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Absence of evidence IS evidence of absence

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Absence of evidence IS evidence of absence
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AgnosticAntitheistPosts: 3Joined: Wed Jun 03, 2009 10:53 pm

Post Absence of evidence IS evidence of absence

When theists are criticised for failing to provide evidence for their views, many are quick to respond that "absence of evidence is not evidence of absence". As catchy as this slogan might sound, I am afraid it is fallacious in the highest degree. In order to discuss this we need to define terms. Evidence is everything that can be used to establish the likely truth of a belief. Let us consider a statement A. Something is evidence for A if it increases the probability that A is true. Let us further consider a case where there is no such evidence for A as implied by "absence of evidence". It is obvious that the probability A has now is only the probability it has without evidence. So how can we determine it? There is a great amount of statements that are true. There is however an enormously larger amount of statements which are not. To get the odds that A is part of the former we need to divide the former by the latter. Since the former is way smaller than the latter the result is tiny. If the chance that A is true is tiny, it follows logically that the chance that it is false is huge, since any statement must either be true or false. We have shown that the absence of evidence leads us to high probability of falsehood and is thus evidence of such. We can conclude that the statement "absence of evidence is not evidence of absence" is wrong. Of course we haven't proven that something that lacks evidence is defnitely not true, but that isn't what is asked for.
Sun Feb 07, 2010 11:36 am
5810SingerPosts: 982Joined: Sat Nov 28, 2009 2:51 pm

Post Re: Absence of evidence IS evidence of absence

AgnosticAntitheist wrote:When theists are criticised for failing to provide evidence for their views, many are quick to respond that "absence of evidence is not evidence of absence". As catchy as this slogan might sound, I am afraid it is fallacious in the highest degree. In order to discuss this we need to define terms. Evidence is everything that can be used to establish the likely truth of a belief. Let us consider a statement A. Something is evidence for A if it increases the probability that A is true. Let us further consider a case where there is no such evidence for A as implied by "absence of evidence". It is obvious that the probability A has now is only the probability it has without evidence. So how can we determine it? There is a great amount of statements that are true. There is however an enormously larger amount of statements which are not. To get the odds that A is part of the former we need to divide the former by the latter. Since the former is way smaller than the latter the result is tiny. If the chance that A is true is tiny, it follows logically that the chance that it is false is huge, since any statement must either be true or false. We have shown that the absence of evidence leads us to high probability of falsehood and is thus evidence of such. We can conclude that the statement "absence of evidence is not evidence of absence" is wrong. Of course we haven't proven that something that lacks evidence is defnitely not true, but that isn't what is asked for.


"Absence of evidence is not evidence of absence", unless I'm very much mistaken is a corruption of the phrase: "Absence of proof is not proof of absence."

The latter statement is the one I've heard for about 30yrs or so, and I think the theists you've heard have picked up a bastardised version of it.
I'm sure you'll appreciate that the word "proof" changes the whole tenor of the phrase.
Sun Feb 07, 2010 12:29 pm
nasher168League LegendUser avatarPosts: 2518Joined: Wed Feb 25, 2009 5:34 pmLocation: Derby, UK Gender: Male

Post Re: Absence of evidence IS evidence of absence

I agree that it is evidence, although obviously it is not proof. It could be that we are wrong, and the gods/God simply doesn't choose to show themselves.
It is evidence of absence only to the extent that the absence of evidence for a heliocentric system was evidence of a geocentric system 1000 years ago.
A great Charity
Apologies for my absence of late.
Sun Feb 07, 2010 6:45 pm
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Aught3ModeratorUser avatarPosts: 4290Joined: Fri Feb 27, 2009 3:36 amLocation: New Zealand Gender: Male

Post Re: Absence of evidence IS evidence of absence

Bloody Carl Sagan and his popularisation. It does need to be made clear to people that absence of evidence, when evidence should be present, is evidence of absence.
Wanderer, there is no path, the path is made by walking.
Sun Feb 07, 2010 9:22 pm
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nasher168League LegendUser avatarPosts: 2518Joined: Wed Feb 25, 2009 5:34 pmLocation: Derby, UK Gender: Male

Post Re: Absence of evidence IS evidence of absence

Aught3 wrote: absence of evidence, when evidence should be present, is evidence of absence.


What he said.
A great Charity
Apologies for my absence of late.
Mon Feb 08, 2010 5:42 pm
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DemojenPosts: 614Joined: Fri Feb 27, 2009 3:34 am

Post Re: Absence of evidence IS evidence of absence

Absence of evidence IS evidence of absence


I hate when people bring up this argument like it can hold any water. Beyond the misrepresentation of the phrase originally made, concluded with the previous post demonstrating it's *APPROPRIATE* application, I'm always left awe struck by the sheer stupidity of the argument in and of itself.

Even if we presume that it's true with no respect to the facts of the matter, neither is it that an absence of evidence is a license to make shit up...Sit on your laurels, sit on your thumb, but don't preach using this phrase as a logical support for any metaphysical bullshit you want to be true...It won't float.

If anyone believes that absence of evidence is not evidence of absence, then they need to go back to grade two.
They've clearly sacrificed their own ability to identify patterned logic.
Nunc ergo vos
"I think therefore you are"
Mon Feb 08, 2010 7:52 pm
DeistPaladinUser avatarPosts: 337Joined: Sat Feb 28, 2009 10:35 pmLocation: Louisville, KY USA

Post Re: Absence of evidence IS evidence of absence

This seems to be a variation on the assertion that the "argument from silence" is a logical fallacy, a term ironically often used by people who try to justify their "argument from ignorance" regarding Bible "history".

As Aught has said, "when evidence should be present" is key here. Carl Sagan's ECREE (extraordinary claims require extraordinary evidence) seems to be a good rule of thumb.

If someone tells me their house was broken into, I'd accept that claim with no evidence. Such things happen all the time and the fact that I've heard no stories in the media about the breakin is of no consequence. The "silence" in the media is not evidence his home wasn't broken into.

If someone tells me a spacecraft blew up their house and then flew away into the sky, I'd expect to see that incident reported in the local media. Here "silence" is evidence that the event didn't happen because it's so unusual we should expect that it would have been reported.

It's the same reason I "have a bias toward naturalism". Well, yes, I do. I have a bias toward the way reality actually is observed to work time and time again. I have a bias toward what I experience from the moment I open my eyes in the morning to when I go to bed at night. If you have any proof that either faith healing and speaking in tongues actually works, or even did at one time as reported in the Bible, I need to see evidence. Claiming "argument from silence" is actually a cover for "argument from ignorance."
"The (only) Word of God is the Creation we behold"
- Thomas Paine

http://www.godvsthebible.com
Mon Feb 08, 2010 8:40 pm
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nemesissUser avatarPosts: 1259Joined: Sun Sep 13, 2009 7:29 pm

Post Re: Absence of evidence IS evidence of absence

to extend on the house example.

say i make a claim that someone has broken into my house to the police.
however, there is no sign of an attempt of someone trying breakin forcefully, no items have taken or placed somewhere else.
the police will say no one has broken into my house.
i can't go like "oh yeah, proof that someone didn't broke into my house!"

the police would think im crazy for thinking that.
in this case, absence of evidence/proof IS evidence/proof of absence.

but what i think is that were dealing with it in the wrong way.
it not just evidence, it must be POSITIVE evidence.

as example;
there are alot of things that are yet explained by evolution, for those you can make a case for a claim such as goddidit.
however, thats just negative evidence, you got to have some good positive evidence for that claim that also explains all the rest which CAN be explained by evolution.
Thu Feb 11, 2010 2:54 pm
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