Following on my post Lineage societies and the genealogical proof standard leading genealogy blogger Randy Seaver and others commented "I'm unclear as to your meaning of "probabilistic approach." How would that work?"
It isn't straightforward. Neither is mastering the skills needed to be a certified genealogist yet many rise to the challenge.
The previous post quoted Elizabeth Mills at http://learn.ancestry.com/LearnMore/Article.aspx?id=803
"The most we can do is to establish probability through an expert analysis of the evidence known to date."There's further enlightenment in Elizabeth Mills, “Working with Historical Evidence: Genealogical Principles and Standards,” Evidence: A Special Issue of the NATIONAL GENEALOGICAL SOCIETY QUARTERLY, NGSQ 87 (September 1999): 165–84, available at http://www.voicespast.com/NGS/091222_1141/appendix/evid.pdf
"Levels of ConfidenceWith no concrete definitions the use of these terms is anything but transparent, hardly the hallmark of professionalism.
Within sound genealogical studies, information statements about dates, identities, places, relationships, and similar matters are frequently prefaced by such terms as apparently, likely, possibly, or probably—all denoting that the stated “fact” is clouded by doubt. To date, these terms have no concrete definitions; practically speaking, they take on whatever shade each individual researcher provides with his or her supporting detail."
The same article continues by referring to, while not endorsing, a three level probability scale:
• Possibility, used at the “speculation” stage—a term comparable to the math/physics concepts intuition and guess.Finally, Mills, Elizabeth Shown. Professional Genealogy: A Manual for Researchers, Writers, Editors, Lecturers, and Librarians. Baltimore: Genealogical Pub., 2001, page 463 refers to a range of probability expressions:
• Probability, used at the “hypothesis” stage—a term comparable to the math/physics concepts proposal and conjecture.
• (Reasonable) certainty, used at the “proof” stage—a term signifying a convincing degree that is comparable to the math/physics concept verification.
Possibly There is a remote possibility .......He could have
Probably There is a slight chance .......He must have
Certainly There is a chance ..... Her certainly must have
All those references are at least a decade old. Shouldn't time move on in developing genealogical methodology?
Virtually Impossible = 0.0001%
Extremely Improbable = 1%
Very Improbable = 5%
Improbable = 20%
Slightly Improbable = 40%
Even Odds = 50%
Slightly Probable = 60%
Probable = 80%
Very Probable = 95%
Extremely Probable = 99%
Virtually Certain = 99.9999%
If the genealogical profession were to agree they saw advantages in adopting some such probability scale as a standard then the profession could move on to how to assess the probability.
Those whose minds are open to the possibility of such an approach should read the first few chapters of Richard Carrier's book or watch him explain the use of Bayes' Theorem in exploring historical issues at http://www.youtube.com/watch?v=HHIz-gR4xHo to get an idea of how that might work. Don't be put off by his style of presentation. There are other YouTube videos on Bayes' Theorem including a series starting at http://www.youtube.com/watch?v=XR1zovKxilw which I found to be one of the most understandable.
Neither of these are presented in a genealogical context.
More to come later ...