Scholars disagree about how Jesus understood his life and his mission. Countless labels have been applied to him: cynic sage, apocalyptic prophet, rabbi, exorcist, Messiah. But everyone agrees that he existed, right?

Historians and religion scholars do. But a surprising number of people hold the view that the existence of Jesus is a myth: he is not just a heavily mythologized historical figure, but pure or nearly pure fabrication from start to finish. Jesus mythicists have a substantial web presence, and their views have been promoted in films such as Religulous and Zeitgeist.

It might seem best to ignore such fringe claims. But as we know from debates over evolution and other subjects, views that no expert finds persuasive can still have an impact on public discourse, education and much else.

As a group, the Jesus mythicists can seem like a strange mirror of the state of scholarly thinking on Jesus: the only thing they agree on is Jesus' nonexistence. Yet a few major trends are discernible.

One popular strand of mythicist thinking, associated with D. M. Mur­dock (and her pseudonym Acharya S), maintains that Jesus was invented on the basis of earlier deities, astrological entities and myths—in particular the ancient myths about dying and rising fertility gods. A viewpoint of this sort once had some currency among scholars, and in the 19th and early 20th centuries many people were attracted to the idea that Christianity owed much to non-Jewish religious figures and ideas. But along with acquiring more sensitivity to anti-Semitism, scholars encountered evidence for the diversity of first-century Judaism and were able to trace elements of Christianity to various Jewish sources—and so they discarded views similar to those now promoted by Murdock and other mythicists.

Another strain of mythicism views Jesus as a fictional creation based on Jewish scriptures. Noting the common Christian belief that Jesus was predicted in the Jewish scriptures, they reverse the relation and say that Jesus was invented on the basis of those earlier texts. Historical scholars see things very differently, pointing out the differences between the content of the supposed Messianic prophecies and the life of Jesus—thereby creating difficulties for conservative Christian apologists and mythicists alike.

Some mythicists, following the lead of Earl Doherty, think Jesus was initially understood as a purely celestial figure believed to have done battle with heavenly powers—and to have been crucified and buried somewhere other than on Earth. They make much of the relative paucity of references to the details of Jesus' life in the earliest sources, which are Paul's letters. They then dismiss or attempt to explain away the details of his life that are in the letters—mentions of his birth, Davidic descent, burial and a brother whom Paul says he met. Few letter writers in the ancient world (or today) stress the historical existence of the people they mention—but this ­doesn't seem to carry much weight with mythicists.

One of the poignant ironies about mythicism is its popularity among those who style themselves as freethinkers. Such individuals usually have no trouble criticizing apologists for young Earth creationism or other fringe viewpoints, spotting their weak arguments and taking them to task for rejecting mainstream science. Yet mythicists adopt many of the same weak modes of argumentation that they otherwise criticize.

Jesus mythicism serves as a cautionary tale. It is possible to think critically about a great many subjects and yet to shield one area from scrutiny. People tend to be selectively critical.

That is why the role played by the guild of scientists, historians and other experts is important. Critiquing unpersuasive ideas and arguments is the stuff that scholarly publication is made of. Scholarship thrives on critique: researchers try to come up with something new, while their peers subject it to critical scrutiny. In this context, an overwhelming consensus does not attain the level of certainty, but it is highly likely to be correct. And there is no disputing that the consensus among historians is that Jesus existed.

A significant number of Jesus mythicists appear to be former conservative Christians who have become atheists. Perhaps having been trained early on to think in all-or-nothing terms, they are now inclined to deny that the Bible was right about anything. Others may find it is far easier to view Jesus as a fabrication than to enter into the tumultuous waters of historical investigation.

It is easy—and to a certain extent appropriate—to dismiss mythicists and their pseudohistorical methods and claims. But there is a lesson to be learned from them. All people are prone to being deceived—and to deceiving themselves. Fervent belief can move us to offer an Amen before our minds have weighed or investigated claims. A desire for certainty can also lead us to seek simple answers, confidently offered, rather than the cautious and heavily qualified answers that experts give. But the cautiousness of experts doesn't indicate a lack of confidence in their methods or conclusions. It reflects the humility that comes with awareness of complexity.

Did the historical Jesus exist? His­torical study can only say "probably," but in this instance it says it with a high degree of confidence. Mythicists are never able to come up with a scenario in which it is probable that one or more Jews invented a figure that they claimed to be the anointed one, the descendant of David who would restore the kingdom of his ancestor; that, furthermore, they invented the claim that this figure had been crucified by enemy powers; and that they proceeded to try to persuade their fellow Jews to believe their message about this Messianic figure, so at odds with Jewish expectations.

Is that version impossible? No—very few things are. But the fact that something isn't impossible doesn't make it likely. Professional historians use historical tools to answer historical questions, and their best estimation is far more likely to be on target than that of nonexperts who reject scholarly consensus in favor of their own preferences.