"Extraordinary claims require extraordinary evidence."

[Magical Realist]

Ahh yes. The clarion call for all dedicated skeptics and would-be debunkers al la their holy pope Carl Sagan. But what exactly WOULD BE extraordinary evidence? Would anything ever be enough?

It all goes straight to epistemology. How can we really KNOW anything?

I guess if something extraordinary happens to other people, then by definition it ISN'T extraordinary evidence. But if it happens to you then it is? What more evidence does one need than the immediate presentation of their senses? It is the very foundation of empiricism itself.

[Yazata]

"Extraordinary claims require extraordinary evidence"... "required" to accomplish what?

To convince somebody of something that they don't already believe in, I guess. And in the case of the skeptic debunkers, to convince them of something that they don't want to believe in.

So this supposed epistemological maxim seems to me to be less about some objective epistemological logic than it's about individual psychology.

What is an "extraordinary claim"? 'Extraordinary' literally means exactly that: extra-ordinary. Unexpected or unusual in other words. And that is very much a function of who is making the judgement, a function of what their experience has been and what their expectations are.

The skeptic debunkers seem to me to want to make 'extraordinary' mean something less subjective and more objective. I have considerable sympathy with that move, but they need to clarify and defend what they mean. How might 'extraordinary' be redefined to mean something stronger than 'unexpected'?

Perhaps a contradiction with physical law, or something like that. As David Hume put it, a violation of the order of nature. (Which is how he defined 'miracles'.)

Of course whatever we accept as physical law is historically and culturally contingent, so the desired objectivity starts to get fuzzy. A violation of physical law today doesn't mean the same thing as it might have meant in early medieval times. And it might not mean the same thing 500 years from now either.

What's more, many of the things that the skeptic-debunkers treat as "extraordinary claims" don't necessarily violate any physical laws at all. The UAP's arguably don't. Perhaps some accounts of their motions do seem to violate principles of inertia, but the mere existence the UAPs doesn't. Even the existence of crashed flying saucers and alien pilots on ice wouldn't seem to violate physical law. Nevertheless, it's all supposed to be "extraordinary claims".

But why??

[Syne]

Evidence only needs to be as extraordinary as the claim. Hence the saying. So asking "what would be extraordinary evidence" is pointless without reference to a specific claim. But in general, there are standards of scientific evidence.

Since epistemology covers approaches that range from objective to subjective, it's far too easy for people to cherry-pick subjective approaches.

In philosophy of science, on the other hand, evidence is understood as that which confirms or disconfirms scientific hypotheses and arbitrates between competing theories. For this role, evidence must be public and uncontroversial, like observable physical objects or events and unlike private mental states, so that evidence may foster scientific consensus.
- https://en.wikipedia.org/wiki/Empirical_evidence

Evidence must be publicly available for everyone to evaluate its veracity. Secondhand testimony, videos, pictures, etc. do not afford uncontroversial access to the evidence, because they always leave doubt and unanswered questions. Doubt and uncertainty are the opposite of compelling.

[Magical Realist]

Evidence must be publicly available for everyone to evaluate its veracity.

As if there can even be a unanimous agreement of when something is adequately evidenced. Events that really happen are stubbornly perspectival. Two people can witness the same thing and reach entirely different conclusions about what it was. A man in the 13th sees the sun rising each day as solid evidence that it revolves around the earth. A man in the 21st century sees it as solid evidence the earth itself is revolving. The experience of something evidencing itself as something real that objectively happened does not rely so much on the nature of the evidence itself as it does on the conceptual perspective of the investigator. It's why skeptics are less interested in knowing the truth of what actually happened than they are in defending and bolstering their current consensually supported scientific worldview. A vague and entirely aesthetic standard of extraordinariness thus provides them with sufficient grounds for dismissing any event out of hand that doesn't fit into that worldview. Not because of the subjectivity of the eyewitness account but because of the subjective interpretation of what can even count as adequate evidence. As Yazata put it: "So this supposed epistemological maxim seems to me to be less about some objective epistemological logic of confirmation than it's about individual psychology."

[Syne]

Comparing what people thought in difference centuries is not comparable to what different, contemporary people think now.
Even if it were, no one, even centuries apart, disputed that the sun rose each day. IOW, the evidence was indisputable, even if the explanation was not. The veracity of evidence is determined by how indisputable it is, not how you explain it.

The "conceptual perspective of the investigator" is explanation, open to personal subjectivity. Explanation is not evidence.
There's nothing vague about the extraordinary. Everyone can readily tell the ordinary and mundane from the unusual and extraordinary.

Again, some epistemological approaches accept subjective experience. If you cherry-pick those, it is about individual psychology.
That's why philosophy of science is more appropriate for discussing evidence. Epistemology is more suited for discussing experience.

[Magical Realist]

Extraordinariness is always relative to one's worldview that they already live in. If you only believe in physical things and matter, then an event suggesting something other than that would be de facto extraordinary and essentially impossible. If you are a dualist where mind and matter are two aspects of reality, then non-physical phenomena are not in principle so extraordinary or impossible at all. Aside from having no explanation for them, no evidence will ever convince anyone whose worldview automatically excludes such a phenomenon from ever happening at all. What counts as evidence will always be interpreted in terms of how well it fits their presupposed worldview.

[confused2]

My thinking is that the hallmark of an extraordinary claim is that it conflicts with existing beliefs .. any evidence has to be even more convincing than whatever lead to the current belief.

Actual explanations may not be particularly important .. maybe what matters more is 'the fact that..' .. for example general relativity gives the maths of how mass interacts with spacetime but no clue as to why or how it does it.

[Syne]

Extraordinary in terms of an individual's experience is subjective. Scientific evidence is objective. Conflating the two is a pointless exercise.
It's a very neat little worldview, that those who do not accept the extraordinary as evidence, in and of itself, must have a materialist/physicalist view. It's a shame that such a neat view of people doesn't account for those of us who are dualists (idealistic monists but practical dualists). We have plenty of explanations, but they do not comport with your subjective worldview. Talking about "no evidence will ever convince anyone" is some heavy-handed projection.

As soon as you can produce a captured UFO, alien, bigfoot, etc. everyone is perfectly willing to accept their existence. That would be evidence comparable to the claim. Hell, if you can predict or replicate the experience of one, where people could make successive tests, observations, and readings, most skeptics would happily accept that as evidence. Because either would allow us to test possible explanations, instead of simply accepting the dogma of the true believers.

[Magical Realist]

As soon as you can produce a captured UFO, alien, bigfoot, etc. everyone is perfectly willing to accept their existence. That would be evidence comparable to the claim. Hell, if you can predict or replicate the experience of one, where people could make successive tests, observations, and readings, most skeptics would happily accept that as evidence. Because either would allow us to test possible explanations, instead of simply accepting the dogma of the true believers.

The testable and replicable is only a small subset of overall reality. In no way can it define what is to be regarded as real. So much of reality happens to us without having to be evidenced or explained. Examples include conceptual models like Einstein's view of spacetime and the implications of quantum physics, which receive their apodicticity from mathematics and geometry.

Everyday life as well is bristling with states and phenomena that happen purely phenomenally, like color and pain and love or consciousness itself, without any need to be verified at all. Anomalous phenomena are like these, happening over and over again in the same yet compellingly personal ways and places that prove them to be real and objective facts of our reality. Even if they are just hallucinatory, one must still account for the fact that they DO recur over and over again in consistent ways to millions of normal and sane people all over the world. Not to mention the plethora of video and photographic and radar and audio recordings of such.

People who deny experiences and events and anecdotes solely because they have no explanation for them or that they can't be studied like a dead frog or repeated over and over again are just denying what they accept as given everyday---that we are all basically living in an ongoing reality largely unexplainable and unverifiable and unpredictable in scientific terms.

[Syne]

Yes, purely subjective experience happens all the time. But in most cases, people have the good sense to not claim it is some real thing out there.
Relativity and QM receive their validation from experimental verification of their predictions... against repeatable real world phenomena.

Again, conflating the subjective and the objective is a pointless exercise.