How confident can we be that Jesus Christ actually lived?
The historical evidence for Jesus of Nazareth is both long-established and widespread. Within a few decades of his supposed lifetime, he is mentioned by Jewish and Roman historians, as well as by dozens of Christian writings. Compare that with, for example, King Arthur, who supposedly lived around AD500. The major historical source for events of that time does not even mention Arthur, and he is first referred to 300 or 400 years after he is supposed to have lived. The evidence for Jesus is not limited to later folklore, as are accounts of Arthur.
Few people are citing Arthur as being definitely a real person. He's a mythological character. He's also set in a culture that didn't keep written records and set during a time of a number of conquests so records would have been patchy even if they existed, which they didn't. The comparison with ancient Rome, a highly literate and bureaucratic society that produced many thousands of miles of writing and numerous records of even the most trivial things, is silly.
What do Christian writings tell us?
The value of this evidence is that it is both early and detailed. The first Christian writings to talk about Jesus are the epistles of St Paul, and scholars agree that the earliest of these letters were written within 25 years of Jesus’s death at the very latest, while the detailed biographical accounts of Jesus in the New Testament gospels date from around 40 years after he died. These all appeared within the lifetimes of numerous eyewitnesses, and provide descriptions that comport with the culture and geography of first-century Palestine. It is also difficult to imagine why Christian writers would invent such a thoroughly Jewish saviour figure in a time and place – under the aegis of the Roman empire – where there was strong suspicion of Judaism.
Christian writing about Christianity is an unreliable source, especially that far back and during the period of time in which Christians were using political manipulation to conquer the Roman empire. Consider, for example, the matyrdom stories from a bit later. There's no reason to believe any of them are factual.
It's very easy to imagine why Christian writers would invent the most important thing for their religion, their saviour-god-man. It's also very easy to imagine why they'd invent the very thing that differentiated Christianity from Judaism, since there was damn all chance of Judaism conquering the Roman empire. The strong suspicion of Judaism isn't a reason why Christian writers wouldn't seek to differentiate themselves from Judaism. Very much the opposite.
What did non-Christian authors say about Jesus?
As far as we know, the first author outside the church to mention Jesus is the Jewish historian Flavius Josephus, who wrote a history of Judaism around AD93. He has two references to Jesus. One of these is controversial because it is thought to be corrupted by Christian scribes (probably turning Josephus’s negative account into a more positive one), but the other is not suspicious – a reference to James, the brother of “Jesus, the so-called Christ”.
About 20 years after Josephus we have the Roman politicians Pliny and Tacitus, who held some of the highest offices of state at the beginning of the second century AD. From Tacitus we learn that Jesus was executed while Pontius Pilate was the Roman prefect in charge of Judaea (AD26-36) and Tiberius was emperor (AD14-37) – reports that fit with the timeframe of the gospels. Pliny contributes the information that, where he was governor in northern Turkey, Christians worshipped Christ as a god. Neither of them liked Christians – Pliny writes of their “pig-headed obstinacy” and Tacitus calls their religion a destructive superstition.
Which is evidence of the existence of Christians and what they believed. Not evidence of Jesus. Including Tacitus' reference, which is a statement of what Christians believed and not a statement of historical records. Tacitus did not go to Judea and consult the historical records, nor did he send anyone else to do so.
Did ancient writers discuss the existence of Jesus?
Strikingly, there was never any debate in the ancient world about whether Jesus of Nazareth was a historical figure. In the earliest literature of the Jewish Rabbis, Jesus was denounced as the illegitimate child of Mary and a sorcerer. Among pagans, the satirist Lucian and philosopher Celsus dismissed Jesus as a scoundrel, but we know of no one in the ancient world who questioned whether Jesus lived.
Jesus was undoubtably a historical figure, but that doesn't mean he was a real person. King Arthur is a historical figure. Robin Hood is a historical figure. Historical figures don't have to be real. They just have to be believed to be real by enough people with enough power to make them of at least some historical importance.
Personally, I think there was a person of uncertain name who started a sect of Judaism unorthodox enough to spin off into a sequel religion. It had to start somehow and charismatic preachers are the usual way. But I don't think it's definitely proven.
