Extraordinary claims require extraordinary evidence.
Sagan's formulation, with earlier versions in Laplace and Hume. Its practical use is to make the required evidence proportional to the prior, which is Bayesian updating stated as a slogan.
In practice
- A colleague reporting that the lift is broken is believed; a colleague reporting that the lift was sabotaged is asked how they know.
- A claim that a supplier missed one delivery needs an email; a claim that they are defrauding you needs considerably more.
- Subject
- Science & Epistemology
- Essay
- Rules for weighing claims