The earliest complete Josephan manuscript we have is from the ninth century(page 398 in The Reliability of Josephus: Can He Be Trusted?) copied countless times from the original to our earliest copies by Christian scribes over a span of some 700+ years or so. Of course, this makes accidental and deliberate interpolation (additions to the text) possible.
Josephus is known for two (apparent) mentions of Jesus: the Testimonium Flavianum and in one brief passage where a certain James who was stoned is said to be “brother of Jesus, called Christ.” Both suffer a double dilemma: a case against their authenticity: that they were interpolated— added later to the text — and they are insignificant; that even if authentic they do not constitute evidence for the existence of Jesus.
Let’s take a look at the James passage first:
And now Caesar, upon hearing the death of Festus, sent Albinus into Judea, as procurator. But the king deprived Joseph of the high priesthood, and bestowed the succession to that dignity on the son of Ananus, who was also himself called Ananus. Now the report goes that this eldest Ananus proved a most fortunate man; for he had five sons who had all performed the office of a high priest to God, and who had himself enjoyed that dignity a long time formerly, which had never happened to any other of our high priests. But this younger Ananus, who, as we have told you already, took the high priesthood, was a bold man in his temper, and very insolent; he was also of the sect of the Sadducees, who are very rigid in judging offenders, above all the rest of the Jews, as we have already observed; when, therefore, Ananus was of this disposition, he thought he had now a proper opportunity. Festus was now dead, and Albinus was but upon the road; so he assembled the sanhedrin 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: but as for those who seemed the most equitable of the citizens, and such as were the most uneasy at the breach of the laws, they disliked what was done; they also sent to the king, desiring him to send to Ananus that he should act so no more, for that what he had already done was not to be justified; nay, some of them went also to meet Albinus, as he was upon his journey from Alexandria, and informed him that it was not lawful for Ananus to assemble a sanhedrin without his consent. Whereupon Albinus complied with what they said, and wrote in anger to Ananus, and threatened that he would bring him to punishment for what he had done; on which king Agrippa took the high priesthood from him, when he had ruled but three months, and made Jesus, the son of Damneus, high priest. (AJ 20.9.1)
Josephus discusses many characters who may well be messianic figures, like Jesus ben Ananias, but he does not call them “christ,” and historians feel that Josephus does not generally speak about messianic things so as not to upset his Roman peers. That general fact about Josephus (a) outlines a strong case for the ‘christ’ passages being interpolated. Interpolation is also supported by (b) Josephus’ comment that many high and mighty Jews were outraged over James’ death, an improbability if the James in Josephus passage was a leader in a fringe sect (as Christianity was at the time). (C) Other Christian traditions about James the Just as well as the book of Acts show no knowledge of this event, just as if it Josephus‘ comment about James “called Christ” was a later interpolation and not what really happened to the Christian James (the text with that phrase removed would render this James the brother of Jesus son of Damneus, mentioned in the context of the passage). Additional reasons for suspecting the passage is a forgery can be found in Carrier, Efron, and Allen. One especially strong argument from Efron for the entire passage being interpolated is quoted from the previous link:
First of all, the unfavorable portrait of Ananus is in polar opposition to the admirable personage which Josephus, in Jewish War overwhelms with praise, and devotes an emotional eulogy to, with not the slightest hint of religious deviance or Sadduceeism. It is true that opinions and evaluations sometimes change in Josephus’ second and more critical version. Thus, in his apologetic autobiography, Josephus in self defense somewhat dims Ananus’ lustre, but there is no trace of a diametrically opposite view of him. Acts of the Apostles, however, in a picture resembling the dubious episode outlined above, stresses the unfavorable aspects of Ananus (Annas) the high priest, and his Sadducee retinue, avidly persecuting the Christians without pity. (334)
Strong as a case for interpolation is, Points A-C could also be understood as evidence for Robert M. Price’s theory (outlined in The Case Against the Case for Christ p.103-5) that Jesus ben Damneus was the ‘christ’ in question and not Jesus of Nazareth. Ben Damneus was a high priest, an anointed one and therefore a ‘christ.’ If Josephus called Ben Damneus ‘christ’ even in spite of not typically using the word, it could be to give the word ‘christ’ a more positive connotation than the typically rebellious christs known to romans. Point B is explained by Price’s theory because Jesus of Nazareth was not intended and instead a to-be high priest was (It makes more sense for these righteous Jews to be upset at the death of the brother of the new high priest Ben Damneus instead of Jesus of Nazareth) (C) happened because Christians of the time would have had less reason to mistake this James as their James (belonging to the same time and culture and therefore not seeing ‘christ’ as a solid identifier since many people were indeed ‘christs’ or anointed ones) or perhaps not knowing of the James passage or thinking it was a James of theirs, so they formed no stories similar to Josephus’. I favor interpolation, but both Carrier’s/Efron’s and Price’s hypotheses outcompete the standard hypothesis that Josephus spoke of the Christian James.
The Testimonium Flavanium, the longer passage about Jesus, also has been suspected a later interpolation by many, and for very good reasons (see the previously cited work from Allen). But the reasons for that are well trodden territory. “Josephus” names no source for this information, which damages its value. What is the best inference we can make concerning the source of information for the TF? It has over 20 similarities with the gospel of Luke and therefore Josephus, at best, is simply passing on information from Christian sources. But it’s worse than that, because Josephus also mentions a historical Hercules (here) and most tellingly seems to say here that Hercules married a granddaughter of Abraham (Aphra’s daughter; Apher, perhaps a slight variant spelling or masculine form is mentioned in the same passage as a son of Abraham through his wife Ketura). Fact is, Josephus did not have a “magic decoder ring” that allowed him to infallibly tell who was mythical and who was not, and the only chance we get to test his judgement, he fails. It is even worse than that, because of course Josephus also accepts Adam, Noah, Abraham, Moses and other Old Testament characters without a whiff of skepticism though critical scholarship as acknowledged them as mythical since the 70’s.
Of course, one might object that since each of those people allegedly existed in the far distant past and perhaps it would be far harder for Josephus to believe in a mythical person invented in his own century. To paraphrase Robert M. Price, it would not be much easier for Josephus to tell whether or not Jesus was historical than it is for us now! He is right. The gospel of Mark was written outside Palestine, in Greek (not the same language spoken by 1st century Palestinians which was a form of Hebrew called Aramaic) some forty years after the events in question in a time when people had far lower lifespans than today and outbreaks of violence and famine had killed many in the intervening time. Additionally, many Jews were “scattered around” during the Diaspora and had to find a new place to live. Investigating the gospel events would have been damned hard even from the time Mark put pen to paper and would have gotten harder each year as living eyewitnesses would have gradually died off, among other issues. Moreover, no one, least of all Josephus, ever details having done a hardcore FBI level investigation of earliest Christian beliefs or what their results were, nor is very plausible anyone had the time, know-how, or motive to. As such, a mere sixty years between Josephus’ writing and Jesus’ alleged lifespan is not too little time for a legend to emerge. Especially not given the fertile ground present for such a legend; Josephus mistaking a fictive earthly narrative about Jesus for a history would only place him among the ‘outsiders’ to whom “all things come in parables, so that ‘Seeing they may see and not perceive, And hearing they may hear and not understand’…” (Mark 4:11-12)
Most important to all of this is that the latest peer-reviewed assessment of the extrabiblical evidence for Jesus (written by a historicist!) is largely in agreement with the worthlessness of it, and even in agreement that both passages we have discussed are interpolated (added later, forged). Chris Hansen writing for the American Journal of Biblical Theology Feb. 2021:
“In what follows, I will make the case that the extrabiblical evidence is likely not that useful for establishing that Jesus did, in fact, exist as there are numerous epistemological problems with all of it, but that it does, however, aid historicists more than those who challenge the historicity of Jesus in one very important respect: it demonstrates that early Christians were not believing in a celestial Jesus, but one who had lived as a historical person on Earth.” (p.4)
“To begin, we can look at what I would consider the reconstructed sources, these being in the Testimonium Flavianum (TF) and book 20 of Antiquities by Josephus (Antiquities of the Jews 18.3.3 and 20.9.1 respectively). While many academics would regard these as authentic, the present author does find it likely that these were wholesale interpolations in the work of Josephus, based on the arguments of Ken Olson, Ivan Prchlík, and N. P. L. Allen.” (p.6)