LOGIC and 9/11: Assessing the Evidential Weight of Expert Opinion

By Will Fenio
911debunkers.blogspot.com

It is interesting how easily smart people can slip into poor reasoning when attempting to refute skeptics of the official 9/11 story. One such mistake comes up when discussing the multitude of architects, engineers and other experts that have publicly doubted the NIST account of the WTC building collapses. Debunkers often concede that more than 2,000 experts (in relevant fields) have indeed voiced such skepticism; but they object that this number is actually just a small fraction of the total pool of such qualified professionals (most of whom have not publicly voiced this skepticism). The insinuation is that such skepticism is unwarranted, since it is only expressed by a minority of the people that work in those areas. Unfortunately, there is a formal logical fallacy that underlies this rhetorical strategy. It is called affirming the consequent.
Formally, it can be expressed as the following syllogism.
Premise 1.) A, therefore B
Premise 2.) B
Conclusion: A 

Or, in this case,

Premise 1.) [A] If a person is an expert that publicly criticizes the official 9/11 story, then [B] they doubt the official 9/11 story.
Premise 2.) [B] An expert doubts the official 9/11 story.
Conclusion: Therefore, [A] that expert will publicly criticize the official 9/11 story.

Obviously, the conclusion in this argument form does not follow. One can visualize it in a Venn diagram (see below). If all members of A are members of B, that doesn't entail that all members of B belong to A. There may be many more experts that doubt the official story, but for one reason or another (careerism, fear of ridicule, peer pressure, etc.), refuse to voice their objections. 

Another crucial consideration is that not all experts in relevant fields have even looked into the issue and scrutinized the data. The only germane opinions are the ones of experts that have evaluated the data in a scientifically dispassionate way. If that group became our set C (see diagram), it may be that B would be a relatively large subset (if not coterminous with C). We can also represent the totality of those with relevant expertise as the biggest set [D], becoming the outermost circle in the Venn diagram.  By appealing to this totality, debunkers may be covertly treating set C as coterminous with set D, and contrasting that fallaciously conflated set with A.  But the only ratio that matters is that of subset B (i.e. all the relevant experts that doubt the official story) and set C (i.e. the entire pool of relevant experts that have evaluated the data in a scientifically dispassionate way). Unfortunately, this ratio is not easily accessible.  However, given the myopic bias that plagues the official explanations advanced by NIST (and derivative parties), it wouldn’t be surprising if B encompasses a majority of the members of set C.  It would certainly be a mistake to infer that A:D (undoubtedly, a small ratio) accurately reflects B:C (which may be very large).  Once these substantive categorical nuances are introduced, A:D becomes largely irrelevant to assessing the evidential weight of credentialed opinion on the issue of the WTC building collapses, insofar as appeal to expert consensus is concerned.



Related:

FAQ #9: Why does AE911Truth Represent Only a Small Percentage of Architects and Engineers?

http://911debunkers.blogspot.com/2011/12/faq-9-why-does-ae911truth-represent.html