Richard Carrier is a chowderhead of epic proportions. He has a Ph.D. in Ancient History, and somewhere along the way, one suspects in a required Gen-Ed math class populated with math-phobic Humanities students, he learned some freshman-level probability. He then, to his credit I suppose, parlayed his minimal mathematical knowledge into a cottage industry (well, more like a local Kwik-Mart than an industry) based on convincing the rubes that he could apply Bayes's Theorem to the question of whether Jesus existed. He highlights his ignorance by calculating probabilities to three significant figures. (He has also, along the way, assured us that he knows more about quantum entanglement than the physicists and more biology than the biologists. He is a true super-genius.)
If you are mathematically inclined, "Tim Hendrix" has provided, a rigorous, scholarly smackdown of Richard Carrier.
If you have a Ph.D. in History you should not be permitted to apply Bayes's Theorem or mention Quantum Mechanics. These are micro-aggressions against mathematicians and physicists. We deserve safe spaces impenetrable to the disease of pseudo-intellectualism, of which Richard is a carrier (ba-dum-dum.)