Proving a negative?

[JustAnotherSkeptic]

Hi everybody! I've been lurking a while, but this is my first post.

I've been running this "can't prove a negative" thing through my head for a while, and I wanted to get other's opinions. Let's take a standard example:

The easter bunny doesn't exist.

Can't prove that, cause it's a negative, right? So, turn it around:

The easter bunny does exist.

Easy to prove, just present ole big ears himself and your all set.



Ok, but now this is where I get myself confused:

A falling object doesn't always go down.

That's a negative, but it's just as easy to prove as our last positive statement. Just show your object that's falling up and you've proven it. And the converse, positive statement, seems like the non-provable one:

A falling object always goes down.



On reflecting on all this, it seems to me that it's not a negative that you can't prove but a 'universal'. Anybody have any thoughts?

(oh, and, btw, I'm psychic, I've seen bigfoot, and I can cure any desease with my aura. )

 

[jmercer]

One problem is that in the EB situation you're citing a specific, and in the second case (falling up), you're citing a possibly infinite set of events looking for an exception.

Also, remember - assuming sapience on the part of the EB, unless you have a way of coercing appearance of a magical being, it's also not possible to demostrate that it exists... similar to the God problem.

 

[jmercer]

Also, "Falling up" is kinda poor terminology - you might want to rethink it to be more specific, because falling is always down by definition.

 

[JustAnotherSkeptic]

One problem is that in the EB situation you're citing a specific, and in the second case (falling up), you're citing a possibly infinite set of events looking for an exception.

Exactly. That's sort of the meat of my ponderings. Isn't it the infinite set of events you talk about that is the non-provable situation, not the inherent negation of a claim? It's just that it seems the two often become the same thing.

Also, remember - assuming sapience on the part of the EB, unless you have a way of coercing appearance of a magical being, it's also not possible to demostrate that it exists... similar to the God problem. [

Yes, you've got me there. But I was just trying to use the EB as a logical stand in. In other words, taking it for granted that I've met whatever criteria of evidence you'd need to for the EB, I've proven his existance by meeting that criteria.

falling is always down by definition

Ok... true. But that's really getting off on a tangent to what I was trying to get at. I was wondering about my logical questions, not really whether my ability to provide examples couldn't be picked apart

(Sheesh, not even a 'welcome to the forum'. This place is tough )

 

[John Jackson]

It is possible to prove a negative as long as the proof involves detectable properties.

“My pen is not red”, or “there is not a telephone on my desk”, are easy to prove.

There are no photons emitting from my torch – provable, as photons are detectable.

I am not sending out telepathic messages – not provable, as telepathic messages cannot be detected.

The problem with paranormal claims is that people cling to them because they haven’t been disproved; but, of course, it’s not possible to prove that something doesn’t exist if indeed it does not. This results in claims like, “PSI phenomena have never been disproved” actually being meaningless.

 

[John Jackson]

Oh, and welcome to the forum.

 

[jmercer]

Oh, and welcome to the forum.

Oops! Ditto.

 

[JustAnotherSkeptic]

The problem with paranormal claims is that people cling to them because they haven’t been disproved; but, of course, it’s not possible to prove that something doesn’t exist if indeed it does not. This results in claims like, “PSI phenomena have never been disproved” actually being meaningless.

Yes, absolutely. There are lots of reasons not to try and disprove somebody's claim, such as what I believe you're stating- that disproving existence of something (what I called above 'proving a universal') is impossible. And, of course, it's not your burden to disprove what somebody else is claiming. If they want others to believe them, the onus is on them...

I've got some good replies from you guys, thanks! Where I was going with all this is that it's always bothered me when I hear people repeat the mantra "You can't disprove a negative." Firstly because it just never rang true in that simplified form, since the original intent was really, "You can't disprove the existence of something", which is a much different statement. And secondly because when said, it basically accepts the burden of proof inherently, and moves on to "I would prove it if I could, but I can't." That, to believers, sounds like a cop out.

To the statement, "You can't prove it's not true", I much prefer the statement, "I'm not attempting to prove anything one way or the other. It's YOU who are trying to prove something. So let's see it."

 

[MRC_Hans]

Hi everybody! I've been lurking a while, but this is my first post.

Well, welcome out of the lurking closet .

I've been running this "can't prove a negative" thing through my head for a while, and I wanted to get other's opinions. Let's take a standard example:

The easter bunny doesn't exist.

Can't prove that, cause it's a negative, right? So, turn it around:

The easter bunny does exist.

Easy to prove, just present ole big ears himself and your all set.

Precisely.

Ok, but now this is where I get myself confused:

A falling object doesn't always go down.

That's a negative, but it's just as easy to prove as our last positive statement. Just show your object that's falling up and you've proven it. And the converse, positive statement, seems like the non-provable one:

A falling object always goes down.

#1 is not falsifiable. You can prove that it is true by presenting an object that falls up, but that is proving a positive (namely "an object exist that does not fall down"), but you cannot prove a negative, because you cannot prove that no object exists anywhere in the universe that will fall up.

# 2 is a positive statement, and it is falsifiable. But difficult to falsify.

On reflecting on all this, it seems to me that it's not a negative that you can't prove but a 'universal'. Anybody have any thoughts?

Both are right, or nearly: You cannot prove a negative, and it is often virtually impossible to prove universality.

(oh, and, btw, I'm psychic, I've seen bigfoot, and I can cure any desease with my aura. )

Bigfoot is my uncle, say hello to him from me.

Hans

 

[MRC_Hans]

It is possible to prove a negative as long as the proof involves detectable properties.

“My pen is not red”, or “there is not a telephone on my desk”, are easy to prove.

There are no photons emitting from my torch – provable, as photons are detectable.

I am not sending out telepathic messages – not provable, as telepathic messages cannot be detected.

The problem with paranormal claims is that people cling to them because they haven’t been disproved; but, of course, it’s not possible to prove that something doesn’t exist if indeed it does not. This results in claims like, “PSI phenomena have never been disproved” actually being meaningless.

Detectable properties AND a closed logical system. For instance your torch: There are only two possibilities: It emits photons, or it doesn't, so positive evidence for one falsifies the other. Incidentially, your torch emits photons whenever its temperature is above 0K .

You are quite right about paranormal phenomena.
Hans

 

[jmercer]

Exactly. That's sort of the meat of my ponderings. Isn't it the infinite set of events you talk about that is the non-provable situation, not the inherent negation of a claim? It's just that it seems the two often become the same thing.

Mmm... yes and no. There are negatives that can be proven, but they all resolve themselves as material actions, objects, or phenomena. Infinity does throw a monkey wrench into the idea, because it's impossible to demonstrate an infinite set.

However, unique events are also often inherently unprovable as a negative because they're unique and can't be repeated or observed; such as a claim that "Jesus Christ did not rise from the dead", etc..

Yes, you've got me there. But I was just trying to use the EB as a logical stand in. In other words, taking it for granted that I've met whatever criteria of evidence you'd need to for the EB, I've proven his existance by meeting that criteria.

Very true, assuming that the criteria is agreed on. I understand what you're driving at - but I don't have any answers for you other than the suggestion to not use a magical being in the discussion because it really creates some serious problems with defining proof.

Ok... true. But that's really getting off on a tangent to what I was trying to get at. I was wondering about my logical questions, not really whether my ability to provide examples couldn't be picked apart

I gotcha. In a way, though, our ability to define the problem affects the likelyhood of resolving the question... language for these discussions is really critical, because it's so easy to assume we're both talking about "apples".

(Sheesh, not even a 'welcome to the forum'. This place is tough )

Yeah, I do apologize - I didn't notice this was your first posting. And you really are welcome here.

 

[John Jackson]

Incidentially, your torch emits photons whenever its temperature is above 0K .

You've found the word I should have used: "falsifiable".

If a claim is not (potentially) falsifiable, it is rendered meaningless.

 

[Paul C. Anagnostopoulos]

Welcome!

I try to say "It's difficult to prove a universal negative." You can prove "There is no elephant in my living room." You cannot prove "There is no elephant anywhere."

And, as everyone has said, watch out for false dichotomies: There are problems with evolution, so ID must be true. No one will say it that directly, but they're saying it nonetheless.

And never waste your time trying to disprove an anecdote from a believer, unless you can find a logical flaw in it.

~~ Paul

 

[H3LL]

Deleted post as Paul said the same thing in less words.

 

[jmercer]

If a claim is not (potentially) falsifiable, it is rendered meaningless.

Is that really true, though? For example, quantum theory states that one can know the exact velocity or the exact position of a particle - but not both simultaniously. I don't know how you'd falsify that claim, but it's not meaningless.

Also, there's the so-called "observer" effect where the act of measuring the state of a particle supposedly defines it's state. There's no way to actually prove or disprove that claim (by definition!), but there's a commercially available encryption process that makes use of this property.

I'm playing devil's advocate here, but I think it's important to be careful when making absolute statements.

 

[Santa666]

Though no one has brought it up as an example. I would like to interject that I do, in fact, exist.

HO HO HO, Merry Xmas.

That damn bunny is always trying to one-up me for exposure.


Santa

 

[Paul C. Anagnostopoulos]

jmercer said:
Is that really true, though? For example, quantum theory states that one can know the exact velocity or the exact position of a particle - but not both simultaniously. I don't know how you'd falsify that claim, but it's not meaningless.

I believe you can prove Heisenberg:

http://www.cbloom.com/physics/heisenberg.html

It's one of the most misunderstood concepts in all of physics.

~~ Paul

 

[c4ts]

Though no one has brought it up as an example. I would like to interject that I do, in fact, exist.

HO HO HO, Merry Xmas.

That damn bunny is always trying to one-up me for exposure.


Santa

You really ought to send an elf hitman to fix him.

 

[Nex]

[...]It's one of the most misunderstood concepts in all of physics.

Gee, I can't fathom why. What is that, ancient Greek?

 

[Jeff Corey]

No, it's six feet.