The "you cannot prove a negative" argument

[glaucon]

stateofmind,

Generally speaking, the question you're asking here is logically illegitimate.

Doreen's point here is to be well noted:

Given that things that did not have evidence later did have evidence and are now considered true, I think it would be very odd to decide that everything is false unless it is proven true - or the weight of evidence indicates it is true.

So, the answer to your question runs thusl:

A negative cannot be proven. This is because only [positive] assertions can be proven. However, the assertion of A, does imply its denial [ not-A, or, B say, in this case..], if it is indeed the case that A has a legitimate contrary.
So, typically, a negative can be 'proven', if and only if this negative is the logical contrary of a correlate positive that can be proven. This methodology is known as reductio ad absurdum.

See: RAA

And its root: Propositional Logic

This is a fairly decent exposition of PL for the layperson: Propositional logic

 

[Doreen]

Just wanted to add that

You cannot prove a negative.

is a negative, and thus, if correct, cannot be proved - though it could be, despite itself, true (only it isn't).

 

[glaucon]

Just wanted to add that

You cannot prove a negative.

is a negative.

lol

Nice.

Though, also astute.

Re-translated then into: you can prove a positive.
Which is, in fact, the case. As I noted above.

 

[stateofmind]

Generally speaking, the question you're asking here is logically illegitimate.

What question were you referring to exactly?

 

[Raithere]

Given that things that did not have evidence later did have evidence and are now considered true, I think it would be very odd to decide that everything is false unless it is proven true - or the weight of evidence indicates it is true.

We were discussing argument in terms of evidence vs no evidence in which case I think my point stands. If we grant validity to arguments without supporting evidence how can we make any distinction between arguments at all? Every assertion would be equal unless it posed a logical contradiction or fallacy.

Admittedly this is a simplification, in the real world we don't really come up with cases where there is no evidence. Typically is it a question of the quality and interpretation of the evidence in which case belief does run a spectrum just as you state.

~Raithere

 

[glaucon]

What question were you referring to exactly?

The first: "Can a 'negative' be proven"?

 

[Read-Only]

We were discussing argument in terms of evidence vs no evidence in which case I think my point stands. If we grant validity to arguments without supporting evidence how can we make any distinction between arguments at all? Every assertion would be equal unless it posed a logical contradiction or fallacy.

Admittedly this is a simplification, in the real world we don't really come up with cases where there is no evidence. Typically is it a question of the quality and interpretation of the evidence in which case belief does run a spectrum just as you state.

~Raithere

I agree. And psychologically, it's far to easy for many folks to buy into anecdotal "evidence" like the claims made in "testimonials" in TV commercials. If that weren't true, you wouldn't keep seeing so many of them.

Proving a positive isn't some sort of mysterious, magical thing - it simpy requires a methodical, repeatable procedure. But proving a negative can be impossible. For example, I have no means at my disposal of proving that those people giving the testimonials in those ads did NOT actually use the product and found it to be personally effective.

 

[Doreen]

We were discussing argument in terms of evidence vs no evidence in which case I think my point stands. If we grant validity to arguments without supporting evidence how can we make any distinction between arguments at all?

Precisely the way you do here. You can describe what you think the evidence is and how strong it is - or the lack thereof or the weakness. But to label everything false that does not have evidence (for you or people in general) is guaranteed to be incorrect on occasion, and further there is no need to do this. If someone has a gun to you head and says 'true or false, if you don't decide I will shoot.' OK, then you have to come down on one side. But otherwise one can be agnostic, for example - in the general sense, not just around the issue of God - iow say that it cannot be decided. Or one can say there is insufficient evidence to support the belief - on your part, in general. One can even remain silent. Plus the other options I gave above.

In a sense to say everything that is not supported by evidence (now) is false, is unsupportable. It is an assertion that you should consider false.

 

[stateofmind]

Precisely the way you do here. You can describe what you think the evidence is and how strong it is - or the lack thereof or the weakness. But to label everything false that does not have evidence (for you or people in general) is guaranteed to be incorrect on occasion, and further there is no need to do this. If someone has a gun to you head and says 'true or false, if you don't decide I will shoot.' OK, then you have to come down on one side. But otherwise one can be agnostic, for example - in the general sense, not just around the issue of God - iow say that it cannot be decided. Or one can say there is insufficient evidence to support the belief - on your part, in general. One can even remain silent. Plus the other options I gave above.

In a sense to say everything that is not supported by evidence (now) is false, is unsupportable. It is an assertion that you should consider false.

Doreen you have a way of getting right the heart of the matter and expressing your thoughts very clearly. Your post above is exactly what I've always thought about the "you can't prove a negative" argument but put in a much more eloquent way.

 

[Raithere]

I agree. And psychologically, it's far to easy for many folks to buy into anecdotal "evidence" like the claims made in "testimonials" in TV commercials. If that weren't true, you wouldn't keep seeing so many of them.
Proving a positive isn't some sort of mysterious, magical thing - it simpy requires a methodical, repeatable procedure. But proving a negative can be impossible. For example, I have no means at my disposal of proving that those people giving the testimonials in those ads did NOT actually use the product and found it to be personally effective.

I do agree. But this falls into the middle ground. Anecdotal evidence is unrigorous and highly unreliable but it is evidence. Essentially it is weakly correlative. The problem with anecdotal evidence is precisely that it's so damn convincing despite its unreliability. I believe it's because this is truly the way our brains are wired. Identifying correlations is a useful survival tool, even if it is wrong a lot.

Precisely the way you do here. You can describe what you think the evidence is and how strong it is - or the lack thereof or the weakness. But to label everything false that does not have evidence (for you or people in general) is guaranteed to be incorrect on occasion, and further there is no need to do this.

How can you describe or measure the strength of nonexistent evidence? What you describe here is the measure and debate over evidence, not its lack.

Supposition may be entertained, granted a suspension of disbelief, for a variety of purposes but this does not grant them any ontological validity. At the very least one must demand an argumentative or theoretical grounding.

As far as occasionally being wrong, well, that's inevitable. But since experience is finite and imagination (as far as we can tell) is infinite we will improve our chances of being right dramatically by limiting belief to that for which we have at least a modicum of evidence.

In other words, you'll be wrong far more often by affording validity to every idea. And on those occasions when you do happen to be right, it will only be by accident... not because you have increased your knowledge. You can get every correct answer on a multiple choice test if you check every box on the page. But that doesn't mean you know anything.

~Raithere

 

[Raithere]

But otherwise one can be agnostic, for example - in the general sense, not just around the issue of God - iow say that it cannot be decided. Or one can say there is insufficient evidence to support the belief - on your part, in general. One can even remain silent. Plus the other options I gave above.

I parsed this out because it's an issue I've been struggling over for some time. Strictly speaking agnosticism is an epistemological position rather than an ontological one. So to take an epistemologically agnostic position really doesn't define one's stance regarding ontology. We could go with ontologically indeterminate or borrow from quantum mechanics and call it a superposition but this doesn't really seem to reflect belief as you can't believe that something does and does not exist simultaneously. One can flip back and forth but then once again it's a positive or negative assertion and not really a middle ground. One can withhold judgment but I find that somewhat disingenuous and not really internally consistent. Take it as an aside if you like, I don't think it affects the rest of the dialogue and I'm always interested in hearing another pov.

~Raithere

 

[Read-Only]

I parsed this out because it's an issue I've been struggling over for some time. Strictly speaking agnosticism is an epistemological position rather than an ontological one. So to take an epistemologically agnostic position really doesn't define one's stance regarding ontology. We could go with ontologically indeterminate or borrow from quantum mechanics and call it a superposition but this doesn't really seem to reflect belief as you can't believe that something does and does not exist simultaneously. One can flip back and forth but then once again it's a positive or negative assertion and not really a middle ground. One can withhold judgment but I find that somewhat disingenuous and not really internally consistent. Take it as an aside if you like, I don't think it affects the rest of the dialogue and I'm always interested in hearing another pov.

~Raithere

Hi, Raithere,

I don't see any problem with withholding judgment by taking the position that's there's simply not information (yet) to make an intelligent decision. (And in some cases, there never will be.)

In fact, that's precisely my attitude toward most news articles when they first appear because there's practically always more to the story than is being told.

 

[stateofmind]

I don't see any problem with withholding judgment by taking the position that's there's simply not information (yet) to make an intelligent decision. (And in some cases, there never will be.)

What cases in which there will never be enough information to make an intelligent decision are you referring to?

 

[Cowboy]

It's not just something that people "believe in", it's an accepted fact.

Want an example, eh? OK, prove I'm not living in an alternate universe from you and have tapped into your Internet.

It's not a fact, but it's the general rule. For example, a background check could prove that I'm not a convicted criminal. But yeah; in most cases you can't really prove a negative.

 

[stateofmind]

It's not a fact, but it's the general rule. For example, a background check could prove that I'm not a convicted criminal. But yeah; in most cases you can't really prove a negative.

The same investigation, if successful, will prove both the positive and the negative. They are not separate like you imagine them.

 

[Cowboy]

The same investigation, if successful, will prove both the positive and the negative. They are not separate like you imagine them.

In that case, there's really no such thing as "proving a negative". Problem solved.

 

[Nasor]

This is a false argument.

You assume the positive and use reductio ad absurdum. This is how you can prove a negative.

I will prove it is false there exists a greatest integer. In other words, I will prove a negative.

For example, assume there exists a greatest integer, say G.

Yet, for any integer, x + 1 is an integer by the inductive hypothesis.
In addition, by the properties of integers, x + 1 > x.

So, take G + 1.

This is greater than the G, a contradiction.

It's generally accepted that you CAN prove a negative when you're dealing with a logical system that allows you to rigorously define your starting axioms, like mathematics. Usually when people say "you can't prove a negative," they're not talking about that sort of system.

But of course, even with mathematics, how do I know for sure that your argument is correct? Yeah, it looks like it makes total sense to me, but how can I be sure there's not some error in your proof that my fallible human logic in unable to detect? It wouldn't be the first time someone thought a proof made sense, when it really contained a hidden error.

 

[Doreen]

I parsed this out because it's an issue I've been struggling over for some time. Strictly speaking agnosticism is an epistemological position rather than an ontological one. So to take an epistemologically agnostic position really doesn't define one's stance regarding ontology. We could go with ontologically indeterminate or borrow from quantum mechanics and call it a superposition but this doesn't really seem to reflect belief as you can't believe that something does and does not exist simultaneously. One can flip back and forth but then once again it's a positive or negative assertion and not really a middle ground. One can withhold judgment but I find that somewhat disingenuous and not really internally consistent. Take it as an aside if you like, I don't think it affects the rest of the dialogue and I'm always interested in hearing another pov.

~Raithere

Sure, agnosticism is an epistomological position applied to a specific assertion about ontology. I am not saying you or one should be agnostic, just mentioning it as another position that seems to me more rational that assuming that every position without sufficient evidence at this time should be considered false.

I understand how we as humans tend to have trouble withholding judgment. It feels more natural to come down on one side or another. But we can do this implicitly - via actions - and most people do have issues they have not completely decided, whether political, social, philosophical, etc. Have you decided 100% we do or do not have free will? (that example might not work, but I am sure if you look around at your beliefs you will find some that are tentative.)

To say 'I doubt it.' is not merely withholding belief. Nor is saying 'I see no reason for me to believe that.'

To say, 'There is no evidence so it is false.' is jumping past a lot of middle ground. Further is leaves no room for people who may have experiences different from yours and which make their beliefs rational, even, despite the lack of public evidence at this time. I had a friend with a variety of symptoms. She was told over and over that she was not sick, all her tests came back negative. People even wrote essays about the hysterical nature of women like my friend. It became a popular target, this group, along with UFO believers and so on.

Oops. Then they found discovered that these people did in fact have a virus. Science and technology improved. It took ten years for her condition to be acknowledged as, in fact, not hypochondria or signs of a mental illness or slacking.

Now here's my point...

I am not saying that the doctors should have said

You are right. You have an illness, despite the lack of evidence.

But, they should have had the epistemological humility to say....

We can find no evidence of an illness, but we cannot be sure. We would like you to consider the possibility that this may have an emotional basis.

1) This is accurate and the history of medicine provides other examples - both in relation to individuals and also to groups - to support an open ended reaction.

2) It is not a statement of belief without evidence, which their assured utterances that her belief she was sick was false was an example of.

3) It leaves room for both the patient and the doctors to learn.

I think the urge to tidy everything up into neat categories of true and false is one we should question. And it is not logical.

 

[Doreen]

How can you describe or measure the strength of nonexistent evidence? What you describe here is the measure and debate over evidence, not its lack.

I was speaking in general. Many 'supernatural' positions have some evidence. Take ghosts. We have photos, experiences, videos even of objects moving. Of course scientists have other explanations of these experiences and phenonmena, but there is some evidence. I was not merely speaking about the theism/atheism divide.

Supposition may be entertained, granted a suspension of disbelief, for a variety of purposes but this does not grant them any ontological validity.

I never said it did. I am saying that your assertion that it must be false has no validity.

At the very least one must demand an argumentative or theoretical grounding.

You are leaping away from the point I am making. At no point am I saying that you should believe these other people.

As far as occasionally being wrong, well, that's inevitable.

Actually no. You are guaranteeing errors, where a more cautious position will make less. We went from comparing you, the non-believer taking some position where you do not make a specific claim to you the non-believer claiming it must be false. We are not comparing your position to the position of the believer. I notice this pattern a lot in discussions like this. If I focus on the skeptics position, at a certain point, the skeptic, seemingly without noticing they are making this shift, begin to compare their position with the believers position as if this justified their own. But this is not relevent to your position. What is is given that you find no reason, currently to believe, do you decide the believers assertion must be false, or do you not take such and absolute stand.

To take the stand that it must be false is to go against your own criteria for truth.

But since experience is finite and imagination (as far as we can tell) is infinite we will improve our chances of being right dramatically by limiting belief to that for which we have at least a modicum of evidence.

Where did I say you should not limit belief? You in fact are extending your beliefs when you say these things must be false. You are, right now, defending extending your beliefs.

In other words, you'll be wrong far more often by affording validity to every idea. And on those occasions when you do happen to be right, it will only be by accident... not because you have increased your knowledge. You can get every correct answer on a multiple choice test if you check every box on the page. But that doesn't mean you know anything.

Ibid.

You are also assuming, as seems very common, that believers do not base their beliefs on experience and how the belief works for them. There is also the assumption, implicit in all this, that everyday beliefs held by skeptics are not also based on a lack of evidence. Shall we switch over to the politics forums?

 

[Faure]

I really don't understand the "you can't prove a negative" argument either. It usually rests on a level of skepticism that, if we accepted it, would render most common positive statements unprovable as well.

Usually when laymen use the word "proof" in philosophical discussions they, for some reason, use a standard of proof that is totally untenable in nearly every aspect of normal human existence (including science).

In any case, I don't understand the "you can't prove a negative" argument as anything more than standard, smug yet sophomoric skepticism. Taking normal standards of proof I can prove all sorts of negatives.