We do know of some historians who's work has survived, and lived in the area at the time of the events in question. Philo of Alexandria is one such example, he is a noted Roman Historian with ties to the Royal House of Judea and almost certainly would have been in Jerusalem at some points during the lifetime of Jesus. Yet, no mention is made of Jesus at all in his works.
That's puzzling, as even if he didn't follow Jesus, he would have certainly written about a man who lead such a popular movement. He wrote about, and we still have records of much less important local holy men or false prophets. In Jesus case, the whole town showed up to meet him, and things culminated in an illegal trial in front of the Roman Governor himself, and execution, and then he rose from the dead. No historian would have totally ignored a major incident like that.
Philo is the most notable example, however there are other contemporary historians who should have had some knowledge of Jesus if the gospel stories are true, and we have nothing more but silence from them as well.
In essence, we have some notes from historians decades after the fact, far removed from the time or place, and they usually are only relaying beliefs that Christians at the time held. It's also worth noting that even these historians were either Pagan or Jewish, so even being a couple decades removed from the events in question, they heard the stories and didn't think they were credible either, or they would have become Christians themselves.
The historians at the time had no idea of the events in question. Meaning they were either fabricated, or Jesus was such a minor figure that he wasn't noticed by any significant number of people. Even if it's option #2, that wipes out huge key chunks of the gospel narrative.
This is patent nonsense.
Philo is not a Roman Historian, but an Alexandrine Jewish Philosopher. He wrote a number of Torah commentaries in Greek, works on Stoicism and Hellenistic philosophy from a Jewish perspective, and two fragmentary contemporaneous pieces - The latter two is the only thing partially extant even close to perhaps 'history writing', but neither are Hellenistic histories.
These are Against Flaccus and the Embassy to Gaius (Gaius being Caligula's real name). The former is a complaint on the Roman treatment of Alexandrine Jewry; and the latter an account of the madness of Caligula as a method to complain of the bad treatment of Alexandrine Jewry by Rome. We are lucky if Philo even mentions Jerusalem therein, which he does once or twice - for instance to complain of Pilate bringing in votive shields, and juxtaposing this to Caligula wanting his statue placed in Synagogues. Philo fails to mention major events in Judaea, disturbances with Parthia, even an possible uprising in Upper Egypt! It is simply irrelevant to his narrative. There are also major discrepancies between his two accounts. You would not expect him to have mentioned Jesus, so this is absolute nonsense to try and use this as justification for discounting Gospel events. Philo mentions Therapeutae (who may be a form of Essene) and a few minor prophetic candidates - but because they were Egyptian and relevant to his narrative or his philosophy. Jesus would not be. The text is widely available in Classics archives.
So who are all these phantom historians that should have mentioned events in 1st century Judaea, but failed to? Our only real sources here are Josephus and a short summary by Tacitus. Judaea was a backwater Roman province, the only reason they cared was strategic - as it held the flank of Syria to the Parthians, and the land route to Egypt. To expect Roman writers to mention it frequently is ludicrous - now you want them to mention one prophet from there, of many, specifically? This is the equivalent of wanting 19th century British writers to have written on the internal affairs of the Mpondo tribe in Pondoland in Africa. They would only do so if relevant to their own history - as the British write on the Anglo-Zulu war for instance, or Romans write on Judaea about the First Revolt or when there was need to oppose Parthia.
So broadly, our only sources for the period in Judaea is Josephus, the Gospels and Acts, a summary of Roman intervention by Tacitus, and a few random mentions - like Pliny talking of the Dead Sea and how Essenes lived around there with their funny antics, akin to how we might write about Amish or Buddhist monks in travelogues or National Geographic.
So, you wouldn't expect Tacitus to mention Jesus here - though he does elsewhere say he was crucified under Pilate - as he is writing a short summary on military intervention prior to the Jewish War by Syrian governors.
So at heart, we only have Josephus' lack to account for. Josephus however does mention Jesus in the Testimonium Flavium, though corrupted by a redactor. The lost original form most definitely mentioned Jesus, as he goes on to mention James his brother, later. There is even a more neutral Arabic translation of Josephus that may in fact closer represent the original. Josephus was a Pharisee though, who is an opponent of Jewish Messianism in general - his whole account is Pro-Roman propaganda, trying to excuse the Flavians and simultaneously the Jews for revolting, by painting earlier Julio-Claudian governors in a bad light. Again, the Gospel narrative doesn't fit his schema; and we also know Josephus ommited inconvenient things - such as Claudius expelling the Jews from Rome.
The idea that other extent historians should have mentioned the Gospel events is simply untrue. Potentially, we do have fragmentary or quoted writings that may do so in part, but they aren't clear enough to call in isolation - such as Thalles or Phlegon as mentioned above, the Babylonian Talmud's 'Yeshu on a Tree', or Ben Serapion. Just having miracles isn't enough. Hellenistic writings were full of the stuff, from Appolonius of Tyana, to Scipio's Imagines talking to him, to the dead rising before the battle of Pharsalus in Lucan, to omens around Livia, to chasms swallowing men whole like Marcus Curtius.
This is merely a silly argument made and believed because people no longer read classics; or involves serious misrepresentation, obfuscation or being disingenuous, like when Carrier attempts to discard Josephus - literally our only real extra-biblical source, just because it agrees quite well with mentioned things in Acts and such.
The Gospel of Thomas is widely dated to the first century, the view that it quotes the Diatesseron is the opinion of Nicholas Perrin, who's theory has been examined and discredited by other historians. It is far from a consensus historical view, in fact Perrin is the only person who's ever really promoted that idea.
No, the Gospel of Thomas as we have it now is dated to the 4th century. Certain Logia it contains have been found in the Oxyrhyncus Papyri from the 2nd century, but in a different order and certainly not all of it. These are anyway less controversial logia to boot. So the Gospel of Thomas draws on 2nd century material, perhaps even 1st century as some hypothesise an oppositional relation to the Gospel of John, but most certainly represents a later redaction and expansion of material. It is not a first century source.
