Sep 26 2011
Spontaneous Human Combustion (SHC) is one of those classic pseudosciences that have been around for a long time – like astrology, Big foot, and the Bermuda Triangle. I put it in the same category as the myth that we only use about 10% of our brain capacity; it’s widely believed, but no one really cares that much. It’s just something people hear about and have no reason to doubt, so they lazily accept it. I did when I was younger (in my pre-skeptical days), you hear about it on TV and think, “Huh, isn’t that interesting.”
It’s therefore a good opportunity to teach critical thinking skills. People’s brains are clogged with myths and false information, spread by rumor and the media, and accepted due to a lack of having the proper critical thinking filters in place. It’s disappointing, however, when people who should know better, or whose job it is to know better, fall for such myths.
Recently an Irish coroner concluded that a man died from SHC, and it is reported:
The West Galway coroner, Ciaran McLoughlin, said there was no other adequate explanation for the death of Michael Faherty, 76, also known as Micheal O Fatharta.
The coroner said: “This fire was thoroughly investigated and I’m left with the conclusion that this fits into the category of spontaneous human combustion, for which there is no adequate explanation.”
First, let’s play a game of name-that-logical-fallacy. The core fallacy the coroner is committing is the argument from ignorance. The investigation could not find a cause for the fire, therefore here is the specific cause – SHC. The conclusion should rather be – we don’t know what caused the fire.
The coroner said the case “fits into the category” of SHC – but how? Did it have any features that are known to correlate with gold-standard cases of SHC? That is what we generally mean when we say that something fits a defined category. It seems that the coroner only means – unexplained (back to the argument from ignorance).
The case is a good example of why scientists and experts need to have critical thinking skills in addition to their area of expertise. Knowing a lot of information about a complex subject area does not necessarily also grant critical thinking skills – knowledge of logic, heuristics, and mechanisms of self-deception. This is why scientists fall prey to magicians or con-artists, and sometimes even deceive themselves and take their careers down the rabbit hole of pseudoscience.
Let’s get back to the argument from ignorance – someone might argue that it is reasonable, if no external source of fire is found, that we conclude it was therefore spontaneous. In medicine we sometimes make what is called a “diagnosis of exclusion;” once all other diagnoses have been eliminated, we are left with a diagnosis for which there is no positive evidence. But the analogy breaks down in two very important ways.
When we make a diagnosis of exclusions we are appealing to a known entity, whereas SHC is an unknown entity. For example, migraine headaches are often a diagnosis of exclusion. But migraines are a known entity, they are characterized by specific signs and symptoms, and we understand something about what causes them. We have identified specific physiological processes that are involved with migraines. We just do not have any diagnostic confirmatory tests that are sensitive and specific enough to be useful, so we rely on clinical features and ruling out anything serious that can have similar features.
SHC, on the other hand, has never been confirmed to exist – not a single case. The entire hypothesis is based upon the argument from ignorance, strange cases of immolation where the source is not discovered by investigation. I should note that many cases presented as SHC do not even fit this category as there are obvious external sources of ignition or fire, like smoking or fire places. But if we take the best cases, they are based entirely on not knowing what the source of fire was.
There are no proposed mechanisms of spontaneous ignition that even approach plausibility. There are no cases where a person spontaneously combusts while being witnessed, or cases where other animals (animals that do not routinely use fire) spontaneously combust. There are no cases of near combustion, where someone heats up for an unknown reason but does not reach the ignition point. Nor are there cases where someone combusts spontaneously but survives to tell the tale.
All we have are cases where a corpse is found burned, with fire damage to the surroundings, and no witnesses as to what happened. In many cases there are obvious fire sources. In other cases there are no obvious sources, but there are potential sources. In decades of investigating fires it makes sense that there will be the occasional case where the source of fire cannot be discovered. The alternative is to believe that fire investigators will be 100% successful in explaining every case they come upon, which is an unreasonable expectation.
This falls under, therefore, what I call the residue effect. For any frequent phenomenon there will be a certain number (a residue) of cases that defy explanation, just by chance alone, because there are quirky, unique, or highly unlikely circumstances. Very unlikely things happen all the time, given enough opportunity. It is therefore not only the argument from ignorance, but utter folly to conclude that such cases have a paranormal or fantastical explanation, rather than they are just unusual but still mundane cases.
The coroner in this case should have concluded that the cause of the fire was unknown, not that it fit into a non-existent category of SHC. But at least he provided another teaching moment for the promotion of critical thinking.
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