sources independently offer roughly the same portrait of a person or event from the past, that portrait takes on greater plausibility.

And here is where Aslan's theory must finally give up. Few contemporary scholars - whether Christian, Jewish or non-religious - doubt that the New Testament sources (known as Mark, Q, L and Paul) were written independently of each other: in other words, the authors of these texts did not have access to the writings of the others. Just as few specialists would dispute that all four of these sources portray the message of Jesus as involving a radical ethic of non-violence, inclusivity and love. The source known as Q, dating from around the 50s AD, even contains a story of Jesus' compassion toward a Roman soldier and his scolding of Israel for not having the faith of this pagan overlord.

All of this gives the competent historian a high degree of confidence that, whatever else may be doubted about him, Jesus was about as far from being a political revolutionary as a first-century Jew could be.

Litany of errors

Finally, the list of exaggerations and plain errors in Zealot bear testimony to Aslan's carelessness with concrete history. If this were presented as a work of fiction, there would be no shame in such oversights. But if this were handed in as an essay in an Ancient History Department, it would most likely fail, not just because of the numerous inaccuracies, but because of the disturbing confidence with which they are habitually stated.

Aslan repeatedly calls revolutionary leaders of the first century "claimed messiahs," when this crucial term hardly ever appears in our sources and certainly not in the contexts he is claiming.

Aslan pontificates on questions such as Jesus's literacy (or illiteracy, in his judgment) with a cavalier style that does not represent the complexities involved.

He rushes to dismiss some Gospel passages as "fabulous concoctions" while accepting others as "beyond dispute" - and the only rhyme or reason I can detect is whether a passage fits with the story he wishes to tell.

He informs us that Mark's Gospel says "nothing at all about Jesus's resurrection," overlooking the plain narrative signals of Mark 14:28 and 16:7.

He declares that Mark's portrayal of Pilate's prevarication over the execution of Jesus was "concocted" and "patently fictitious." We are told that this Roman governor never baulked at dispatching Jewish rabble-rousers. This overlooks the widely-discussed evidence that Pilate did precisely this just a few years earlier with some Jewish leaders from Jerusalem.

Weirdly, Aslan says in passing that the letters of Paul make up "the bulk of the New Testament." In fact, they represent only a quarter.

He dates the destruction of Sepphoris near Nazareth to the period of the tax rebellion of AD 6, when in fact this city was destroyed by Varus a decade earlier in the troubles following Herod's death in 4BC.

He says that the traditions of John the Baptist were passed around in writing in Hebrew and Aramaic throughout the villages of Judea and Galilee. This is baseless.

He claims that Stephen, the first Christian martyr, was from the Hellenistic diaspora (and was therefore liable to fall for the un-Jewish perversion of Jesus's message he heard in Jerusalem). This is pure invention, and overlooks the fact that many Greek-speaking Jews like Stephen lived in Jerusalem for generations. They even had their own Greek-speaking synagogues.

Aslan's claim that "the disciples were themselves fugitives in Jerusalem, complicit in the sedition that led to Jesus's execution" is disproven by the complete absence of evidence for any Roman attempt to arrest the followers of Jesus. Indeed, this is one of the reasons specialists remain confident Jesus was never viewed as the leader of a rebel movement.

He says a certain Jesus son of Ananias, a prophetic figure who appeared in Jerusalem in the early 60s AD, spoke about the appearance of the "Messiah." Our sole source (Josephus) says nothing of the sort.

Aslan avers that even Luke, a Pauline "sycophant," avoids calling Paul an "apostle" since only the twelve bear the title that Paul so desperately tried to claim for himself. In fact, Luke happily calls Paul and his colleague Barnabas "apostles" (Acts 14:14). Almost everything Aslan says about Paul and his place in ancient Judaism and Christianity is either wildly exaggerated or plainly false.

I could go on, but it would begin to look impolite

Damaging history

The most disappointing thing about the fanfare accorded to a book like Zealot is not that it will undermine the Christian faith (it will not); even less that it poses a challenge to the consensus of working scholars (it certainly does not). It is that it chips away at the public's confidence in history per se.

For a brief moment, Reza Aslan will be heralded as a breakthrough author. In a month or so, some other theory, equally unsubstantiated and certainly contradictory, will get the same kind of airtime. Such works are generally ignored by working scholars, who tend to be suspicious of anything that bypasses the peer review process.

The general public, however, over time experiences breakthrough fatigue - an increasing contempt coupled with a decreasing curiosity toward any new claim about the man from Nazareth. The net effect is a weary scepticism that we can know anything about the historical Jesus or about history at all.

The Jesus depicted in Zealot is certainly a figment of the imagination of a professor of creative writing, but he is likely to do concrete damage to the public's appreciation of a vast and worthwhile academic discipline. Aslan's Jesus is giving history a bad name.

John Dickson is an author and historian specializing in early Jewish and Christian history. He is a director of the Centre for Public Christianity and Honorary Fellow of the Department of Ancient History, Macquarie University.