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#15177968
People keep repeating the erroneous belief that “you cannot prove a negative”.

This is incorrect.

First of all, it contradicts itself. It is itself a negative claim. If it were true, it would then be impossible to prove this negative claim, in which case it would be incorrect to argue that this particular negative claim is the only one that is proven to be true in all circumstances.

Secondly, we have real world examples. An alibi is a good example of proving a negative. The idea is to prove to the police that someone did not commit a crime. This is a negative claim. By providing evidence of being in another location at the same time, the person with the alibi has supported the negative claim that they did not commit the crime.

Third, we have examples of proven negative claims in the abstract, such as the law of non-contradiction. This law is a negative claim and can be proven logically.

Four, many (all?) negative claims can be rewritten as positive claims and vice versa.

Please stop using this meme as an actual argument, or more commonly, a reason to not provide evidence for a claim.
#15177975
Very interesting thread

Pants-of-dog wrote:People keep repeating the erroneous belief that “you cannot prove a negative”.

This is incorrect.

First of all, it contradicts itself. It is itself a negative claim. If it were true, it would then be impossible to prove this negative claim, in which case it would be incorrect to argue that this particular negative claim is the only one that is proven to be true in all circumstances.


But you can say, however, that the burden of proof falls on the person making a positive claim. I refer here to analogies like Russell's teapot analogy, where the point is that inability to prove someone is wrong is not necessarily a good argument.

Pants-of-dog wrote:Secondly, we have real world examples. An alibi is a good example of proving a negative. The idea is to prove to the police that someone did not commit a crime. This is a negative claim. By providing evidence of being in another location at the same time, the person with the alibi has supported the negative claim that they did not commit the crime.


But in that case, it was done by proving a positive claim that is incompatible with the negative claim.

Pants-of-dog wrote:Third, we have examples of proven negative claims in the abstract, such as the law of non-contradiction. This law is a negative claim and can be proven logically.


It's questionable whether this is something you can prove or if it's an axiom. It is true however you can prove inexistence (or more precisely, impossibility of existence) by contradiction, if you accept the law of noncontradiction as an axiom.

Pants-of-dog wrote:Four, many (all?) negative claims can be rewritten as positive claims and vice versa.

Please stop using this meme as an actual argument, or more commonly, a reason to not provide evidence for a claim.


Then you could actually try to reframe it as the positive claim you want to be proven, if that is in fact true.
#15177978
wat0n wrote:Very interesting thread

But you can say, however, that the burden of proof falls on the person making a positive claim. I refer here to analogies like Russell's teapot analogy, where the point is that inability to prove someone is wrong is not necessarily a good argument.


This does not address the fact that it is a logical contradiction to argue that it is impossible to prove a negative claim.

Burden of proof is a whole other subject. The fact that people use this meme to shift burden of proof does not seem relevant.

But in that case, it was done by proving a positive claim that is incompatible with the negative claim.

It's questionable whether this is something you can prove or if it's an axiom. It is true however you can prove inexistence (or more precisely, impossibility of existence) by contradiction, if you accept the law of noncontradiction as an axiom.


People have made proofs.

But this is immaterial since, as you say, it is possible to prove non-existence.

Then you could actually try to reframe it as the positive claim you want to be proven, if that is in fact true.


I have tried that in the past. People then accuse me of making a strawman and go back to the same but differently worded negative version of their argument.
#15177981
Pants-of-dog wrote:This does not address the fact that it is a logical contradiction to argue that it is impossible to prove a negative claim.

Burden of proof is a whole other subject. The fact that people use this meme to shift burden of proof does not seem relevant.


Why not?

Pants-of-dog wrote:People have made proofs.

But this is immaterial since, as you say, it is possible to prove non-existence.


Is it possible to prove non-existence without having to prove impossibility of existence?

Pants-of-dog wrote:I have tried that in the past. People then accuse me of making a strawman and go back to the same but differently worded negative version of their argument.


Maybe you could then explain how is your different wording of the original negative claim now a positive one.
#15178053
Eh, by definition if an event never happened it can leave no evidence. You are then left with an argument that no evidence is the evidence which can work both ways (does a tree in a forest make a sound if nobody is around to hear?). So then who has the burden of truth? That is right the person who has the ability to provide evidence. If they can't, are they wrong (Does God exist)? Not necessarily, but that is irrelevant in a court of law.
#15178056
Words.

That's right. Words. On their own they hold no power. They have to be accompanied by context, social momentum but in most cases some kind of evidence or example one can point to.

Pants-of-dog raped me. That's right he did. Totally.

In minecraft.
#15178100
B0ycey wrote:Eh, by definition if an event never happened it can leave no evidence. You are then left with an argument that no evidence is the evidence which can work both ways (does a tree in a forest make a sound if nobody is around to hear?). So then who has the burden of truth? That is right the person who has the ability to provide evidence. If they can't, are they wrong (Does God exist)? Not necessarily, but that is irrelevant in a court of law.


And to prove an event E did not happen is not nearly the same as proving that it's impossible for the same event E to have ever happened. The negation of "event E happened" is "event E has not happened", not "it's impossible for event E to have ever happened" or "it's impossible for event E to ever happen". The latter two statements do imply the negation ("event E has not happened") but just because the claim "event E has not happened" is true it doesn't mean the claims "it's impossible for event E to have ever happened" and "it's impossible for event E to ever happen" are true.

So that's why I ask: Is it possible to prove a negative without having to prove an impossibility?
#15178111
wat0n wrote:So that's why I ask: Is it possible to prove a negative without having to prove an impossibility?


No. That is why you have the 'Law of Parsimony' and of course 'Beyond Responsible Doubt'. You can deduce things from other facts to reach a conclusion that something didn't happen but that is completely different than asking for proof of something not happening. Nothing explains this better than the recent election where people were asking for evidence that voter fraud not happen. What do you want, video of fraud not happening or for me to produce the non existent ballot papers for you to see? But you can of course deduce voter fraud didn't happen by the lack of evidence of voter fraud, the amount of people needed to both keep this secret and be part of the scam, the person making the claim being a proven liar and the fact that Trump created a ponzi to dupe his minions to pay off his election defeat.
Last edited by B0ycey on 24 Jun 2021 16:38, edited 1 time in total.
#15178112
I've thought about this issue a lot a few years ago. The conclusion I came to was that whoever first said "you cannot prove a negative" vastly oversimplified a complex philosophical issue. The most charitable interpretation of "you cannot prove a negative" I can give is that you cannot prove the negative of an existentially quantified proposition where the quantified variable ranges over an infinite set via an exhaustive search. Such statements are of the form ~ Exists (x : X), P(x), and are equivalent to Forall (x : X), ~P(x). One way to prove a universally quantified proposition like this is to check that every instance of x satisfies ~ P(x). This is easily done if x ranges over a finite set, but it's obviously impossible otherwise.

There might still be other ways to prove such propositions. For example, we could prove that an x with some property P(x) cannot exist if we can derive a contradiction from it. Excepting such simple cases, the only other way to prove a negative would be to deduce it from some already proven universally quantified propositions. Now, some philosophers believe that there are no non-trivial universally quantified empirical propositions that have been proven. Hence, they believe that there is no way to prove any interesting universally quantified proposition or negative existentially quantified proposition about the outside world at all.
#15178115
I can prove that not all swans are white by showing a black swan.

So, that would be proof of a negative claim that does not prove an impossibility, as far as I can tell.
#15178119
Pants-of-dog wrote:I can prove that not all swans are white by showing a black swan.

So, that would be proof of a negative claim that does not prove an impossibility, as far as I can tell.


Why would that be a negative? Swans exist.
#15178136
Pants-of-dog wrote:The claim “not all swans are white” is a negative claim.


I think you don't understand what can't prove a negative means then. The term negative in that sentence means something that doesn't exist or hasn't happened (absence of). Not that the sentence is a known lie. As swans exist, there is not a negative in that sentence. A negative would be "Not all Dragons are Green".
#15178137
Pants-of-dog wrote:I can prove that not all swans are white by showing a black swan.

So, that would be proof of a negative claim that does not prove an impossibility, as far as I can tell.


Yes, that would be a negative universally quantified proposition. Every such proposition is equivalent to a positive existentially quantified proposition (e.g., "not all swans are white" is equivalent to "there is a non-white swan"). Such propositions are different from the ones I was talking about in my other post.

ABOUT THE BURDEN OF PROOF:

It is incorrect to say that the burden of proof falls on the person making the positive claim, and not on the one making the negative claim. To understand why, we have to understand the concept of a judgment. A judgment is an attitude towards some proposition, either an acceptance or rejection. Thus, given a proposition P, if we accept it, then we have made the judgment that P. If we reject it, then we have made the judgment that not-P.

It is only judgments (of either kind) that incur an epistemic debt. The person making the judgment that P (or the judgment that not-P) faces the burden of proving that P (or not-P). The only person that does not face any burden of proof is someone who has not made any judgment about the truth of P, i.e., someone who is agnostic about P.
#15178141
B0ycey wrote:I think you don't understand what can't prove a negative means then. The term negative in that sentence means something that doesn't exist or hasn't happened (absence of). Not that the sentence is a known lie. As swans exist, there is not a negative in that sentence. A negative would be "Not all Dragons are Green".


No, B0ycey, you are the one who is confused about what negative means. A negative proposition is one that has the word "not" at the highest level of logical precedence.
#15178145
Saeko wrote:No, B0ycey, you are the one who is confused about what negative means. A negative proposition is one that has the word "not" at the highest level of logical precedence.



I am fully aware of what the statement means Saeko thank you. I deal with it's meaning daily. Can't prove a negative is not a proposition. It is a statement of intent.
#15178147
B0ycey wrote:I think you don't understand what can't prove a negative means then. The term negative in that sentence means something that doesn't exist or hasn't happened (absence of). Not that the sentence is a known lie. As swans exist, there is not a negative in that sentence. A negative would be "Not all Dragons are Green".


Sure.

Then it is not quite accurate to say that you cannot prove a negative.

It would be more accurate to say that some negative claims can be proven and some cannot.
#15178150
B0ycey wrote:I am fully aware of what the statement means Saeko thank you. I deal with it's meaning daily. Can't prove a negative is not a proposition. It is a statement of intent.


"You can't prove a negative" is definitely a proposition.
#15178151
Pants-of-dog wrote:It would be more accurate to say that some negative claims can be proven and some cannot.


Sure. But a claim is not a philosophical deduction. If you want to say claims can be proven false, well I agree given they can. We do after all have liable.
#15178153
Saeko wrote:"You can't prove a negative" is definitely a proposition.


In what sense? Is it your opinion that the sentence is wrong and that is your proposition or is it merely a statement of action to deduce burden of proof (intent). But I warn you now if you believe the former, that isn't how the sentence is executed in the scientific community or court of law. :roll:
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