Original artwork, not a still
Extraordinary claims require extraordinary evidence.
— Cosmos: A Personal Voyage • 1980
Behind the line
What it means
Our interpretation.
It is a sceptic's rule of thumb in six words: the stranger the claim, the better the proof must be. It has grown into the 'Sagan standard', invoked against ghost sightings, free-energy machines and cold fusion alike, and sometimes turned on genuinely new science. Sagan did not invent the principle, but his phrasing made it stick.
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In context
Spoilers for Cosmos: A Personal VoyageShow the scene
Sagan says this in Cosmos episode 12, 'Encyclopedia Galactica', while discussing UFO and alien-abduction stories. Having argued that older civilisations probably exist in the galaxy, he insists that what counts is hard evidence, rigorously and skeptically examined, not what sounds plausible or what witnesses claim. The idea was not new. Sagan had written the line in his 1979 book Broca's Brain, the sceptic Marcello Truzzi used the wording 'extraordinary proof' a year earlier, and Hume's 1748 essay on miracles is the deeper root.
Sources (2)
- Wikiquote: Carl SaganCosmos: A Personal Voyage, Episode 12 'Encyclopedia Galactica' (about 1 min 10 sec)Reference checked
- Wikipedia: Extraordinary claims require extraordinary evidenceLead and history sectionsReference checked
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