To begin, let’s look at what Pliny has to say about the christians he had to deal with:
They asserted, however, that the sum and substance of their fault or error had been that they were accustomed to meet on a fixed day before dawn and sing responsively a hymn to Christ as to a god, and to bind themselves by oath, not to some crime, but not to commit fraud, theft, or adultery, not falsify their trust, nor to refuse to return a trust when called upon to do so. When this was over, it was their custom to depart and to assemble again to partake of food–but ordinary and innocent food.
Note that there is no ‘Jesus of Nazareth’ to be found in the writing of Pliny. Just saying…
Ehrman quite rightly underscores this fact:
This is all he [Pliny] says about Jesus: the Christians worshiped him by singing to him. He does not, as you can see, even call him Jesus but instead uses his most common epithet, Christ. Whether Pliny knew the man’s actual name is anyone’s guess. One might be tempted to ask as well whether he knew that Christ was (at one time?) a man, but the fact that he indicates the songs were offered to Christ “as to a god” suggests that Christ was, of course, something else.
Indeed, we could further wonder whether these christians knew the Christ they worshiped by any another name, such as Jesus. Or whether they thought the Christ they worshiped had recently been crucified on earth (or more specifically Palestine) anytime in the previous 100 years.
That the few words Pliny records about his christians does absolutely nothing to say anything about an historical Jesus (let alone a ‘Jesus of Nazareth’ who’d been crucified) tells us quite a bit about the sort of thing that has to be accepted as evidence to make a case for a specific historical reality.
That even under torture Pliny couldn’t get such basic ‘facts’ about the supposed ‘historical Jesus’ tells us even more: there is perhaps a stunning ignorance among some who are called christians about the gospel narratives which emerged around this time. They seem to have no clue that Christ was named Jesus, that he was crucified, that he lived at a specific time in a specific place, or taught anything or warned about the coming ‘end of the world’.
Including Pliny on a list of ‘witnesses to Jesus of Nazareth’ seems rather like padding out the list.
I realize I should try to tease out more what an ‘historical Jesus’ entails: thus far I’ve only put a focus on the phrase ‘Jesus of Nazareth’ because that’s part of the title of Ehrman’s book. In the introduction Ehrman describes him:
How is it that a scarcely known, itinerant preacher from the rural backwaters of a remote part of the empire, a Jewish prophet who predicted that the end of the world as we know it was soon to come, who angered the powerful religious and civic leaders of Judea and as a result was crucified for sedition against the state – how is it that within a century of his death, people were calling this little-known Jewish peasant God?
Contrast this story to what information can be gleaned from Pliny – no Jesus, no apocalyptic preaching, no Judea, no Judaism, no crucifixion.
There’s a rather largish gap between the two. Yes, Pliny’s christians are worshiping a god they call christ, but there’s nothing that indicates recent Judaic roots.