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Proving a negative?

Proving universal negatives is not only POSSIBLE, but NECESSARY. It's what the scientific process does. We confirm propositions by falsification - by showing what is not so - and looking at what's left.

People who say we can't disprove things, are denying the scientific process itself.
 
Francois Tremblay said:
Proving universal negatives is not only POSSIBLE, but NECESSARY. It's what the scientific process does. We confirm propositions by falsification - by showing what is not so - and looking at what's left.

People who say we can't disprove things, are denying the scientific process itself.
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So how is it done?
 
jmercer said:
Also, "Falling up" is kinda poor terminology - you might want to rethink it to be more specific, because falling is always down by definition.
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I bought a helium ballon for my 2 year old son the other day and to my surprise - it fell up :)
 
Technically it didn't fall up, the atmosphere around it fell and the far less dense balloon was forced upwards by the pressure.
 
JustAnotherSkeptic said:
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.
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I think it's means proving the non-existence of something or proving that there's no evidence for something.

Negatives are proven all the time. This phrase is just abused too much.
 
Francois Tremblay said:
Proving universal negatives is not only POSSIBLE, but NECESSARY. It's what the scientific process does. We confirm propositions by falsification - by showing what is not so - and looking at what's left.

People who say we can't disprove things, are denying the scientific process itself.
Click to expand...

The scientific process isn't about "proving universal negatives", or anything else like that. It's a methodology for testing specific hypotheses, which are either proven or disproven during the testing.

The scientific process (as taught to virtually every high-school student)

1) Identify the problem or question which is the central point of your scientific investigation.

2) Develop a hypothesis. A hypothesis is an educated guess which is specific and testable.

3)Test the hypothesis. The procedure must be designed to answer the specific problem.

4) Evaluate the data. Once you have finished your experiment, you must determine if the data collected answers the hypothesis. Often the data is unconvincing or the hypothesis is disproved. When this happens you might need to think of a new procedure for your experiment or a new hypothesis.

What something more formal?

1. Observation and description of a phenomenon or group of phenomena.

2. Formulation of an hypothesis to explain the phenomena. In physics, the hypothesis often takes the form of a causal mechanism or a mathematical relation.

3. Use of the hypothesis to predict the existence of other phenomena, or to predict quantitatively the results of new observations.

4. Performance of experimental tests of the predictions by several independent experimenters and properly performed experiments.

Show me, Francois, where "proving universal negatives" is a part of the scientific process... or even a stated goal of it. Any definition from any reliable authoritive source will do.
 
The "you cannot prove a negative", is also to be viewed as a rule of debate. In this context, it should really be: You cannot require anybody to prove a negative.

And here it does not matter if that particular negative happens to be a provable one; what matters is that you cannot enter a claim into a debate and require to other part to prove you wrong. Whoever enters a claim has the duty to provide evidence for it.

Hans
 
MRC_Hans said:
The "you cannot prove a negative", is also to be viewed as a rule of debate. In this context, it should really be: You cannot require anybody to prove a negative.

And here it does not matter if that particular negative happens to be a provable one; what matters is that you cannot enter a claim into a debate and require to other part to prove you wrong. Whoever enters a claim has the duty to provide evidence for it.

Hans
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Good thing I read all the way to the end; I was going to say the same thing.

Proving a negative depends on the situation, as has been shown here. It depends on the parameters defining the system and the definitions of the statements requiring evidence.

Firstly 'proof' is a mathematical term, not scientific. Proving something in science is subjective as it relies on a personal level of evidence a person might be satisfied with. Hence the statement should be 'you cannot provide evidence for a negative'.

This raises the old debate 'is absence of evidence the same as evidence of absence?'. Part of the argument here will rest on 'within what system?'.

If I draw a circle on the ground and say 'there is no rabbit inside the circle', you can be satisfied that the absence of a rabbit according to your eyes suffices as ample proof. Make that circle larger, and it will slowly get to the point where you will have to use inductive reasoning (most of the circle has no rabbit, therefore I will assume that the rest has no rabbit as well). Past a certain point, that will not stand as an argument either as searching the circle is impractical.

The typical run of the debate often relies on a claim for the positive being addressed. If I say 'The Easter Bunny does not exist', I am really claiming 'I have not yet seen evidence supporting any claim that EB exists'. Definitions are the biggest tripping point.

Athon
 
athon said:
*snip*
The typical run of the debate often relies on a claim for the positive being addressed. If I say 'The Easter Bunny does not exist', I am really claiming 'I have not yet seen evidence supporting any claim that EB exists'. Definitions are the biggest tripping point.

Athon
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Enter the "working assumption", another point believers often get wrong. So you say the Easter Bunny does not exist. This does not mean that you have positive proof of its non-existence, nor does it mean that you think absense of evidence is evidene of absense. It simply means that you observe that the idea is illogical, has no evidence to support it, and all observations of the alleged activities of the EB have more parsimonious explanations. So, till such time as evidence for the EB is presented, you have decided to leave it our of your world-picture.

Hans
 
Athon, Hans - I completely agree, and that was well written. The thing that bugs me the most about when people who have chosen to leave something out of their worldview forget that it's a choice on their part, and argue about it as if it's a proven fact.

In my case, I choose not to believe in the EB; if I met an adult who believed in the EB and wanted to debate it, I'd present my argument based on my logic and any pertinent facts. I wouldn't, however, simply take the position "This is nonsense. The EB doesn't exist." regardless of what I believe the truth is based on my understanding of the facts. Because if I make a claim - "The EB doesn't exist" - I then can be asked to prove it, which may be beyond my abilities.
 
Actually, that's a good point. Believers often say "You claim [insert belief system] is wrong, so you must prove your claim". While this is, technically, a fallacy, it is not entirely unreasonable. Whoever seeks the debate has a duty to provide evidence for his/her position, even if it is a negative one.

Hans
 
MRC_Hans said:
Actually, that's a good point. Believers often say "You claim [insert belief system] is wrong, so you must prove your claim". While this is, technically, a fallacy, it is not entirely unreasonable. Whoever seeks the debate has a duty to provide evidence for his/her position, even if it is a negative one.
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I must disagree there.

Surely the whole JREF challenge is a position of asking someone to demonstrate their claim is true? It isn't up to Randi to prove the opposite position is true.

Similarly if I meet someone who makes a claim about something, it is surely not my requirement to disprove their claim, it is the original claim that must be proven.

I would find that attempt to shift the burden of proof entirely unreasonable.

When you say:
Actually, that's a good point. Believers often say "You claim [insert belief system] is wrong, so you must prove your claim".
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This is misrepresenting the claims that are being made.
The claim that the belief system is wrong is not actually the important claim being made. In such a scenario, it is, in the first instance, the claim that the belief system is correct that is the main claim and the one that must be logically defended.

What evidence can we provide for our position other than that there is no evidence?

I am quite surprised to see you take this position after the number of times I have seen you ask homeopaths to provide evidence of their claims.
 
Hi, Ashles - while you were addressing Hans, I just wanted to throw my own "2 cents in", as the saying in the US goes. :)

The JREF doesn't make any claims; they challenge them. If Randi made a negative claim - "Homeopathy doesn't work" - the Homeopaths of the world would be justified in saying "Prove it" - and proving that particular negative would be tough. There will always be an excuse about why the proof is incomplete, or a "special case exists", etc. However, critical thinking and skepticism should operate in an unbiased fashion; if a claim is made, it should undergo the same level of examination regardless of source.

I think this is why JREF doesn't actually make any claims, but instead created the JREF Challenge; the Challenge itself won't ever actually prove that woo-stuff doesn't exist. Instead, it creates an overwhelming record of failure regarding the claims that it does exist.

I guess I'm stating the obvious, but I believe the JREF uses this specific strategy in the hopes that those who are initially unsure about this stuff will eventually be won over. Because while it may be very difficult - or even impossible - to absolutely disprove something, there's a point where the proof becomes overwhelming. :)

Hm. I just realized something. JREF's entire strategy is based on "negative proof", or a "lack of proof"... interesting, I never really considered it in that context before. Good thread - thanks for starting it, JAS!
 
minor derail

Falling Up

I tripped on my shoelace
And I fell up--
Up to the roof tops,
Up over the town,
Up past the tree tops,
Up over the mountains,
Up where the colors
Blend into the sounds.
But it got me so dizzy
When I looked around,
I got sick to my stomach
And I threw down.

- Shel Silverstein
 
But Randi DOES provide evidence that nonsense claims are nonsense. They violate the laws of physics as we understand them. They are easily faked by certain methods. Certain psychological phenomina are similiar to them.

Ultimately, the burden of proof is always on the person making a claim, but when they refuse and continue making their claim we have to present some kind of counter argument.

I'm suprised you brought up the homeopathy threads, Ash. Though the burden of proof was on the h'paths of course, but we constantly provided scientific observation as to why the entire system on which homeopahty is based is impossible according to all previous observations we have made about our world. That was what made them look more ridiculous than anything else.
 
jmercer said:
The JREF doesn't make any claims; they challenge them. If Randi made a negative claim - "Homeopathy doesn't work" - the Homeopaths of the world would be justified in saying "Prove it" - and proving that particular negative would be tough. There will always be an excuse about why the proof is incomplete, or a "special case exists", etc. However, critical thinking and skepticism should operate in an unbiased fashion; if a claim is made, it should undergo the same level of examination regardless of source.
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I don't see 'Homeopathy doesn't work' as a claim in the same way as 'Homeopathy does work' is a claim.

'Homeopathy doesn't work' (and any sceptical 'claim') is always going to be a response to an initial claim.

And most sceptical claims of this nature are based on the fact that there is no evidence for the initial claim.

Surely in such a debate the onus is firmly on the original claim (which will change scientific knowledge) to provide evidence. Without that a counterclaim is merely a request for evidence (or rather an illustration of the lack of evidence) put in a more strident way.

A claim that something doesn't work or doesn't exist, pretty much by definition, cannot ever have evidence, merely a lack of it.

Unfortunately that means (I would have thought) that in these cases we cannot use deduction, only induction to form conclusions. And of course that is very unsatisfactory. Hence the problem.
Thus it must always be up to the original claim to prove the existence as that is the only was we can ever reach a definitive conclusion.
The non-existence can only ever be assumed (albeit with very good reason).
 
delphi_ote said:
I'm suprised you brought up the homeopathy threads, Ash. Though the burden of proof was on the h'paths of course, but we constantly provided scientific observation as to why the entire system on which homeopahty is based is impossible according to all previous observations we have made about our world. That was what made them look more ridiculous than anything else.
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I know, but as we know, just because a theory appears to violate previously observed evidence, does not make it incorrect. If it works, it works and it would only mean that our current theories were incorrect.

The strongest evidence against homeopathy is not that it appears to violate current assumed science, but that it just doesn't work in any proper testing.

Scientific knowledge has been superceded too many times for us to assume that the fact that something appears to work in ways we don't understand means that it cannot exist.
While this is one of the arguments against homeopathy I don't think it is the strongest because if homeopathy really did work it would be obvious that our current theories were incorrect.
The fact that it doesn't work is its biggest logical downfall.
 
Ashles said:
I don't see 'Homeopathy doesn't work' as a claim in the same way as 'Homeopathy does work' is a claim.

'Homeopathy doesn't work' (and any sceptical 'claim') is always going to be a response to an initial claim.

And most sceptical claims of this nature are based on the fact that there is no evidence for the initial claim.

Surely in such a debate the onus is firmly on the original claim (which will change scientific knowledge) to provide evidence. Without that a counterclaim is merely a request for evidence (or rather an illustration of the lack of evidence) put in a more strident way.

A claim that something doesn't work or doesn't exist, pretty much by definition, cannot ever have evidence, merely a lack of it.

Unfortunately that means (I would have thought) that in these cases we cannot use deduction, only induction to form conclusions. And of course that is very unsatisfactory. Hence the problem.
Thus it must always be up to the original claim to prove the existence as that is the only was we can ever reach a definitive conclusion.
The non-existence can only ever be assumed (albeit with very good reason).
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Well, yeah. Which brings us around full circle to why proving a negative is so hard - and sometimes, impossible.

However, I have to quibble with you over one thing - a claim is a claim, regardless of source, prompting or situation. Just because saying "Homeopathy doesn't work!" is a skeptical reaction to people saying "Homeopathy does work!" doesn't make it any less of a claim. But as you say, it's clearly difficult to prove because it's a negative statement. ("doesn't work")

But I have to assert the one point that I'm not willing to yield - ANY claim is subject to the skeptical response "prove it" - including "Homeopathy doesn't work!" De rules are de rules. :D

I think that we may be just wrestling with semantics at this point.
 
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