Six years ago I wrote a small, daily piece (Bayes Theorem Proves Jesus Existed And Didn’t Exist) about the use of probability in proving or disproving the existence of God. I’m against it.
I began with a quote by Keynes on Bayes’s Theorem:
No other formula in the alchemy of logic has exerted more astonishing powers. For it has established the existence of God from the premiss of total ignorance; and it has measured with numerical precision the probability the sun will rise to-morrow.
I next said:
Probability carries with it “a smack of astrology, of alchemy.” Comte, Keynes reminds us, regarded the application of the mathematical calculus of probability as “purement chimérique et, par conséquent, tout à fait vicieuse.”
Now these are minds better than mine giving manful advice about over-relying on probability. Heed them. Indeed, as anybody who has regularly read this blog knows, probability is misused with shocking abandon. We all know how probability, mainly through statistical models, is used to “prove anything” — a phrase I trust is recognized for what it is, a figure of speech and not a complete logical treatise on probability misuse (although I’ve done that, too!).
…there is not one, but two books which argue that a fixed, firm number may be put on the proposition God Exists. The first by Stephen Unwin is called The Probability of God: A Simple Calculation That Proves the Ultimate Truth, in which he uses Bayes’s theorem to demonstrate, with probability one minus epsilon, (the Christian) God exists.
This is countered by Proving History: Bayes’s Theorem and the Quest for the Historical Jesus by the very concerned Richard Carrier (pictured above), whose uses Bayes’s theorem to prove, with probability one minus epsilon, that the Christian God does not exist because Jesus himself never did.
There we have it: probability proving two diametrically opposite conclusions. Alchemy indeed.
It’s obvious the “equations” “probability one minus epsilon” are mild jokes, probabilistic figures of speech, and not meant as rigorous mathematical proofs that Unwin and Carrier came to these exact precise figures. It’s equally obvious we have two people using probability to argue both sides of a question.
It wasn’t obvious to Richard Carrier. He felt stung at the time of the post, which was later reprinted, and went then into a sort of minor frenzy. In one comment at the time he said:
…Bayes’ Theorem is simply the mathematical model for the arguments historians are already making. If they can’t make a probabilistic argument that Jesus existed, then they can’t claim to know Jesus probably existed. And then we’d all have to concede we don’t know Jesus probably existed. Sink the ship of arguing from probabilities, and all probability arguments go down with it. And with that, all human knowledge. Thus, you have to address what I actually argue, not pretend it’s some sort of advanced significance testing like in the sciences. It’s just an argument that something probably happened in history. And as such is as valid as any other argument that something probably happened in history. Unless no such arguments are valid!
By pointing out improper uses of probability, I have managed to sink All human knowledge! What powers I have! (I always knew I was special.)
Apparently Carrier doesn’t understand Bayes’s theorem isn’t really needed, that it stands or falls based on its inputs. And that the inputs are the only important things worth discussing. Carrier’s inputs are on the order of the Bigfoot conspiracy theories. For Carrier, don’t forget, claims Jesus never existed. Not just that Jesus wasn’t God, but that the man himself did not exist.
Anyway, Carrier spun himself around in circles lo those many years ago. And I forgot about the post, which after all only made a small point.
Carrier didn’t forget. Evidently, the wound I caused festered and never healed. Carrier, we presume, retreated to some dark corner to cherish the injury, only to reemerge two weeks ago with an extraordinarily long piece—found by reader swordfishtrombone—-in which he produces multiple points of evidence proving I’m a “liar”.
His title is “Why Christians Are Terrified of Probability Theory.”
Yeah, sure, Carrier. I’m quivering.
Here are the first two “lies” of which he says I’m guilty:
The title says Briggs is talking about examples of Bayes’ Theorem being used to prove “Jesus Existed (And That He Didn’t).” But he gives no example anywhere in his piece of Bayes’ Theorem ever being used to prove Jesus existed! Lie number one.
In fact, Briggs gives no actual example of Bayes’ Theorem being used to prove Jesus didn’t exist, either. He cites only my book Proving History. In which I never argue any conclusion about the historicity of Jesus. Much less mathematically. Lie number two.
Yet Briggs claims Unwin “uses Bayes’’ theorem to demonstrate, with probability one minus epsilon, that the Christian God exists.” Lie number three.
Number four is my favorite:
Moreover, Unwin’s conclusion is that the probability of God’s existence based on his examination of the evidence is only 67%. Yet Briggs claims Unwin got the result of “probability one minus epsilon,” epsilon being a mathematician’s term for a very small number (in fact, usually infinitesimally small). In other words, Briggs lied. He said Unwin found the probability to be arbitrarily close to 100%. In fact, Unwin found it was far more ambiguously around 67%. Strange lie for Briggs to tell. But alas. Lie number four.
You can read the others, which are equally or more frivolous.
The real problem might be that Carrier was embarrassed by other articles I wrote showing his errors. And so he took his frustration out on a toss-away article by using lawyer-like insinuations about niggling details that nobody cares about.
How about this article? “Richard Carrier’s Argument To Show God’s Existence Unlikely Is Invalid And Unsound“.
Richard Carrier’s argument to show that God probably didn’t create the universe, and therefore He probably doesn’t exist, in Carrier’s “Neither Life nor the Universe Appears Intelligently Designed”, like many attempts to use probability in defense of atheism or theism, is invalid and unsound, and based on fundamental misunderstandings of who God is and of the proper role of probability.
Carrier introduces Bayes’s probability theorem, but only as a club to frighten his enemies and not as a legitimate tool to understand uncertainty. I must be right, he seems to insist, because look at these equations. Bayes’s theorem is a simple means to update the probability of a hypothesis when considering new information. If the information comes all at once, the theorem isn’t especially needed, because there is no updating to be done. Nowhere does Carrier actually needs Bayes and, anyway, probabilistic arguments are never as convincing as definitive proof, which is what we seek when asking whether God exists.
Even lower down is a section on Carrier’s many probability errors.
He repeats many of these errors in his new Pity-Me-Richard-Carrier article:
Taking probability theory seriously, entails exposing assumptions to the light of day, that once exposed, destroy the Christian faith. The resulting cognitive dissonance is so powerful only two options are available to the believer: make shit up (like Unwin and Swinburne, they fabricate fantastical probabilities that have no plausible basis in logic or reality) or declare probability itself the enemy. Briggs picks option B. Meanwhile, all peer reviewed work on the question finds the opposite: that history is in fact Bayesian.
History is not Bayesian, Carrier. Any my work has been peer reviewed, too, which makes it true and indisputable.
Your work, Carrier, has also been peer reviewed. And your peers say harsh things. Which is why Carrier also doesn’t like it when I link to atheist Tim O’Neill’s “History for Atheists” site, which has many articles proving—as in proving—Carrier’s many historical mistakes.
Bear with me for one last quote, as it involves Bayes again.
Two years ago Carrier brought out what he felt was going to be a game-changer in the fringe side-issue debate about whether a historical Jesus existed at all. His book, On the Historicity of Jesus: Why We Might Have Reason for Doubt (Sheffield-Phoenix, 2014), was the first peer-reviewed (well, kind of) monograph that argued against a historical Jesus in about a century and Carrier’s New Atheist fans expected it to have a shattering impact on the field. It didn’t. Apart from some detailed debunking of his dubious use of Bayes’ Theorem to try to assess historical claims, the book has gone unnoticed and basically sunk without trace. It has been cited by no-one and has so far attracted just one lonely academic review, which is actually a feeble puff piece by the fawning minion mentioned above. The book is a total clunker.
The “detailed debunking” is not mine, but Tim Hendrix’s “Richard Carrier’s ‘On the historicity of Jesus’ A Review From a Bayesian Perspective“. Fifty-seven pages of solid debunking.
“Tim Hendrix” is a pseudonym. “Hendrix” was evidently worried he or his family would be hounded by Carrier’s “fawning minions” (O’Neill’s phrase). And perhaps be called “a liar” by Carrier himself.
You needed have worried, “Tim”. I’ve had mosquito bites that hurt worse than Carrier’s insults.
A decade of the rosary has been said for you, Richard. Miracles do happen!