Quotation
Last reviewed:
“Extraordinary claims require extraordinary evidence.”
Carl Sagan · Thinkers beyond philosophy · Modern · 1979 and 1980
What does it mean?
A stranger claim needs a stronger case than a familiar one, and it is still worth pursuing. The usual reading keeps both halves: do not shut the door, and do not let the door swing on a light push. A competing reading uses the short sentence as a way to dismiss anything unfamiliar without looking, which drops the line in Broca's Brain about pursuit. He popularised the wording in Cosmos in 1980. Chapter 5 of Broca's Brain, 1979, is the fuller form. Laplace and Marcello Truzzi had already asked for proof in proportion to the strangeness of the claim. The sentence is well attested as his. The standard is older than he is.
Did Carl Sagan really say this?
The library’s label is Well attested. He said this wording, and he made it famous. In Broca's Brain, chapter 5, the sentences are: the extraordinary should certainly be pursued, but extraordinary claims require extraordinary evidence. Cosmos, episode 12, uses the short form about claims of alien visits. The idea is older. Laplace wrote that stranger facts need stronger proofs. Marcello Truzzi wrote in the 1970s that extraordinary claims require extraordinary proof. Sagan popularised this wording. He did not found the standard.
Where it comes from
Cosmos, television series (1980), episode 12, Encyclopedia Galactica; also Broca's Brain (1979), chapter 5
Approximate date: 1979 and 1980.
How to use it
A neighbour in York who reports a medical cure from one vivid story is owed a hearing and a heavier demand than a claim about the bus being late. Proportion is the rule. Sneering is not what he asked for, and gullibility is not either.
A mindset reading
Ask how extraordinary the claim is, and then ask what evidence would match it. If you cannot say what would count, you are not using the sentence. You are wearing it.
Understand the philosophy
The short form is Cosmos, episode 12. The two-sentence form is Broca's Brain, chapter 5. The key word is extraordinary, applied to the claim and then to the evidence. Chapter 12 of The Demon-Haunted World is the kit for doing the test. The origin note is part of the citation. Leaving Laplace and Truzzi out makes Sagan look like the first sceptic, which he was not.
- knowledge
- mind
FAQ
What does it mean?
A stranger claim needs a stronger case than a familiar one, and it is still worth pursuing. The usual reading keeps both halves: do not shut the door, and do not let the door swing on a light push. A competing reading uses the short sentence as a way to dismiss anything unfamiliar without looking, which drops the line in Broca's Brain about pursuit. He popularised the wording in Cosmos in 1980. Chapter 5 of Broca's Brain, 1979, is the fuller form. Laplace and Marcello Truzzi had already asked for proof in proportion to the strangeness of the claim. The sentence is well attested as his. The standard is older than he is.
Did Carl Sagan really say this?
Well attested. He said this wording, and he made it famous. In Broca's Brain, chapter 5, the sentences are: the extraordinary should certainly be pursued, but extraordinary claims require extraordinary evidence. Cosmos, episode 12, uses the short form about claims of alien visits. The idea is older. Laplace wrote that stranger facts need stronger proofs. Marcello Truzzi wrote in the 1970s that extraordinary claims require extraordinary proof. Sagan popularised this wording. He did not found the standard.
Which work is it in?
Cosmos, television series (1980), episode 12, Encyclopedia Galactica; also Broca's Brain (1979), chapter 5 Approximate date: 1979 and 1980.