Assumptions baked into the VMS carbon dating

[eggyk]

One problem with the report, IMO, is that it does not accurately express the real assumption underlying the combination. I forget their exact words (and don't have the report to look at right now), but they said the assumption was basically that all the parchment was from the same source. That is actually not the effective assumption. The real assumption is more like this:

• The differences in the results from the four samples are mostly due to measurement error, residual contamination or other sources of uncertainty and, if that could all. be removed, then the dates for the four samples would very likely be the same... because the samples are very likely all from the same stock (or source) of parchment.[
  

I'm taking from the document linked on voynich.nu: You are not allowed to view links. Register or Login to view.

Here is the quote in that document that justifies averaging the results: 

The precision of any measurement can be increased if measurements are repeated. Given the clustering of the dates for the four Soxhlet treated samples, and the nature of the object (a book), one can argue that in fact, a single object was measured 4 times.

This is pretty explicitly saying that they are treating the 4 seperate folio samples as 4 samples of 1 object, specifically for the purpose of increasing precision.

Given that the manuscript folios share a common script, seem to have similar or related content, are all the same size, and were all bound together, it is pretty reasonable to assume they were all part of one production, put together around the same time, and using a common source of parchment. That may be completely wrong! But it is certainly more likely to be correct than not. So our prior belief is somewhat > 50%, at least. And since the four results overlapped substantially, it is reasonable to use that prior belief to resolve the (relatively minor) differences in the dating results across the samples. If they had varied wildly, then the assumption that their differences were all due to subsumed measurement errors, contamination uncertainties and such, would be difficult to defend.

As I stated before, the logic of book -> single object is not necessarily true. Many composite manuscripts containing similar content with different dates exist. Other manuscripts contain various works written at different times on the same parchment.

I was also under the impression that the VMS is assumed to have been bound later, meaning the folios were at one point seperate and unbound. It seems interesting to me that the justification behind this calculation was that because they were bound together in a book, the seperate folios can be considered one object. While at the same time, other reseach seperately suspects that the sheets of parchment were originally unbound and seperate. 

And you are effectively confirming what I said in the OP, which is that this assumption fundamentally comes down to a common script shared across the pages. This presumes that we know the context of voynichese - how many people could write it, understand it, and for how long a period of time. Why is it more likely that it was one production, instead of a student continuing the work of his teacher? 

I agree with much of the rest of what you are saying, too. As I mentioned, I am okay with much of the uncertainty and inherent variability that comes from carbon dating. My issue is basically with the final averaged range that was calculated. And yes indeed, it doesn't mean that the VMS date is wildly wrong either; it is almost certainly still a medieval object from broadly the same time period. But a range of, say, 1380-1450 has quite different implications for research than 1404-1435. I am of the opinion that we should seriously consider the wider range for purposes of research, to prevent missing crucial leads.