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#1 |
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Sagan’s “extraordinary claims require extraordinary evidence” is nonsense. Here’s why
I have distilled the following discussion from another thread because I feel it is important enough to deserve a thread of its own.
Yes, you’re getting close, but strictly speaking there is also no such thing as “good” (or “bad”) evidence either. Evidence is evidence. You either have it or you do not. The preceding adjectives (“extraordinary”, “good”, etc), especially without context, are subjective and emotive value judgements that should have no place in true sceptical debate (with the implied constraints of conforming to the strict standards of critical thinking, logic and science). “Sagan is also widely regarded as a freethinker or skeptic; one of his most famous quotations, in Cosmos, was, "Extraordinary claims require extraordinary evidence."[40] This was based on a nearly identical statement by fellow founder of the Committee for the Scientific Investigation of Claims of the Paranormal, Marcello Truzzi, "Extraordinary claims require extraordinary proof."[41] This idea originated with Pierre-Simon Laplace (1749–1827), a French mathematician and astronomer who said, "The weight of evidence for an extraordinary claim must be proportioned to its strangeness."[42]” (http://en.wikipedia.org/wiki/Carl_Sagan) Like a game of Chinese whispers, the true meaning of the message becomes distorted over time to end in complete nonsense. That is, LaPlace’s sensible “weight of evidence” becomes in Sagan’s hands the nonsensical phrase “extraordinary evidence”. …and no matter the “eminence” of the person stating it, it remains nonsensical. We should thus, as ever, be forewarned about simply accepting without critical thought received “wisdom”. All is often rarely what it seems. Yes, you are describing Laplace’s “weight of evidence”, but critically, an “extraordinary amount” of evidence does not make the evidence itself “extraordinary”. The “people at which it is aimed” do not understand it in equal proportion to the people who state it – because it is nonsense dressed up as wisdom. Corrected that for you… (but ‘scientists” can be forgiven, for they simply do not understand what they say). Precisely. I believe therefore, that when anyone who considers themselves to be a true sceptic is tempted to refer back to Sagan’s nonsensical statement containing the phrase “extraordinary evidence”, they should actually refer back to LaPlace and quote his statement (eg here: http://www.todayinsci.com/L/Laplace_...Quotations.htm) containing his eminently accurate and sensible phrase "weight of evidence”. Of course one can paraphrase LaPlace if one considers his language too archaic for a modern audience. One can also include Sagan in such a paraphrase to get the best of both worlds! Thus: To paraphrase both Sagan and LaPlace: Extraordinary claims require a greater weight of evidence. Now we can argue over whether that contention itself actually has rational meaning… ![]() As fls points out, the adjective “extraordinary” in “extraordinary claims” is itself a post hoc rationalisation. Surely a claim is made and supporting or contrary evidence is put forward by the debating parties. How can we know a priori that a claim is “extraordinary? After examination of the “weight of evidence”, what if it turns out to be a true claim? Surely then the claim becomes, by definition, “ordinary”. The point is, one simply cannot make the a priori value judgement. …and of course if Sagan’s statement ( "extraordinary claims require extraordinary evidence"”) was not already shown to be nonsense, this puts the final nail in the coffin. Quite simply, the veracity of any claim must be assessed according to the “weight of evidence”. It is only after such an assessment that we might consider using adjectives to describe either the claim or the evidence – and that only if we no longer consider ourselves to be true sceptics! |
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#2 |
Troublesome Passenger
Join Date: Apr 2010
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Somewhere in that wall of straw, you typed "evidence is evidence." I quite agree.
When some credible evidence is offered for, say, alien spacecraft visiting our blue planet, one is helpless but to examine it. Credible, able to withstand scrutiny; not extraordinary, but credible. Not photos of tossed hubcaps. Not blimps. No special pleading for that evidence either. |
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#3 |
a carbon based life-form
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#4 |
Show me the monkey!
Join Date: Jul 2005
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Bigfoot believers and Bigfoot skeptics are both plumb crazy. Each spends more than one minute per year thinking about Bigfoot. |
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#5 |
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#6 |
Master Poster
Join Date: Jul 2007
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Ordinary claim: This is a cup of coffee.
Extraordinary claim: This is a magical cup of coffee. I am going to require different levels of evidence to believe these two claims. The ordinary claim I may believe just on the look and smell alone. The extraordinary claim will require more evidence--extraordinary evidence. I will need to observe evidence of the extraordinary nature of the claim. Just looking and smelling like coffee is not enough. Ordinary claim: I went to taco bell for lunch. Extraordinary claim: I ate lunch on the moon. I will believe the first claim in most cases just on someones word because it's quite ordinary. The second claim will require more evidence. |
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#7 |
Illuminator
Join Date: Nov 2006
Posts: 3,790
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As most of the posters above, I believe you're misinterpreting Sagan's line. I believe, but cannot prove, that he meant that an extraordinary claim must be matched with specific, irrefutable evidence that also matches the quality of the claim.
For example, someone can say "I can cure your hunger." and offers you a sandwich. That's pretty good evidence. However, if the claim was "I can solve world hunger", the sandwich doesn't quite cut it. |
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#8 |
Penultimate Amazing
Join Date: Apr 2009
Location: Iowa USA
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Nice try.
Better luck next time. |
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#9 |
Tergiversator
Join Date: Aug 2006
Posts: 17,998
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What's the best argument for UHC? This argument against UHC. "Perhaps one reason per capita GDP is lower in UHC countries is because they've tried to prevent this important function [bankrupting the sick] and thus carry forward considerable economic dead wood?"-BeAChooser |
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#10 |
Hostile Nanobacon
Join Date: Jul 2008
Posts: 30,587
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Santa Claus lives at the North Pole and delivers presents to all the good little boys and girls on Christmas eve.
Rramjet, is that an ordinary claim or is it extraordinary? |
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#11 |
Philosopher
Join Date: Aug 2006
Posts: 6,721
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*sigh*, Roger,
1. I had bacon and eggs for breakfast 2, I had bacon and eggs for breakfast at The Restaraunt at the End of The Universe. I could show you a photo of a plate of bacon and eggs, with me next to it, or even shovelling a bit of bacon into my mouth. I could even photoshop a picture of an alien standing next to me while shovelling a bit of bacon into my mouth Would you accept Statment 2 as accurate in either of these examples? Which one is the more likely statement, and why do you think (if you do) that I need more evidence for statement 2 than statement 1. Norm |
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#12 |
a carbon based life-form
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#13 |
Penultimate Amazing
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#14 |
Metasyntactic Variable
Join Date: Oct 2006
Posts: 6,623
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Let me give it a try:
1a. More than <something> is extra-<something>. 1b. More than ordinary is extra-ordinary. 2a. Ordinary evidence is sufficient only for ordinary claims. 2b. Extra-ordinary evidence is sufficient only for extra-ordinary claims ::a. Ordinary evidence is required for ordinary claims. ::b. Extra-ordinary evidence is required for extra-ordinary claims. I know that this must violate some rules regarding syllogistic reasoning, and may run afoul of equivocation, as well. But there may be another reader who is more skilled in this type of thinking to present the idea in a way that is both clear and concise to even the most deluded among us. For the record, I also think that the OP is trying to make a case for allowing unsupported anecdotes {fantasies, ideas, legends, myths, opinions, rumors, et cetera} to be admissable as evidence. |
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Belief is the subjective acceptance of a (valid or invalid) concept, opinion, or theory; Faith is the unreasoned belief in improvable things; and Knowledge is the reasoned belief in provable things. Belief itself proves nothing.
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#15 |
Obsessed with Reality
Join Date: Aug 2001
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We cannot know that a claim is extraordinary, but we can make a judgement that it is. We can judge a claim to be extraordinary when, if true, it would revolutionize our knowledge of the natural world and/or oblige us to modify the laws of physics that have been experimentaly corroborated over and over again for centuries. So, please answer this: if I say that I can move physical objects solely with the power of my mind, is it ordinary or extraordinary claim? |
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The Universe is not required to be in perfect harmony with human ambition - Carl Sagan |
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#16 |
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What makes “This is a magical cup of coffee” an extraordinary claim? Could it be perchance that you are applying a post hoc rationalisation according to a particular belief of yours (based on examination of the evidence of course…) that “There are no such things as magical cups of coffee”?
However, when a claim is made, how can you a priori decide if the claim is “extraordinary” or not. Of course you cannot – you have to wait until after the evidence is examined to make that judgement call. That is why a general statement that requires “extraordinary” claims” to be treated somehow differently than “ordinary” claims is a nonsense. One simply cannot do that in science. All claims must be a priori treated equally according to the strict protocols of critical thinking, logic and the scientific method. Until the evidence is in, one simply cannot know what adjective might be applicable. But that is just the point. You are saying here that you actually require a greater weight of evidence to convince you of … what precisely… that your a priori belief is incorrect? But that is only your particular belief system and it may be completely misguided (ie; not generalisable). That is why, in science (as in critical thinking and logic) such a priori belief systems are carefully guarded against. Generalisability not only applies post hoc but also a priori (so they cannot be held hostage to personal belief systems). Looks (and smells) can be deceiving. More evidence according to your own particular belief system maybe (that is your subjective opinion), but how does more evidence equate to “extraordinary” evidence. “More” does not equal “extraordinary” by any accepted definition. Now you are getting closer to it. But still you are second guessing the outcome. No, the second claim merely requires evidence! Moreover, you would not seek evidence for the first claim simply because it does not particularly matter to you one way or other. However, if your life or death hinged on the claim “I went to taco bell for lunch.” (such as a murder was committed at KFC during lunch, for which your are being blamed) then you would be required to supply evidence. Moreover, to you, the claim that you were the murderer in KFC is an extraordinary claim – presumably because you know the evidence that you could not have been the murderer (a post hoc rationalisation in other words), but to the CSI police, who deal with these things all the time, the claim that you were the murderer is just an ordinary claim that they deal with generally all the time. To them the claim is entirely ordinary. Your second claim (“I ate lunch on the moon.”) only seems extraordinary because we have already run over the circumstantial evidence against that claim in our minds (ie; that no space agency has recently sent any rockets to the moon and your name has never come up in relation to astronauts). Again, the claim only becomes subjectively “extraordinary” after we examine the evidence (in this case circumstantial – but it IS still powerful enough for us to reject your claim!). If you (or anyone) maintained the claim, then we (anyone) would simply require evidence in support of that claim – and notably, the only evidence you could supply would be ordinary evidence. For example you were on a particular rocket that launched from a particular place and that landed on the moon at a time that allowed you to have lunch there). That is ordinary evidence. Nothing “extraordinary” about it at all. So I am still waiting for Sagan’s “extraordinary evidence” to be defined and an example of it provided. Until then, it remains a nonsense phrase. |
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#17 |
Illuminator
Join Date: Sep 2003
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It's just as extraordinary to claim you have had lunch on the moon as it is to be able to prove it with a photograph, some rock samples, and a signed letter from NASA.
You have to fight Occam's razor here. If there's a simple and common explanation for something, you have to overcome it with stronger or better evidence, thus making your explanation the simpler one. |
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#18 |
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#19 |
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#20 |
Illuminator
Join Date: Oct 2009
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A claim is called "extraordinary" based on how the evidence for it and the evidence against it compare.
Do you understand that, at least? |
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#21 |
Obsessed with Reality
Join Date: Aug 2001
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Exactly!, and that evidence must be extraordinary. A piece of evidence of the like "a friend of mine told me he had lunch on the moon" is not enough, though it would be enough for the claim of "lunch at the KFC". Why?, because the extraordinary evidence of poeple having lunch at KFC already exists.
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You've been told and explained over and over, comprehensibly. If you don't want to listen, that's another matter. |
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#22 |
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Yes, but that judgement of yours is a post hoc rationalisation, made [i]after[i] consideration of the extant evidence.
No, I don’t see your claim as extraordinary at all. Many, many people have made such a claim throughout history. It seems an entirely ordinary claim to make in the context. That does not mean that I necessarily believe that claim. I would of course require you to provide evidence for that claim before I did. But answer me this: What evidence could you supply (if your claim was true) that would constitute "extraordinary evidence"? |
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#23 |
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You are (as it seems most people here are) missing a critical point in my argument. So far all you have been describing to me is ordinary evidence (eg: "people having lunch at KFC" is entirely ordinary). However, you all seem to be equating “more evidence” with “extraordinary evidence”. “Look” and “smell” is not enough evidence in particular circumstances because, while for day-to-day purposes it does not particularly matter if we get it wrong, on weighty issues, such as life or death, then more evidence than mere “look” or “smell” is needed – and more evidence is needed because we know look and smell can be deceiving. I can only reiterate” More does not equal “extraordinary”.
Cannot anyone give an example of “extraordinary evidence”? |
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#24 |
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#25 |
Obsessed with Reality
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I don't understand this. As I said, it's a judgement based on the impact that such a claim, if true, would have on our knowledge of how the world works.
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Looks like you didn't read what I wrote. A claim does not become ordinary because many people have made it, but because of the reasons I stated above.
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The Universe is not required to be in perfect harmony with human ambition - Carl Sagan |
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#26 |
Penultimate Amazing
Join Date: May 2008
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Already answered it.
Conclusive irrefutable evidence or series of evidence that is superior to the evidence against the claim. In other words, either move the object right now that will withstand scrutiny that it isn't a trick or fraud(which all prior knowledge says it will likely be) or give me more evidence than the evidence shows that you are not insane. You see: Moving an object with your hand is "ordinary" evidence. It could be a complete trick. Some magicians enjoy doing mundane tricks. Tricks that require complex skills but look like normal activity by laypeople but then no one will care. Moving an object with your "mind" will require "extraordinary" evidence. This will require more controls to prevent things like fraud or trickery as the cause of this effect is unknown and that this is universally done via trickery. |
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"The method of science is tried and true. It is not perfect, it's just the best we have. And to abandon it with its skeptical protocols is the pathway to a dark age." -Carl Sagan "They say a little knowledge is a dangerous thing, but it's not one half so bad as a lot of ignorance."-Terry Pratchett |
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#27 |
Penultimate Amazing
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"The method of science is tried and true. It is not perfect, it's just the best we have. And to abandon it with its skeptical protocols is the pathway to a dark age." -Carl Sagan "They say a little knowledge is a dangerous thing, but it's not one half so bad as a lot of ignorance."-Terry Pratchett |
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#28 |
Graduate Poster
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"The lie is different at every level." Richard C. Hoagland |
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#29 |
post-pre-born
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#30 |
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But it is only judged to be so after the evidence has been examined (a post hoc rationalisation in other words). That is why one cannot apply a general claim such as “extraordinary claims require extraordinary evidence” as an a priori general rule – because a priori we have no idea what might constitute and extraordinary claim (and that is even before we get to trying to understand what on earth might constitute "extraordinary evidence”).
Please tell me you understand that at least. |
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#31 |
post-pre-born
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#32 |
Penultimate Amazing
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"The method of science is tried and true. It is not perfect, it's just the best we have. And to abandon it with its skeptical protocols is the pathway to a dark age." -Carl Sagan "They say a little knowledge is a dangerous thing, but it's not one half so bad as a lot of ignorance."-Terry Pratchett |
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#33 |
I would save the receptionist.
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Well, RJ, you're right ... sort of. When lay people talk about evidence, they're using common sense definitions in what is actually a highly specialized field. I studied for years to understand the rules of evidence and I apply those rules in practice every day to convince people of my way of thinking. Throwing legal jargon around isn't gonna help anyone, though. So let me come at it another way. If I want to say, "Bob drives a red car," I'll need evidence. So, I produce his neighbor, who sees a red car parked in Bob's driveway, his coworkers who see Bob get into a red car at the end of the day, and a traffic cop who saw a red car with a flat time on the side of the road and stopped to find Bob next to the car. That seems like decent evidence that Bob drives a red car. However, there's a lot of evidence I could have included but didn't: whether Bob even exists; whether Bob ever learned to drive; whether Bob's finances allow him to afford a car; whether Bob knows how to change the oil on a car; and more. All of that would help make it more likely that Bob drives a red car. Why didn't I include witnesses to testify to those things? Because assuming that Bob exists, can drive, knows the rules of the road, manages to swing the price of gas, etc. - those are all easy assumptions. They are consistent with what we know about the vast majority of people like Bob. Now, imagine that I wanted to prove that Bob was, although human, originally born of Tau Ceti 6. The problem there is that we have no knowledge whatsoever about what that type of person would or would not be like. So we can't make any assumptions. In order to prove the matter, then, we'll need much, much more exhaustive evidence. What we know about life won't help us this time. And all that evidence must be consistent with everything else we already know. So, I wouldn't say that extraordinary claims require extraordinary evidence. I would say that claims which are not part of normal human experience require far less information be assumed, and thus demand that far more information be aduced. |
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#34 |
Obsessed with Reality
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The Universe is not required to be in perfect harmony with human ambition - Carl Sagan |
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#35 |
Graduate Poster
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Quote:
The evidence provided for such a claim must therefore be more than the "here I picked up a rock on the moon for you" kind. |
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#36 |
ancillary character
Join Date: May 2009
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I just ran across this thread, and it seems to tie in well with the news of Stephen Hawking's new book. According to the reports, Hawking says this:
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#37 |
Guest
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But that is merely ordinary evidence. How does evidence that is “conclusive” or “irrefutable” or that is part of a ‘series” or somehow “superior” make it extraordinary?
Agreed. So perhaps I can come at this from a different angle. Critically, what makes it “ordinary”? |
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#38 |
Graduate Poster
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OK, back to the lunch on the moon thing. If the person telling me he had lunch on the moon once is Buzz Aldrin, his word is all the evidence he really needs to provide. If on the other hand, the person telling me this is some semi-literate guy who wrote a book about secret space programs and is claiming to have made the trip in a secret spaceship that uses anti-gravity devices, I'm going to need a whole lot of evidence about who he really is, who he has worked for, where he went to school, just for starters. In fact, unless he can land the thing in my yard to look at it, not much will convince me. That is extraordinary evidence.
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#39 |
Penultimate Amazing
Join Date: May 2008
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Because it has to meet a burden that is much higher than any mundane claim since it has to overwhelmingly contradict all that is known.
Having one scientific study that confirmed Einsteinian Relativity is pretty mundane. It is likely just accepted without much scrutiny. Having one scientific study that contradicts Einsteinian Relativity is extraordinary. It is not just accepted. It is placed under more scrutiny. It will be repeated multiple times before it is accepted. Having one scientific study that conclusively allows man to float using superduper Gravitons would be pretty conclusive extraordinary evidence.
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"The method of science is tried and true. It is not perfect, it's just the best we have. And to abandon it with its skeptical protocols is the pathway to a dark age." -Carl Sagan "They say a little knowledge is a dangerous thing, but it's not one half so bad as a lot of ignorance."-Terry Pratchett |
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#40 |
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"The lie is different at every level." Richard C. Hoagland |
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