Do extraordinary claims require extraordinary evidence?

Carl Sagan famously said that extraordinary claims require extraordinary evidence. But is he right?

RESOURCES

THE USUAL...

[the.thinking.failure]

Thanks for the short and sweet video, Joe! Super great.

[logans.butler]

If I claimed I had a fire-breathing dragon in my garage, that would be pretty extraordinary, but if I showed it to a skeptic face-to-face he would most definitely believe (once all other variables and probabilities are ruled out), but is that extraordinary evidence? Doesn't seem so to me, it just feels like regular evidence, which would have worked for any other ordinary claims but it does work.

[SumNutOnUb]

Basically, all claims require "sufficient evidence". What is sufficient depends on the perceived likelihood of the claim.

[squatch]

The problem with the statement is that what counts as "extraordinary" is relative to the speaker. It's also relative to the culture and to history. UFOs, which were once considered an amusing fantasy, are now taken seriously, despite there being really no substantial or "extraordinary" evidence.

[rectorsquid]

It also seems like there is another reason to require extraordinary evidence for extraordinary claims: Being wrong about a mundane claim is not likely to cause too much trouble for anyone but being wrong about an extraordinary claim could be world-altering.

[DigitalGnosis]

It's basically uncharitably interpreting the claim, which is worded sloppily, because it's unclear in what sense the evidence is understood to be extraordinary. Though that same sloppy phrasing is probably why the claim has caught on as a zinger.

[cinemaclips]

"It's not gonna bite you." Let me hope you know that there are people who are trying to make extraordinary claims for example that someone rose from the dead 2000 years ago wholeheartedly hate that slogan.

[danisetiawan-hrid]

the question is, how much evidence that considered extraordinary evidence ?

[vondertann]

If an extraordinary claim is the one with low initial probability, then it seems that extraordinary evidence is not necessary. It would be sufficient to provide a lot of ordinary evidence (evidence, which increases the probability by a small amount).

[PBRimmer]

Perfect video, very well explained and defended! And I would need extraordinary evidence indeed to change my mind on that.

[kosmosgalactic]

The slogan turns on the ambiguity of the second use of 'extraordinary' as force of evidence or quantity of evidence. It's mostly used to shut down argumentation not encourage it.

[AttilaM-px]

So the correct version is "Claims that are very unlikely to be true require very strong evidence before an impartial party can accept them as true."?

[bernardwills]

Some extraordinary claims are just fine with ordinary evidence. Trinidad just beat Brazil 11-1 in the World Cup! My evidence for this astonishing claim? The sports page which just reports the score without any extra investigation or diligence though the score is so shocking.

[lanceindependent]

This is one of the most concise and obviously correct points you've made, Joe. I have a suggestion: It'd be cool to make a major contribution to critical thinking and intro to logic courses, a kind of updated "principles of reasoning or "informal fallacy" list that includes this and many of the other mistakes you highlight, and that goes over many common *misuses* of informal fallacies. I dunno. An open source textbook, a paper or two, some blog entries....some way of circulating this kind of stuff out there.

Too many textbooks include the same boring old list of things like "slippery slope" and "ad hominem, " and I haven't seen anyone collate and clearly describe lots of the ACTUAL mistakes people make.

Btw, did THIS one make it onto your list: "You can't compare X to Y!" Often people make this claim when you compare two things that are very different or have major salient similarities or differences that are unrelated to the similarity or difference relevant to your comparison. It's extremely common, and a very serious mistake. More generally, people struggle a lot with comparisons, often completely missing the point of analogies, comparisons, and so on. I think this is worth attention from both philosophers and psychologists.

[scotthutson]

Short, sweet and reasonable. Thanks for once again correcting the internet Joe!

[theboombody]

Well, I never thought I'd see people willing to get slammed on a mat full of thumbtacks, but I was proven wrong there. Many times. Reality is strange.

[MyMy-tvfd]

I just want see the alien/ET for myself - the actual creature. Some people might feel that to be an uneasonable demand, not just extraordinary - but the subjective requirement is just a personal judgment

[matthewlorang]

Of course, assigning prior probabilities is its own kind of beast.

[ThatisnotHair]

I think extraordinary is about novelty and uniqueness. Demonstration of something that no one has seen before and only expected under your hypothesis. Opposite of ordinary, which is something that ussualy seen before and no one is shocked of it.

[jaskitstepkit]

Can you give us an example for an " extra ordinary" claim?