I’m writing to ask the group opinion on the validity of the statement in the subject:
“Extraordinary claims require extraordinary proof.”
I’m of the opinion that there is no such category of proof. There is simply proof.
That is, something is simply proved, or not.
Take the example of someone claiming to be able to fly, unaided.
For proof, all they need to do is rise from the ground and fly around.
The claim of flying may be extraordinary, but the proof is simple.
I once wrote a letter to either Skeptic or Skeptical Inquirer magazine about this, since they regularly spout this phrase.
As far as I know, it was never published, and I never received a response.
When they “discovered” superluminal neutrinos it would have changed science forever. To ask an entire generation of scientists to rework everything they know might understandably make them want to turn round and say ‘are you absolutely sure?’ Perhaps someone might correct me here but that Italian experiment seemed solid enough to normally have its findings accepted as fact but it really was contradicting everything else that is regarded as true so extra confirmation is fair enough. The problem it has for me is that if the experiment is proved wrong, what other apparently well-executed experiments have led us astray?
Which sort of invalidates your argument, unless you want to argue that there aren’t gradations in the strength of evidence.
People do use the “proof” form of the phrase, but I suspect they still mean something pretty close to “evidence” rather then proof in the sense of something that provides logical certainty. When scientists talk about “proof” they usually mean “strong evidence” for something, rather then the words meaning in formal logic.
If I turned on the TV and saw someone flying around, I would expect that there should be additional scrutiny to make sure that the aviator did not use CGI, wires, or some other special effects. When I saw Usain Bolt on TV run the 100 meter dash in 9.6 seconds, it seemed pretty plausible to me.
Same thing would apply if I saw some kind of demonstration in person. The proof of David Copperfield making the Statue of Liberty disappear is not simply that I saw the Statue of Liberty disappear, for example.
Outside of mathematics (which I can’t address with authority) there is mostly just evidence. You can have eye-witnesses, photos, video footage, expert testimony, personal experience, but it rarely adds up to true proof. (Witness the case of Uri Gellar and the media.)
As for extraordinary claims, I would demand a higher level of evidence when putting my life at risk, than if I was putting $5 at risk. Society should demand a higher level of evidence if there are great dangers involved, or if claims contradict useful, long-standing beliefs.
Right. I’d even argue that the phrase “extraordinary proof” is a useless term. If evidence proves something, it does or it doesn’t; the proof itself is neither extraordinary or ordinary, simply correct or incorrect. When scientists (or statisticians, which is as close as I’ll get) disagree on whether a proof is valid, they don’t argue whether or not it’s extraordinary, they just argue as to whether it’s correct.
As Fiendish says, if that claimed proof contradicts previous claimed proofs, the new claimed proof will be subject to more scrutiny–again, not because the claim was “extraordinary”, but because it contradicted previous proofs. I think the phrase “extraordinary” is a kind of shorthand for “something that has been proven invalid in previous experiment/theory”. Randi just happens to be attacking a lot of the woo-woo stuff; if I were debating my colleague on a point about predictive modeling it would be a bit of hyperbole to call his arguments “extraordinary.”
Its not meant to be a statement of some sort of formal scientific procedure, just a statement about a heuristic that most people probably use without realizing it anyways.
If I tell you I saw James Randi last week, and show you a picture of him and I hanging out at a bar, you’ll probably believe me.
If I tell you I saw Bigfoot last week, and show you a picture of him and I hanging out at a bar, you probably won’t believe me.
Some claims are pretty clearly more extraordinary then others, and thus have a higher burden of proof.
Not. Nothing is ever proven. Instead, people are persuaded. “Proof” implies that a factual situation can objectively be demonstrated to exist, and conclusions that are irrefutably drawn from those facts can be made with no intuitive leaps or interpretations. That never, ever, happens. Neither human minds nor reality itself works like that.
If I made the claim that I could fly, unadied, and then proceeded to rise from the ground and fly around in front of you, your first response would be “That’s very clever… I can’t figure out how you’re doing that”. You would absolutely NOT start out with the assumption that I was doing it without any kind of technological assistance. Demonstrating that I wasn’t would require proving a negative. You would gradually be persuaded that I wasn’t using a device or creating an illusion only after a protracted period of generating hypotheses and ruling them out by checking. Then you would go on from there to a second assumption: that in some as-of-yet unclear fashion, I was taking advantage of natural laws and circumstances, in such a way that were you to stand where I was standing and have all the variables apply to your situation as they applied to me, those same natural laws would enable you to fly around, unaided —— some freak of air currents, a gravitational anomaly, etc. You would STILL not quickly or simply assume that I, personally, had a built-in unique ability to fly.
I always take it to be a comparison of what we already know is possible and probable and the claim that is being made. e.g.
I claim I saw a sparrow in my garden? well the only thing questionable there is my eyesight and memory.
I claim that an alien was having a shower in my bathroom? well you have the same concerns as above plus a whole lot more. So it is reasonable to be demanding of far more evidence as you have a bigger credibility gap to bridge.
But as others have said, it isn’t a rule or a law or anything like that. Just a neat little soundbite to capture how we already interact with the world.
I think the idea of that statement is that if you’re making a claim that’s hard to swallow, you’re going to need to make sure you do your homework so that you can convince people. That makes sense to a certain degree. Like with the example of bigfoot upthread, because most people are so skeptical of bigfoot’s existence, a couple photographs won’t be enough to make the case, where a couple photos may be enough to convince someone that I may have met some celebrity.
However, I also think that, akin to what the OP points out, it’s dangerous. What if bigfoot is real and I present two legitimate photographs of bigfoot that pass any level of reasonable scrutiny but it still doesn’t convince anyone because they’re looking for extraordinary evidence, but I could photoshop a picture of me meeting a celebrity and people might not scrutinize it to the same degree because its much more believable. That is, the implication seems to be that if I’m going to make an extraordinary claim I need to put in more effort, but that should be a self-enforcing because skepticism naturally demands strong evidence. So the dangerous part comes in when something intuitively seems to be true or is reasonable enough that skepticism doesn’t kick in, and it ultimately isn’t true, and so we end up accepting something that isn’t true because of lack of due diligence.
So, really, only testing extraordinary claims seems silly, so it really only makes sense if stated as “Claims require evidence.” which just makes it a silly tautology. Instead, I’d rather it be more that the amount of diligence should be proportional to the impact of the claim. We shouldn’t spend too much time determining if I met a celebrity because there’s not really that much of a problem if I’m wrong. But if we’re talking about something with a major impact, whether it’s confirming something we already believe or wildly different, like the superluminal neutrinos, we HAVE to pay due diligence because the impact of being wrong is so much worse.
While ‘extraordinary’ is not the most accurate wording, an extraordinary claim requires ‘comprehensive’ proof. Simply citing a single example to demonstrate a claim that otherwise denies accumulated experience and knowledge is not a useful point of argument. In a scientific sense, an extra level of evidence is necessary to conclude proof in a paradoxical situation. If reason alone is contra-indicative to physical evidence, both approaches must be re-examined.
As the originator of this thread, I find the response extraordinary!
After carrying this annoying thought around in my head for years, within minutes I find a whole group of people willing to seriously engage in it’s discussion.
I think I’ve found a new hangout.
Anyway, I didn’t come here with an axe to grind, I was looking for other perspectives, which I have received in abundance.
In regards to the origin and exact wording of the statement I found this on Wikipedia:
An extraordinary claim requires extraordinary proof.
— Marcello Truzzi, On the Extraordinary: An Attempt at Clarification, Zetetic Scholar, Vol. 1, No. 1, p. 11, 1978
Carl Sagan popularized this as “Extraordinary claims require extraordinary evidence”.[15] However, this is a rewording of a quote by Laplace which goes, “The weight of evidence for an extraordinary claim must be proportioned to its strangeness.” This, in turn, may have been based on the statement “A wise man, therefore, proportions his belief to the evidence” by David Hume.[16]
Of course, now we’re faced with deciding if “proof” is the same as “evidence”.
I’m just going to watch the conversation develop for awhile and enjoy the discussion.
Ok, I just rose from the ground and flew around the room.
<that’s not good enough>
Ok, here’s a buddy of mine who will agree that I just flew around the room.
<that’s not good enough>
Ok, here’s a photo of me flying around my living room
<that’s not good enough>
Ok, here’s a video of me flying outside
<that’s not good enough>
Ok, you stand over there in the “viewing zone” I will stand over here on this handy stage and levitate with no visible means of support
<I saw Lance Burton do the same thing in Vegas>
Ok, you set up the staging area, ensure there are no possible means of support, provide me with plain cotton underwear and a jumpsuit, that I will get dressed in under supervision. I will enter the area under supervision, fly into the air, then hover while you inspect the area for any technological trickery.
<Ok, THAT is good enough>
What is extraordinary is not the evidence itself, but the work that is done behind the scenes to ensure the evidence presented is accurate and thoroughly supports the claim.
Speaking as a research scientist, I can tell you that 5% of science is discovering things, and 95% is trying to prove that you really did discover what you thought you discovered.