Carrier is very much into Beyesian statistics and uses it throughout the book. His conclusion shows the probability low for an historical Jesus and high for a mythical one.
And I saw someone else use that exact same formula (Bayes’ Theorem) to argue that the Resurrection was the most likely explanation for what happened to Jesus. You can use it to argue for anything you want if you just put the right numbers into it. I don’t take it particularly seriously when it comes to arguing about things like this.
Actually, there was an essay (no longer online) criticizing people who rely too much on Bayes’ Theorem that happened to mention Richard Carrier. I’ll share that excerpt, which I thought was amusing:
"Another over-enthusiastic Bayes fan is the historian and “New Atheist” loudmouth Richard Carrier, who in his book Proving History claims that any valid historiographic method should be reducible to Bayes’ Theorem. In the general sense, this claim couldn’t be less interesting: both Bayes and historians are concerned with getting at “truth” by processing “evidence”, and pointing this out will enlighten no one. And in the specific sense, the claim couldn’t be more stupid. The idea that historical evidence and theses could be reduced to probability values, and that plugging them into Bayes’ Theorem would make historical research more accurate or reliable or rigorous, is not only the worst kind of technocrat fantasy, it’s also completely unworkable.
In general practice, there’s no way to come up with meaningful figures for the right-hand side of the Bayes equation, and so Bayesians inevitably end up choosing values that happen to justify their existing beliefs. The Reverend Bayes originally used his theorem to prove the existence of God, while in his next book, Carrier will apparently use the same theorem to disprove the existence of the historical Jesus. I myself have applied it to a thornier subject: the problem of uncovering academic frauds. In fact, by (name removed by moderator)utting the precise values for what I believe about academic frauds, their likelihood of spreading pseudoscientific ********, and the likelihood that pseudoscientific ******** is precisely what Carrier is spreading, I have used Bayes’ Theorem to calculate that Richard Carrier is almost certainly a fraud, to a confidence level of five sigma."