Sagan's Standard

 

Atheists and materialists love to cite Sagan's standard: “Extraordinary claims require extraordinary evidence.” I think the concept ultimately comes from David Hume.

It is simply an admission of confirmation bias. You resist anything that differs from your existing beliefs. For what else makes a claim “extraordinary”?

Or else it is an expression of the ad populum fallacy; if by “extraordinary” is meant an assertion not often made. Truth is not determined by vote.

It is the evidence itself that determines whether a claim is “extraordinary.” The same standard of evidence applies to all assertions.