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Wednesday, March 22, 2006

Two kinds of skepticism

As I mentioned in my post of March 11, some interesting issues were raised on the unfortunate March 10 episode of Numb3rs. There was no explicit mention of the dispute between two kinds of skepticism, but that was actually the underlying theme of the episode.

The premise behind the show was that a soi-disant psychic was helping the FBI. Charlie was of course dismissive of the whole thing, pointing out that psychics are charlatans. But Larry, the physicist, claimed that a skeptic should maintain an open mind about paranormal phenomena even though there has never been any scientific evidence for it. Therein lies the dispute: if you have no evidence on either side — no evidence for and no evidence against a phenomenon — how do you decide whether to believe in the possibility of its occurrence?

As I said in that March 11 post, extraordinary claims require extraordinary evidence, or at least some evidence. If Griselda claims that she had pizza for dinner on Monday, I have no reason to doubt her. I may also have no evidence for her claim, but the response of a proper skeptic is to ask what toppings she had, not to challenge the claim and say that I can’t possibly believe that she had pizza on Monday unless I have some hard evidence to support this hypothesis. That’s because Griselda’s statement isn’t an extraordinary claim.

But if she says that she ate flamingo tongues on Monday, I will doubt her. I will not merely take a neutral position — no evidence for, no evidence against. Because this is an extraordinary claim, the burden of proof shifts to her side, and the properly skeptical view is to say that I don’t believe it.

One of my students reports that another teacher claims that some extraordinary amount of Internet traffic — 76% maybe, I just don’t remember — consists of pornography. If the claim had been 10%, I might have looked for evidence to support it, but with an outrageous claim I feel no such compulsion. The burden of proof is in the other teacher’s court, not mine.

So how does all this relate to people who claim psychic ability? I know perfectly well that there has never been a shred of scientific evidence behind such claims, so my appropriate response is not neutrality but outright doubt. Despite his name, Larry is wrong. Charlie is right.

And how does this relate to two kinds of skepticism? In the Numb3rs episode, Larry was the moderate skeptic, Charlie the radical skeptic. Moderate skepticism preaches keeping an open mind about everything that has not been explicitly disproved, even if it’s an extraordinary claim for which there isn’t any evidence despite a great many advocates. Radical skepticism is what I have been describing above and is best represented by the popular magazine, the Skeptical Inquirer. Radical skepticism is often derided by its opponents as “scientism,” and indeed its meta-principles often seem like a religion. But it’s what belongs in a scientific framework, unlikely the wishy-washy moderate skepticism that leads to travesties like “intelligent design,” which would be fine in a religious school but not in a science classroom. For the same reason, a show that features the benefits and uses of mathematical thinking should never have stooped to sensationalistic pandering by making ESP seem plausible.

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