Why some of our greatest discoveries were once considered 'impossible'
In short: Is a radical new idea just a fantasy, or is it about to change everything? The Sagan standard suggests that the more shocking a claim feels, the higher the bar for proof. But if we are too strict, do we risk silencing the next great scientific revolution?
The principle known as ECREE—'extraordinary claims require extraordinary evidence'—is often associated with science communicator Carl Sagan, who popularized it in his 1979 book Broca's Brain and the 1980 series Cosmos. While it is a cornerstone of scientific skepticism used to challenge paranormal claims or 'mega-tsunamis,' its roots go back much further. Philosopher David Hume first articulated the concept in 1748, noting that evidence should diminish in proportion to how unusual a fact is. Other figures like Thomas Jefferson and Pierre-Simon Laplace expressed similar sentiments regarding meteorites and solar system stability in the early 19th century.
Mechanistically, ECREE functions similarly to Occam's razor by favoring simpler explanations. In formal hypothesis testing, this relates to the 'null hypothesis,' where we assign a stronger Bayesian prior to the idea that no new phenomenon exists. However, critics like David Deming argue that because Sagan never defined quantitative parameters for what is 'extraordinary,' the standard can be entirely subjective. This subjectivity creates a tension: if applied inconsistently, it can reinforce confirmation biases, suppress innovation, or even exacerbate racial and gender biases in research.
The debate centers on whether ECREE should be a gatekeeper or a guide. Some argue that many paradigm-shifting discoveries were initially dismissed as extraordinary and might have been lost to history under a rigid standard. Conversely, others suggest that publishing unproven extraordinary claims 'pollutes' the scientific literature. Rather than using it to bar research entirely, some psychologists suggest the standard should be used to determine which explanation is best, perhaps by including peer reviews on a claim's plausibility or post-publication evaluations.
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- Summary by Intellect · source: Extraordinary claims require extraordinary evidence
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