The Vent and Rant Thread

[ApK]

Why do people, particularly novelists, insist upon saying "you can't prove a negative?"
That's ridiculous. Of course you can. Sometimes easily. Sometimes you can't, but for that matter, sometimes you can't prove a positive either.

In a completely unrelated peeve, but one that occurred in the same, otherwise very enjoyable novel:
Writers, don't have the guy check the safety on his Chief's Special .38 revolver. With very rare and extraordinary exceptions, revolvers don't have safeties like that. It completely destroys the otherwise believable story world I was enjoying, and 10 more seconds of research when you picked what kind of gun to include would have shown you that.

[Comfy.n]

Just CLICK HERE and prove you like me!

Damn.. I've clicked. xD

[Hitch]

Originally Posted by ApK

Why do people, particularly novelists, insist upon saying, "You can't prove a negative?"
That's ridiculous. Of course you can. Sometimes easily. Sometimes you can't, but for that matter, sometimes you can't prove a positive either.

I'll bite. How? Seriously, what sort of negative do you think you can prove? A positive? If you've done X, chances are, other than obscure things, yu CAN prove it. Paid for something? Proven. Bought something? ditto. Ate a meal that had shellfish in it? Ditto.

But, let's say you get sick at that same restaurant and you end up, 8 hours later, in the ER. How can the restaurant PROVE that they didn't have shellfish or stock that was made with shellfish, in the meal you ate? It's one thing to say "we didn't..." and even if the entire kitchen swears that they didn't use that fish stock...that's not proof. That's testimony. Not the same thing.

In a completely unrelated peeve, but one that occurred in the same, otherwise very enjoyable novel:
Writers, don't have the guy check the safety on his Chief's Special .38 revolver. With very rare and extraordinary exceptions, revolvers don't have safeties like that. It completely destroys the otherwise believable story world I was enjoying, and 10 more seconds of research when you picked what kind of gun to include would have shown you that.

Given the abysmal understanding and treatment of weaponry of all kinds by the vast VAST majority of writers (both Movies/TV and books), this si hardly shocking and it's almost misses the bar for "insipid and stupid." They just...for people who by and large make their livings using weapons as props, etc. it's boggling to me that they'll sit there like maroons and have guns that never need reloading, and on and on. Daft.

Hitch

[ApK]

Originally Posted by Hitch

I'll bite. How? Seriously, what sort of negative do you think you can prove?

Seriously? Let's start with obvious:

My 17 year old daughter didn't kill JFK.
I'll bring in historians, medical doctors and physicists to prove JFK died in 1963, she wasn't born then, and time travel isn't possible, so she couldn't have done it . QED.

Slightly more relevant to the situations I'm referring to:
My client didn't shoot the victim.
The victim was shot at noon by a thin, short white person, as shown on the security footage and corroborated by the three cops who witnessed it.
My client is a 7 foot tall 400 pound black person who at noon was in chains, in this court room, in your presence, your honor, and so could not have done it. QED.

From there, we just get in to various levels of near-certainty, still well beyond any reasonable doubt.

For many, many, many things, for something to have happened, some other things must have also happened or not happened.
If X had happened, it would have precluded Y. We can prove Y, so we've disproved X.
Like Sherlock Holmes observed, a person can't pass through a room without taking or leaving something. Show enough evidence, or lack thereof, of enough of those somethings and you meet any burden of proof.

The kid didn't eat the cookie. The cookie still there, intact. So it can't can't have been eaten, by him or anyone. QED
In your shelffish example, restaurant security footage shows everything the victim touched, ate or drank, and lab tests show no trace of shellfish on any of it or anywhere in our vegan restaurant. Is that enough proof?

ETA: "You can't prove a negative?" Really? Prove it. Ha! Logical paradox, sucka!
(Ooh... I like that. I'll need to use that line in a story sometime.)

they'll sit there like maroons and have guns that never need reloading, and on and on. Daft.
Hitch

I just watched the surprisingly funny "National Lampoon's Loaded Weapon 1." It parodied that with a spoof of Dirty Harry's "I know what you're thinking: Did I shoot 6 shots, or only 5?" with the character saying "Did I shoot 174 shots, or only 173?"

[Hitch]

Originally Posted by ApK

Seriously? Let's start with obvious:

My 17 year old daughter didn't kill JFK.
I'll bring in historians, medical doctors and physicists to prove JFK died in 1963, she wasn't born then, and time travel isn't possible, so she couldn't have done it . QED.

Yes, because that's a physical impossibility. That is, for all intents and purposes, "proof." That's not at all what people mean. You're proving an alternative. That means that proof exists. You aren't in fact proving the negative--you've proven that someone else, alive in 1963, did do the deed. Even if you don't know who that person is.

Slightly more relevant to the situations I'm referring to:
My client didn't shoot the victim.
The victim was shot at noon by a thin, short white person, as shown on the security footage and corroborated by the three cops who witnessed it.
My client is a 7 foot tall 400 pound black person who at noon was in chains, in this court room, in your presence, your honor, and so could not have done it. QED.

Yes, and again, you've made up some scenario in which the accusation would never occur. That doesn't do it, either. Change it so that there's any remote likelihood that it might. What if the person who was shot at noon was shot by someone who is your client's spitting image. Your client is not on video, not on tape. Then what? Prove that he didn't do it. You do not have proof that your client didn't do it. You don't have evidence that someone else did. Now, prove he didn't.

The point is..."proof" means just that. EVIDENCE that can absolutely show that the question under consideration cannot have happened. When you solve the matter by coming up with the alternate scenario, you have not proven a negative--you have proven a positive, that this other perpetrator DID perform the deed.

When people talk about not being able to prove a negative, it's not in some cute scenario in which the reality is easily disputed; it's when the only avenue is doing just that--proving that X did not occur.

From there, we just get in to various levels of near-certainty, still well beyond any reasonable doubt.

Yes, but again, anybody can make up some scenario in which "proof" is easily gathered in the positive for an alternate option, e.g., John Doe was in Tokyo, demonstrably (proof!) when Jane Smith was shot. That IS proof. What you're doing is saying that if there's positive proof that something DID happen, that it's the equivalent of proof that a negative didn't happen. That's not the same legal or logical argument.

For many, many, many things, for something to have happened, some other things must have also happened or not happened.
If X had happened, it would have precluded Y. We can prove Y, so we've disproved X.
Like Sherlock Holmes observed, a person can't pass through a room without taking or leaving something. Show enough evidence, or lack thereof, of enough of those somethings and you meet any burden of proof.

Actually, Locard's theorem, but...fine, not sure how you think that applies. The entire point of Locard is that if the person wasn't there...there won't be any proof that he was NOT. Only that you cannot prove that he WAS. Two different things. Trust me, no court in the world would accept the idea that you didn't leave any hair, fibers, etc. in John Doe's apartment as "proof" that you weren't there. Evidence that you may not have been there? Sure...but not proof.

The kid didn't eat the cookie. The cookie still there, intact. So it can't can't have been eaten, by him or anyone. QED

Again...to test out the argument, you have to have a scenario in which you do not have proof in the alternative. Nobody is going to accuse yon brat of eating the cookie when it's already still intact, now, are they? So, coming up with something like that, beyond being frivolous, does not solve the logic issue.

In your shelffish example, restaurant security footage shows everything the victim touched, ate or drank, and lab tests show no trace of shellfish on any of it or anywhere in our vegan restaurant. Is that enough proof?

Actually, again, it's not "proof." That's evidence. Not the same thing. There's evidence that leads one to believe that it's likely not the restaurant, but no proof that clearly indicates that they didn't do the deed. It's inference and deduction, but not proof. Is it probably 99% good enough? Yes, sure, for a real case in a real world with real video footage, assuming it exists.

"Proof" is indisputable evidence that something is true (or not, let's say for the sake of argument); "evidence" is just something that leads you to believe that something is, or is not, true. They are not the same thing.

Everything you've said in this post--is evidence. NOT proof. Sorry if you think this is hair-splitting, but it's not. You're trying to take apart a logic argument by conflating the two.

Ask yourself how this is proven, if/when the kitchen doesn't have a single camera in sight. What happens then? What's the evidence, or the proof, then?

ETA: "You can't prove a negative?" Really? Prove it. Ha! Logical paradox, sucka!
(Ooh... I like that. I'll need to use that line in a story sometime.)

Evidence is one thing. PROOF is another. Sorry but there it is.

I just watched the surprisingly funny "National Lampoon's Loaded Weapon 1." It parodied that with a spoof of Dirty Harry's "I know what you're thinking: Did I shoot 6 shots, or only 5?" with the character saying "Did I shoot 174 shots, or only 173?"

I'm glad you enjoyed it.

Hitch

[ApK]

"proof" means just that. EVIDENCE that can absolutely show that the question under consideration cannot have happened.

"Proof" is indisputable evidence that something is true (or not, let's say for the sake of argument);

Twice you define proof in terms of providing evidence, and yet you dismiss my providing evidence as a path leading to proof. We agree that proof is matter of sufficient evidence, but you dismiss my evidence examples for...why? Being too clear cut and obvious? I'm giving obvious, clear cut examples for just that reason.
In any court...or laboratory, for that matter...that I can imagine, proof of a MUTUALLY EXCLUSIVE alternative like I've given IS PROOF that the other thing didn't happen.
Indirect evidence leading to logical inference and deduction is simply HOW IT IS DONE when the thing itself is not directly observable, whether positive OR negative.

And the cases where this "You can't prove a negative" comes up is not in cases of two logicians arguing an abstraction. It's in matters of court cases, or sometimes in science related stuff, depending on genre, and so proof is never "absolute." It's "beyond a reasonable doubt" or "to a high degree of certainty."
What they, and you, apparently, are really saying when they say "you can't prove a negative" is either:

"You can't prove a negative...if you define proof as my arbitrarily chosen standard of proof, which will always be just a bit higher than whatever you achieve." (I think that's the "Real Scotsman" fallacy)
or
"You can't prove a negative...if you don't have any evidence." Well, duh. You can't prove a positive without any evidence, either.

This reminds me of another peeve of mine: "Absence of evidence is not evidence of absence." Actually, it often is. It may not be very strong evidence, and it's almost certainly not PROOF, but it often is evidence indeed. Again, this is typically how science is done when stuff isn't directly observable. If X happens, then we should be able to observe Y. We don't see Y. That doesn't PROVE X didn't happen. We may just have failed to detect Y. But it sure is evidence that X didn't happen, and we're going to continue experimenting to see if we find more evidence.

[DNSB]

Last time I looked, quite a few items had been proved by logic and not by evidence.

[Hitch]

Originally Posted by DNSB

Last time I looked, quite a few items had been proved by logic and not by evidence.

I suspect I'm going to be going up/down the thread here, so I'll start here.

Yes, absolutely. No argument means that whatever was proven, was an impossibility in the reverse. That's logic for ya.

For example, one of ApK's examples, how his daughter that was not yet born thus could not have been Kennedy's assassin.

Okay, fine. You could try to argue that that's "proving" the impossible, but it's not--you've proven the inverse. She didn't exist until Year X and thus, while she could have done X things during her lifetime, she could not do things outside of it. Right?

Back later to yammer about the difference between evidence and proof.

Hitch

[HLS]

I won my credit card dispute over my B&N purchase but B&N banned me from shopping online with a credit card. paypal works. makes me mad for this was a one time incident and i spent a fortune at B&N in the past.

[jbjb]

Originally Posted by Hitch

I'll bite. How? Seriously, what sort of negative do you think you can prove?

I'm with ApK here - that generalised claim always really annoys me too. Sure, there are some negatives you can't prove, but there are many positives you can't prove either. Many (most?) assertions can be phrased in a positive or negative way - does that change their provability?

Consider the assertion: "there are no two integers such that one divided by the other yields the square root of two". Clearly a negative assertion, but trivially provable.

Whenever I've had this argument with anyone, it quickly reduces to a weaker assertion: "there's a subset of negative assertions which are unprovable". No argument there, but it's not what the original claim states.

[jbjb]

Originally Posted by ApK

"You can't prove a negative?" Really? Prove it. Ha! Logical paradox, sucka!

Brilliant!

[ApK]

Thank you. JB. Nice to know at least one other person both has a grasp of the obvious truth equal to my own, and also recognizes my brilliance.

Btw, it was a John Lescroart novel that brought up both of the peeves in my post, and this one just came up again today in the next novel in the series, and this time, they kind of lampshaded the issue.
The ME ruled a death "homicide/suicide equivocal." Could be either, no medical way to say for certain.
The cops asked wasn't there someway he could rule out suicide? He said "I can't prove it wasn't suicide. As you like to say, Abe, 'you can't prove a negative.' You'd be better off proving it was a homicide."

Arg! They are mutually exclusive alternatives, so if you prove one happened, then you have proved the other didn't.
I'm just not seeing why the characters, and presumably the author, and also Hitch, don't see it this way.
And again, this is the more or less practical real world stuff where it comes up and bugs me, but it would seem to be also false in pure math and logic, as JB mentioned. Prove 6 is not prime. 2x3=6. QED.
I am missing the source of disagreement. Is this a problem with semantics or definitions, or what?

[ownedbycats]

My knees are exceedingly super-achy today. There's a weather advisory for an incoming rainstorm. Living barometer.

[poohbear_nc]

I too have a weather knee, and now weather shoulders .... exceedingly accurate

[neil_swann80]

Similar ting for me. I've noticed if there's weather my joints hurt.