I am constantly seeing the following Sagan misquote on this board. Do you think we could stop that?
"The absence of evidence is not evidence of absence."
The absence of evidence is, in fact, evidence of absence. Here's the entire quote:
"appeal to ignorance - the claim that whatever has not been proved false must be true, and vice versa (e.g., There is no compelling evidence that UFOs are not visiting the Earth; therefore UFOs exist - and there is intelligent life elsewhere in the Universe. Or: There may be seventy kazillion other worlds, but not one is known to have the moral advancement of the Earth, so we're still central to the Universe.) This impatience with ambiguity can be criticized in the phrase: absence of evidence is not evidence of absence." - Carl Sagan, "The Fine Art of Baloney Detection", Chapter 12
>"The absence of evidence is not evidence of absence." He's not wrong.
Jose Baker
But that's a Martin Rees quote, not Sagan
Ayden Carter
Source? I can find plenty saying that it's Sagan. Perhaps he borrowed from Rees, but it's most definitely verbatim from Sagan's Baloney book.
Dylan Watson
What are you on - meth or crack? Try reading (and thinking) before you post.
Thomas Bell
(Whoops-a-daisy - I should have said: "Perhaps Rees borrowed from Sagan."My life runs backwards in time, apparently, like Merlin.)
Liam Rogers
>Source? I can find plenty saying that it's Sagan. Perhaps he borrowed from Rees, but it's most definitely verbatim from Sagan's Baloney book. en.wikiquote.org/wiki/Carl_Sagan#Misattributed
How is that a misquote? He is still taking the stance that absence of evidence is not evidence of absence in that full quote
Aiden Garcia
I get it - you're talking exclusively about the last 8 words of the Sagan quote: "...absence of evidence is not evidence of absence." You're right, that's Rees - good catch. But you're not denying the rest of Sagan's quote, which casts the Rees quote as an appeal to ignorance...are you? If you are, I'll certainly continue to push my central point, and we'll have to get into the nature of evidence vs. proof, etc. Unfortunately, I'm getting a little sleepy here, so won't have a chance to respond for a while.
Andrew Hughes
you have nothing. sagan meant it exactly as quoted. the extra text does not change anything.
Jason Reyes
Wrong. The absence of evidence IS evidence of absence, and the obverse is an appeal to ignorance. Think, for example, of medical tests. The absence of evidence constitutes evidence of absence (of disease). Not proof, mind you, but evidence. No absurdity exists.
Michael Gray
the dictum is wrong, but sagan meant it, OP quote notwithstanding.
Thomas Wood
so you're saying that because humans didn't have evidence of dinosaur existence 10 thousand years ago, this means that this is evidence for non-existence of dinosaurs? top kek
Christopher Campbell
Your point is a poorly made, and I'm too tired to parse it. If you're saying what I think you are at first gloss, then do not confuse evidence and proof. Science often has evidence of absence that turns out to be incorrect. Think, for example, of the coelecanth, long thought to be extinct, then discovered alive. The absence of living coelecanth was, in fact, evidence of its extinction, but not, as it turned out, proof.
Christian Reed
b-but... evidence and proof are synonyms.....
Jason Gomez
Thank god (the absence of whom I cannot prove but for which I can present near-infinite evidence) that they're not. Good night all...I'm spent.
Luis Gray
>The absence of evidence constitutes evidence of absence (of disease). You're conflating an absence of evidence with evidence. Doctors perform tests to look for diseases, and so they have gathered evidence. Your hypothetical doesn't have an absence of evidence.
Colton Nelson
>I invent the cigarrette >Mm are you sure it doesnt causes cancer? >Well no studies show it so it means is healthy :^)
Wyatt Fisher
>I flip a coin but don't show you it >you have no evidence that it's heads, so you have evidence it's not heads >you have no evidence that it's tails, so you have evidence it's not tails
Robert Edwards
it's true actually wave function collapse
Joseph King
>absence of evidence is not evidence of absence No, absence of evidence is not PROOF of absence
I can't prove that there isn't an invisible supernatural Boeing 747 behind me as I'm typing this, but the lack of evidence for it is huge evidence that there isn't one.
Kayden Thomas
>I can't prove that there isn't an invisible supernatural Boeing 747 behind me just swing a hammer at it
Isaiah Martinez
In case of life there's pretty hard evidence: organic material is all over the universe and there's no way around it.
Parker Ramirez
>The absence of evidence is, in fact, evidence of absence
Even in the full quote, this is not what Sagan is saying.
Andrew Harris
But user, a negative test is evidence of absence. You're retarded. Go back to wherever you came from.
Mason Hernandez
>The absence of evidence is, in fact, evidence of absence. t. brainlet
Brandon Ward
Claiming you can have evidence by doing nothing is lazy science
Austin Cook
Then why isn't the quote "An absence of evidence is not evidence?" Clearly the quote is referring to an absence of evidence for a proposition, which is evidence against that proposition.
Evan Anderson
>Then why isn't the quote "An absence of evidence is not evidence?" Because an absence of evidence is most frequently misused as evidence of absence, i.e. "we don't know if it's there, so it's not there", not "we don't know if it's there, so it's there".
Jace Reyes
That would be evidence that it's healthy, not proof.
If evidence is possible one way or the other, then there cannot be a lack of evidence both ways. If evidence is impossible then it is trivially absent.
Sebastian Rogers
That doesn't answer the question. "We don't know if it's there, so it's not there" does not imply a lack of evidence. I can have evidence that something is true without knowing that its true.
Hudson Kelly
>If evidence is possible one way or the other, then there cannot be a lack of evidence both ways. Evidence is possible in the example I gave, you just have to look at the coin. So which evidence do you have?
Nathan Ward
>Doctors perform tests to look for diseases, and so they have gathered evidence. Your hypothetical doesn't have an absence of evidence. Such an absence of evidence is impossible if evidence is possible. The lack of some possible evidence for a proposition is evidence against that proposition, thus there cannot be a total lack of evidence for or against a proposition. Your interpretation renders the phrase inapplicable to reality.
Luis Barnes
>Such an absence of evidence is impossible if evidence is possible. What evidence does the doctor have before performing the test?
Jose Lewis
>Your interpretation renders the phrase inapplicable to reality. You're treating a lack of evidence as evidence, this is what is truly inapplicable to reality.
Ian Rivera
>Evidence is possible in the example I gave, you just have to look at the coin. The possibility that I could have looked at the coin is not evidence that it is tails or evidence that it is heads, since the probability of my looking at the coin and observing heads is equal to the probability of observing tails. Evidence would have to favor one over the other.
Julian Cox
>The possibility that I could have looked at the coin is not evidence that it is tails or evidence that it is heads Why can't you determine the coin flip by looking at it?
Nolan Adams
You mean what evidence could a doctor have before performing a test? The appearance of the patient, the patient's medical history, the incidence of a particular disease in the population, etc.
So if a doctor performs a test, and does not receive a positive result, the lack of a positive result is not evidence? Because the simple lacking of some possible piece of evidence, not the total absence of evidence, is all one needs to illustrate that a total absence of evidence is impossible.
Hunter Martinez
>So if a doctor performs a test, and does not receive a positive result, the lack of a positive result is not evidence? Why would the result of a test not be evidence?
Luis Adams
I'm saying it is evidence, the lack of a specific piece of evidence can be evidence.
Ian Jones
>I'm saying it is evidence Then we agree on that.
Ryan Hall
So you agree there is no such thing as a total absence of evidence?
Liam Baker
>So you agree there is no such thing as a total absence of evidence? No, I just agreed that the result of a medical test is evidence.
Tyler Miller
You agreed that the lack of a positive result is evidence of a negative result. Which means that a total absence of evidence is impossible.
Lucas Taylor
>You agreed that the lack of a positive result is evidence of a negative result. Well yes, assuming the test is binary then the lack of a positive result must be a negative result, so of course it's evidence of a negative result.
>Which means that a total absence of evidence is impossible. Non-sequitur.
Ryder Sullivan
Anything and its absence is a binary relationship. So the lack of a specific piece of evidence is evidence of the opposite proposition. Which means that there is always evidence for or against a proposition as long as evidence is possible.
Dylan Thompson
>Which means that there is always evidence for or against a proposition as long as evidence is possible. What evidence do you have that the coin I just flipped landed on hands?
Daniel Jones
You can. If the possible evidence is that we looked at the coin and saw heads, then the absence of this event decreases the chance that we saw heads avid increases the chance that the coin landed tails. If we then consider that we did not look at the coin and see tails, this decreases the chance of tails. If the two events are equally unlikely, the chance of tails is decreased back to its original value.
Jack James
bump
Nolan Nelson
>the claim that whatever has not been proved false must be true, and viceversa >viceversa What Sagan meant with that quote was that there are things we don't know to be true and thus, we should continue to say "we don't know" instead of dismissing them as false just because we haven't prove them to be true. You have shit reading comprehension.