system
A chat on subreddit /r/NoStupidQuestions
human
All accounts of Jesus come from after his lifetime. The gospels were mostly written before 100 AD, but well after the death of Jesus, Mark is dated 66-70 AD. None are thought to have been written by eye witnesses.

As for secular sources, Roman historian Josephus makes two references to Jesus in his work around 93-94 AD. One tells the typical narrative of Jesus taught by Christianity….. but many think that could have been faked: added to Josephus’s work by early Christians.

The other reference is most likely Josephus’s, but it roughly goes “James, brother of Jesus who was called the Christ…” and discusses James. 

So those who claim Jesus exists historically because Josephus wrote about him. Well… a possibly faked passage and a passing reference when talking about someone else, not to mention that it was written in 94 AD, isn’t exactly irrefutable evidence to say the least. Josephus was born in 37 AD, a couple years after Jesus was estimated to have died.

Roman senator Tacitus tells the typical Christian narrative in Annals, written in 116 AD. The authenticity of this is not really doubted. But, again, was written essentially a whole lifetime after  Jesus’s supposed death. (Tacitus wasn’t born until 25 years after Jesus supposedly died) 

Other Romans wrote about early Christians, like Suetonius, born in 69 AD, but did not write about Jesus himself.

There are other weaker Roman sources (Pliny the Younger, for example) and other sources, but the story is the same: sometimes it’s not even clear they’re discussing anything more than early Christians, not Jesus himself, and these people were all born after Jesus’s death.
gpt
This is a great write-up. Just to add though that Tacitus was referring to the fire of Rome when talking about Christians, which *did* occur during his childhood. He mentions that Christians were followers of Jesus and that Pilate had him crucified. 

Presumably, Tacitus had access to records that we don't, since he was one of the biggest names in the Roman government. That said, he does get Pilate's job title wrong iirc. 

Honestly, I'm of the opinion that Jesus existed, more through the critereon of embarrassment than anything else. (TLDR is why create a religion around a guy who died the most humiliating death possible, unless it was fairly widely known in the area so couldn't be denied?)

The story also just checks out in a lot of very plausible ways (apocalyptic preacher who recruits from the fishermen, who were being utterly fucked by the Romans. Speaks up about a lot of the ills in society at the time, becomes an inconvenience and gets killed). 

And the movement growing so quickly, to me at least, suggests that there was *some* person or event that it was based on. Even in Tacitus's adult life, there'd have been living witnesses to Jesus's teaching and the crucifixion. 

Any contemporary sources will be impossible to find for a number of reasons, from literacy rates to the fact that until the very end of his life, Jesus was just some guy. A gazillion people claimed to be the messiah. 

I don't buy into the miracles, resurrection and divine birth etc. But it just seems more likely than not, on the balance of evidence, that he existed.