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Author | Topic: Absence of evidence IS evidence of absence | |||||||||||||||||||||||||
DNAunion Inactive Member |
Do aliens exist? Does SuperMan? What about the Saiyan race, or the Jedi Knights, or the fuzzy little Gremlins that transform into nasty beasts when they get wet?
In the absence of any supporting empirical evidence, something (such as the beings listed above) is mere unsupported speculation. A related concept goes like this:
quote: Apparently, not everyone believes this statement to be correct.
quote: quote: This relates back to an earlier statement I made in another thread. But when I made my statement ABSENCE OF EVIDENCE IS EVIDENCE OF ABSENCE I was well aware of Carl Sagan’s position on absence of evidence — it’s actually quite widespread in the SETI/astrobiology world (afterall, they do have an agenda in propagating their fallacy). However, there are several problems with trying to use that saying (and that’s all it is) against my statement. (1) I stated multiple times (in that other thread) that the lack of evidence does NOT prove nonexistence. Had I actually said it DID prove nonexistence, then I would have been guilty. But as things stand here in the real world, I made no logical fallacy. (2) The saying Absence of evidence is not evidence of absence is false; it is a fallacy. It is true only if it is modified, such as by equating the second occurrence of the word evidence with the word proof, as is implied by Sagan’s other statements. That is, it is true that Absence of evidence is not PROOF of absence, but that materially changes the saying to something else: evidence and proof are not the same thing. As literally stated - absence of evidence is not evidence of absence — is wrong, even if spoken by Sagan. In case someone still doesn’t get my (2), let me make a point I already made much earlier in the other thread: To be evidence, an observation does not have to point to the correct position: evidence can point to the wrong conclusion. In fact, science has used evidence that points to the wrong conclusion innumerable times in the past. Evidence gathered through some observations point to a certain conclusion and that conclusion is accepted (for example, when people stood still they didn’t feel the Earth moving — the absence of observed motion of the Earth was evidence that the Earth did not move: hence, the Earth was considered to be stationary). Later, when more and better evidence comes in that contradicts the conclusion the older evidence supported, a new conclusion is reached. But the older observations were still evidence for that other position. And this isn’t restricted to the old days. Even today, science is awash with opposing evidences. Two opposing sides pile up as much evidence as they can to support their position — but only one of the two positions can be correct. So it must be that evidence can point to a wrong conclusion. And consequently, observations that support a particular position are evidence for that position, even if that position turns out to be wrong. Anyone using **critical thinking** would have realized all of the above. Taking that all into consideration, let’s look at the question of whether or not life-not-as-we-know-it exists. Do we have any empirical observations whatsoever to back up the position that life-not-as-we-know-it exists? No. No signs of any kind of life based on anything other than normal biochemistry (organic compounds such as DNA, RNA, proteins, etc.) have been found here on Earth, nor in any meteorites recovered to date, nor in any Moon rocks retrieved from the Moon, nor in any tests performed on Mars’s surface; and SETI hasn’t even detected any radio signals from any kind of ETI (despite 30 or so years trying). This absence of evidence is evidence of absence...what it is not is proof of absence. "Life as we don't know it" is unsupported speculation. [This message has been edited by DNAunion, 11-06-2003]
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DNAunion Inactive Member |
quote: This reasoning is close to what the side opposing me was arguing: since I cannot prove that "life not as we know it" doesn't exist, it exists. [This message has been edited by DNAunion, 11-06-2003]
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DNAunion Inactive Member |
quote: quote: The fact is, not finding the contact lens in front of the bar IS evidence for its not being in front of the bar. Absence of evidence is evidence of absence. Trying to relate this to the "alien thingy", let's not forget that SETI has been "searching space" for decades without success: so in the analogy you'd at least need to have a friend who's been lookin behind the bar for some time and has also failed to find the contact lens. (Then both of your failures combined would be evidence that it is no longer present...perhaps it fell into trash and was taken away, or was stepped on and broken and the pieces scattered, or who knows what: or perhaps it is still there...doesn't matter). But the analogy doesn't work very well for the "life as we don't know it" debate anyway because we know for sure that the thing of interest (contact lens) exists/existed, we just can't find it at this moment. That doesn't parallel the situation in the original discussion. [This message has been edited by DNAunion, 11-06-2003]
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DNAunion Inactive Member |
quote: It is silly to require someone to prove nonexistence in the first place! The rule is, science can never prove non-existence (at least not without an absolute full examination of the entire Universe). By your reasoning, science cannot claim there is no such thing as Superman. By your reasoning, science cannot claim there is no such thing as flying, fire-breathing dragons, or flying pink unicorns, or....... [This message has been edited by DNAunion, 11-06-2003]
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DNAunion Inactive Member |
quote: Actually, that's basically what I said...multiple times (it hinges on what you mean by a conclusion, which could be definitive or tentative). I said we don't know which position is correct, and I said that it is an assumption that life as we know is the only kind of life that can exist, and so on.
quote: Uhm...no I am not. Geez dude, read my posts sometimes before claiming to know what I say. [This message has been edited by DNAunion, 11-06-2003] [This message has been edited by DNAunion, 11-06-2003]
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DNAunion Inactive Member |
quote: quote: quote: I’ll let you read it yourself. I stated this in the other thread.
quote: I will also point out that this thread has left its original topic.
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DNAunion Inactive Member |
I did a little search of the internet to see what others have said. Most hits for "absence of evidence is evidence of absence" seemed to be from general lay people discussing philosophy/religion. I ignored those. I saw several where the phrase was abused by those rejecting it, with the naysayers explicitly or implicitly equating it with "absence of evidence is proof of absence". And I did find a few that confirmed what I said.
quote: quote: quote: quote: edited urls to fix page width - The Queen [This message has been edited by AdminAsgara, 11-06-2003]
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DNAunion Inactive Member |
quote: This one doesn't count against me (if anything, it supports exactly what I have said). This quote incorrectly equates evidence with "proof": i.e., whether a position is actually true or false. This is what I mentioned before: many of the naysayers invoked this flawed distortion of the actual statement, so they are knocking over a strawman. --------------------------------------------------------------------------------
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DNAunion Inactive Member |
quote: This one doesn't count either...no context that supports your position over mine. For all we know Terje also distorts the actual statement (as the quote you gave right above it did).
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DNAunion Inactive Member |
quote: Nor does this one count against me as it too is looking at what is and is not FACT. This again implicitly changes the statement being rejected to "absence of evidence is proof of absence", which is not the actual statement of interest. [This message has been edited by DNAunion, 11-06-2003]
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DNAunion Inactive Member |
quote: Ditto - doesn't count against me. This author is also incorrectly swapping out the actual word evidence for a stronger meaning, such as proof. Of course lack of observations to date of its being transmitted by that mode does not PROVE that it can't be, but the lack of observations to date of its being transmitted by that mode is EVIDENCE that it can't be. [This message has been edited by DNAunion, 11-06-2003]
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DNAunion Inactive Member |
quote: No good either. We have no idea what context is involved. Is Sagan, like a lot of the others you quoted, changing the statement by substituting a stronger word - such as proof - for evidence? Is he basically arguing that absence of evidence is not proof of absence? By the way, in case you didn't know this, there's another famous saying associated with Sagan: "Extraordinary claims require extraordinary proof". A claim that life based on silicon exists seems extraordinary to me...so do you have any extraordinary proof? Nah, you don't have any evidence whatsoever. PS: Note that this "Sagan saying" often times appears as "Extraordinary claims require extraordinary evidence". For some nutty reason, some people seem to think that the words PROOF and EVIDENCE mean the same thing, when clearly they don't. [This message has been edited by DNAunion, 11-06-2003]
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DNAunion Inactive Member |
quote: First, not enough context is given to know if they too are manipulating the statement of interest. And when I tried to determine the context, the link you gave did not work (perhaps it will be working later tonight). Second, this is an ASTROBIOLOGY page - those people have an agenda...they have a need to continue to receive funds and lack of any evidence whatsoever is a bit discouraging to those shelling out big bucks. Of course they have a motive for jumping on the "absence of evidence isn't evidence of absence" bandwagon: it's a matter of job survival for them. [This message has been edited by DNAunion, 11-06-2003]
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DNAunion Inactive Member |
quote: Exactly WRONG. You have materially changed the position: what you knocked down is a mere strawman version of the actual saying "absence of evidence is evidence of absence". I've even pointed out this exact problem (proof or another similar much stronger term being substituted for mere evidence) multiple times in this one thread, and made it clear both in this thread and in the other thread that absence of evidence is NOT PROOF of absence. [This message has been edited by DNAunion, 11-08-2003]
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DNAunion Inactive Member |
quote: I disagree. Looking for them in the kitchen - on the table - and not finding them there is evidence that they are not in the kitchen. It isn't proof, and the evidence may even point towards the wrong conclusion (they very well may be on the microwave), but it is one piece of evidence that supports the position that the keys are not in the kitchen. Also, dragging this back to aliens (I know, this thread is not limited to aliens...), the analogy is weak as it involves searching for something we already know exists. If scientists search Loch Ness for a "monster" and don't find one, is that evidence of absence? And what about flying, pink unicorns? No ones ever seen one - is that evidence of absence? ***************************************
quote: [This message has been edited by DNAunion, 11-08-2003]
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