If our standard for decision making and knowledge is "absolutely, unequivocal certainty" then "best probable analysis" equates to a degree of uncertainty which fails to meet our knowledge standard and we are left "Undetermined." I could say the words "I am absolutely 100%, without reservation certain that this, and only this, is what happened" - but the truth is that that will only occur for some fires. For many fires, there will be logical, plausible alternate hypothesis. My job is to show that, given the facts of this particular fire, this is the most probable of all potential constructs. I may be too philosophical about this and I fully realize that when people’s lives and property are at stake, they want ABSOLUTE CERTAINTY, but I often have trouble offering that in a scenario where I am trying to recreate an event for which all variables cannot be resolved.
We often speak of a "standard of care" and a comparison to medicine - I don't believe that any doctor would ever say "I am absolutely certain that if you take X pill, Y condition will be cured without side-effects or untoward reactions" (as in fires, there may be some limited exceptions) What they often do is say that they have very good results or success with a particular treatment, but the benefits outweigh the risks of certain treatments - that is no guarantee - but represents our best probable treatment regimen. If you want certainty, you can find a doctor who will prescribe an antibiotic for a cold with the guarantee that in 7 -10 days the pills will cure the cold, but the cold was going to go away in a week anyway and all the pills did was give you a mental reassurance of certainty. It was the soothing balm of certainty that we strive for.
I wish I could offer certainty, but my mental and philosophical make-up causes skepticism and doubt. The Supreme Court doesn't expect "scientific certainty" why should we?