There is no real silver bullet, dead cinch smoking gun, it really amounts to a "more likely than not" conclusion about a fairly minimal Jesus.

The most common points of evidence are:

• Paul's reference to "James, the brother of the Lord," in Galatians 1:19 and "the brothers of the Lord" in 1 Corinthians 9:5. Presumably, Paul would not call people Jesus' brothers unless Jesus actually existed.

• The fact of the crucifixion itself. There was no Jewish expectation or prophecy that the Messiah would be crucified. The crucifixion was an embarrassment (Paul himself calls it a "stumbling block to Jews") and is not something that is likely to have been invented about a fictional Messiah. It's like giving James Bond an erectile disorder.

• The progressive development of an early to high Christology. That is, Jesus gets more and more divine the later the writings get. The New Testament also shows stages going from Jesus being exalted as the son of God after his crucifixion (speeches given to Peter and Paul in Acts), to being adopted as the son of God at his baptism (Mark) then at birth (Matthew and Luke) and utimately eternally prexistent (prologue of John). This is a progression that would be expected from legendary accretions to a real person. An invented figure would be expected to divine from the start.

• Criteria of dissimilarity (or embarrassment) The crucifixion is the biggest example, but there are others. The baptism by John is another big one because it appears to put Jesus in a subordinate position to John and it implies he had sins. The evangelists also appear to become increasingly more uncomfortable with it. Matthew has John object and say Jesus should be baptizing him before Jesus gives him the go ahead saying they have to "fulfill all righteousness." Luke kind of tries to cough it into his hand:

"Now when all the people were baptized, it came to pass, that Jesus also being baptized, and praying, the heaven was opened (Luke 3:21).

He says that "Jesus was baptized," but avoids saying that anybody baptized him.

John's Gospel glosses the baptism out completely has the baptist declare Jesus "the lamb of God who takes away the sins of the world."

This apparent, progressive discomfort shows that the baptism of Jesus by John was probably already too well known to deny, so they just had to deal with it, A lot of scholars believe the baptism by John to be the second most certain fact about him after the crucifixion.

• Non-Christian mentions of Jesus in Josephus and Tacitus. Josephus has two relevant passages from Antiquities. The longer one, commonly referred to as the Testimonium Flavianum is universally regarded as at least partially forged, though many serious arguments are made for an authentic core (arguments can be seen in the link above as well as here. This passage is compromised and its evidentiary value is debated, but a second Josephan passage, though much briefer, is regarded as authentic.

Festus was now dead, and Albinus was but upon the road; so he assembled the sanhedrim of judges, and brought before them the brother of Jesus, who was called Christ, whose name was James, and some others; and when he had formed an accusation against them as breakers of the law, he delivered them to be stoned.

Scholars mostly accept this as authentic.

Tacitus was an early 2nd Century Roman historian who wrote the following in his Annals in reference to Nero scapgoating Christians for the fire of Rome:

Consequently, to get rid of the report, Nero fastened the guilt and inflicted the most exquisite tortures on a class hated for their abominations, called Christians by the populace. Christus, from whom the name had its origin, suffered the extreme penalty during the reign of Tiberius at the hands of one of our procurators, Pontius Pilatus, and a most mischievous superstition, thus checked for the moment, again broke out not only in Judaea, the first source of the evil, but even in Rome, where all things hideous and shameful from every part of the world find their centre and become popular. Accordingly, an arrest was first made of all who pleaded guilty; then, upon their information, an immense multitude was convicted, not so much of the crime of firing the city, as of hatred against mankind. Mockery of every sort was added to their deaths. Covered with the skins of beasts, they were torn by dogs and perished, or were nailed to crosses, or were doomed to the flames and burnt, to serve as a nightly illumination, when daylight had expired. Nero offered his gardens for the spectacle, and was exhibiting a show in the circus, while he mingled with the people in the dress of a charioteer or stood aloft on a car. Hence, even for criminals who deserved extreme and exemplary punishment, there arose a feeling of compassion; for it was not, as it seemed, for the public good, but to glut one man's cruelty, that they were being destroyed.

There is debate over whether Tacitus actually had independent evidence for his account of the crucifixion or whether he was just repeating what Roman Christians themselves were saying in Tacitus' own day. It's not the strongest rung on the ladder, but it's one of the most commonly cited.

The arguments don't end there, but begin to become weaker there, The end result is that Christianity more probably was inspired by the ministry and crucifixion of a real person than that it was completely mythological.

It should be said, that while there is a vast consensus that some kind of real Jesus existed historically, that does not mean they think that the Gospels are accurate depictions of him, but mythologized treatments after his death. They think Jesus existed, but that he was just a normal human, not a literal miracle worker or incarnate God.

My answer to the argument and evidence for the historical Jesus is in the FAQ.

But I want to take this opportunity to answer a slightly different question – why is Christ Mythicism all over the internet, and why don’t scholars take it seriously.

Among academics trained in relevant fields, i.e. 1st century studies of Roman Judea, with knowledge of Koine Greek, Hebrew, Aramaic, early Christianity, 2nd temple Judaism, Hellenic culture in the Near East, and historical methodology, zero academic historians find Mythicism compelling. It’s not even a disputed theory, it’s a non-starter. That’s how much disdain historians in this field have for Mythicism, and that’s why they don’t generally write about it.

But the internet is a different kettle of fish. It’s pseudo-democratised, and anyone with an opinion can write anything. Which is why conspiracy theories love the internet, and why Mythicism thrives online – because it’s a type of conspiracy theory.

Academics, in contrast, generally do not have strong online presences. Because for professional academics, online fora count for pretty much nothing in their professional-social identities. They write for other academics, that’s their peer community, and what counts are peer-reviewed publications, journal articles, books, etc.. Academically speaking, no one even cares that much if you write history books for the masses. Good on you, make some money, but it’s overall effect on your scholarly standing is very low. So there’s little to be gained for an academic by engaging on an academic level with Mythicism. There’s also little to be gained on a non-academic level by engaging with it either, because Mythicists tend to exhibit conspiracy-theory type psychologising and confirmation bias, and it’s incredibly difficult to persuade them that their wrong. The rabbit-hole gets deeper and deeper.

In recent years, only two academics have written books that treat Mythicisim head-on. One is Bart Ehrman, and his Did Jesus Exist? The Historical Argument for Jesus of Nazareth. Ehrman in his Introduction sets out why he felt compelled to write the book – the continuing stream of inquiries via email about whether Jesus existed, and a very large body of literature that makes the case that he didn’t, despite the fact that none of this literature is written by scholars trained in the relevant fields.

Maurice Casey also wrote a book, Jesus: Evidence and Argument or Mythicist Myths?, partly because he thought Ehrman did a ‘not-bad’ amateuresque job! In Casey’s view, Mythicists are fundamentalists. Atheist fundamentalists who were, usually, ex-Christian fundamentalists, and because of their fundamentalist mindset flip from that version of (American) fundamentalism to the equally but oppositely dogmatic Mythicist fundamentalism.

Casey’s book, by the way, is a fun read because he lays all sorts of smack-down all over the place. And for the Aramaic insights. So, academics have little to gain from engaging mythicists, little interest in writing populist material for the internet, and little respect for Mythicism in general. That’s why, in terms of the contemporary sociology of history, the internet has a slew of websites for Mythicism, and not that many that are dedicated to showing Mythicism is wrong, even though the consensus is, overwhelmingly, that Jesus was a historical figure.

Oop...Just found the FAQ with answers to similar questions regarding the historical Jesus. I'll leave this post for now in case it receives an answer that can supply some degree of insight that answers in the older posts didn't (as I suppose my question is slightly different to others and could receive a different sort of answer), but will delete it if recommended. Cheers.

Hi there, there is always more to be said on a topic such as this, but you may be interested in the "did Jesus exist?" section of our FAQ.