Do extraordinary claims require extraordinary evidence?
Pseudo-skepticism and the issue of burden of proof
You might have heard the catch phrase “Extraordinary claims require extraordinary evidence,” which is often uttered by skeptics against anyone who purports to believe in extra sensorial perception, UFOs, unlikely conspiracy theories, god, and a large variety of other dubious notions.
It is often attributed to one of the founding fathers of the American skeptical movement in the 1970s, the astronomer Carl Sagan, who did in fact use it in a Cosmos/PBS segment aired on 14 December 1980. Sagan, however, borrowed the phrase from Marcello Truzzi, an American (and Danish born) sociologist who co-founded (together with the legendary Paul Kurtz) what was known as the Committee for the Scientific Investigation of Claims of the Paranormal (CSICOP) in 1976. (Nowadays CSICOP is known as CSI, the Committee for Skeptical Inquiry.)
Truzzi’s original phrase was “An extraordinary claim requires extraordinary proof,” as he put it in the first issue of his journal, Zetetic Scholar, published in 1978. In turn, Truzzi himself borrowed the sentiment from the 18th French astronomer Pierre-Simone de Laplace, who said that “the more extraordinary a fact is, the more it needs to be supported by strong evidence.” The Scottish Enlightenment…
