You can't prove a negative

Educational materials and discussion promoting the use of critical thinking skills

Moderators: ryguy, chrLz, Zep Tepi

You can't prove a negative

Postby ryguy » Tue Dec 07, 2010 2:40 pm

pigswillfly wrote:Yeah, I'm for real. The burden is on Zep Tepi to prove "the fact that not a single bonafide expert has disagreed with the findings. Not one. In the entire world."

He has made that claim now let him back it up. Produce the EVIDENCE, please. The burden is not on me to disprove him.


Why is this such a difficult concept for people to understand. YOU CAN'T PROVE A NEGATIVE.

If you claim something is true - you need to prove it. If someone claims something isn't true, they don't have to prove anything (hint - you can't prove something isn't true....think about it ffs).

If you disagree with someone that something isn't true, and you believe it is TRUE, the burden of proof ALWAYS falls upon the person claiming that a certain fact is true.

Get it? Is it really that complicated?

Claim something is true - truth requires proof.
Claim something isn't true - does not require proof, because you can't prove a falsehood.

Maybe we need to add this explanation to our forum rules, because so many people get this wrong all the time.

-Ryan
---
"Only a fool of a scientist would dismiss the evidence and reports in front of him and substitute his own beliefs in their place." - Paul Kurtz

The RU Blog
Top Secret Writers
User avatar
ryguy
1 of the RU3
 
Posts: 4920
Joined: Thu Feb 23, 2006 3:49 am
Location: Another Dimension


Re: Nuclear Demolition

Postby Access Denied » Tue Dec 07, 2010 4:47 pm

ryguy wrote:Maybe we need to add this explanation to our forum rules, because so many people get this wrong all the time.

I don’t know how many times I have to link to this before it sinks in…

http://en.wikipedia.org/wiki/Argument_from_ignorance

From Sagan’s “Baloney Detection Kit” in The Demon-Haunted World: Science as a Candle in the Dark that ought to be required reading…

"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."

And…

"In some circumstances it can be safely assumed that if a certain event had occurred, evidence of it could be discovered by qualified investigators. In such circumstances it is perfectly reasonable to take the absence of proof of its occurrence as positive proof of its non-occurrence." (Introduction to Logic, Copi, 1953, Page 95)

Let me know and I’ll incorporate this into the rules for easy reference. :)
Men go and come but Earth abides.
User avatar
Access Denied
1 of the RU3
 
Posts: 2740
Joined: Tue Jan 09, 2007 7:32 am
Location: [redacted]

Re: Nuclear Demolition

Postby ryguy » Thu Dec 09, 2010 2:16 pm

Access Denied wrote:"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."

And…

"In some circumstances it can be safely assumed that if a certain event had occurred, evidence of it could be discovered by qualified investigators. In such circumstances it is perfectly reasonable to take the absence of proof of its occurrence as positive proof of its non-occurrence." (Introduction to Logic, Copi, 1953, Page 95)

Let me know and I’ll incorporate this into the rules for easy reference. :)


The quotes above aren't quite what I was referring to...lol. Proving truth is fairly black and white, but the above quotes reference "proving" something isn't true, and unfortunately they conflict with each other. The absence of evidence definitely is NOT evidence of absence - I strongly agree with the first quote!

However, the second quote states that it's "perfectly reasonable" to take the absence of proof as "positive proof" of its non-occurrence. In my mind the absence of proof is only evidence that either there is either a non-occurrence, or investigators haven't had enough time to make a discovery - but I do find drawing the non-occurrence conclusion very unreasonable if anyone believes in the future progress of science!

-Ryan
---
"Only a fool of a scientist would dismiss the evidence and reports in front of him and substitute his own beliefs in their place." - Paul Kurtz

The RU Blog
Top Secret Writers
User avatar
ryguy
1 of the RU3
 
Posts: 4920
Joined: Thu Feb 23, 2006 3:49 am
Location: Another Dimension

Re: Nuclear Demolition

Postby Access Denied » Thu Dec 09, 2010 6:53 pm

ryguy wrote:The quotes above aren't quite what I was referring to...lol.

[hangs head in shame and heads back to the drawing board]

In hindsight those quotes were kind of confusing.

Let me try this again...

Evidence of absence
http://en.wikipedia.org/wiki/Evidence_of_absence

The difference between evidence that something is absent (e.g. an observation that suggests there are no dragons) and a simple absence of evidence (e.g. no careful research has been done) can be nuanced. Indeed, scientists will often debate whether an experiment's result should be considered evidence of absence, or if it remains absence of evidence (e.g. the experiment could have missed what it was looking for).

The confusion is worsened since arguments from ignorance and incredulity are often (wrongly) advanced in debates as proper 'evidence of absence'. A case in point: arguing "There is no evidence that this mysterious remedy does NOT work, therefore it works". Basically, this argument from ignorance relies on a lack of research to somehow draw conclusions. While this is a powerful method of debate to switch the burden of proof, appealing to ignorance is a fallacy. It is to such impatient, inappropriate conclusions that Carl Sagan referred when he said "Absence of evidence is not evidence of absence".

Carl was criticizing the misuse of this phrase in the context of the paranormal. In other words, for all practical purposes, it is irrational to believe in dragons in the absence of any evidence for their existence because if dragons existed, arguably there should be some. Given this absence of evidence, If one wishes to argue for the existence of dragons, one must present a rational argument to explain why there isn’t any or, more preferably, actually present some. :)

More specifically…

To be confident that we have evidence of absence of mice in the attic, we need a confident method of detection. Of course, in carefully designed scientific experiments, even null results can be evidence of absence. For instance, a hypothesis may be falsified if a vital predicted observation is not found empirically. At this point, the underlying hypothesis will be rejected or revised, or even rarely add ad hoc explanations. Whether the scientific community will accept a null result as evidence of absence depends on many things, including the detection power of the applied methods, and the confidence of the inference.

In the case of dragons, it would seem some dragon bones should sufiice as a confident method of detection. :)

Also…

Distinguishing absence of evidence from evidence of absence
http://en.wikipedia.org/wiki/Argument_f ... of_absence

Absence of Evidence is a condition in which no valid conclusion can be inferred from the mere absence of detection, normally due to doubt in the detection method. Evidence of absence is the successful variation: a conclusion that relies on specific knowledge in conjunction with negative detection to deduce the absence of something. An example of evidence of absence is checking your pockets for spare change and finding nothing but being confident that the search would have found it if it was there.

Formal argument

By determining that a given experiment or method of detection is sensitive and reliable enough to detect the presence of X (when X is present) one can confidently exclude the possibility that X may be both undetected and present. This allows one to deduce that X cannot be present if a null result is received.

Thus there are only two possibilities, given a null result:

    1.Nothing detected, and X is not present.
    2.Nothing detected, but X is present (Option eliminated by careful research design).
To the extent that option 2 can be eliminated, one can deduce that if X is not detected then X is not present and therefore the null result is evidence of absence.

So, in conclusion…

Absence of evidence is evidence of absence.

Nothing more, nothing less.

One can not prove a negative in the sense that one can not prove dragons don’t exist in the absence of any evidence that they do. The burden of proof lies with one who asserts the positive is true...
Men go and come but Earth abides.
User avatar
Access Denied
1 of the RU3
 
Posts: 2740
Joined: Tue Jan 09, 2007 7:32 am
Location: [redacted]

Re: Nuclear Demolition

Postby ryguy » Fri Dec 10, 2010 2:59 pm

Access Denied wrote:
Whether the scientific community will accept a null result as evidence of absence depends on many things, including the detection power of the applied methods, and the confidence of the inference.

In the case of dragons, it would seem some dragon bones should sufiice as a confident method of detection. :)


Yes! You hit the nail on the head. Particularly the fact that accepting a null result as evidence of absence is not something taken lightly by the scientific community. I cringe when I see it done as flippantly as when believers try to claim that absence of evidence proves something must be true because it hasn't been proven untrue...lol. We really have to avoid claiming something has been proven untrue except under the rigorous conditions described in the quote above.

Distinguishing absence of evidence from evidence of absence
http://en.wikipedia.org/wiki/Argument_f ... of_absence

Absence of Evidence is a condition in which no valid conclusion can be inferred from the mere absence of detection, normally due to doubt in the detection method. Evidence of absence is the successful variation: a conclusion that relies on specific knowledge in conjunction with negative detection to deduce the absence of something. An example of evidence of absence is checking your pockets for spare change and finding nothing but being confident that the search would have found it if it was there.


Yes! And the key is always whether there's doubt in the detection method - and that cuts both ways. If there's doubt in the detection method, then all evidence that "proves" something has to be questioned even more carefully and harshly. By the same token, doubt in the detection method (as is usually the case in the paranormal) makes it that much less likely the scientific community will allow the absence of evidence to be used to say a hypothesis has been thoroughly falsified.

So, in conclusion…

Absence of evidence is evidence of absence.

Nothing more, nothing less.


Absolutely - but I would add the caveat of..."unless there are no existing, good detection methods that can be trusted."

So I guess we agree for the most part. Maybe we should have a thread just for this topic...LOL

-Ry
---
"Only a fool of a scientist would dismiss the evidence and reports in front of him and substitute his own beliefs in their place." - Paul Kurtz

The RU Blog
Top Secret Writers
User avatar
ryguy
1 of the RU3
 
Posts: 4920
Joined: Thu Feb 23, 2006 3:49 am
Location: Another Dimension

Re: You can't prove a negative

Postby Access Denied » Sun Dec 12, 2010 3:30 am

ryguy wrote:Yes! You hit the nail on the head. Particularly the fact that accepting a null result as evidence of absence is not something taken lightly by the scientific community. I cringe when I see it done as flippantly as when believers try to claim that absence of evidence proves something must be true because it hasn't been proven untrue...lol.

That’s really the point. Going back to your original formulation as it seems we have gone full circle now thanks to my confusing quotes lol…

Claim something is true - truth requires proof.
Claim something isn't true - does not require proof, because you can't prove a falsehood.


Actually you can prove a negative by constructing a valid deductive argument…

You Can Prove A Negative

So it seems we need to figure out a better way of wording that. I was thinking with the added caveat of “in the absence of any evidence to the contrary” at the end of the second statement but that seems a little awkward.

Quite simply it’s impossible to prove something’s false without evidence it’s possibly true… there’s nothing to refute! After all, this is what led to the formation of the Church of The Flying Spaghetti Monster and the Pastafarian belief that Pirates are absolute divine beings… :)

http://en.wikipedia.org/wiki/Flying_Spaghetti_Monster

Image

ryguy wrote:We really have to avoid claiming something has been proven untrue except under the rigorous conditions described in the quote above.

Agreed, rigorous conditions have been set when it comes to claims of the parnormal, ET visitation, and 9/11 so in this case we can say with some authority that so far, absence of evidence is evidence of absence.

What are some examples of those rigorous conditions one might ask?

Parnormal: The JREF One Million Dollar Paranormal Challenge
ET visitation: An ET or ET artifact.
9/11: Evidence that planes hijacked by terrorists did not cause the destruction.

ryguy wrote:Yes! And the key is always whether there's doubt in the detection method - and that cuts both ways. If there's doubt in the detection method, then all evidence that "proves" something has to be questioned even more carefully and harshly.

Agreed, when it comes to the kind of claims we examine here there is little to no doubt in the rigorous detection method required to reject the acceptance of the null hypothesis within the scientific community.

ryguy wrote:By the same token, doubt in the detection method (as is usually the case in the paranormal) makes it that much less likely the scientific community will allow the absence of evidence to be used to say a hypothesis has been thoroughly falsified.

See above. In this case the doubt is in the detection methods used by proponents as evidence of presence, not absence.

ryguy wrote:Absolutely - but I would add the caveat of..."unless there are no existing, good detection methods that can be trusted."

This is what I meant when I said one must present a rational argument to explain the absence of evidence.

ryguy wrote:So I guess we agree for the most part.

For the most part I think. :)

ryguy wrote:Maybe we should have a thread just for this topic...LOL

Done.

(moved it here for lack of a better place to put it lol)
Men go and come but Earth abides.
User avatar
Access Denied
1 of the RU3
 
Posts: 2740
Joined: Tue Jan 09, 2007 7:32 am
Location: [redacted]

Re: You can't prove a negative

Postby RICH-ENGLAND » Sun Dec 12, 2010 3:42 am

hi guys,

nice discussion, now this is a perfect example of something that could go in a new subforum as proposed by m0riarty for his videos. a sort of learning zone that would teach critical thought and examples of things that one should know when evaluating a claim.

thanks

rich
ATS HAS TURNED INTO A "BALLOONATIC" ASYLUM
User avatar
RICH-ENGLAND
Focused on Reality
Focused on Reality
 
Posts: 343
Joined: Mon Nov 29, 2010 4:06 am

Re: You can't prove a negative

Postby m0r1arty » Sun Dec 12, 2010 11:33 am

This is exactly the type of thinking that deserves it's own subforum by way of a library of critical thought.

Proving a negative is all the rage these days amongst the great unwashed.

We've all seen 'debunk this!' or 'Prove that it's not...' in our travels.

=D>

-m0r
Thanks to BIAD for the avatar!
User avatar
m0r1arty
Reality Is In Sight
Reality Is In Sight
 
Posts: 225
Joined: Mon Feb 15, 2010 1:54 pm

Re: You can't prove a negative

Postby Access Denied » Sun Dec 12, 2010 6:23 pm

m0r1arty wrote:This is exactly the type of thinking that deserves it's own subforum by way of a library of critical thought.

Done. 8)
Men go and come but Earth abides.
User avatar
Access Denied
1 of the RU3
 
Posts: 2740
Joined: Tue Jan 09, 2007 7:32 am
Location: [redacted]

Re: You can't prove a negative

Postby ryguy » Mon Dec 13, 2010 1:09 pm

Oh...this is going to be a very fun forum. :-)
---
"Only a fool of a scientist would dismiss the evidence and reports in front of him and substitute his own beliefs in their place." - Paul Kurtz

The RU Blog
Top Secret Writers
User avatar
ryguy
1 of the RU3
 
Posts: 4920
Joined: Thu Feb 23, 2006 3:49 am
Location: Another Dimension

Re: You can't prove a negative

Postby longhaircowboy » Tue Dec 21, 2010 11:00 pm

Ok I get the whole can't prove a negative thing and since this is about critical thinking allow me to throw this bit out there.
Over my lifetime I have investigated many, many UFO sightings(I couldn't give you an exact number but it's alot) and never found any to be an alien craft. Sure there's a small number of unexplainables but they aren't actual craft(at least near as I can tell). So just what have I proved after all these years? That UFOs don't exist? That aliens don't exist?
All the sightings I investigated started as UFOs but then I found most of them to be explainable. Does this mean I've proved a negative or a positive? I hope I've laid this out in a manner that's understandable. And I hope to get some feedback that can put me on the right track(if I'm off track).
Btw I got this idea after reading this thread.
Save a horse, ride a cowboy.

Memory...is an internal rumor.
George Santayana
User avatar
longhaircowboy
Focused on Reality
Focused on Reality
 
Posts: 319
Joined: Mon Feb 12, 2007 3:05 am
Location: Florida

Re: You can't prove a negative

Postby ryguy » Wed Dec 22, 2010 12:24 pm

Oh - this is a brilliant example! Thank you for posting it LHC.

longhaircowboy wrote:Over my lifetime I have investigated many, many UFO sightings(I couldn't give you an exact number but it's alot) and never found any to be an alien craft. Sure there's a small number of unexplainables but they aren't actual craft(at least near as I can tell). So just what have I proved after all these years?


You've proven, beyond a shadow of any doubt, that the specific cases you investigated had a natural explanation. That's all you've proven. Well not, all in any sense to belittle the work - because that's actually quite a task and not many people have the energy, drive and determination to prove so many cases have explainable causes.

That UFOs don't exist? That aliens don't exist?


No. Tom may disagree with me (or not?), but you haven't proven UFOs (in the sense of the word meaning extraterrestrial visitors) or aliens do not exist. What you have proven is that cases where people may originally have assumed to be extraterrestrial - those had earthly explanations. That's something tangible and "real" that you can hold in your hand (that the cause was earth-bound) - that can be proven. Something that isn't in your hand (that aliens don't exist) can't be proven.

However, you have provided a great deal of support for people on the side of the fence that are working toward the hypothesis that UFO sightings have earthly causes.

If you ever find someone pointing to such evidence and saying it proves that aliens don't exist, I'd recommend waiting until NASA discovers some single-cell organism on Mars or some other planet in our solar system and forward them the news story. In one fell swoop you've destroyed their "scientific theory".... :-)
---
"Only a fool of a scientist would dismiss the evidence and reports in front of him and substitute his own beliefs in their place." - Paul Kurtz

The RU Blog
Top Secret Writers
User avatar
ryguy
1 of the RU3
 
Posts: 4920
Joined: Thu Feb 23, 2006 3:49 am
Location: Another Dimension

Re: You can't prove a negative

Postby chrLz » Wed Dec 22, 2010 12:41 pm

(I see Ryguy beat me to it, pretty much.. SNAP! But I've said it in a different way, so I'll post this anyway..)

longhaircowboy wrote:Ok I get the whole can't prove a negative thing and since this is about critical thinking allow me to throw this bit out there.
Over my lifetime I have investigated many, many UFO sightings(I couldn't give you an exact number but it's alot) and never found any to be an alien craft.

May I be a devil's advocate, and ask - why were you considering alien craft as a possibility? :twisted:

I mean, of all the other things you attributed as likely causes, weren't they all well-proven phenomena?

But alien craft aren't. We have as much evidence of fairies and unicorns as we do of alien craft - in fact, probably more... So why didn't you consider supernatural sources, for instance?

Science works by building on knowns. Shall we say 'compellingly proven' knowns... You need to use some sort of solid background as you push the envelope outwards, and there isn't much point simply attributing an idea or myth - no matter how popular, as a theory. Indeed, that's pretty much against the rules of the 'Scientific Method'. The idea/myth needs to be proven first, then you can toss it into the mix of possible explanations. Otherwise, any manner of ridiculous explanations are valid.

Sure there's a small number of unexplainables but they aren't actual craft(at least near as I can tell). So just what have I proved after all these years?

Lots of stuff. Including, I would guess..
- That you are a good investigator, by the sound of it.
- That you can identify possible known causes.
- That there are a large number of visible phenomena that may not be familiar to the average observer.
- That some observers may not be 100% accurate in their reports.
- That the mind/eye combination is wonderful at 'making' something fit into their sphere of knowledge and/or imagination.
- That some folks (heaven forbid) make up stories for sh!ts and giggles or to drum up hits for their sites (Hi Bill!)...

or various combinations of the above.

That UFOs don't exist?

Unidentified objects in the sky don't exist? Of course they do. Please don't add to the misuse of 'UFO'! NO-ONE in their right mind disputes that UFO's exist. Just seeing a distant bird in the sky is, technically, a UFO.

That aliens don't exist?

I didn't think, by your description, that you were investigating whether or not aliens exist. Were you? The only way to prove that, is to get out there and find one, or incontrovertible/compelling proof of their existence. And even a shiny rotating saucer-like disk moving at incredible speeds.. does not mean 'alien'.

About all we can say at this time is that, to date, there is no compelling evidence that aliens have visited, or are visiting earth. Nor have we observed compelling evidence of their existence via SETI, etc. But that doesn't mean they don't exist. (can't prove a negative..)

All the sightings I investigated started as UFOs but then I found most of them to be explainable.

Sounds like the story of my life. As a kid I saw some awesome stuff, and a couple of them were probably alien, so I thunked... But then I grew up, learned stuff, saw stuff, identified and researched stuff, and thought back about the stuff I was so impressed by as a kid... and realised what they were. Not alien (nor fairies, unicorns..).

Does this mean I've proved a negative or a positive?

Neither. You have simply applied investigative skills and changed some/many UFO's into IFO's. Well done!

Personally, I blame the media... :P
"To wear the mantle of Galileo, it is not enough that you be persecuted by an unkind establishment. You must also be right." - Robert L. Park (..almost)
User avatar
chrLz
Moderator
 
Posts: 258
Joined: Tue Nov 09, 2010 9:47 am

Re: You can't prove a negative

Postby Access Denied » Sun Dec 26, 2010 7:25 pm

longhaircowboy wrote:So just what have I proved after all these years?

In addition to what Ryan and chrLz have said so well, I would like to point out what you have proven (through independent replication of the experiment) is investigating UFO reports is a waste of time as far as science is concerned. The Air Force figured this out over 40 years ago after 20 years of doing the same.

[not to mention improvements in radar technology and coverage effectively eliminated any possible advantage to soliciting reports from the public from a defensive standpoint]

While it may be helpful to those who are genuinely concerned about what they saw to have a rational explanation, which is why many of us are here, there will always be some small residual of cases from which no conclusions can be drawn simply due to the subjective nature of human observation and experience.

The reason I bring this up is because one of the points I was trying to make in this thread is you can effectively prove a negative (e.g. ET are not visiting Earth in UFOs) by constructing a proper (i.e.. falsifiable) experiment for detecting evidence of absence. In this case, if one postulates that if ET are visiting Earth in UFOs then we should be able to detect their spaceships flying around in our atmosphere (as many people claim to be able to do with their eyes) then all we have to do is perform an objectively verifiable (by using scientific instruments)experiment to positively detect this.

As it turns out, this is a fairly simply experiment to perform as discussed elsewhere in this forum by Astrophotographer. All one has to do is setup a relatively inexpensive network of cameras to detect the presence of UFOs in the atmosphere. If after years of observation of a statistically significant portion of the sky in multiple locations and through analysis (e.g. triangulation) of anything picked up by these cameras we find nothing that can’t be explained by conventional means then we can say with some authority ET are not visiting Earth in UFOs. Why haven’t any UFOlogists done this?

Of course this wouldn’t prove ET are not visiting Earth in nanomachines but as far as I know nobody is reporting that phenomenon… :)
Men go and come but Earth abides.
User avatar
Access Denied
1 of the RU3
 
Posts: 2740
Joined: Tue Jan 09, 2007 7:32 am
Location: [redacted]

Re: You can't prove a negative

Postby longhaircowboy » Thu Dec 30, 2010 10:33 pm

DOH. So in other words, I'm no Mulder just some stiff chasing lights in the sky. But hey I'll take absence of evidence. I don't think there's enough unexplaineds to point to alien craft mostly because those reports don't mention any solid object. The few that I've been unable to explain simply don't match up to anything.
Oh and chrlz I didn't mean to use UFO in that context. When I go out on an investigation I start with no assumptions as to what it is. It's just a UFO and I mean to find out just what it really is. That was probably a litte slip up on my part because I started out as a believer back in the late sixtys after be primed by all the great UFO movies back then(mostly from the fiftys). You know impressionable youth and all that.
Anyhow thanks all for the great responses.
Save a horse, ride a cowboy.

Memory...is an internal rumor.
George Santayana
User avatar
longhaircowboy
Focused on Reality
Focused on Reality
 
Posts: 319
Joined: Mon Feb 12, 2007 3:05 am
Location: Florida


Google

Return to Skepticism & Critical Thinking

Who is online

Users browsing this forum: Bing [Bot] and 2 guests

cron