one of his most famous quotations, in
Cosmos, was, "Extraordinary claims require extraordinary evidence"
[63] (called the "Sagan Standard" by some
[64]). This was based on a nearly identical statement by fellow founder of the
Committee for the Scientific Investigation of Claims of the Paranormal,
Marcello Truzzi, "An extraordinary claim requires extraordinary proof."
[65][66] This idea had been earlier aphorized in
Théodore Flournoy's work
From India to the Planet Mars (1899) from a longer quote by
Pierre-Simon Laplace (1749–1827), a French mathematician and astronomer, as the Principle of Laplace: "The weight of the evidence should be proportioned to the strangeness of the facts."
[67]