https://iai.tv/articles/carl-sagan-was-w...-auid-2348
EXCERPTS: . . . Nevertheless, “extraordinary claims require extraordinary evidence” is a favourite saying of scientists, sceptics, and debunkers of all stripes. It was made famous by the astrobiologist and science communicator, Carl Sagan, who probably borrowed it from the sociologist Marcello Truzzi...
Unfortunately, the famous dictum about extraordinary claims (sometimes known as Sagan’s dictum or Sagan’s standard) is often wielded in a rather less insightful way. It’s a good slogan: the repetition of “extraordinary” gives it a nice formal symmetry, which makes it seem almost self-evident, requiring no further thought or justification.
But as we have just seen, at least some extraordinary claims do not require extraordinary evidence. We proved the claim about Caesar’s last breath with just a little textbook knowledge and a bit of arithmetic. You might object that this particular claim was not extraordinary in the right way for Sagan’s dictum validly to apply. But what is the right way? What does it take for a claim to be so “extraordinary” that it requires “extraordinary evidence” for us to take it seriously? What, indeed, is “extraordinary evidence”?
[...] To think about this clearly we should start by recognising that “extraordinary” is a slippery word with multiple meanings. If we treat any proposition that seems out of the ordinary as an “extraordinary claim” then Sagan’s dictum becomes little more than a distillation of bias or prejudice; an excuse for not thinking harder. In that case, we would be better off without it...
[...] Usually, however, neither hypotheses nor lines of evidence come with unequivocal probabilities attached to them. What is the probability that ghosts exist? It is not obvious how to answer this, but that doesn’t mean that Sagan’s dictum is useless here...
[...] Now we can see why some extraordinary claims require extraordinary evidence and some don’t. Those that do are either highly improbable (requiring highly unambiguous evidence) or counter to a weight of evidence that seems to rule them out (which the new evidence must somehow be reconciled with); those that don’t are simply out of the ordinary or counterintuitive, like the claim about Caesar’s last breath...
[....] True scepticism aims to follow the evidence as diligently as possible, not simply to exclude radical or outlandish conclusions in advance (Truzzi called that “pseudoskepticism”). Sagan knew this better than anyone, arguing that science must balance “the most ruthless skeptical scrutiny” with “an openness to new ideas, no matter how bizarre or counterintuitive they may be”. Indeed, the more we learn about the universe, the more bizarre, counterintuitive, and extraordinary it seems to be... (MORE - missing details)
EXCERPTS: . . . Nevertheless, “extraordinary claims require extraordinary evidence” is a favourite saying of scientists, sceptics, and debunkers of all stripes. It was made famous by the astrobiologist and science communicator, Carl Sagan, who probably borrowed it from the sociologist Marcello Truzzi...
Unfortunately, the famous dictum about extraordinary claims (sometimes known as Sagan’s dictum or Sagan’s standard) is often wielded in a rather less insightful way. It’s a good slogan: the repetition of “extraordinary” gives it a nice formal symmetry, which makes it seem almost self-evident, requiring no further thought or justification.
But as we have just seen, at least some extraordinary claims do not require extraordinary evidence. We proved the claim about Caesar’s last breath with just a little textbook knowledge and a bit of arithmetic. You might object that this particular claim was not extraordinary in the right way for Sagan’s dictum validly to apply. But what is the right way? What does it take for a claim to be so “extraordinary” that it requires “extraordinary evidence” for us to take it seriously? What, indeed, is “extraordinary evidence”?
[...] To think about this clearly we should start by recognising that “extraordinary” is a slippery word with multiple meanings. If we treat any proposition that seems out of the ordinary as an “extraordinary claim” then Sagan’s dictum becomes little more than a distillation of bias or prejudice; an excuse for not thinking harder. In that case, we would be better off without it...
[...] Usually, however, neither hypotheses nor lines of evidence come with unequivocal probabilities attached to them. What is the probability that ghosts exist? It is not obvious how to answer this, but that doesn’t mean that Sagan’s dictum is useless here...
[...] Now we can see why some extraordinary claims require extraordinary evidence and some don’t. Those that do are either highly improbable (requiring highly unambiguous evidence) or counter to a weight of evidence that seems to rule them out (which the new evidence must somehow be reconciled with); those that don’t are simply out of the ordinary or counterintuitive, like the claim about Caesar’s last breath...
[....] True scepticism aims to follow the evidence as diligently as possible, not simply to exclude radical or outlandish conclusions in advance (Truzzi called that “pseudoskepticism”). Sagan knew this better than anyone, arguing that science must balance “the most ruthless skeptical scrutiny” with “an openness to new ideas, no matter how bizarre or counterintuitive they may be”. Indeed, the more we learn about the universe, the more bizarre, counterintuitive, and extraordinary it seems to be... (MORE - missing details)