The process called the Genealogical Proof Standard, is explained in the book as providing "a way to differentiate correct from incorrect information, to determine unspecified relationships, and to demonstrate that (genealogical) research results are credible."
With the GPS its axiomatic that if you follow the process you "minimize the risk of polluting sound research with dubious conclusions."
I have two concerns regarding this "textbook on genealogical methods and reasoning in the 21st century."
First, if anything says 21st century genealogy it's DNA evidence. Yet there is only a single paragraph on DNA evidence in the whole book. As renowned genealogist Helen Leary wrote in 1998 “Science and the law are in agreement: there is only one way to prove kinships beyond reasonable doubt — DNA.” At that time she had to add the caveat that such testing was not practicable. The 21st century has changed that. Spectacular successes in tracing kinships of adoptees, where documentary evidence was unavailable or unproductive, is just one area that bears witness that DNA deserves more than this passing mention.
Second, the text, and the GPS, skirt the question of expressing confidence. The emphasis is on resolving conflicting evidence. A section on page 75 deals with unresolved conflicts.
"Stopping short of proof, we may state that the point is unresolved, summarize the related evidence, and explain why the conflict is not resolved. We can express a belief that one side of an unresolved conflict is more likely correct. The discussion should make it clear to readers that we are presenting an opinion, not a conclusion from evidence. Recognizing that in such cases we have no conclusion or proof – all we have is a possibility – we qualify the discussion with words like perhaps and possibly."Chapter 1, Genealogy's Standard of Proof , makes it clear that "standards stop short of absolute certainty." A proof is still liable to be overturned by new evidence. So the difference between a "proof" which is not absolutely certain and unresolved conflicting conclusion possibilities is the degree of confidence. The solid line drawn between proof and absence of proof is an invention of the genealogical establishment.
As Jones writes in his preface clients look to a professional genealogist for a determination of the reliability with which genealogical findings reflect the past. Is a finding nearly certain, highly likely, probable, somewhat likely, etc? Unfortunately this book, and the GPS, fail when it comes to providing any such standard. A client cannot be confident that a professional genealogist's expression of reliability is based on a reproducible standard.