Jim,

What you seems to be saying in differnet terms is the old axiom in this profession, that evryu fire is unique and the investigator relies on his knowledge training and experience to make and support the determination. This is called inductive reasoning, and has permeated our profession for years. Most importnatly though, it doesn't meete to days standards for an expert (ala Daubert) and the Scientific Method.

"It's not what I beleive, it's what I can prove" is a great line from the movie "A Few Good Men." It's also sound advice for fire investigators today. The most important part of relying on the Scientific Method as the accepted methodology for fire investigation is that the results of testing ones hypothesis produces valid and reliable results. Precisely this means that different investigators at different times, relying on the same set of facts using the same methodology (and same knowledge base) SHOULD find similar results (or conclusions).

In my experience, different conclusinos most often result from selective use of the certain and not all facts, but mostly the improper methodology (and improper analysis for a variety of reasons), poor training, and failing to have any proof or evidence of deductive reasoning (e.g. testing the hypothesis) for the claim being made.

If the claim being made does not have any proof, or cannot be reproduced, or in any way be tested to ensure similar results, the claim is not supported and fails. Unfortunately, what often happens is that someone makes a (negative) claim in the absence of proof states their claim is true because it cannot be disproven. This is logical reasoning fallacy called "arguing from ignorance" or the fallacy of "shifting burden of proof." It requires the skeptic to the claim to do the work to try disprove the negative hypothesis which is impossible in many cases.

The inability to disprove a claim, particularly a negative claim, is not the same this as proving it (the claim) true.

Denny Smith