Spontaneous Human Combustion
Today we're going to point our skeptical eye at one of the mainstays of the paranormal: spontaneous human combustion (SHC). The idea is that people can, while simply minding their own business, burst into flames, with no external source of ignition. It's not a medically recognized phenomenon, and no explanation exists that can reasonably account for any but a few of the many stories. Thus, it's found a firm home in the world of the strange, that subdivision of Earthly phenomena that is studied and promoted by only a few fringe researchers and outsiders. That doesn't mean it's wrong though; and we're going to look at it as closely as we can.
Spontaneous human combustion is a little different from most paranormal phenomena, in that it's a claim of no external source for the fire. That people have burned up is the fact that's not in question; the question is the theory of what caused them to burn. In this case, believers are asserting that there was no conventional cause. Their job is, in effect, to prove a negative. Proving a negative is different from the null hypothesis. The null hypothesis for an unexplained fire is simply to say that no cause is known, which is different from stating authoritatively that there is no cause. Thus, the burden of proof still rests on the claimant, even in this case. Science does not allow us to make the jump from "the cause of the fire is unknown," therefore "the cause is known and it's spontaneous human combustion." Science allows unanswered questions; indeed, science exists because of unanswered questions. The lack of an answer proves only that we don't know something yet, it does not prove the existence of the paranormal.
Stories of SHC generally fall into one of two categories. The first type is the discovery of a body that burned while nobody was present, usually almost completely to ashes but for a few bits like the hands or feet. Even bones are burned away. The second type is a dinner party or some other event, where many witnesses all see one person suddenly go up into flames for no evident reason, and the flames are usually extinguished before the person can be killed. For each of these two types, there are a few very prominently repeated examples that you'll find on the Internet or in books. We'll give two examples of each.
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People catching on fire is not especially uncommon. It happens all the time. The only thing differentiating the cases classified as SHC is that no source of ignition was found; the fires are said to have been spontaneous. Other than that, there's nothing especially remarkable about them. The fires burned in a familiar manner, and the injuries are what would be expected. But these cases of the Second Kind are also rare; probably more rare than the First Kind. The reason is that these are unsolved, whereas the First Kind cases are generally solved, at least to the satisfaction of the investigators. These two cases of the Second Kind are famous only because there was no source of ignition found. No cigarettes, open flames, or sparks were found near either Jeannie Saffin or Phyllis Newcombe; but it's not scientifically permissible to conclude that their combustions were spontaneous. Maybe they were; but just because we didn't find the cause hardly means that there wasn't one.
More:
http://skeptoid.com/episodes/4258