First appearance of "Extraordinary claims require extraordinary evidence."

[Podkayne]

One finds this quote, and many variations, sprinkled throughout the skeptisphere, usually attributed to Sagan, who certainly used it often, but does anyone know when this sentiment was first published or uttered?

[Northern_Piper]

It has some similarities to Ockham’s Razor, but going the other way. Ockham’s points to choosing the simpler explanation; this one flips it and calls for more weight to support a more complex explanation.

but whether they’re linked in logical philosophy, I don’t know.

[bonzer]

This article by Massimo Pigliucci from Skeptical Inquirer last year suggests that the first appearance of the specific phrase was back in 1976 in Marcello Truzzi’s editorial in the first issue of The Zetetic, the magazine that became Skeptical Inquirer after Truzzi broke with CSICOP.

Pigliucci’s main point in the piece is to discuss the commonly made observation that the theme dates back, at the very least, to Hume on miracles.

[Podkayne]

Thanks, bonzer. The reason I was looking was that I found this quote from a letter by Thomas Jefferson in 1808:

A thousand phenomena present themselves daily which we cannot explain, but where facts are suggested, bearing no analogy with the laws of nature as yet known to us, their verity needs proofs proportioned to their difficulty.

and I thought it’d be amusing to put it side-by-side with the extraordinary claims quote from Sagan, with a date quoted for that, as well, but I couldn’t figure out when he’d first said it. From the article you linked to, looks like it was in Cosmos.

[Northern_Piper]

Checked with my philosopher brother, who came back with the same passage from Hume that bonzer cited:

@David Hume

A wise man, therefore, proportions his belief to the evidence.

(An Enquiry concerning Human Understanding, sec. 10, part 1, p. 110).

Given Hume’s influence in the Enlightenment, he may have been the inspiration for Jefferson’s comment as well.

[ianzin]

In a separate thread, Bonzer drew my attention to this thread and suggested it would be helpful to post the following reference.

‘The Zetetic Scholar’, Volume 1, Number 1, published by Marcello Truzzi, 1978. Page 11, article by M. Truzzi, ‘On the Extraordinary: An Attempt At Clarification’:

"In dealing with claims alleging paranormal events, a basic question concerns the degree of evidence needed to establish such claims. As the paper by Laurent Beauregard (in this issue) points out, this is not a simple matter and is one which must take into account one’s prior orientation to the world. In the simplest terms, I have expressed the matter in the statement: ‘An extraordinary claim requires extraordinary proof’. "

In this passage it seems that Truzzi is quoting himself, but there is no direct reference or footnote stating where he had previously expressed this statement. However, on the page immediately after this article is a bibliography which may or may not have been intended to be associated with the article (it is unclear). In this bibliography, the only supplied cite pertaining to Truzzi is: “Definitions and dimensions of the Occult: towards a Sociological Perspective,” Journal of Popular Culture, 5, #3, Spring 1972, 635-646.

Truzzi’s Zetetic Scholar article, quoted above, is an analytical philosophical piece about what we mean when we declare something to be ‘extraordinary’, and he uses the term ‘extraordinary proof’ to mean proof that is unusual or unlike that which is familiar and normally encountered.

[Cliffy]

@Podkayne

One finds this quote, and many variations, sprinkled throughout the skeptisphere, usually attributed to Sagan, who certainly used it often, but does anyone know when this sentiment was first published or uttered?

BTW, while there’s little connotational difference, in my experience Professor Sagan usually used the word “proof” at the end of the statement. Just a nitpick, mostly made so that I could namedrop.

–Cliffy

[bonzer]

While waiting to see what you’d find ianzin, I did some digging via Google and discovered that a handful of websites - like this one - quote Truzzi as follows:

And when such claims are extraordinary, that is, revolutionary in their implications for established scientific generalizations already accumulated and verified, we must demand extraordinary proof.

This is cited as “Editorial, The Zetetic, vol. 1 (1) (Fall/Winter 1976), page 3-6. The quote appears on page 4.” It’s presumably this, which predates “On the Extraordinary” by two years, that Pigliucci’s footnote is a reference to.

[ianzin]

@bonzer

This is cited as “Editorial, The Zetetic, vol. 1 (1) (Fall/Winter 1976), page 3-6. The quote appears on page 4.”

Puzzling, because Zetetic volume 1, issue 1, is dated as 1978. At least my copy is.

[samclem]

The Cleveland Public Library Catalogue says they have

The Zetetic.
Buffalo, N.Y. : Committee for the Scientific Investigation of Claims of the Paranormal, c1976-c1977.
Item Description: 2 v. : ill. ; 23 cm.SemiannualVol. 1, no. 1 (fall/winter 1976)-v. 2, no. 1 (fall/winter 1977).

[bonzer]

Sure you’re not confusing The Zetetic Scholar with The Zetetic, ianzin?

[samclem]

@Cliffy

BTW, while there’s little connotational difference, in my experience Professor Sagan usually used the word “proof” at the end of the statement. Just a nitpick, mostly made so that I could namedrop.

–Cliffy

The earliest Sagan quote I could find in the newspapers was in the NYTimes, Dec. 16, 1977.

Extraordinary claims require extraordinary evidence.

[ianzin]

@bonzer

Sure you’re not confusing The Zetetic Scholar with The Zetetic, ianzin?

Yes, I was confusing the two. Well spotted. I have the first issue of Zetetic as well.