Posted: Jan 24, 2012 11:49 pm
logical bob wrote:Looks like sophistry to me. Setting out the historical techniques he wants to talk he lists the criterion of embarrassment as "if it was embarrassing it must be true". Now I'm no defender of the criterion, but to attack it in such a caricatured strawman of a form is just silly.

Just what is the 'criterion of embarrassment' supposed to show?

Notice that Carrier works through his equations on the neutral proposition that Jerusalem had a public library and then, when explaining the advantages of Bayes theorem brings in Historical Jesus examples as in

For example, as Porter and Thiessen have both observed, it’s inherently unlikely
that any Christian author would include anything embarrassing in a written account of his
beliefs, since he could choose to include or omit whatever he wanted. In contrast, it’s
inherently likely that anything a Christian author included in his account, he did so for a
deliberate reason, to accomplish something he wanted to accomplish, since that’s how all
authors behave, especially those with a specific aim of persuasion or communication of
approved views. Therefore, already the prior probability that a seemingly embarrassing
detail in a Christian text is in there because it is true is low, whereas the prior probability
that it is in there for a specific reason regardless of its truth is high.

You forgot to include the paragraph which explains what this is an example of:

2. Bayes’ Theorem will inspire a closer examination of your background knowledge,
and of the corresponding objectivity of your estimates of prior probability.

Whether you are aware of it or not, all your thinking relies on estimations of prior
probability. Making these estimations explicit will expose them to closer examination and
test.
Whenever you say some claim is implausible or unlikely because ‘that’s not how
things were done then’, or ‘that’s not how people would likely behave’, or ‘other things
happened more often instead’, you are making estimates of the prior probability of what
is being claimed. And when you make this reasoning explicit, unexpected discoveries can

This goes in front of the paragraph you cited above. Carrier is not 'working' the Bayes Theorem here but giving examples of where its application would be helpful. You're faulting Carrier for failing to do something only you imagined he set out to do.

and

For example, Paul refers to James the Pillar as the Brother of the Lord, and to the
Brothers of the Lord as a general category of authority besides the Apostles. It is assumed
this confirms the historicity of Jesus. But which is more likely, that a historical (hence
biological) brother of Jesus would be called the Brother of the Lord, or that he would be
called the Brother of Jesus? In contrast, if we theorize that ‘Brother of the Lord’ is a rank
in the Church, not a biological status, then the probability that we would hear of
authorities being called by that title is just as high, and therefore that Paul mentions this
title is not by itself sufficient evidence to decide between the two competing theories of

Notice that these don't actually contain any mathematical thinking at all. It's the usual argument presented in the usual format. Presumably now it's rigourous though, because it's an example of the advantages of maths.

Again, you failed to quote the introductory paragraph:

3. Bayes’ Theorem will force you to examine the likelihood of the evidence on
competing theories, rather than only one
— in other words, forcing you to consider
what the evidence should look like if your theory happens to be false (What evidence can
you then expect there to be? How would the evidence in fact be different?). Many
common logical errors are thus avoided. You may realize the evidence is just as likely on
some alternative theory, or that the likelihood in either case is not sufficiently different to
justify a secure conclusion.

Here Carrier is simply showing how application of Bayes theorem will help would-be historians from making the common mistake of failing to take into account competing theories. Again Carrier is not claiming he is 'working' the Bayes Theorem in this example.

Carrier cannot be faulted for not doing what he didn't claim he was going to do.

And anyway,

You can use Bayesian reasoning without attempting any math, but the
math keeps you honest, and it forces you to ask the right questions, to test your
assumptions and intuitions, and to actually give relative weights to hypotheses and
evidence that are not all equally likely.

That's handy isn't it? I was worried we might have to do some work here, so it's a relief to know that mathematical rigour transfers to these standard arguments from the equations on the previous page by a sort of logical osmosis.

It seems you are misunderstanding what Carrier is saying.

It's like knowing how a logical syllogism works - you don't have to frame every argument you make in such terms, but knowing the form helps you make better arguments and better able to understand the arguments of others.

And you may not have noticed that he says it is better to do the maths.

Even better

Bayes’ Theorem has been proven formally valid. Any argument that violates a valid
form of argument is itself invalid. Therefore any argument that violates Bayes’ Theorem
is invalid. All valid historical arguments are described by Bayes’ Theorem. Therefore any
historical argument that cannot be described by a correct application of Bayes’ Theorem
is invalid. Therefore Bayes’ Theorem is a good method of testing any historical argument
for validity.

... so nerny-ner-ner-ner-ner.

A more lucid refutation of an argument was never typed.

But really - have you got any rational reasons to not like what is written here?

I say bullshit.

You might think differently once you actually grasp what historian Richard Carrier is talking about.