I don't follow this. If the Diatessaron was written about 160 AD and it is what it is believed to be, a harmonization of the four Gospels that made it into the NT, the the four Gospels existed before that date.
Is your point that the Diatessaron may not have been written in 160 AD? OK, but that doesn't make the statement wrong it just invalidates the use of the Diatessaron as evidence for the Gospels before 160 AD.
Yes. I am suspicious about all dates which come from bible scholars, theologians, and Christian writers.
I was not always suspicious about those dates. But the more I see & read in HJ threads like this, and the more sceptic books I have read trying to check any of this, the less I think we can trust the accounts presented by theologians or bible scholars such as Bart Ehrman, and that includes the dates they quote for any of this early writing in support of a real HJ.
But even if there was canonisation of four selected gospels by 160AD, that is now a very long time after the period of 26-26AD when Pilate was said to be the governor of Judea.
I tried to run down how reliable the Diatessaron date was before I made the post about it, but I didn't succeed. Do you have an idea that it was written later than the generally accepted date? Even without that evidence it looks like that available evidence suggests that the latest date for the creation of at least one of the Gospels might be around 130 AD. There is, at least, the mention by Papias in the list that Kapyong provided and Marcion's writings which are dated to between 130 and 140 on the Early Christian Writing site. Also Marcion was expelled from the Catholic church for heresy in 144 and presumably his writings were complete by then.
Well, again, 130AD is the sort of date that I already suggested for the first gospels (before Kapyong posted the list), and that’s a far cry from claims that people would have known g-Mark by about 75AD and thus should have spotted any mistaken claim there saying Pilate was governor only 40 years earlier. Now, instead of 75AD, we are talking about whether people in general might have known by 130AD or 160AD what the gospels had said about Pilate executing Jesus around 30AD! That’s a pretty big difference if we are talking (as I think you were) about living people having personal adult memory of Pilate governing in 26-36AD!
And again - who was doing this harmonisation around 160AD, and where was this being done? In Jerusalem or Galilee? Or further afield in Judea? Or in another land entirely; Rome, Alexandria, Syria, Turkey, where? And how much of the specific contents would be known on the streets of Jerusalem such that Roman ruling officials would take notice of mistaken ideas about anyone called Pilate as executioner of a religious Jewish messiah from a century before?