I would consider it progress, not proof. The age is the elephant in the room and dancing around with talks of blood and limestone doesn't address that it's not even half as old as it should be. Arguing favorably that it is that old would be a good step in the right direction.
Jabba wants to mount an inductive case based on circumstantial evidence. Sadly he's approaching it from such a comically biased direction that he can't see the radiocarbon dating as a "circumstance" he must include.
Aside briefly, let's recall Jabba is trying to equivocate between two meanings of "circumstantial evidence." Even accepting
arguendo that circumstantial evidence is useful in this case, Jabba's shenanigans surrounding it are inexcusable. "Is X circumstantial evidence?" he asks. "Is X circumstantial evidence of authenticity?" He's asking for individual examples of circumstantial evidence in order to blur the distinction between
one individual line of evidence that participates in a circumstantial case, and the entire case itself. The latter may be probative. The former certainly is not.
How can I say that with such confidence? Because the difference between circumstantial evidence and direct evidence is exactly the difference between support and mere consistency. A single piece of evidence may be consistent with several hypothesis. As such it may be considered circumstantial evidence. But of what? Of nothing. It is circumstantial in nature. It is not evidence supporting of some particular hypothesis over another. Specifically it is not evidence supportive of one of the several consistent hypotheses over the other.
In this debate even the word "evidence" becomes putty in Jabba's hands. Were I not to write this caution, I'm sure Jabba would -- as he has before -- co-opt this post to ask, "Are you saying I have evidence?" There is a neutral meaning to "evidence," but when you want to start talking about support for a hypothesis then you need one of the more qualified definitions. I can speak of "evidence in the case," but you won't know without further discussion whether I intend the evidence to be inculpatory or exculpatory.
How do bits of circumstantial evidence -- individually inconclusive -- form a case? By means of convergence and consilience. A single bit of "circumstantial evidence" proves nothing either way. By definition, a single bit of "circumstantial evidence" cannot by itself support one hypothesis over another, except those hypotheses that are simply inconsistent with the evidence. (Jabba has co-opted this exclusion principle and misapplied it to his claims.) We don't consider hypotheses that are inconsistent with any of our evidence. We consider only consistent hypotheses.
Hence I cannot give you a single example of "circumstantial evidence in favor of X?" if by that is meant a single bit of evidence. I can give you an example of circumstantial evidence that may be developed into evidence for X, but that requires additional effort. I can give you an example of a case for X composed entirely of circumstantial evidence, but that would not be just a single item. In essence, what Jabba is asking for simply doesn't exist by definition.
So what is "convergence" in this sense? As I said, you assemble the body of relevant evidence. You postulate in each case what possible collection of causes produced that one observation. That hypothesis set becomes a category of hypotheses that is susceptible to propositional (categorical) reasoning. Now if you do this honestly and carefully for each line of evidence, and the set of hypotheses common to all of them contains but one hypothesis, then the evidence is said to have converged. Not all bodies of circumstantial evidence do this. But the important thing to remember is that
circumstantial evidence does not support a hypothesis unless there is convergence.
This is why circumstantial evidence must be taken as a whole in order to have any probative value. The logical analysis simply doesn't occur unless there exist several categories of hypotheses whose intersection can be reasoned.
Blood is circumstantial evidence. It is arguably consistent both with authenticity and certain artificial means of production. Limestone is circumstantial evidence. Even more so than the blood, it is simply refractory to the question of authenticity. Limestone on the cloth would occur simply from the cloth's known history since 1300 CE, regardless of its history, if any, before then. Are these things circumstantial evidence
of authenticity? Clearly not. Taking the intersection of the hypotheses sets, we find no unity or clarity. The evidence, as considered here, does not converge. There is no proof here by circumstantial evidence.
Jabba's categories of hypothesization are simply just so far out there as to be irretrievably biased. He wants to consider things like blood and limestone to be a body of evidence that favors authenticity. He wants to consider the radiocarbon evidence to be in a separate body of evidence that favors forgery. He wants to put them on opposite sides of a scale and argue over which way the scale tilts. And he concludes it tilts toward authenticity.
But if you want to reason "circumstantially," then you have to throw all the pertinent evidence into the same pot and look at those hypotheses sets. Lo and behold, when you factor in the weave, the blood, the limestone, and the carbon isotopes and look at the intersection of hypotheses, you find fairly easily that the evidence has converged toward forgery.
Following Jabba's logic, such an exercise would "prove" that blood or limestone is "circumstantial evidence of forgery." But such is not the case. (Jabba commits this error, but in the direction of authenticity.) Not only is it circular reasoning, it commits one of a number of compositional fallacies.
The probative value of the
body of evidence does not distill upon its constituents. Just because the Senate may do various things does not mean each individual senator can do any of those things. The power of the Senate is vested in the convened body, not in its elements. Commensurately the proof of a case founded upon circumstantial evidence is vested in the body of it, not in each or any of its elements. Without providing the body and showing convergence, one has no case.
Now onto consilience. This is a different perspective on convergence, which shows merely a common thread in all the hypotheses explaining all the elements of evidence. The law of parsimony tells us that, all other things being equal, the hypothesis that requires the least assumption is most likely to be the truth. But we can go one better. Within the purview of one line of evidence we can apply knowledge to determine, of all the possible ways to explain it, which one most
likely explained it.
We do this irrespective of all other lines of evidence. The key to consilience is that we scrupulously avoid bias intruding from other lines of evidence and from some hovering overall conclusion. (Crime labs, incidentally, generally do not do this, which is a big reason why scientific findings in the legal sense are not compatible with pure scientific inquiry.) When we come to the table with evidence that not only converges, but converges to the strongest hypothesis that individually explains each element of evidence, we have a case that can meet a standard of probativity that establishes reliable fact.
The strongest explanation for the radiocarbon dating is that it is, in fact, the scientifically indicated date. Explanations that it arose from switched samples, from non-representative samples, or by means of coercion or conspiracy have been tested and are simply not convincing explanations for that particular bit of evidence. If you develop the other lines of evidence accordingly, but without regard to carbon dating or to whether you favor authenticity or not, you come up with similar comparisons.
And the consilient finding among all the pertinent evidence is that the shroud is an artifice that is roughly 700 years old.
Jabba says he can provide an argument from consilience to the contrary. But he clearly won't, so we reject his argument as bluff and bluster.
