What Carrier did was to project the hypothesis space. That is legitimate at the modest cost of an assumption within the subsequent analysis that one of the chosen pair is true.True, but it is a little more than that. Dr Carrier isn't just saying he is pitting two competing theories -- celestial Jesus vs historical Jesus -- against each other, he is saying that all probability space is defined by those two theories. That is, any other mythicist theory is subsumed by his celestial theory.
Carrier is of course also entitled to his view of how much of the total a priori probability these two hypotheses subtend. But that estimate is irrelevant to the "Bayesianness" of the subsequent "match-play" analysis. Whether 99.99% or 0.01%, he assumes away whatever else remains, and his Bayesian analysis proceeds from there in the same way, with the same warrants, regardless of how much he assumed away up front to get down to two.
That he really, really likes just those two? Fine. It's subjective probability, it only represents his personal confidence anyway. Your own confidence may differ, but even if your confidence does depart from Carrier's a priori, you might still accept the defeat of a relatively mainstream historicist proposition a posteriori.
What I would recommend to a "Wellsian" is to boil the case down to something of comparable specificity with the disputed portion of Carrier's basic satement of mythicism. (I am assuming that Wells would agree with all of the rarely disputed "background" portion described in my previous post).Arguably not. If you plug in Wells' mythicist theory using Carrier's own odds, it appears to come out as likely or even more likely than Carrier's celestial theory. Whenever Carrier reasons that "this is unexpected if Jesus was a man who lived recently" then the same odds can be applied to Wells' theory. Obviously the full case needs to be run, but at worst Wells' theory is demonstrably more than "a tenth of one percent" using Carrier's own odds.
Then you could do a comparison of "like with like," basic Carrier versus basic Wells, starting with the prior plausibility, and then updating by whatever bits of evidence bear differently on those two hypotheses.
OK, but it is usual and useful to develop mutually exclusive contenders. Conceptually, there is an overlap (earthliness) between two of the three hypotheses under discussion (Carrier's two and a Wellsian hypothesis of comparable specificty, to be developed). But formally, the fully stated hypotheses are still exclusive:That's true enough. But if (1) Wells' earthly mythical theory approaches the celestial mythicist theory in strength, and (2) there is overlap between an earthly historical Jesus and an earthly mythical Jesus; then that suggests that there is a foundational problem with how Carrier's case is grounded.
Carrier-historicist: Jesus real-life-human and earthly
Carrier-mythicist: Jesus mythical and celestial
Wells-mythicist: Jesus mythical and earthly
It is a matter of free preference whether an analyst wishes to mount another "match-play," this time between Carrier's and Wells's versions, or redo Carirer's analysis with three contenders instead of two. It's about the same amount of work either way, but maybe one would be clearer than the other. The force of the outcome should be the same.