Let's put this common refrain to rest~ something that I hear all the time in arguments concerning religion.  It goes something like this:

" Remember, you can't prove a negative!"

Really people?

This has become much more common, especially in the arguments amongst Atheists and agnostics concerning certainty, and it really puzzles me how people can be skeptical and free-thinkers, yet take to an idea so easily and not question it.  I will elaborate on this a little more once I have the time, but let me start all of those "can't prove a negative" types off with a question~ " I am not sitting at my desk."  Thats a negative claim.  Are you telling me that there is no way to confirm or disprove that?

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lol While thats true, it actually is at the heart of this thing.  A negative claim is merely the inverse of a positive, and thus should be provable given the absence of necessary evidence for a positive claim.
The absence of evidence does not mean there is not evidence yet to be found.
I know, right? Rationalists my ass
"There is no crow in this box" is easy to prove.  "There is no "god"™ in this or outside this or in some parallel universe--not so simple.
right, but that is what i intend to cover upon elaboration~ that as definitions become less distinct (so that its easier to hide their failings) and more conceptual, it is indistinguishable from non-existence~ so the harder they make disproving it, the more and more non-existent it becomes.  its like, if I said "this thing is a wrench"~ well, we know what the definition of a wrench is, and certain parameters of the definition, such as weight, density, colour, etc etc~ but If I said " this is a thing"~ well, that is more of a concept than a reality, especially if I have nothing to show you.  The more indistinct the definition becomes (ie residing in a parallel dimension) the less it is actually a thing at all (by any definition) until it becomes only a thought, and thoughts, my friend, do not answer prayers.
Ambiguity is philosophy's friend as it is religion's friend.
The point is simply that -in anything except trivial cases- proving a negative is practically impossible. That is the crux of the issue. Sure, you can prove trivialities like "There is no elephant in my room" or "There is no cat in my trunk".
But just stretching the claim to propositions that are slightly less trivial, like "There is no black widow spider hiding somewhere in my house" makes it immediately clear that the workload is starting to increase exponentially. In order to prove that claim I'd have to have a whole team of people searching through my house in sections (so the alleged spider can't move through the sections) for possibly several days.
Increasing the claim again, once we get to "There is no purple black widow with yellow spickles hidden somewhere in Belgium" and we are already far beyond what can be practically proven. The same is true for flying reindeer somewhere on the North Pole, Atlantis somewhere on the bottom of the sea, fairies living in some unexplored part of our forests, God living in some unspecified realm 'outside' the universe, etcetera...

All of these are -while perhaps theoretically provable in a theoretical sense- just impossible to prove in any practical sense. That's why we say that proving negatives cannot be done.

But moreover and more importantly, it's not anyone's responsibility to be able to disprove a negative.

Right.  Might I also mention that "triviality" has nothing to do with it~ location is one of the definitional parameters, and in those examples it is just such a broad one that it makes testing it difficult using simple methods~ but even that can be offset if the other parameters are changed.  "there is no black widow in this tea-pot," (location changed) or "there is no empire state building in pennsylvania" (change of another parameter, namely size)

All in all, however, it doesn't really speak the efficacy of proving a negative~ indeed Matt admitted that it can be done~ that admission is really all that is needed to make this point.

What do you need to prove something? I say the only thing that can prove something is evidence that has been put through the scientific method. Evidence itself cannot provide proof for everything that exists or happens. A magician will offer "magic" as evidence that the impossible is true, but our reason tricks us, so we need the scientific method as a tool to augment our reason. So, proof is evidence, but lack of evidence does not mean there is not evidence yet to be found. Lack of evidence is not proof of a negative!!!!!
I'm guessing there will still be flying cars in 2134, because we've had them since 1950: http://www.popularmechanics.com/cars/news/pictures/flying-cars-in-h...

Hi John,


"Well, that may be a question of trying to prove a negative, but the inverse of that question is just as hard to prove as the original version. You have simply discovered a set of questions that are hard to answer.  It has nothing to do with the questions being "proof of a negative"."


Fair point.

The nuance I would make there is that you assume both claims are made in a vacuum, i.e. you're assuming that I would make the claim that "There is a black widow spider in my house" for no reason at all, and that I would then have to go out and find the evidence.


One of the reasons proving a negative is so hard (assuming that you're right) is that there's never a point you can stop and see that you're right; you have to follow the rigorous proof through all the way.

For instance, if I go out to prove that Atlantis once existed, all I really have to do is find my first piece of good evidence and then I'm done. Now, even if I'm right, that might still be a difficult quest; but that's not the point: the point is that if I am in fact right, then I will be able to eventually find some evidence and I'll be able to stop right there.

However, if I want to go out to prove that Atlantis never existed, the quest never stops until I have in fact explored every square metre of the world's oceans. Logically speaking, my proof is not rigorous until I have walked through the entire set.


So I can't say that I fully agree. The workload required to prove negatives is still volumes more than the reverse. I think that's also what happens in our daily lives: we're faced with claims that, if they were really true, proponents should have little difficulty providing some evidence to show that there's a there there; yet, because they are not in fact true, they are still a pain in the ass to actually disprove.


But yes, Park, you're correct to say that it is theoretically possible. It just isn't usually practically feasible.


Kind regards,



I get your point, but I don't think there is an equivalency here~ if we say Atlantis once existed, first Atlantis needs to be defined.  Just saying some city somewhere on some island existed and then disappeared is quite different than a mythological city of high technology~ we can know this because the first question asked when you find your 'good' evidence is "how do you know its from Atlantis?"

Thats what I'm trying to get at~ if a claim is made, it has to be specific, such as the claim for god, or else it retreats into concept, not reality.  An idea cannot be attacked from the negative until it is properly defined~ however, we are so used to people making vague claims to something in the positive that we forget to define them.

If we had a clear-cut definition for something like a city of Atlantis, where approximations of it attributes and location could be determined, then yes, we would be able to prove it does not exist (that is, if it doesn't.)


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