New & Improved Critical Thinking Course

Cover image of Bo Bennett's new edition of Logically Fallacious.I’ll be teaching critical thinking skills online this November. With a new, easier, lower priced textbook: Logically Fallacious: The Ultimate Collection of Over 300 Logical Fallacies, the new Academic Edition, by Bo Bennett of The Humanist Hour. Get your copy now! And register today! Class starts November 1.

Learn the basics you need in logic, cognitive science, and reasoning about probability, to be a better, sharper thinker, about everything that matters in your life.

Or spread the word. Tell any of your friends or contacts who might be interested. Lots of people might want to hone their knowledge and skills in this domain. And this class is all about helping with that.

What will this course cover? Why take it? Here is the course description…

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Speaking for Columbus Rationality Next Month!

Cover of Richard Carrier's book Proving History. Illuminated stained glass Jesus in darkened room as peered at through a cross cut-out in an iron cathedral door. Title and author name below.I will be speaking on Bayesian history and epistemology for Columbus Rationality and the Secular Student Alliance at OSU in Columbus, Ohio, on Monday, November 16th, at 7:30pm in Lazenby Hall (room 021) on the OSU campus. Details here.

I Will duscuss Bayesian reasoning and its application and status in the field of historical research; and how the analysis of the methods actually used by historians today reveals it is all Bayesian, and can be improved and better understood by recognizing this. I will also discuss the role and contents of my book Proving History: Bayes’s Theorem and the Quest for the Historical Jesus (available in print, kindle, and audible); and likewise of supporting books by Aviezer Tucker, David Hackett Fischer, and C. Behan McCullagh.

I’ll have copies of Proving History and On the Historicity of Jesus on hand.

Tim Hendrix on Proving History

Tim Hendrix wrote a critical analysis of my book Proving History two years ago, and recently made it available online. Coincidentally I also just discovered a review of the book in College & Research Libraries Reviews, which had been published in June of 2012 (pp. 368-69). That was only one long paragraph, but I was surprised it understood the book and took a positive angle on it, concluding:

The use of a mathematical theorem to establish reliable historical criteria can sound both threatening and misguided. However, Carrier describes and defends the theorem in layman’s terms, demonstrates that historians actually think in terms of probabilities while rarely quantifying them, shows how all other axioms and rules in historical methodology are compatible with the theorem, and then gives it a practical workout on recent studies on the historicity of Jesus … [in which] Carrier shows how the criteria for judging whether or not Jesus was a historical figure (coherence, embarrassment, multiple attestation, contextual plausibility, etc.) are replaceable by Bayes’s Theorem, which “if used correctly and honestly . . . won’t let you prove whatever you want, but only what the facts warrant.”

Hendrix (who has a Ph.D. relating to Bayesian studies) gives it a much closer look on its technical aspects in applying Bayes’ Theorem. There are some issues of grammar that suggest English might not be Hendrix’s first language (he also uses British spelling conventions), but his writing is good enough to work around that (most of the time).

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Everyone Is a Bayesian

Greg Mayer posted at Jerry Coyne’s blog on “Why I am not a Bayesian.” In his explanation, he goes wrong at three key points. And they are illustrative of common mistakes people make in trying to understand or apply Bayesian reasoning. In reality, Mayer is a Bayesian. He just doesn’t understand why. Here is the breakdown. [Read more…]

McGrath on the Rank-Raglan Mythotype

Cover of Richard Carrier's book On the Historicity of Jesus. Medieval icon image of Jesus holding a codex, on a plain brown background, title above in white text, author below in white text.Yesterday I addressed McGrath’s confused critique of portions of On the Historicity of Jesus (in McGrath on OHJ: A Failure of Logic and Accuracy). He has also published a second entry in what promises to be a series about OHJ, this one titled “Rankled by Wrangling over Rank-Raglan Rankings: Jesus and the Mythic Hero Archetype” (let me know if more arrive in future). This entry is even less useful than the first. Here are my thoughts on that.

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Live, This Sunday, on Atheist Analysis!

Advert for the episode of Atheist Analysis, graphically representing the basic info in the post, plus a picture of Richard Carrier editied to have him holding Bayes' Theorem in his hand.The vidcast Atheist Analysis, which streams live at 10pm Eastern this Sunday (Feb. 22) and takes questions from the audience during the show, will be interviewing me. The topic: why Bayes’ Theorem is awesome. (Also, of course, what Bayes’ Theorem is, how non-mathematicians can understand and use it, and especially how it models reasoning about claims in history.) After me they are interviewing FtB founder Ed Brayton, to talk about his comedy, and efforts to make the atheism movement more inclusive and ethical. And then up is Michigan activist Mitch Kale (I think they mean Mitch Kahle) and (I presume) his local fights for church state separation. So it sounds like a pretty good show to catch!

Tune in!

A Bayesian Brief on Comments at TAM

I was asked about remarks made by Chris Guest (President of the Australian Skeptics, Victorian Branch) at this year’s TAM. He gave a quick twenty minute talk on Bayesian reasoning and its abuses, with which I entirely concur. (This talk begins with Guest’s introduction at timestamp 48:30.) He criticizes my work briefly at the end, but understanding his remarks there require understanding his remarks throughout the talk. His only mistake is that when he gets to my work, he makes one crucial mathematical error that invalidates his entire critique…
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Knitting Fans, Behold Some Awesome Ancient Roman Tech!

There’s this guy, you see, who knitted his way to a solution to an infamous problem in Roman history. This might be a bit premature (since academic journals haven’t weighed in yet), but I am persuaded that the mystery of the ancient Roman dodecahedrons has been solved. And why I’m persuaded affords a handy example for teaching how Bayesian reasoning works in making good historical inferences. [Update: This case likewise shows how Bayesian reasoning can incorporate new facts so as to change what’s likely: experts in the comments to this article subsequently persuaded me that a full accounting of the facts in my Bayesian model does not get as positive a result for this thesis as I had initially thought.]

A What?

Photograph of a bronze dodecahedron recovered from the ancient Roman Empire, described in the text.I suppose I should begin by explaining what a “mysterious ancient Roman dodecahedron” is. It’s not just any dodecahedron from ancient Rome (I’ll show you an unrelated example shortly), but a very peculiarly consistent oddity that no one has been able to explain (mainly because no writing survives mentioning it). It’s a common object. Some hundred or so have been found, originating in the 2nd century A.D. and spanning a couple of centuries afterward. But only in France and northern and eastern Europe. It’s weird looking. And has peculiar features. Some are of stone manufacture, but most are cast bronze.

Another example like the one above, this one lacks the grooves mentioned in the text.Some typical examples (one from Wikipedia, another from the Birmingham Musem) are shown to the right. Each is a twelve-sided hollow object, the sides generally symmetrical (an isohedron, so it looks a little like a twelve-sided die, something old-school role-playing-gamers will recognize), but every side has a circular hole in it, and the holes are different sizes, but the pattern of sizes (the sequence and arrangement) is the same on every object, even though the size of the object (and thus size of the holes) varies considerably, from kind of tiny (one and a half inches total diameter) to about the size of what would have then been a large adult fist (a little over four inches). The holes also sometimes have a sequence of parallel carved rings around them (sort of like gutters or guidelines in the face of the object), but many do not, so these appear to be a decorative flourish (a typical accent found in Roman tech of the time, where common utilitarian objects can be prettied up with some artsy flourishes like that).

But importantly, every corner of these objects has a solid knob sticking out of it, a bollard narrower at its base than at its tip (many of these just look like attached spheres), for twenty knobs in all. This most of all prevents the twelve-sided die analogy from quite being right, that plus the fact that the holes being of different size means each face has a different weight. They also aren’t inscribed with anything…a fact that is far more crucial to determining their purpose than you might at first think.

Just search “Roman dedocahedron” in Google Images and you’ll find dozens of examples. And yet…

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If You Learn Nothing Else about Bayes’ Theorem, Let It Be This

There are two things one learns from Bayes’ Theorem that are the windows to everything else Bayesian reasoning can ever teach you. And there is a lot it can teach you besides these two things. But here I’m cutting to the chase of the two that are most essential: theories cannot be argued in isolation, and prior assumptions matter.

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A New Bayesian Calculator

Bill Seymour has developed a new, more advanced Bayesian calculator for public use, and he would like people to beta test it and offer advice, or even develop it further.

For this open-source Bayes’ Theorem calculator, Seymour writes:

My intent was to find the middle way between, on the one hand, highly technical (and expensive) commercial software used in the sciences and statistics, and on the other hand, the toy Bayes’ Theorem calculators that abound on the Web. Some features of my calculator are:

  • Hypotheses can be saved in permanent storage so that users can work on several at once as part of a larger project.
  • Complete hypotheses can have any number of alternates.
  • Priors and consequents can be almost any arithmetic expression that evaluates to a probability between 0 and 1.
  • Prior and consequent expressions can contain terms that refer to other hypotheses.
  • Probabilities can be entered, and displayed, as decimal numbers, percentages, or odds.
  • The program happily works with what Carrier calls a fortiori probabilities: ranges of values like “20% to 40%”.

If you’re interested, here are some links:

I’ve given the code the open-source Boost Software License which isn’t viral like the GPL and others are said to be; so if you’d like to use some of my ideas in a program of your own, the open-sourceness (if that’s a word) of my code won’t infect yours.

And I explicitly invite others to help with this project. In particular, I think it really should be a downloadable executable that can be run off-line. Unfortunately, writing GUIs isn’t in my wheelhouse (my failing, not GUIs’).

If anyone would like to create a Windows or OS X version; have at it. I’ll even host your source code on my Web site if it’s open-source and high-quality. (But be warned that I’m a professional programmer, and also an old fart, with some curmudgeonly ideas about how quality code should be written.) You’ll find my e-mail address at the end of the documentation.

So if you are interested, check that out. I have also added a link to these materials on my old calculator page so users have the option of both.