When we meet Jesus of Nazareth at the beginning of the Gospel of Mark, almost surely the oldest of the four, he’s a full-grown man. He comes down from Galilee, meets John, an ascetic desert hermit who lives on locusts and wild honey, and is baptized by him in the River Jordan. If one thing seems nearly certain to the people who read and study the Gospels for a living, it’s that this really happened: John the Baptizer—as some like to call him, to give a better sense of the original Greek’s flat-footed active form—baptized Jesus. They believe it because it seems so unlikely, so at odds with the idea that Jesus always played the star in his own show: why would anyone have said it if it weren’t true? This curious criterion governs historical criticism of Gospel texts: the more improbable or “difficult” an episode or remark is, the likelier it is to be a true record, on the assumption that you would edit out all the weird stuff if you could, and keep it in only because the tradition is so strong that it can’t plausibly be excluded. If Jesus says something nice, then someone is probably saying it for him; if he says something nasty, then probably he really did.

So then, the scholars argue, the author of Mark, whoever he was—the familiar names conventionally attached to each Gospel come later*—added the famous statement of divine favor, descending directly from the heavens as they opened. But what does the voice say? In Mark, the voice says, “You are my Son, whom I love; with you I am well pleased,” seeming to inform a Jesus who doesn’t yet know that this is so. But some early versions of Luke have the voice quoting Psalm 2: “You are my Son; today I have begotten you.” Only in Matthew does it announce Jesus’ divinity to the world as though it were an ancient, fixed agreement, not a new act. In Mark, for that matter, the two miraculous engines that push the story forward at the start and pull it toward Heaven at the end—the Virgin Birth and the Resurrection—make no appearance at all. The story begins with Jesus’ adult baptism, with no hint of a special circumstance at his birth, and there is actually some grumbling by Jesus about his family (“Only in his home town, among his relatives and in his own house, is a prophet without honor,” he complains); it ends with a cry of desolation as he is executed—and then an enigmatic and empty tomb. (It’s left to the Roman centurion to recognize him as the Son of God after he is dead, while the verses in Mark that show him risen were apparently added later.)

The intractable complexities of fact produce the inevitable ambiguities of faith. The more one knows, the less one knows. Was Jesus a carpenter, or even a carpenter’s son? The Greek word tekto¯n, long taken to mean “carpenter,” could mean something closer to a stoneworker or a day laborer. (One thinks of the similar shadings of a word like “printer,” which could refer to Ben Franklin or to his dogsbody.) If a carpenter, then presumably he was an artisan. If a stoneworker, then presumably he spent his early years as a laborer, schlepping from Nazareth to the grand Greco-Roman city of Sepphoris, nearby, to help build its walls and perhaps visit its theatre and agora. And what of the term “Son of Man,” which he uses again and again in Mark, mysteriously: “The Son of Man is Lord even of the Sabbath.” As Diarmaid MacCulloch points out in his new, immensely ambitious and absorbing history, “Christianity: The First Three Thousand Years” (Viking; $45), the phrase, which occurs in the Gospels “virtually exclusively in the reported words of Jesus,” certainly isn’t at all the same as the later “Son of God,” and may merely be Aramaic for “folks like us.”

Belief remains a bounce, faith a leap. Still, the appetite for historical study of the New Testament remains a publishing constant and a popular craze. Book after book—this year, ten in one month alone—appears, seeking the Truth. Paul Johnson has a sound believer’s life, “Jesus: A Biography from a Believer,” while Paul Verhoeven, the director of “Basic Instinct,” has a new skeptical-scholar’s book, “Jesus of Nazareth” (Seven Stories; $23.95). Verhoeven turns out to be a member of the Jesus Seminar, a collection mostly of scholars devoted to reconstructing the historical Jesus, and much of what he has to say is shrewd and learned. (An odd pull persists between box-office and Biblical study. A few years ago, another big action-film director and producer, James Cameron, put himself at the center of a documentary called “The Lost Tomb of Jesus.”)

What the amateur reader wants, given the thickets of uncertainty that surround the garden, is not what the passionate polemicists want—not so much a verdict on whether Jesus was nasty or nice as a sense of what, if anything, was new in his preaching. Was the cult that changed the world a product of Paul’s evangelism and imperial circumstance and the military embrace of one miracle-mystery cult among many such around? Or was there really something new, something unheard of, that can help explain the scale of what happened later? Did the rise of Christendom take place because historical plates were moving, with a poor martyred prophet caught between, or did one small pebble of parable and preaching start the avalanche that ended the antique world?

Ever since serious scholarly study of the Gospels began, in the nineteenth century, its moods have ranged from the frankly skeptical—including a “mythicist” position that the story is entirely made up—to the credulous, with some archeologists still holding that it is all pretty reliable, and tombs and traces can be found if you study the texts hard enough. The current scholarly tone is, judging from the new books, realist but pessimistic. While accepting a historical Jesus, the scholarship also tends to suggest that the search for him is a little like the search for the historical Sherlock Holmes: there were intellectual-minded detectives around, and Conan Doyle had one in mind in the eighteen-eighties, but the really interesting bits—Watson, Irene Adler, Moriarty, and the Reichenbach Falls—were, even if they all had remote real-life sources, shaped by the needs of storytelling, not by traces of truth. Holmes dies because heroes must, and returns from the dead, like Jesus, because the audience demanded it. (The view that the search for the historical Jesus is like the search for the historical Superman—that there’s nothing there but a hopeful story and a girlfriend with an alliterative name—has by now been marginalized from the seminaries to the Internet; the scholar Earl Doherty defends it on his Web site with grace and tenacity.)

The American scholar Bart Ehrman has been explaining the scholars’ truths for more than a decade now, in a series of sincere, quiet, and successful books. Ehrman is one of those best-selling authors like Richard Dawkins and Robert Ludlum and Peter Mayle, who write the same book over and over—but the basic template is so good that the new version is always worth reading. In his latest installment, “Jesus, Interrupted” (HarperOne; $15.99), Ehrman once again shares with his readers the not entirely good news he found a quarter century ago when, after a fundamentalist youth, he went to graduate school: that all the Gospels were written decades after Jesus’ death; that all were written in Greek, which Jesus and the apostles didn’t speak and couldn’t write (if they could read and write at all); and that they were written as testaments of faith, not chronicles of biography, shaped to fit a prophecy rather than report a profile.