According to the font of knowledge, Wikipedia, the oft-quoted expression, “An extraordinary claim requires extraordinary proof,” is due to Macello Truzzi. See Marcello Truzzi, “On the Extraordinary: An Attempt at Clarification,” 1(1) Zetetic Scholar 11 (1978). I certainly recall hearing a similar statement from Carl Sagan, who popularized the expression on his PBS specials. But Pierre-Simon Laplace, in his Bayesian phase, stated the matter best, over two centuries ago:
“The weight of evidence for an extraordinary claim must be proportioned to its strangeness.”
Martin Fleischmann and his associate, B. Stanley Pons, might have avoided some embarrassment if they had taken Laplace’s maxim to heart. With a very low posterior probability, they needed an extraordinary likelihood ratio to make their claimed outcome of “cold fusion” credible.
In March 1989, Fleischmann and Pons held a news conference to announce their illusory discovery of so-called “cold fusion.” The immediate reaction from many in the media was uncritical acclaim. Fleischmann and Pons made the front page of major newspapers, and the covers of the then popular weekly news magazines (Time and Newsweek). The media frenzy was clearly justified if the claim were true. Their spectacular claim invited attempts at replication, but no amount of wish bias could make dream into fact. Scientists from around the world, including the American Physical Society and from the United States Department of Energy, in short order, put Fleischmann and Pons’ claim to rest.
Martin Fleischmann died earlier this month, and the New York Times published a lengthy obituary. Douglas Martin, Martin Fleischmann, Seeker of Cold Fusion, Dies at 85, N.Y. Times A18 (Aug. 12, 2012). Not surprisingly, the Times focused on the “cold fusion” fiasco, and the discredited research claim of Fleischmann and Pons. The obituary quoted Richard Petrasso, a Massachusetts Institute of Technology physicist who, in a 1991 interview, expressed his initial conviction that Fleischmann and Pons’ work was an “absolute fraud,” but later softened in noting that the two scientists “probably believed in what they were doing.” William J. Broad, “Cold-Fusion Claim Is Faulted on Ethics as Well as Science, ” New York Times (Mar. 17, 1991).
Petrasso was probably correct, but his interpretation, while charitable, highlights the power of wish and confirmation biases in science. Fleischmann was a capable, well-trained scientist. He received his doctorate from the University of London, held respectable academic appointments, and was elected a fellow of the Royal Society. He had over 240 articles published in journals. While social constructivists anguish over corporate influence in science, a great deal of really bad science receives a pass because wish and confirmation biases are so commonplace. The Times quoted Fleischmann as saying, in 2009, that “unless we get fusion to work in some fashion, we are doomed, aren’t we?” Perhaps his sense of doom helped make his slippery evidence easier to accept. According to the obituary, Fleischmann and Pons planned their experimental approach while hiking in Utah. Whiskey was involved.
Inexpensive, limitless energy attracted a great deal of attention. Unfortunately, many science and health claims do not elicit prompt attempts at replication, and the public and the scientific communities are often willing to accept claims at face value. They would be prudent to heed Laplace’s dictum. I can think of any number of litigation claims which evaded expert witness gatekeeping because of violations of Laplace’s guidance.
As for Fleischmann’s death, the obituary in the Times probably suffices to prove the fact.
