Miracle of the Shroud IV - The Phantom Image

[hugh farey]

Funny, sindonists claim that the artist must have been better than da Vinci. .....

To be fair, there are many that don't.

The Church was the richest and most powerful entity in Europe at that time, but it was far from united. There were bitterly warring fractions, even at exactly the time of the shroud two competing Popes. The Church people did not (usually) fight with swords, but with murder, assassinations, deceit, and intrigue. On the side, secular kings, nobles, warlords, etc were waging bloody local wars, while at the same time trying to be on reasonable terms with the Church. Human life and dignity, and the truth were all extremely negotiable values.

Yes. I agree with that absolutely.

The fabric of the shroud was indeed very valuable at the time^*), but that's no guarantee whoever used it had actually paid for it. Or else, whoever donated it might have been promised an easy passage to Heaven in return.

Also true. But there's no doubt it was a high quality bit of cloth, not so much in the weaving, which required quite an elaborate loom and setting up but was fairly easy after that, but in the fineness of the thread, which was virtually unknown then, and still is. I had hoped to commission an accurate reproduction of the weave (that's how I know how expensive it is!), but linen at 30 threads per cm is impossible to obtain, at least in Europe.

The artist might not have been overly concerned with authenticity: Few people would have the slightest notion of how an authentic shroud might look, so the important part was that it be recognized as the shroud of JC, which meant that the image should look like the person on the crucifix next to it in the church.

Also true; but very few of the shrouds of which we have mention refer to any image at all. The 'authenticity' of a relic seems to have depended far more on its credentials than on what it actually looked like. So if the Shroud was intended originally as a 'relic' it did not need an image (but it has got one), but it did need episcopal credentials (which it didn't have). It is interesting that although the pope insisted that the cloth be displayed without sanctification and with a bold pronouncement that it wasn't real, he did allow it to be displayed at all, as if he thought it wasn't just a money-making forgery.

The immediate denouncement can very easily come from a competing fraction, which would, of course, hardly be happy if the competition owned the most sacred relic one could think of.

That, of course, means that we can hardly take d'Arcis as much more evidence than any disgruntled competitor, but it is, at least, the very first documented mention of the shroud's existence.

I find it difficult to condemn d'Arcis as an out-and-out liar. That is, of course, the view of a great many who think the Shroud authentic, and it seems true that his cathedral had just fallen down...

 

[hugh farey]

That may be the case in general, but not with the objections which Jabba has raised, and he is the only person currently championing authenticity in this thread. His objections have shown to be nonsense more than once, however they very much do question the expertise and/or motivation of the technicians:

That's a wonderful collection of whinges, many of which are entirely justified, but few of which have any bearing on the competence of the radiocarbon labs themselves. The Church's ignoring of the protocols, selection of the samples and recording of their taking cannot be blamed on the labs, and had no effect on the date. The British Museum's summary paper for the journal Nature, and how it dealt with the statistical anomaly derived from all three labs, which is admittedly fairly cryptic in places, is also not the fault of the individual labs. There may have been some leakage of the results before the agreed announcement date, which, if confidentiality had been agreed, was bad practice, but it did not effect the date.
The statement that Richard Dawkins and Christopher Ramsey think that 'it' is controversial is a little disingenuous, I think. As a topic of discussion there is no doubt whatever that the Shroud arouses controversy, but that hardly means that either of these men doubt that it is medieval.

 

[Jabba]

Blood/What difference does it make?

...
Forgive me, Jabba, as I may have missed an earlier post in which you defined your terms, but could you say what P,A,x and L stand for?

Hugh,
- Sorry about that. I guess that I never did discuss that formula in this thread...
- Fortunately, Jay probably did a better job of defining the terms than I would have, anyway. My disagreement with Jay is his reference to "thin air." If you agree with him, I'll try to explain my reasoning better.

 

[JayUtah]

Fortunately, Jay probably did a better job of defining the terms than I would have, anyway.

Because I understand the applicability of statistical modeling and you do not.

My disagreement with Jay is his reference to "thin air." If you agree with him, I'll try to explain my reasoning better.

Why are you waiting for Hugh's permission? It's highly disrespectful of you to demonstrate that you are in fact reading my posts and are deliberately ignoring them.

Your values for L(x|A) and L(x|~A) are not anything you've computed, but simply quantities you've arbitrarily chosen. When asked to justify them you referred not to any quantitative argument, but to your handwaving circular claim that the presence of limestone preferentially supported authenticity. As I already noted (but you ignored), that's in direct contradiction to what Hugh actually told you about the limestone. What Hugh told you was expressly, in the language of your model, that L(x|A) = L(x|~A).

Don't wait for Hugh to hold your hand. Explain yourself now, please.

 

[wollery]

...
I estimate that the probability that a forgery has limetone on it to be 96%. Can you refute that figure?
Hans

Hans,
- See below.

...
- What we're doing here is trying to determine the new probability of an old hypothesis when certain new info is added. In the limestone case, we learn that there is all sorts of limestone on the shroud. In my estimate, the likelihood of so much limestone being on the shroud -- given that the shroud is authentic -- is maybe 95% -- while the likelihood of so much limestone being on the shroud -- given that the shroud is inauthentic -- should be no more than, say, 50%. The reason for this relatively small likelihood -- given inauthenticity -- is our lack of knowledge about the shrouds origin under this "given." This forgery might have a lot of limestone on it -- but then again, it very well might not...

...
- Again, if I understand what you're saying, "context" is the key -- but in the sense that we simply don't have much context if the shroud is not authentic, and this lack of context on the inauthentic side increases the likelihood of no, or little, limestone on the cloth -- which decreases the likelihood that the cloth is inauthentic...
- That's a lot of twists and turns -- hopefully, I ended up in the right direction.

Sorry Jabba, but a lack of context doesn't allow you to give a low probability, it merely means that you can't know what probability to assign.

If the Shroud had been stored in a pristine plastic box since it was first made then the probability of it having limestone on would be approximately 0%. If it was regularly used to scrub a limestone floor then the probability would be 100%. Without context how do you know which end of the scale the probability lies on. If it's not authentic then where was it made?

Your figure of 50% has no basis in anything other than your need for it to be lower than the probability for the "authentic" case. You cannot produce any context to justify that probability, it is simply asserted, which is what is commonly referred to as plucking a number out of thin air.

 

[Craig4]

Hans,
- See below.

Once again, this is so screwed up, it's not even wrong. Limestone on the cloth means it was somewhere there was limestone. That's all.

 

[pgwenthold]

Limestone on the cloth: how do you rule out that it wasn't just a burial cloth from someone who died 700 years ago? Didn't they use tombs then, too?

 

[Mojo]

A in his model is "The cloth is authentic." ~A is the negation: "The cloth is not authentic."

Since this is Jabba's equation I wouldn't rely on that. See the "immortality" threads (linked from post #2852 above) where he repeatedly, despite careful correction, tried to specify both A and ~A. Here he could well be defining ~A as "the cloth is 700 years old".

 

[JayUtah]

Since this is Jabba's equation I wouldn't rely on that. [...] Here he could well be defining ~A as "the cloth is 700 years old".

This is very true. He has assiduously ignored the posts where I carefully explained his categorization error in this case.

 

[hugh farey]

P(A|x)=(L(x|A)*P(A)/((L(x|A)*P(A)+L(x|~A)*P(~A))

Thank you, Jabba, and also JayUtah for explaining the terminology, although I can't say I understand the difference between probability and likelihood. However, I can't say I am much the wiser afterwards. What exactly is P(A|x)? JayUtah tells me it is 'the probability of hypothesis A given observation x. What is hypothesis A?
a) That any given cloth is a 1st century burial cloth.
b) That the Shroud of Turin is a 1st century burial cloth.
You see, I don't think you can present the second alternative in this simple Bayesian way. If all anyone knew about the Shroud was that it was a cloth, and it had limestone on it, could he conclude that it had a 2:1 chance of being a 1st century burial cloth, as your calculation seems to imply? On the other hand, if he knew anything else at all about the Shroud, should that not be included in your equation?

I should be grateful for clarification.

 

[JayUtah]

I can't say I understand the difference between probability and likelihood.

Don't try, unless the abstract statistics of stochastic processes is something you enjoy. Probability obeys several laws, one of which is being limited to values in the interval [0,1]. Likelihood is analogous to probability, but not so limited. It describes the notion of what favorable set of conditions would have to hold in order for a particular observation affected by those conditions to be observed a certain way.

 

[abaddon]

Limestone on the cloth: how do you rule out that it wasn't just a burial cloth from someone who died 700 years ago? Didn't they use tombs then, too?

Well see Italians never used limestone for buildings. Except for the colliseum and pretty much any public building, but as per Jabba, there is no way that got on the CIQ because it was never kept in a limestone structure after 1 CE, for which I am sure he has evidence. Sure he has.. Now he has painted himself into the claim that limestone only existed in 1CE. He now has to figure out how to claim that it wasn't one of the most common materials for public buildings at the time the cloth was fabricated, the medieval period. That dust from same would be everywhere, that quarryies for limestone were commonplace in the region at the medieval period, That Roman era limestone from Roman era buildings were commonly recycled in said period, that limestone was used for many other purposes in said period and that he has no evidence at all that such materials were not used in the creation of said image giving him a Bayesian probability of precisely 0 for his claim of authenticity.

Now, Jabba will try to argue that with Hugh's covert support, but one must wonder why anyone would propound such an argument.

 

[Slowvehicle]

Well see Italians never used limestone for buildings. Except for the colliseum and pretty much any public building, but as per Jabba, there is no way that got on the CIQ because it was never kept in a limestone structure after 1 CE, for which I am sure he has evidence. Sure he has.. Now he has painted himself into the claim that limestone only existed in 1CE. He now has to figure out how to claim that it wasn't one of the most common materials for public buildings at the time the cloth was fabricated, the medieval period. That dust from same would be everywhere, that quarryies for limestone were commonplace in the region at the medieval period, That Roman era limestone from Roman era buildings were commonly recycled in said period, that limestone was used for many other purposes in said period and that he has no evidence at all that such materials were not used in the creation of said image giving him a Bayesian probability of precisely 0 for his claim of authenticity.

Now, Jabba will try to argue that with Hugh's covert support, but one must wonder why anyone would propound such an argument.

...don't overlook the fact that CaCO₃ is a primary component of gesso...

 

[Craig4]

Limestone on the cloth: how do you rule out that it wasn't just a burial cloth from someone who died 700 years ago? Didn't they use tombs then, too?

Well, the limestone, like the blood isn't useful in establishing "authenticity" since it can only have been deposited on the cloth after it was made which is sometime after 1290.

 

[Craig4]

Hugh,
- Sorry about that. I guess that I never did discuss that formula in this thread...
- Fortunately, Jay probably did a better job of defining the terms than I would have, anyway. My disagreement with Jay is his reference to "thin air." If you agree with him, I'll try to explain my reasoning better.

Don't worry about it. Your formula doesn't add any value to the discussion since it does nothing to overcome the carbon dating evidence. The only thing that can help you is dating the Shroud. All else is meaningless.

 

[MRC_Hans]

The British Museum's summary paper for the journal Nature, and how it dealt with the statistical anomaly derived from all three labs, which is admittedly fairly cryptic in places, is also not the fault of the individual labs.

In fact, it wasn't the fault of anybody. It was simply a reasonable way to correlate the three data sets.

Hans

 

[MRC_Hans]

Also true. But there's no doubt it was a high quality bit of cloth, not so much in the weaving, which required quite an elaborate loom and setting up but was fairly easy after that, but in the fineness of the thread, which was virtually unknown then, and still is. I had hoped to commission an accurate reproduction of the weave (that's how I know how expensive it is!), but linen at 30 threads per cm is impossible to obtain, at least in Europe.

It makes no sense to compare modern industry products with medieval artisan's work. There is no rocket science in the cloth, just excellent handiwork. Modeen industry products are made to sell in volume at competitive prices, high class medieval artisan's work was made to sell as expensively as possible, since there was always some that could pay.

Also true; but very few of the shrouds of which we have mention refer to any image at all. The 'authenticity' of a relic seems to have depended far more on its credentials than on what it actually looked like. So if the Shroud was intended originally as a 'relic' it did not need an image (but it has got one), but it did need episcopal credentials (which it didn't have).

Probably had from the outset, but it got caught in clerical intrigue.

It is interesting that although the pope insisted that the cloth be displayed without sanctification and with a bold pronouncement that it wasn't real, he did allow it to be displayed at all, as if he thought it wasn't just a money-making forgery.

The churces were full of representations. Statures, pictures, etc, etc.
CHurch work was politics back then. (As if much of it ain't still )

I find it difficult to condemn d'Arcis as an out-and-out liar. That is, of course, the view of a great many who think the Shroud authentic, and it seems true that his cathedral had just fallen down...

I didn't say he was a liar. I just said he was not impartial.

Hans

 

[Jabba]

Blood/What difference does it make?

Thank you, Jabba, and also JayUtah for explaining the terminology, although I can't say I understand the difference between probability and likelihood. However, I can't say I am much the wiser afterwards. What exactly is P(A|x)? JayUtah tells me it is 'the probability of hypothesis A given observation x. What is hypothesis A?
a) That any given cloth is a 1st century burial cloth.
b) That the Shroud of Turin is a 1st century burial cloth.
You see, I don't think you can present the second alternative in this simple Bayesian way. If all anyone knew about the Shroud was that it was a cloth, and it had limestone on it, could he conclude that it had a 2:1 chance of being a 1st century burial cloth, as your calculation seems to imply? On the other hand, if he knew anything else at all about the Shroud, should that not be included in your equation?

I should be grateful for clarification.

Hugh,
- A is the hypothesis that the shroud is authentic. ~A is the complement of A -- IOW, the shroud is not authentic.
- The other info we have about the shroud has been taken into account as estimates for P(A) and P(~A).
- Unfortunately, this stuff is difficult to get one's brain around if one hasn't had much practice at it (the category that Jay puts me in).

 

[Mojo]

- The other info we have about the shroud has been taken into account as estimates for P(A) and P(~A).

How did you factor in the probability of a piece of cloth that has been carbon dated at 700 years old having been around in the first century?

 

[JayUtah]

The other info we have about the shroud has been taken into account as estimates for P(A) and P(~A).

No it hasn't. First, your clearly predispositional analysis has been rejected for the reasons given. As explained, you can't go from the proposition that we can't know the sources of limestone to a low likelihood of it being legitimately present on a forged cloth. Hugh even tried to explain that to you, but you brushed past him to assert exactly the opposite of what he said. I have also explained this to you. And since it's obvious you are reading my posts, I would like a justification from you for why you have not addressed that explanation.

Further, you don't explain where the actual numbers come from. That's because it's obvious you just made them up. And as explained, made-up numbers don't provide a rational basis for further computation even in stochastic models.

Unfortunately, this stuff is difficult to get one's brain around if one hasn't had much practice at it (the category that Jay puts me in).

You are very much in that category. While you are able to work the equations, it is obvious you don't know what the models mean. As I said, fringe claimants often turn to a caricature of Bayesian modeling to lend the illusion of rigor to what is fundamentally just begging the question with numbers. You're simply begging the question with numbers.

Since no one is buying your bluff, kindly dispense with the pseudo-mathematics and produce the evidence you've been asked for.