Talk:Absence of evidence

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Editorial notes
  • Requires further examples
  • Also clearer explanations required not invoking too much Bayesian style maths
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Elephant[edit]

There seems to be a desire to remove the following without debate

  • Take another even more obvious example. Someone maintains that they keep an elephant in their garage. A perfectly normal visible large grey elephant. You go to look and you cannot see any elephant. You enter the garage, which is quite small, and look around it. There is no elephant smell or any elephant droppings. In fact there is a total lack of evidence of any sort which would suggest there is an elephant in the garage. You would quite reasonably assume that the absence of elephantine evidence indicated the absence of the elephant.

Please explain before deleting.--Weirdstuff (talk) 20:51, 13 December 2013 (UTC)

It's painful to read and adds nothing to the article that isn't clearly stated already. PowderSmokeAndLeather: Say something once, why say it again?.Moderator 20:54, 13 December 2013 (UTC)

Should say “The absence of evidence is not the evidence of absence.”[edit]

The author has made a mistake or not researched properly. The correct skeptical maxim from Carl Sagan and others is “The absence of evidence is not the evidence of absence.” No skeptics anywhere would agree with what this article says. You might know better than the scientific community or Carl Sagan but you should try to counter Carl Sagan and at least acknowledge that you consider his view and other scientists to be wrong.— Unsigned, by: 2.123.63.8 / talk / contribs

Um, thanks for your opinion about knowing the thoughts of every skeptic and scientist in the world. -EmeraldCityWanderer (talk) 13:20, 28 April 2016 (UTC)
Strangely enough, as a human being, Carl Sagan has the ability to be... wait for it... wrong. Herr FuzzyKatzenPotato (talk/stalk) 14:00, 28 April 2016 (UTC)
You write "No skeptics anywhere would agree with what this article says..". Google is your friend - it's easy to find criticisms of the quote by skeptics.--Bob"Life is short and (insert adjective)" 14:08, 28 April 2016 (UTC)
I wouldn't say wrong but it's a cherry picked incomplete sound byte :-) If you walk outside for a week and don't see any dragons it's not exactly fair to say dragons don't exist anywhere on Earth. If people spent centuries looking across the world for dragons and didn't find a single shred of evidence (living dragons, remains, scat, broken shit, photos/video) it would be pretty fair to say they don't, and have never, existed on Earth. In both you have an absence of evidence to differing degrees. Sagan made the comparison like that to the invisible dragon in his garage on Cosmos that was excluded from the cherry pick. -EmeraldCityWanderer (talk) 14:24, 28 April 2016 (UTC)

So let me get this right[edit]

So, if there isn't evidence for a claim, that's evidence against it? For example, there is no evidence for the existing of the illuminati which justifies me my belief that the illuminati existing today is just bunk, correct?

On a side note, I got into a debate with a religious person; I said there's no evidence for the existence of God, he then attempted to counter my argument by saying "absence of evidence is not evidence of absence", he was wrong, I imagine?--WMS (talk) 21:26, 9 August 2016 (UTC)

Not quite. If there isn't evidence for a claim when there should be evidence for the claim, then that's evidence against it. Compare:
Situation 1, where Absence of Evidence = Evidence of Absence: Alice says there is a ham sandwich in Box X. Bob spends hours -- nay, years -- searching inside Box X and finds no sandwich. Bob concludes that Alice is wrong.
Situation 2, where AOE != EOA: Alice says there is a ham sandwich inside Building X. Bob fails to look inside Building X whatsoever. Bob concludes that Alice is wrong.
32℉uzzy; 0℃atPotato (talk/stalk) 21:55, 9 August 2016 (UTC)
Oh, alright, I get it now. Thank you.--WMS (talk) 19:39, 11 August 2016 (UTC)

The condition in the definition is unnecessary[edit]

The visual demonstration is simultaneously a demonstration of bias and central tendency. The comparison to universes is needless and muddles the matter. Also, the dots where evidence is present is apparently completely extraneous. Apparently we just know that the shaded areas observations confirm the hypothesis. What isn't known is why. You're as likely in a blue dot to conclude you are outside of the orange circle as in. There's an equivalence problem with assuming you are in the orange circle given you are on an orange dot, besides. The observations within and without are descriptively identical.

Simply put, you cannot conclude that something is true or untrue merely on having justified it with evidence, but merely that it is a justified belief which stands to prove true; probabilities are not certainties. Evidence can only provide inductive clues. They cannot reliably predict a future outcome - the very point of hypothesis testing - on a series of observed past events unless you can be sure that those observations represent a natural constant. That's the problem of induction in a nut shell. Common counterexamples to this include exercises where probabilities decline over repeated occurrences like coin flipping or timekeeping.

"This is because we are significantly more likely not to see evidence for a hypothesis when it is false than not to see it when it's true."

An open-ended statement so loaded with presumption that it is rendered fully meaningless. This is only possible given all other things remain equal. They seldom do. Ultimately the reliability, usability and importance of evidence is a subjective preference established by criteria for usability or admissibility, development and choice of methodology, by comprehensive understanding of the qualities and properties of exhibited evidence, by how well it reinforces predictions - itself a function of subjective probability estimates, by the absence of noise, by the absence of contamination.

Basically set aside 25 years and read this http://www.iep.utm.edu/conf-ind/ — Unsigned, by: Lambchowder / talk / contribs

...But first, set aside 2 minutes and read this: On talk pages, please sign your comments using four tildes (~~~~) or by clicking on the sign button: SigButt.png on the toolbar above the edit panel. You can also indent successive talk page comments using one more colon (:) for each line. Thank you. Reverend Black Percy (talk) 11:41, 17 May 2017 (UTC)

When you don't have the evidence[edit]

I believe there is no God and there is no life after death, but I do not claim to know these things. Claims of Hauntings, contacting ghosts with ouiji boards, psychic powers, 'visiting the other side', and recalling past-life memories via hypnotherapy, have all failed to stand up to scientific scrutiny and been debunked. One bitter truth I must accept is that my own position on death cannot possibly be verified. Positive evidence in favor of the nonexistence of an afterlife isn't there and is probably impossible, and obviously I won't be able to experience nonexistence firsthand because well...I won't exist anymore. If I am right about what happens to us after we die then I will simply never find out and neither will anyone else.

I consider it a reasonable default position that when we die we simply go extinct, but the only evidence I see for this conclusion is the lack of evidence against it. The alternative is that some afterlife does exist but that communication between here and hereafter isn't possible, is possible but a method of achieving it has yet to be devised, or a method already exists but is a closely guarded secret. The best I can argue is that my own position passes Occam's razor as it makes the fewest assumptions. — Unsigned, by: 96.244.117.228 / talk

@96.244.117.228 I would like to point out that there is no verifiable evidence for an afterlife, ergo the correct default position is that there isn't one. Using this logic we can safely conclude that we are correct in our assumptions due to all alternative theories either failing to meet the burden of proof or becoming inconclusive. ☭Comrade GC☭Ministry of Praise 14:08, 11 July 2018 (UTC)
@GrammarCommie While I understand what you mean, and I mostly agree with you (as well as 96.244.117.228), there is just one minor problem. You claim that "we can safely conclude that we are correct...due to all alternative theories..." except that there is one position that no one can disprove. It's that there is an afterlife, but you can only get there once you die and it has no effect noticeable in our world. Yes, it is unfalsifiable, and I don't believe it is particularly likely to be true, so I live my life as if there was no afterlife. I'm just interested because I'm thinking of writing a fictional story about that idea. (One thing to note: In certain multiverse theories, this is considered to happen; even under materialism, because another universe could have an exact copy of your mind right before your death. While none of those theories have been proven, some people, including atheists, believe they are true or likely to be true for various reasons). 24.5.8.227 (talk) 05:54, 9 December 2018 (UTC)
@24.5.8.227 If a claim can neither be proved nor disproved it seems highly questionable to treat as a fact. And in the case of an afterlife there are multiple claims and assumptions involved. Just food for thought. And to be clear, are you considering writing a fictional story around the idea of an afterlife? Or around the experience of being unsure and living as if there were no afterlife? Depending on the answer I might be able to recommend some books for inspiration. ☭Comrade GC☭Ministry of Praise 14:10, 9 December 2018 (UTC)
@GrammarCommie I was thinking about writing a fictional story about the existence of an afterlife. BTW, I was not treating the existence of an afterlife as proven fact at all; I was mentioning it in terms of fiction (which commonly deals with low-probability things, see the TVTropes article "Plausible Deniability"). Also, as the OP mentioned, whether there is an afterlife or not is falsifiable - but only after you die. 24.5.8.227 (talk) 22:50, 9 December 2018 (UTC)

Meaning of “absence of evidence”[edit]

While the probabilistic explanation is mathematically sound, there are ways to make sense of the phrase “absence of evidence is not evidence of absence”:

  • Several theories of the evidential relation have been put forward, an overview can be found in the Internet Encyclopedia of Philosophy. By “evidence of A”, one might mean not simply “something which makes A more probable (e.g., increasing its probability from 0.001 to 0.0011)” (positive-relevance account) but “something which makes A actually probable/evident (making the probability at least, say, over 0.5)” (high-probability account). This is what Martin Rees might have had in mind (I am not saying that it is a good choice of words). It is indeed the case that absence of compelling evidence is not necessarily compelling evidence of absence.
  • We previously considered an event B not occurring such that P(A | B) > P(A). But now consider something of which it is not even possible for us to have any evidence. Under the positive-relevance account, this absence of evidence is not evidence of anything (because it is necessary). In particular, you may take a certain event, e.g., 2 + 2 being equal to 4; its probability is already 1, nothing which further raises it is possible. It sometimes also makes sense to condition over almost impossible (zero-probability) events. Let X be uniformly distributed over [0, 1]. In a sense, P(X < 0.5 | X = 0.4) = 1 > P(X < 0.5) = 0.5 while P(X ≥ 0.5 | X ≠ 0.4) = P(X ≥ 0.5) = 0.5.

Carl Sagan was misinterpreted by some as having criticized the phrase “absence of evidence is not evidence of absence”. However, he did not mean that something in it can be criticized, but offered it as (containing) criticism. This is clear from the fact that he is talking about the appeal to ignorance as a fallacy: “Among these fallacies are: […] 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.”

He also used the phrase on another occasion (Dragons of Eden: Speculations on the Evolution of Human Intelligence): “A few students of the subject seem to have concluded that, because they have been unable to isolate and localize all higher brain functions, no future generation of neuroanatomists will be able to achieve this objective. But absence of evidence is not evidence of absence.” In this case, he really says himself that AOE is not EOA rather than just talking about the mantra. -- Ivan (talk) 11:22, 11 March 2019 (UTC)