How Do You Prove Something Doesn't Exist?

[Father of Worlds]

To prove that something does not exist, you must either prove that its existence would necessarily have effects that are not observed (if there's a man-eating dragon in my garage with no self control, then going into the garage would result in getting eaten. I can go in without getting eaten. Therefore, there isn't a man-eating dragon with no self control in my garage) or prove that it's logically incoherent (there are not, anywhere in the universe, any 3-sided cubes). The former depends on extreme specifics (I didn't prove that there are no man-eating dragons with no self control, just that there aren't any of those in one specific place). The latter depends on very broad categorizations (all cubes have 6 sides, everywhere, all the time). Otherwise, the best you can get is "there's absolutely no reason to think that X is real, therefore I'll assume it isn't for the moment."

In the OP case of Avo and Skorm being fictionalized, even if you could prove that there was in fact a trader who'd invented them, all that would prove was that the idea of them entered in to the popular consciousness through someone saying something he believed to be false. That doesn't prove that Avo and Skorm aren't also, quite independent of anyone's belief about them, real. If I could prove with absolute certainty that the bible was entirely fictionalized, that nobody represented in it existed, that nothing depicted in it happened, and that everyone who wrote the stories down knew that they were lying, that would not prove that god didn't exist. Just that the events and stories depicted in the bible are not accurate reflections of reality.

 

[Kathinka]

reminds me of this one comic..where is it..ah yes^^

in all seriousnes though: yes you can prove the nonexistence of something by evidence. how hard this evidence is to find might be another story.

 

[Spoonfoon]

It is sometimes possible to display that it is impossible for a phenomenon to occur. That is effectively the same as proving that it is non-existent.

 

[ThePinkAcidSmurf]

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

It is not.

 

[Taldeer]

The absence of evidence is not the evidence of absence. Basically, you can't prove something isn't there, just because there is no evidence, which means you can't disprove something, EVER.

While I agree completely with the first part of this statement, and it's a very good answer to the OP question, I don't agree with the latter statement that you can't disprove something ever. You can't prove that something isn't there by not finding evidence that it is there, but you can prove it isn't there by finding evidence that it, in fact, isn't.

 

[Sojoez]

Carl Sagan's quote can be used in two different ways.
Namely aliens.
We haven't seen and aliens therefore they don't exist. However the universe is so incredibly large that the possibility is there for them to exist. Therefore, the absence of evidence does not mean evidence of absence.
However, when someone claims to have seen aliens he needs proof to assert his claim. Because there absence of evidence DOES mean that he is lying.

In short. "Absence of evidence does not imply evidence of absence" only works in theoretical principles.

 

[Chris646]

You can prove something doesn't exist by going onto Google and searching for what you're asking about.
But in all seriousness, you can prove something does not exist, within reason. I could say that there is a firebreathing dragon in my backyard, but you can easily disprove that by observing my backyard.

 

[BlackWidower]

It's impossible. You can't prove a negative.

 

[DanDanikov]

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

It is not.

What I think he means is that if reality is infinite...

The problem is that infinite possibilities and infinite reality are mutually exclusive.

- Given that in an infinite reality, where anything that can happen will happen, everything that can happen must be limited to prevent paradox (because you cannot have a set of all sets- it cannot contain itself).

- A finite reality, anything could happen, but because it's finite, it's only some of them do (so in some ways, everything is conceivable, rather than possible).

 

[Amphoteric]

I can disprove the existence of things inside a certain area, I mean I can prove that there are no australians in my living room.

You can't disprove anything completely though, except in maths. You can disprove that 2+2=7 by proving that 2+2=4

 

[Thumper17]

Well their are things like "Prove this heavy thing cant float" that we can prove.

 

[Kirkby]

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.

Ah but you didnt read my statement correctly. Anything that CAN exist will exist somewhere. Meaning that if it cannot exist through the laws of science and math it will not exist. An odd number ending in two goes against the basic fundamentals of maths and thus cannot exist anywhere.

 

[MagnetoHydroDynamics]

*many a comment with:*
Basically you can't...

I beg to differ

How I disprove something's existance?
Ask you to produce proof of the contrary.

http://en.wikipedia.org/wiki/Philosophic_burden_of_proof
http://en.wikipedia.org/wiki/Scientific_burden_of_evidence

 

[Kirkby]

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

It is not.

But if it was.... = P

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.

Also the universe is not infinite, conservation of mass/energy
Edit: To weigh in, the onus of proof should fall to those trying to prove existence, not those trying to prove a lack thereof.

That was the point i was hoping people would pick up on. The IF bit of what i said.. But u did so cookie to u (extra cookies for bringing equations into it) xD Though it does ask an interesting question as too whats after the universe if it isnt infinite...

i also agree with ur edit.

 

[Alphakirby]

Well you can't if it doesn't exist then it's impossible to get evidence of it because you don't know what it does. Not to say that everything can exist,obviously the 50 billion people who tried to find the loch ness monster or bigfoot and failed have to be showing a sign.

 

[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.

Ah but you didnt read my statement correctly. Anything that CAN exist will exist somewhere. Meaning that if it cannot exist through the laws of science and math it will not exist. An odd number ending in two goes against the basic fundamentals of maths and thus cannot exist anywhere.

Ok, fine then, it still doesn't follow.

Why would the universe being infinite mean that everything that 'can exist' (whatever that means outside of maths) would?

 

[Use_Imagination_here]

It is impossible to prove or disprove anything absolutely certainly. Period.

 

[Use_Imagination_here]

I can disprove the existence of things inside a certain area, I mean I can prove that there are no australians in my living room.

You can't disprove anything completely though, except in maths. You can disprove that 2+2=7 by proving that 2+2=4

Not necessarily. There's still an infinite amount of ways you could be wrong about that.