Miracle of the Shroud IV - The Phantom Image

[hugh farey]

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).

You're telling me. You seem to know a lot more about Bayesian statistics than I do, so I hope you can clarify a few more things.

Presumably we start with the premise that we don't know whether the Shroud is either authentic or not. If we knew, then P(A) and P(~A) would be 1 and 0, or 0 and 1, whichever we knew.

Now, in your calculation, P(A) is the probability that the Shroud is authentic, given all we already know about it, but excluding the information about the presence of limestone - is that right? And then P(A|x) is the probability that the Shroud is authentic, given all we already know about it, and including the information about the presence of limestone.

Now if I may try to spread out your equation a bit - and please correct me if I get it wrong, but on the right hand of the equation there seem to be 9 opening parentheses, but only 7 closing parentheses. Surely this cannot be correct? The calculation seems to depend on the number and positioning of these parentheses, so I should be grateful if you could check them. Will that be OK?

Is this correct?

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

Removing the the dangling parentheses:

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

Unfortunately, I can't see the rationale behind your multiplying and dividing. I've been doing a bit of experimenting with coins to try to work out what we need. Would you be so kind as to check my working?

The probability of three fair coins falling all heads is 1/8. However, if we are told that one of the coins has a 75% chance of being two-headed, then the probability of the three coins falling all heads is (1/8 * 2) * 3/4 = 3/16. I multiplied the original probability by 2 as, by separating one of the coins, the probability of the other two both falling heads is doubled.

That seems to work. It also works with two coins. The probability of two fair coins falling all heads is 1/4. However, if we are told that one of the coins has a 75% chance of being two-headed, then the probability of the two coins falling all heads is (1/4 * 2) * 3/4 = 3/8.

In more general terms, the probability of x coins all falling heads is 1/2^x, assuming ignorance of the chance of any coin being double-headed. If one of them has a 75% chance of being double headed, the chance becomes:

(1/2^x) * 2 * 3/4

Now let's use your figures.
You give P(A) as 0.1, and therefore P(~A) as 0.9, which is generously in favour of non-authenticity, and you give L(x|A) as 0.95 and L(x|~A) as 0.5, which is debatable.

So, the probability of the Shroud being authentic, given a 50/100 chance of limestone, is 10/100. However, if we are told that there is an 95/100 chance of limestone being present, then the probability of the Shroud being authentic is 10/100 * 2 * 95/100 = 1900/10000 = 19/100.

If this is correct, then why do we have to divide by anything?

Many thanks to anybody who has got this far!

 

[MRC_Hans]

Well done, Hugh. This could be fun!

Hans

 

[Jabba]

Blood/What difference does it make?

You're telling me. You seem to know a lot more about Bayesian statistics than I do, so I hope you can clarify a few more things.

Presumably we start with the premise that we don't know whether the Shroud is either authentic or not. If we knew, then P(A) and P(~A) would be 1 and 0, or 0 and 1, whichever we knew.

Now, in your calculation, P(A) is the probability that the Shroud is authentic, given all we already know about it, but excluding the information about the presence of limestone - is that right? And then P(A|x) is the probability that the Shroud is authentic, given all we already know about it, and including the information about the presence of limestone...

Hugh,
- So far, so good. It's very good having you around.

...Now if I may try to spread out your equation a bit - and please correct me if I get it wrong, but on the right hand of the equation there seem to be 9 opening parentheses, but only 7 closing parentheses. Surely this cannot be correct? The calculation seems to depend on the number and positioning of these parentheses, so I should be grateful if you could check them. Will that be OK?

Is this correct?

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

Removing the the dangling parentheses:

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

- Yes. Or, at least, I think so. I do have trouble with my parentheses.
- I'll have to think more seriously about the rest of your story..

 

[JayUtah]

I'll have to think more seriously about the rest of your story..

Will you be giving any thought to what anyone else has said? I must say the continued rudeness you've displayed by referring to what people have said (thereby showing that you read their posts) without addressing what was said has left serious doubts about your commitment to effective debate.

 

[hugh farey]

I meant to add that if Hugh seems to think it was improbable for a medieval artist to have obtained such a costly cloth, and that if Hugh doesn't believe the cloth is authentic, then what's his more probable origin hypothesis?

Sorry, I missed this earlier on. No, I didn't say that. It was the fact that the artist actually had obtained a costly cloth that made me think he was probably good at his job. Producing a 'holy relic' could have used a costly cloth, but did not need an image, which was denounced as a fraud anyway. A relic without credentials was always a dodgy proposition, and the Shroud didn't have any for over 50 years. Producing a ceremonial cloth to be used in a senior cathedral on Easter Sunday is, in my opinion, a better reason to get as good a cloth, and as good an image, as possible. Many of these were undoubtedly made, but none survive, and although I have not found any descriptions of painted images on these shrouds, I live in hope!

 

[JayUtah]

Sorry, I missed this earlier on. No, I didn't say that. It was the fact that the artist actually had obtained a costly cloth that made me think he was probably good at his job.

Oh, I see. That makes sense. I had just never heard your origin hypothesis explained comprehensively, so I was wondering.

 

[MRC_Hans]

Sorry, I missed this earlier on. No, I didn't say that. It was the fact that the artist actually had obtained a costly cloth that made me think he was probably good at his job. Producing a 'holy relic' could have used a costly cloth, but did not need an image, which was denounced as a fraud anyway. A relic without credentials was always a dodgy proposition, and the Shroud didn't have any for over 50 years. Producing a ceremonial cloth to be used in a senior cathedral on Easter Sunday is, in my opinion, a better reason to get as good a cloth, and as good an image, as possible. Many of these were undoubtedly made, but none survive, and although I have not found any descriptions of painted images on these shrouds, I live in hope!

There is another scenario: The shroud was not originally meant to pass as a relic, but only as a ceremonial object. Medieval churches are full of such objects. The object was either ordered by the Church or some artisan made it on his own initiative and donated to a church, in hope of some compensation, either financially or in the form of absolution (or both). Again, countless examples exist in history. (Not of shrouds, but plenty of other artefacts).

Hans

 

[MRC_Hans]

Hugh,
- So far, so good. It's very good having you around.

- Yes. Or, at least, I think so. I do have trouble with my parentheses.
- I'll have to think more seriously about the rest of your story..

So, you purport to use statistics to argue your point, but you feed imaginary data into your calculations, and you haven't got your formulas right.

How exactly do you expect anybody to take you seriosuly at all?

Hans

 

[JayUtah]

There is another scenario: The shroud was not originally meant to pass as a relic, but only as a ceremonial object.

Hugh covered that earlier. He mentioned that if this were the case, we might expect it to be known previously under that identity. That is, someone somewhere would have said, "No, that's not a relic because at my old church in Cité-de-la-Idée we used it as a prop in the passion play."

 

[abaddon]

"No, that's not a relic because at my old church in Cité-de-la-Idée we used it as a prop in the passion play."

Technically, every celebrated mass is a "passion play with props".

 

[Mojo]

Hugh covered that earlier. He mentioned that if this were the case, we might expect it to be known previously under that identity. That is, someone somewhere would have said, "No, that's not a relic because at my old church in Cité-de-la-Idée we used it as a prop in the passion play."

Unless its use for such a purpose is for some reason discontinued, and it is put aside and then rediscovered long enough after for there to be nobody that remembers it. I suppose this sort of scenario would require the cloth to be at least a century older than its emergence as a relic.

 

[JayUtah]

Unless its use for such a purpose is for some reason discontinued...

Or any number of other possible scenarios. I asked Hugh for his hypothesis just so I would know how what he thought. I hadn't intended to test or debate it.

 

[abaddon]

Unless its use for such a purpose is for some reason discontinued, and it is put aside and then rediscovered long enough after for there to be nobody that remembers it. I suppose this sort of scenario would require the cloth to be at least a century older than its emergence as a relic.

Well, I attended a Catholic funeral about 2 weeks ago, and it seemed to me that the altar cloth was pretty much a match for the form factor of the CIQ. From memory they all are.

Bit of a chicken and egg question then. Is the CIQ created to match altar cloths, or are altar cloths created to match the CIQ?

Dunno the answer to that one, but I will hazard a guess that the CIQ was intentionally modelled on altar cloths form factor.

 

[hugh farey]

Well, I attended a Catholic funeral about 2 weeks ago, and it seemed to me that the altar cloth was pretty much a match for the form factor of the CIQ.

Altar cloths do tend to be long and thin, and the Shroud could have been made to be used as one, or, in my opinion more probably to be displayed in front of or behind the altar, on a reredos. To my mind this explains another aspect of the Shroud, namely the head to head image, rather than a feet to feet one. I think that the last thing to be covered by a shroud is the head, and that, if anyone were to be laid on a long thin cloth to be folded over, they would be laid with the fold at the feet end, not at the head end, as in the Shroud. However, as a ceremonial image, the idea of the heads being at the ends of the cloth, and four feet together in the middle of the altar in front of the tabernacle, seems somewhat ludicrous, which is why I think the image was made head to head.

 

[MRC_Hans]

Hugh covered that earlier. He mentioned that if this were the case, we might expect it to be known previously under that identity. That is, someone somewhere would have said, "No, that's not a relic because at my old church in Cité-de-la-Idée we used it as a prop in the passion play."

Well, maybe someone did. 700 years is a long time. Also, it was generally detrimental to your health to speak against church authorities.

If you have studied recent history, e.g. WW2, you will notice how many holes in our knowledge exist about exactly what happened just a few decades ago.

Hans

 

[abaddon]

Altar cloths do tend to be long and thin, and the Shroud could have been made to be used as one, or, in my opinion more probably to be displayed in front of or behind the altar, on a reredos. To my mind this explains another aspect of the Shroud, namely the head to head image, rather than a feet to feet one. I think that the last thing to be covered by a shroud is the head, and that, if anyone were to be laid on a long thin cloth to be folded over, they would be laid with the fold at the feet end, not at the head end, as in the Shroud. However, as a ceremonial image, the idea of the heads being at the ends of the cloth, and four feet together in the middle of the altar in front of the tabernacle, seems somewhat ludicrous, which is why I think the image was made head to head.

And it is exactly that kind of ambiguous post which convinces me that you are a sindonist.

And Jabba himself also believes you are a sindonist. You have doubled the mountain you need to climb. You have voluntarily chosen to claim to the sindonists that you are not a sindonist whilst simultaneously supporting and propagating sindonism. It is more than a little odd.

Feel free to do so. FOS is free for all. But do not expect anyone to buy the baloney.

 

[wollery]

And it is exactly that kind of ambiguous post which convinces me that you are a sindonist.

And Jabba himself also believes you are a sindonist. You have doubled the mountain you need to climb. You have voluntarily chosen to claim to the sindonists that you are not a sindonist whilst simultaneously supporting and propagating sindonism. It is more than a little odd.

Feel free to do so. FOS is free for all. But do not expect anyone to buy the baloney.

He's talking about how and why the shroud was manufactured for christ's sake!

Why the flipping nora would a sindonist be pointing out that an authentic shroud would be more likely to be feet together, whereas the head to head version is more likely if created by an artist as an altarcloth??

This is exactly the sort of bullplop, seeing only what you want due to a preconceived idea, that skeptics are always railing against when it comes from others.

How you can see that post as anything other than supporting non-authenticity I have no idea. There is absolutely nothing ambiguous in that post!

Seriously, take your blinkers off and read it carefully, then please explain to me how it is ambiguous, and how it supports, in any way, an authenticist position.

 

[abaddon]

He's talking about how and why the shroud was manufactured for christ's sake!

Why the flipping nora would a sindonist be pointing out that an authentic shroud would be more likely to be feet together, whereas the head to head version is more likely if created by an artist as an altarcloth??

This is exactly the sort of bullplop, seeing only what you want due to a preconceived idea, that skeptics are always railing against when it comes from others.

How you can see that post as anything other than supporting non-authenticity I have no idea. There is absolutely nothing ambiguous in that post!

Seriously, take your blinkers off and read it carefully, then please explain to me how it is ambiguous, and how it supports, in any way, an authenticist position.

Because of this kind of crap...

I think you're right. However, imagine, for a moment, an exactly similar scenario to the 1988 sampling of the Shroud, perhaps with Professors Jull and Ramsey and any others of the original team still active, this time working on fresh samples, extracted, as were Perluigi Baima Bollone's in 1978, from a 'blood-soaked' area of the Shroud. Imagine, with rather more sophisticated techniques, that minute flakes of this 'blood' were radiocarbon dated, by the same three laboratories, and that the dates were as convincingly 1st century as the previous ones were 14th century. That would cause a bit of head-scratching. Without knowing which date was wrong, authenticists and non-authenticists would have to fall back on the other evidence to make up their minds as objectively as they could. What fun that would be!

Imagination. A super substitute for reality according to Hugh because it's "fun" to do that.

 

[wollery]

Because of this kind of crap...



Imagination. A super substitute for reality according to Hugh because it's "fun" to do that.

You said that Hugh's post was ambiguous and made him seem like a sindonist. I asked you what was ambiguous in the post you quoted, and how it made him seem like a sindonist.

Try answering the question you're asked.


Sent from my iPhone using Tapatalk

 

[hugh farey]

The inability to view any kind of evidence except as supporting one's preconceived position is spreading, I see, and does not seem to apply only to authenticists. Jabba's logic is catching.

More seriously, the fact that not everything is known about the Shroud does not weaken the evidence that it is medieval, but it stimulates worthwhile discussion. Charles Freeman suggests than an ordinary well-known artefact could 'become' a holy relic if a miracle was suddenly associated with it. However, although I do think a painted sheet could suddenly become 'sanctified', I don't think it could suddenly become the Shroud of Christ, unless a) no one knew where it had come from and b) it was attested to by a number of bishops. I don't think this happened with the Shroud. Nor do I think an attempt to introduce such a holy relic in such a small and otherwise insignificant village not far from a major cathedral was a sensible idea, which is why I don't think the Shroud was made for Lirey church. I think it possible therefore that Geoffroy de Charny brought it back from one of his excursions (and why not while held for ransom in England?) as an interesting artefact of no particular sanctity, and then after he died it was suddenly produced by some not too far-sighted clerics as the Shroud. The only thing that holds me back is d'Arcis claiming that it had been attested by the artist who painted it. Did Bishop Henri enquire as far as England for provenance? It's possible, but pushing our scenario beyond the quite likely into sheer guesswork.

Hey, ho. More crap, I expect... Pearls before swine, caviar to the general and all that....