Proving a negative?

[John Jackson]

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

I agree with this point; at least where paranormal issues are involved.

To say, “homeopathy doesn’t work” is reasonable because in quality trials it cannot be shown to work. In other words there are some empirical data available to back up the claim.

A statement such as, “the afterlife doesn’t exist” however, is a different matter. The afterlife is (as far as I know) an unfalsifiable claim: whether in the positive or the negative. To claim to know that it doesn’t exist is to leave oneself open to the “prove it” challenge that we skeptics are so keen to issue to others.

Claims require evidence.

 

[tsg]

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Scientific knowledge has been superceded too many times for us to assume that the fact that something appears to work in ways we don't understand means that it cannot exist.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.

The problem with testing is that it can only show that it didn't appear to work in this particular instance. Every effort can be taken to eliminate as many variables as possible, but there will always be some that can't be eliminated. It may be entirely possible that only people with a certain characteristic respond well to homeopathic treatments that none of the tests attempted to isolate. The amount of science that would have to be wrong, however, for homeopathy to work is pretty staggering. There is enough evidence to refute the claims of why homeopathy works to make it reasonably certain that it can't. The tests where homeopathy failed are just icing on the cake. A failed test is simply "absence of evidence", in other words, the best a test can say is "the test doesn't support the claim". The science refuting homeopathy is "evidence to the contrary", which is much stronger. A test showing homeopathy to work would also have to explain why the evidence against it working is incorrect.

 

[tsg]

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.

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

As a rule, I try to refrain from making claims like "X doesn't exist/work" and rather state "there is little evidence that X exists/works and plenty that shows why it shouldn't". In some cases, I'll go so far as to say "everything we know about [physics|chemistry|astronomy|etc.] says that it can't". Both put the onus on the claimant to support his claim.

 

[Ashles]

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

Mostly yes.

But tsg ilustrates one point I think is important about the fact that a failed test only means that it failed in that particular instance (a huge part of the homeopaths' defence).

Science should work by observations then tests, but paranormal and pseudoscience claims often work by someone misinterpreting something and then formulating theories which are untestable, or fail testing. But the theories still endure.

Saying that all claims are equal puts scepticism in an impossible situation because it cannot ever hope to come to conclusions.
And I honestly don't think it is true.
Nobody here genuinely thinks the IPU exists or that we should expend any effort in analysing any claims relating to it. Why? Because there are degrees to which lack of evidence are overwhelming.
If I say the IPU doesn't exist it would not be seriously challenged by anyone. No requests for proof would be required.
So what claims require evidence is a matter of degree, not an absolute.

If there is no logical reason for us to believe a thing is true in the first instance, why is it an equal claim to say that thing doesn't exist?
Surely non-existence should be the default position of anything until we have an actual reason to think it exists in the first place.

 

[jmercer]

Surely non-existence should be the default position of anything until we have an actual reason to think it exists in the first place.

Agreed.

 

[tsg]

Saying that all claims are equal puts scepticism in an impossible situation because it cannot ever hope to come to conclusions.
And I honestly don't think it is true.

This a particular pet peeve of mine: the idea that all opinions are equally valid, even those which are entirely uninformed or demonstrably wrong. It's also a wedge that psuedoscience uses to give validity to their claims. ID in particular uses "evolution isn't proven" as an argument that their "theory" is just as valid, ignoring, of course, the mountains of evidence supporting one theory and no real evidence supporting the other.

If there is no logical reason for us to believe a thing is true in the first instance, why is it an equal claim to say that thing doesn't exist?

It's a matter of semantics. "There is no reason to believe that X exists" (or even "there is good reason to believe it doesn't exist") and "X doesn't exist" differ in one respect: the former suggests that, should sufficient evidence be produced, the claim will have validity (and places the obligation of supporting the claim on the claimer) while the latter suggests (to me, anyway) a claim of "it isn't possible" that places the obligation of proof on me. It's the difference between "it's unlikely" and "it's not possible". I can't say for certain that free-energy devices can never work, but I have plenty of reasons to believe it very unlikely that they can.

Surely non-existence should be the default position of anything until we have an actual reason to think it exists in the first place.

I see it like this: Science says "why?" Pseudoscience says "why not?" For some, the possibility of a claim being true is enough for them to believe in it regardless of whether or not it has actually been observed.

 

[jmercer]

I see it like this: Science says "why?" Pseudoscience says "why not?" For some, the possibility of a claim being true is enough for them to believe in it regardless of whether or not it has actually been observed.

I liked your post in every way, except for this last sentence. Science doesn't concern itself with "why"; that's the realm of philosophy. Science concerns itself with "how".

Pseudoscience tries to crossbreed philosophy with science. As a result, they get a series of sterile freaks, often stillborn.

 

[Ashles]

I agree with you both.

Interesting thread.

 

[John Jackson]

Science says "why?" Pseudoscience says "why not?"

That's an excellent way to put it - I'll use that. Then copyright it.

For some, the possibility of a claim being true is enough for them to believe in it regardless of whether or not it has actually been observed.

It's the classic argument to ignorance.

 

[tsg]

I liked your post in every way, except for this last sentence. Science doesn't concern itself with "why"; that's the realm of philosophy. Science concerns itself with "how".

Pseudoscience tries to crossbreed philsophy with science. As a result, they get a series of sterile freaks, often stillborn.

I was speaking more in terms of "why?" and "why not?" responding to the statement "this should be believed".

 

[tsg]

That's an excellent way to put it - I'll use that. Then copyright it.

Feel free. But I have to warn you, I may have stolen it from somebody else.

It's the classic argument to ignorance

AKA, appropriately enough, "God of the Gaps".

 

[jmercer]

I was speaking more in terms of "why?" and "why not?" responding to the statement "this should be believed".

Ah. Fair enough, then.

 

[tsg]

It's a matter of semantics. "There is no reason to believe that X exists" (or even "there is good reason to believe it doesn't exist") and "X doesn't exist" differ in one respect: the former suggests that, should sufficient evidence be produced, the claim will have validity (and places the obligation of supporting the claim on the claimer) while the latter suggests (to me, anyway) a claim of "it isn't possible" that places the obligation of proof on me. It's the difference between "it's unlikely" and "it's not possible". I can't say for certain that free-energy devices can never work, but I have plenty of reasons to believe it very unlikely that they can.

Bad form, replying to my own post, I know, but there was something I didn't like about this when I wrote it and I figured out what it was. This gets a little philosophical, so please bear with me.

"There is no evidence that Y exists" is simply a claim in the form of "X doesn't exist" where X is "evidence that Y exists". So, fundamentally, there is no difference at all between the statements "X doesn't exist" and "there is no evidence that X exists". Both are claiming the non-existance of something, which is, by its very nature, unprovable. It is, however, extremely easy to disprove simply by showing X, whether X is the thing in question or the evidence that X exists. It is a claim, a falsifiable one, but also one that can't be proven on it's own.

From a less literal interpretation, though, I still prefer the statement "there is no evidence of the existance of X" to "X doesn't exist" for the reasons I stated above. In response to the claim "X exists" without any supporting evidence, I believe it to be a valid claim regardless of its supportability simply because the evidence of the existence of X should be the burden of the person claiming it.

I'm done rambling.

 

[jmercer]

"There is no evidence that Y exists" is simply a claim in the form of "X doesn't exist" where X is "evidence that Y exists". So, fundamentally, there is no difference at all between the statements "X doesn't exist" and "there is no evidence that X exists". Both are claiming the non-existance of something, which is, by its very nature, unprovable. It is, however, extremely easy to disprove simply by showing X, whether X is the thing in question or the evidence that X exists. It is a claim, a falsifiable one, but also one that can't be proven on it's own.

From a less literal interpretation, though, I still prefer the statement "there is no evidence of the existance of X" to "X doesn't exist" for the reasons I stated above. In response to the claim "X exists" without any supporting evidence, I believe it to be a valid claim regardless of its supportability simply because the evidence of the existence of X should be the burden of the person claiming it.

I'm done rambling.

Far be it from me to interfere with an argument amongst yourselves... ... but I disagree. It's a logical fallacy to assume that a lack of evidence indicates anything other than a lack of evidence.

In example, there's tons of evidence that God exists. Sadly, it's all of highly questionable pedigree, and is strictly anecdotal, or weak. If we throw out that evidence because it doesn't meet our standards for such things, does that logically disprove the existence of God?

Nope.

All it does is eliminate a set of evidence concerning the existence of God that we find questionable. The burden of proof doesn't shift, of course; but the claimants would be correct to state that they supplied proof, which was ultimately rejected and discarded.

 

[MRC_Hans]

Late reply, sorry...

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.

That is correct. Randi says: Come and prove your claim, and you can win a prize. Perfectly legitimate. He invites the opposition to make a claim and support it.

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.

Right, because they entered the debate making a claim. So the onus of proof is on them, period.

When you say:

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.

Maybe I did not make myself sufficiently clear: In a debate, there is no doubt. But if I sort of barge in in somebody and tells him "your easter bunny does not exist!", then he has the right to say: "I have chosen to believe it does, but I have no need to prove it to you, you can believe what you will." ... He has a right to refuse the debate.

For homeopathy, Roger Coghill, Karen Boesen and others like that, it is a little different: They are not just entertaining a private, innocent belief, they have already entered the debate by imposing their claims on others, by basically offering their belief systems for sale, so THEY are fair game, IMHO.

That is what I meant .

Hans

 

[Paul C. Anagnostopoulos]

What Hans said. You make a public claim, you're fair game. That's what the marketplace of ideas is all about.

Hey, that rhymes.

~~ Paul

 

[tsg]

Far be it from me to interfere with an argument amongst yourselves... ... but I disagree. It's a logical fallacy to assume that a lack of evidence indicates anything other than a lack of evidence.

I never said otherwise. The point of my rambling was that "X doesn't exist" and "there is no evidence that X exists" are not logically different as I had originally thought. Both are a claim of non-existence of something, which cannot be proven.

Absence of evidence is not evidence of absence, but, contrary to the pleadings of the pseudoscientist, it is certainly not evidence of existence. The inability to disprove the existence of something only makes it possible. But "possible" does not mean "likely".

 

[jmercer]

I never said otherwise. The point of my rambling was that "X doesn't exist" and "there is no evidence that X exists" are not logically different as I had originally thought. Both are a claim of non-existence of something, which cannot be proven.

Absence of evidence is not evidence of absence, but, contrary to the pleadings of the pseudoscientist, it is certainly not evidence of existence. The inability to disprove the existence of something only makes it possible. But "possible" does not mean "likely".

Ah, ok - I got confused while reading it, I guess.

Too bad Interesting Ian's not here - he would have argued with you over your second paragraph.

"I'm arguing that the existence of fraudulent psychics makes the existence of genuine psychics more likely." - Interesting Ian

 

[tsg]

Too bad Interesting Ian's not here - he would have argued with you over your second paragraph.

"I'm arguing that the existence of fraudulent psychics makes the existence of genuine psychics more likely." - Interesting Ian

I read that thread. Absolutely amazing.

If the existence of real psychics increases the number of fake psychics, then yes, the existence of fake psychics could make the existence of real psychics more likely than if there were no fake psychics. How much more likely is entirely dependent on how many fake psychics are the result of real psychics and how many other factors lead to the existence of fake psychics. Since the idea of real psychics is all that is necessary for the fake psychics to exist, and the existence of real psychics is not necessary for the idea to exist, "how much more likely" is "not much". So, technically, the claim you quoted is true, but misleading. However, if you go back and read the original post which spawned the argument, his claim was that real psychics "almost certainly" exist since fake psychics do. Clearly not the case.

It also ignores the possibility that the existence of real psychics would decrease the number of fake psychics since it would likely be harder to fake being a psychic. There are very few (if any) fake engineers because their designs wouldn't work and, having real engineers designs to compare them to, wouldn't stand up to scrutiny. They can't make infinite excuses as to why it doesn't work because the client simply points to another engineer's work and says, "how come his does?". And if real psychics aren't any more proficient than fake psychics, then it hardly matters if they do really exist.

 

[Bri]

I never said otherwise. The point of my rambling was that "X doesn't exist" and "there is no evidence that X exists" are not logically different as I had originally thought. Both are a claim of non-existence of something, which cannot be proven.

Very interesting thread! Just wanted to add a couple thoughts...

I agree with tsg's statement, so would the "correct" statement be "X has not been proven to exist" or "You have not provided overwhelming evidence that X exists" or "You have not provided more evidence [or more compelling evidence] of the existance of X than the evidence against X" or something similar? Of course, these are only statements in response to a claim that "X" exists. Any positive statement (one that isn't in response to another person's claim) other than perhaps "We cannot know for certain whether or not X exists" would still be a statement that requires evidence to back it up.

Originally posted by Ashles
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.

The JREF Challenge can prove specific claims to be false. For example, a dowser can be proven to not be able to provide evidence of his or her claims, but the Challenge does not attempt to prove dowsing to be false. That said, the JREF Challenge does provide evidence (perhaps even overwhelming and certainly compelling evidence) that dowsing isn't possible by demonstrating an enormous number of people who believe they can dowse and then fail their own tests. Does this disprove dowsing? Of course not, but it doesn't claim to. It does, however, provide some pretty convincing evidence that a lot of people out there who believe that they can dowse can't, and it also demonstrates that not a single one of these claims has ever provided evidence that dowsing works.

The homeopathy argument seems to work the same way. If it hasn't been shown to work in the hundreds of tests that have been done, then we can assume that it doesn't work until sufficient evidence has been provided that it does as with all medical practices. True enough, a claim of "homeopathy never works" is a claim for which evidence cannot be provided, but a claim of "homeopathy hasn't been demonstrated to work" is certainly a claim that one could back up with plenty of evidence.

Originally posted by jmercer
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.

jmercer, I have always enjoyed your posts, and your comments on this thread are no exception. Thanks!

-Bri