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Thread: Absence of evidence IS evidence of absence

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    Absence of evidence IS evidence of absence

    The phrase "Absence of evidence is not evidence of absence." appears in Carl Sagan's The Demon-Haunted World from 1995. I don't know if he is the originator of that phrase or not, but he probably helped to popularize it. The phrase is very popular among religious believers and believers in other sorts of nonsense.

    But it's clearly wrong. Absence of evidence is not proof of absence, it doesn't conclusively settle the issue all by its own. But it is certainly evidence of absence if the evidence could be expected to be there and is not.

    - If we don't find any traces of the Israelites in the Sinai desert around the time of 1200 BCE, it is evidence that there were no massive nomadic wandering of Israelites as described in the Bible.

    - If we don't find any trace of the earliest human evolution in Europe, it is evidence that the earliest evolution of humanity did not take place in Europe.

    - If there is no trace of elves, apart from folklore, then that is evidence that elves don't exist.

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    Something that supports a contention yet does not conclusively settle a contention is supporting evidence.

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    Contributor Speakpigeon's Avatar
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    Quote Originally Posted by Tammuz View Post
    The phrase "Absence of evidence is not evidence of absence." appears in Carl Sagan's The Demon-Haunted World from 1995. I don't know if he is the originator of that phrase or not, but he probably helped to popularize it. The phrase is very popular among religious believers and believers in other sorts of nonsense.

    But it's clearly wrong. Absence of evidence is not proof of absence, it doesn't conclusively settle the issue all by its own. But it is certainly evidence of absence if the evidence could be expected to be there and is not.

    - If we don't find any traces of the Israelites in the Sinai desert around the time of 1200 BCE, it is evidence that there were no massive nomadic wandering of Israelites as described in the Bible.

    - If we don't find any trace of the earliest human evolution in Europe, it is evidence that the earliest evolution of humanity did not take place in Europe.

    - If there is no trace of elves, apart from folklore, then that is evidence that elves don't exist.
    Yes, evidently, we can only all implicitly agree here.


    At least, I don't have any evidence that we don't all agree.


    So, I guess, I do have evidence that we all agree.


    At least to the extent that the absence of evidence of a disagreement can be taken as implicit agreement.


    Seems rather evident now that I think about it.





    EB.

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    Junior Member Poppa Popobawa's Avatar
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    I agree with you, Tammuz. What you would expect to find, if something does not exist, is the absence of any evidence for it.

    But it's possible that you can't find any evidence for something which does exist, maybe the evidence is out of your each, but
    exists somewhere.

    On the other hand, if something is purported to exist, and if the nature of its existence would lead one to expect to
    find evidence in certain situations and ways, then a lack of that evidence, more strongly supports the conclusion that the contention
    of the said something existing, is false.
    Here is the tragedy of theology, in its distilled essence:
    The employment of high-powered human intellect,
    of genius, of profoundly rigorous logical deduction —
    studying nothing.
    { Andrew Bernstein }

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    Senior Member Treedbear's Avatar
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    Right. In other words absense of evidence is evidence of absense when and only when presence must provide evidence. But in between the two versions it becomes a matter of conclusive evidence vs circumstantial evidence.

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    Contributor Speakpigeon's Avatar
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    I still think absence of evidence is evidence of absence.

    If someone disagrees then it's up to them to provide the evidence that the something in question does exist after all. I'm certainly not going to spend any time looking for dragons just to satisfy some pretty idiotic dictum.

    It baffles me how people are happy to just repeat what Wiki says without any critical sense; and how Wiki repeats what some dude said.
    EB

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    Senior Member Treedbear's Avatar
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    Quote Originally Posted by Speakpigeon View Post
    I still think absence of evidence is evidence of absence.

    If someone disagrees then it's up to them to provide the evidence that the something in question does exist after all. I'm certainly not going to spend any time looking for dragons just to satisfy some pretty idiotic dictum.

    It baffles me how people are happy to just repeat what Wiki says without any critical sense; and how Wiki repeats what some dude said.
    EB
    The thing is that absence of evidence must be presented as the evidence itself. It doesn't make sense to state it as a generic case. It's self contradictory and can easily be mischaracterized as simple ignorance. You open a refridgerator door and see there is no milk. The evidence is the act of looking inside and seeing nothing. Not the absense itself. I could ask you for the evidence there is no milk and you'd have to say that you looked and saw none. (Bracing for next insult to my intelligence.)

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    Veteran Member Lion IRC's Avatar
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    Absence of evidence is absence of evidence.

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    Contributor Speakpigeon's Avatar
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    Quote Originally Posted by Treedbear View Post
    The thing is that absence of evidence must be presented as the evidence itself. It doesn't make sense to state it as a generic case. It's self contradictory and can easily be mischaracterized as simple ignorance. You open a refridgerator door and see there is no milk. The evidence is the act of looking inside and seeing nothing. Not the absense itself. I could ask you for the evidence there is no milk and you'd have to say that you looked and saw none. (Bracing for next insult to my intelligence.)
    That's why the justice process requires contradictory representation. Each side presents the evidence it has, which may indeed be as you say "I looked and there was nothing".

    But the absence of evidence can only be taken as evidence of absence. That there is no evidence the guy murdered the victim is taken as evidence that the guy didn't murder the victim. It's a practical thing. You can't start to accuse people just in case. Absence of evidence the other 240 million Americans murdered John is good enough evidence they didn't murder him and should not be tried. So absence of evidence has to be admitted as your first evidence. You have to have due process but you also have to have a resolution and, in this case, there are only two possibilities, the guy did it or he didn't do it. And the system has to decide and justify its decision.

    No guilty until proven otherwise. The word evidence just means "easily perceived or obvious". It's not necessarily anything like a piece of shrapnel or a trace of semen. It can be the glaringly obvious fact that there is no evidence. If it's evident that there's no evidence then this in itself is evident, and therefore it is evidence. You are intelligent and only guilty of starting off in your analysis from concepts that are not fundamental, such as the judicial vocabulary. It's legitimate to look at that but you have to have a critical sense of the fact that the vocabulary the judicial use is a narrowing of the general concept of evidence.

    Obviously, looking inside the fridge and seeing nothing is better evidence than just looking at it from the outside and just assuming there's nothing inside. But again, that's why we get to argue about things in a confrontational way, because your evidence is not mine. From your vantage point, you've seen inside the fridge. I didn't open the fridge because I'm lazy. The God tribe will come and claim there's God inside the fridge and your evidence will be better than mine. But that doesn't make my evidence no evidence at all because i don't have to believe what a bunch of idiots claim because I have plenty other things to do. I will act rationally assuming there's no god inside the fridge even though I never looked inside.

    And I'm quite sure you yourself don't waste your time to open the fridge every minute to check there's not God inside, because, you know, God may well decide not to be in there one minute and then to be there the next. And did you dismantle the fridge? We can always find better evidence, I agree, but better evidence is just that and that doesn't disqualify lesser evidence from being evidence. Minimal evidence is still evidence.

    I rest my case.

    I guess I did good this time controlling myself.


    No! Please don't look at the evidence.

    You really are a bloody idiot.




    EB

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