How Do You Prove Something Doesn't Exist?

[interspark]

i've often thought of this and the only possible way i can think of is to meet the person who made said thing up, like in Fable when the Oracle tells you Avo and Skorm don't exist because they were invented by a trader, anyone think of any other way?

 

[blackhole1]

You don't. In this case I suppose you'd have to take their word for it. Or not, depending on the situation. In general however, everything is nonsense until you have proof that this is not the case. Otherwise you might as well believe any old wive's tale.

 

[b3nn3tt]

You can't, quite simply. But in a situation where this kind of thing arises, the onus of proof is on whoever claims that the thing does exist. So, if I were to claim that Avo and Skorm (to use your example) don't exist and you claim that they do, it's up to you to prove that they do, because it would be impossible for me to prove that they don't.

 

[Thespian]

Make a list of everything that does exist, and check if it's there.

What we often mean when we say "Prove it doesn't exist" we often mean "Prove if we have enough evidence for it to be relevant"

 

[Hoemark]

Well, I can show you there is no grass in my garden, so I proof it doesn't exists there. Proofing that (a) God does not exists is impossible, that's kinda why we still argue about it. In you're example you can not be sure the trader is telling the truth when he says he made Avo and Skorm up, so that's no proof.

 

[Simon Pettersson]

How do you prove that something exist?
You show it to them.
What if you can´t see it?
You let them feel it.
What if it has no scent or surface?

Well eh ... ah I have nothing.

If anyone can continue this then maybe we can have a answer.

If you can´t prove that it exist it doesn´t exist.
Well my thoughts anyway, I belive in what I can See, touch and smell.

And if no one has seen,touched or smelled whats supposed to exist then it doesn´t exist. Except when you found it.

 

[Thaluikhain]

You can't, as such.

However, you can prove the existence of something mutually exclusive.

Say, if someone says that there's a five headed space dragon that made the moon, if you can prove that the moon was made by something else, then there is no moon making five headed space dragon. This doesn't mean that five headed space dragons in general don't exist, however.

Generally speaking, the mere existance of something isn't enough, it's the existance of something that does or did X, and you can test for the X.

 

[Kirkby]

Technically if the Universe if infinite then everything that can exist must exist somewhere = P

 

[Togs]

its a weakness of the scientific method that arises from our language- you can say "there are no black swans" and the sight of one black swan would be enough to disprove that, but no matter how many white swans you see you can never be 100% certain.
That the reason behind a null hypothesis, and also just because you cant prove or disprove something doesnt mean you cant calculate the probability- you could analyse a populations genetic diversity, rate of mutation, the existence of physiological pathways that could produce a black swan if a mutation did arise.
This is one of the many possible counters to that old tired theist arguement of "burden of evidence".

 

[Vohn_exel]

You can't, quite simply. But in a situation where this kind of thing arises, the onus of proof is on whoever claims that the thing does exist. So, if I were to claim that Avo and Skorm (to use your example) don't exist and you claim that they do, it's up to you to prove that they do, because it would be impossible for me to prove that they don't.

This. I'm pretty open minded but I shouldn't have to prove that something doesn't exist. It's much harder to prove that it does.

 

[Jonluw]

You can test for the implications of the subject's existence.
For example, if you're going to prove there is no atmosphere on a planet: You know an atmosphere implies that it would be possible to gain lift in that environment, so you could run a wing over the surface of the planet and measure the lift.
If there is no lift, the implications of the subject's existence are not fulfilled, hence the subject does not most likely exist.
[sub]yeah, I know it's a pretty bad example, but I can't think of anything better right now.[/sub]

If you're talking about proving something doesn't exist at all though (In the case of the atmosphere example, that would be proving no planet in the entire universe has an atmosphere), you're in for a tougher job.
You could still go about like in the first example, searching for effects that are necessarily produced by the subject, were it to exist, but the universe is infinite, so experimentation can only get you that far.

 

[epialesofaergia]

According to Bertrand Russell's 'The Problem with Philosphy,' the only things that do exist are those which we can physically vouch for in very basic ways (i.e. the sense of touch that can be replicated without any other proof of existence like sight or smell). You may not be able to prove that something doesn't exist, but that fact that nobody can prove that is does is grounds enough for reasonable disbelief.

 

[DefunctTheory]

It is possible to prove something doesn't exist... but it's hard as hell.

For instance, you can prove a cat doesn't exist in a box just by looking in the box. Basically, you have to exclude the possibility of existence (In this case, by proving that everything in the box is air, therefor, because you know exactly everything that IS in the box, you know exactly what ISN'T).

Of course, this can't be done for most things. You can't prove there is no intelligent life besides us the the universe unless you quantify everything that IS in the universe, thus excluding intelligent life. You also can't prove that there isn't a cat in the box anywhere, without being able to prove what is actually in every box everywhere.

 

[Aurgelmir]

Sometimes you don't need to prove something exist, just prove how highly improbable it is in order to render it unimportant. Or you can prove it not relevant if you prove something else is more relevant or probable.

All in all if there is no proof for a claim, the claim is by it self rendered irrelevant, and therefore it's existence is no longer meaningful.

 

[4li3n]

There's also that thing where you prove something else is real that's mutually exclusive...

Like proving a ball is red, so it can't be blue...

 

[flamingjimmy]

Technically if the Universe if infinite then everything that can exist must exist somewhere = P

That does not follow at all.

For example there are an infinite number of odd numbers, but none of them end in 2, no matter how high you count.

 

[Your Nightmare]

Without evidence to disprove something, you have to ask where the evidence came from in the first place in order to initially believe in something. I guess..

 

[Aurgelmir]

Technically if the Universe if infinite then everything that can exist must exist somewhere = P

That does not follow at all.

For example there are an infinite number of odd numbers, but none of them end in 2, no matter how high you count.

Not only that, some concepts are man made and that means that if would only exist if you the person believed that what you were seeing is in fact that man made concept. religious Gods is a good example of man made concept that you most likely will not find in the universe, and if you do find a "god" is it really still a god?