Thank you for the reference Jerry, as I had not looked at this earlier section where you discussed Gnosis with GrayMac
I'd agree that the radical, messianic and militant Jewish sects of 1st century Palestine, probably were not "well-defined versions" of Christianity. I advocate for a "mergers and acquisitions" model of the growth of early Christianity. The Roman church grew by co-opting themes from various religions into their own literature, and by recruiting followers from other religions, when they could not directly co-opt the leadership of competing sects.
Our argument is essentially literary, that Biblical Jesus seems to be typologically related to the various Jewish messianic figures mentioned in Josephus, such as Judas the Galilean, The Egyptian, and the Woe-Saying Jesus. These, in turn, also seem to resemble characters found in the Dead Sea Scrolls. So, I conclude that these messianic figures probably did exist, and that the Roman religion strongly appealed to followers of those various messianic figures.
Your observations on GrayMac are quite correct.
Peter and James seem to have been Essene messianic radicals, at least if Eisenman's reading of the DSS is correct. Josephus' depiction of James is also consistent with the idea that James was an Essene radical. So, one might suppose that the church of Peter and James was an Essene sect. And, their sect is depicted as a proto-Christian church in the book of Acts.
Essene theology can easily be seen as proto-Christian, as it was more extreme than Pharisaism, i.e. more anti-Sadducee and more anti-Temple Judaism. However Essenism itself evolved. In my opinion there is a change from older Essenism (the DSS, i.e. before 50 BCE) to the Therapeutae (10BCE-30AD as described by Philo) to the Essenes according to Josephus, which latter must date to about 40-60AD, though many don't agree with me here.
The Sethians and Simonians first appear in the historical record in the 2nd century, as heterodox Jewish-Hellenistic Christian sects. So they might very possibly be connected to the 1st century Essene radical sects, though I'm sure Carrier would complain that there's no real evidence of that. The Mandaeans (possibly aka Nazarenes, Nasoreans and Sabians) also seem related, although again there's no accepted evidence or proof of their status or existence in the 1st century AD or before.
The Carrier pigeon can flap on about whatever he likes

- and I know that above, Jerry, you are merely (and rightly) presenting the standard teachings, the agreed baseline.
The emerging understanding however is that Sethian Gnosticism is older, since it is a specifically anti-Jewish heresy. Mandaeism is a form of Sethian Gnosticism as it invokes the Biblical Seth (Shitil) as a being involved in human salvation, likewise with the Biblical Enosh (Anush) and the more recently introduced Abel (Hibil). This very issue is why I went to the UK last year, but the material evidence is not yet fully written up, let alone published. I have not been invited (yet?) to write up my contribution there - and was unable to due to sickness last October, then my mother's final illness and death after that.
That Mandaeism is nevertheless distinct from Nag Hammadi Sethianism indicates the movement's great age - especially as the Mandaean Ardban (Artaban II) from 12-38AD is intimately involved in the Adiabene scandal revealed by Ralph Ellis. That Mandaeism is not derivative of Nag Hammadi Sethianism is clear from the Second Series of the Four Luminaries (the first series being Harmozel, Oroiael, Daviethe and Eleleth) - these being Gamaliel, Gabriel, Samblo & Abrasax. Mandaeism shares
some of the Second Series characters, notably Samblo and Gabriel, but is different in details. Nevertheless their common origin is quite clear - but this origin in equally clearly a BCE one - and one that is extremely anti-Jewish, despite Mandaeism being soundly based upon Jewish ideas! Mandaeism too, certainly had connections to the earlierst Christianity but is NOT derivative from Christianity.
Yes, and I raised this issue in my original review of Carrier's book. Robert M. Price thinks that the Pauline corpus is mostly, or perhaps entirely, a late forgery. I wasn't meaning to say I'm sure Price is correct, only that it deserves consideration. Carrier's concept of describing the possibilities with a Bayesian probability distribution could be useful here, and I suppose my review could have been clearer.
Much of Paul has been reworked, but the original Paul predates the canonical Gospels. E.g. the Paul-Seneca correspondence lists three epistles, Corinthians, Achaeans and Galatians! Achaeans has been reworked to become 2-Corinthians, while the other two epistles have also been modified. Nevertheless, they with 1-Thessalonians show a pre-canonical Christianity where the Jews kill Jesus rather than lobbying the Romans to do it.
Such material is NOT part of Mandaeism which, like Islam later on, has no interest in a Jesus killed by Jews-&/or-Romans. Instead, Mandaeism upholds John the Baptist as a human being exemplifying their baptismal practices.
Joe Atwill had not seen the two-stage process, but the reworking of Paul's epistles came along with the finalizing of the canonical Gospels, which clearly occurred in the wake of the Bithynian massacres of Christians who would not worship the Emperor but fantasized a heavenly Jesus instead (the Trajan-Pliny correspondence), one Who once lived on Earth under Pontius Pilate! So in no way does this detract from Joe's understanding of the Rome-Jewish War as pivotal in creating Christianity. Rather, it highlights the roles of Basilides and Saturninus whose influence is earlier than scholars imagine as they are revealed by Tactius & Suetonius (Basilides) and Josephus (Satornilus [sic] or Saturninus).
Much confusion over the time of origin of Sethianism has been created by academics such as John D. Turner, who, in his 2001 work,
Sethian Gnosticism and the Platonic Tradition, treats Mandaeism as a side issue as he seems not to recognize it as Sethian. He imagines it all to arise in the 2nd century - hence when the
Gospel of Judas (< 150 AD) was published, he then misrepresented its evidence in order to claim that it was an
early form of Sethian Gnosticism. Rather, it is clearly a
later form of Sethian Gnosticism, revealing his whole dating framework to be quite bogus, especially as his real interest was in studying the Platonic influence in Nag Hammadi texts (in which he does a good job).
Yours faithfully
Claude