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You can't prove a negative, and you don't need to do so

For topics that are more about faith, religion and religious organisations than anything else.
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animist
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You can't prove a negative, and you don't need to do so

#1 Post by animist » January 12th, 2012, 1:22 pm

I am very interested in these two statements, specially in relation to arguing for and against the existence of God. The way I've written the thread name is actually one compound statement of two simpler ones linked by "and", and that's actually what interests me: is there some logical link between them?

I should clarify the first statement, as I have seen websites discussing it but incorrectly assuming that "You can't prove a negative" applies (as you would reasonably think) to ALL statements. I think in fact it is correct only if we limit it to existential statements, eg "there is a God", or "I exist". IMO, when interpreted like this, "You can't prove a negative" - meaning that you cannot prove the non-existence of something (eg God) - is pretty well true: you cannot really disprove the existence of the Flying Spaghetti Monster, or of Bertrand Russell's famous teapot between Mars and Jupiter, nearby aliens, ghosts, etc etc, and probably not of God, though Richard Dawkins comes pretty close to claiming that he has. I can think of some exceptions: I can prove the non-existence of dinosaurs on my hand just by looking at it. So, within very narrowly defined parameters, it is possible to disprove the existence of something. But I cannot prove the non-existence of dinosaurs in the modern world: big as they are, they might be hiding!

The second statement, when clarified in the same way as the first, is a favourite argument of atheists. They say to theists: it's up to you to prove that God exists, not up to me to disprove his existence. (In the same way, sceptics about ghosts say that unless there is palpable evidence of these things, there is no good reason to believe in them). So it is easy to move (as Dawkins says) from mere weak agnosticism, in the sense of taking an even-handed attitude to God's existence or non-existence, to a reasonable if undogmatic atheism which does not even try to disprove God's existence because it does not need to.

What I can't seem to quite get to is linking the two statements logically as well as with "and". It seems to me that, somehow, it's the fact that in principle one cannot disprove God's existence which makes it fair and reasonable to state that the onus on proof is on the theist to prove that his or her God exists. But is it reasonable to argue from one of these things to the other? And if so, why? The theist might agree that one could not prove the non-existence of God and that in fact this was a reason for believing in him!

The attached is related to the general topic, and tries to debunk the "teapot" argument for doubting God's existence. Any argument like the teapot one is an analogy and therefore subject to counter-arguments which show up the differences between the two analogues - anyway, see what you think! About the article or about what I've said.
http://www.arsdisputandi.org/publish/ar ... rticle.pdf

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Dave B
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Re: You can't prove a negative, and you don't need to do so

#2 Post by Dave B » January 12th, 2012, 2:31 pm

How about changing that to read, "A negative is self-evident"? Does that fit. You do not have to prove that which is self-evident, no-one can scientifically measure "God", can't point him out in the street etc, therefore to the fully rational mind "God" does not exist.

Whether or not "he" can be measured in analogue in terms of the effect on a believer's brain, as an fMRI or PET scan, and what this says about "his" existence in an abstract, subjective form, is another argument!
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Re: You can't prove a negative, and you don't need to do so

#3 Post by Nick » January 12th, 2012, 7:48 pm

I can prove the non-existence of dinosaurs on my hand just by looking at it
Hmm.. OTTOMH, I'd say that depends on definitions and parameters for truth. You need to exclude the possibilities of invisible or microscopic dinosaurs, besides possibilities of dinosaurs that you haven't envisaged. I think one can go a long way be challenging what the meaning really is. If it is too fanciful to be useful, not only will you never reach a satisfactory definition, but the futility of claiming it's existence will be apparent for all to see.
What I can't seem to quite get to is linking the two statements logically as well as with "and". It seems to me that, somehow, it's the fact that in principle one cannot disprove God's existence which makes it fair and reasonable to state that the onus on proof is on the theist to prove that his or her God exists. But is it reasonable to argue from one of these things to the other? And if so, why? The theist might agree that one could not prove the non-existence of God and that in fact this was a reason for believing in him!
If you reply that you were only just a moment ago thinking exactly the same thing about the invisible unicorn behind their left shoulder, the absurdity becomes apparent.

I'll now take a look at your linky.

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animist
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Re: You can't prove a negative, and you don't need to do so

#4 Post by animist » January 13th, 2012, 11:04 am

Nick wrote:
I can prove the non-existence of dinosaurs on my hand just by looking at it
Hmm.. OTTOMH, I'd say that depends on definitions and parameters for truth. You need to exclude the possibilities of invisible or microscopic dinosaurs, besides possibilities of dinosaurs that you haven't envisaged. I think one can go a long way be challenging what the meaning really is. If it is too fanciful to be useful, not only will you never reach a satisfactory definition, but the futility of claiming it's existence will be apparent for all to see.
I don't know the definition of OTTOMH but I do completely agree with you about: definition, definition, definition! It should precede any argument!
Nick wrote:
What I can't seem to quite get to is linking the two statements logically as well as with "and". It seems to me that, somehow, it's the fact that in principle one cannot disprove God's existence which makes it fair and reasonable to state that the onus on proof is on the theist to prove that his or her God exists. But is it reasonable to argue from one of these things to the other? And if so, why? The theist might agree that one could not prove the non-existence of God and that in fact this was a reason for believing in him!
If you reply that you were only just a moment ago thinking exactly the same thing about the invisible unicorn behind their left shoulder, the absurdity becomes apparent.
yes, agreed!
Nick wrote: I'll now take a look at your linky.
goody!

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animist
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Re: You can't prove a negative, and you don't need to do so

#5 Post by animist » January 13th, 2012, 11:39 am

Dave B wrote:How about changing that to read, "A negative is self-evident"? Does that fit. You do not have to prove that which is self-evident, no-one can scientifically measure "God", can't point him out in the street etc, therefore to the fully rational mind "God" does not exist.

Whether or not "he" can be measured in analogue in terms of the effect on a believer's brain, as an fMRI or PET scan, and what this says about "his" existence in an abstract, subjective form, is another argument!
I don't think "A negative is self-evident" does fit, and you are probably a firmer atheist than me! I am not sure why you think that (all?) negatives are self-evident, maybe you misunderstand me? I certainly don't think it is self-evident that God does not exist, and I would not call all believers irrational. This is almost my point: God may exist, it is just that there needs to be some sort of reason to believe - the Resurrection is a reason, but not good enough IMO. I am working up to asking the Theologicans exactly why they believe!

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Re: You can't prove a negative, and you don't need to do so

#6 Post by stevenw888 » January 13th, 2012, 11:41 am

OTTOMH - Off the top of my head
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Re: You can't prove a negative, and you don't need to do so

#7 Post by Manuel » January 13th, 2012, 2:59 pm

That which can be asserted without evidence, can be dismissed without evidence.

Always liked that line.

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Dave B
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Re: You can't prove a negative, and you don't need to do so

#8 Post by Dave B » January 13th, 2012, 3:15 pm

animist wrote:
Dave B wrote:How about changing that to read, "A negative is self-evident"? Does that fit. . . .
I don't think "A negative is self-evident" does fit, and you are probably a firmer atheist than me! I am not sure why you think that (all?) negatives are self-evident, maybe you misunderstand me? I certainly don't think it is self-evident that God does not exist, and I would not call all believers irrational. This is almost my point: God may exist, it is just that there needs to be some sort of reason to believe - the Resurrection is a reason, but not good enough IMO. I am working up to asking the Theologicans exactly why they believe!
I was just posing that as an idea, but your point,
I certainly don't think it is self-evident that God does not exist, and I would not call all believers irrational.
is one to ponder. First I will have to find a really solid definition for "rational" in the context of believing in the immaterial (so-far-as-science-can-determine-at-the-moment)! Perhaps I conflate rationality and science too readily? But yes, I am a fairly hard atheist, so far as any theos that exists outside of the human brain is concerned anyway.

Not ant-theist though, so long as they do not disturb me with their beliefs I will respect those beliefs and their right to hold and celebrate them (privately). I have even done work to raise funds for our local church - building loos for the users!
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thundril
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Re: You can't prove a negative, and you don't need to do so

#9 Post by thundril » January 13th, 2012, 3:30 pm

Thundril's first law of serendipity links the two directly: the impossible often proves unneccesary. Bit of a fudge, as it uses 'proves' to mean 'turns out to be'.
More seriously, I thought Alvin Plantinga's stab at this 'reasonable belief' argument was strong, and remarkably candid. Unlike our Theologican friends, Plantinga admits that believing is not a matter of choice. This surprised me, as the idea that one can choose what to believe seemed for a while to be one of the clear differences between theist and atheist world-views.
Regrettably I don't have much time online these days, so have only read the opening paragraphs of your linked article. Now I've downloaded it (in the local coffe-bar-with-Wifi!) I will take it home for a good read, and get back to you.
Best of luck with asking the Theo's why they believe, as opposed to passively letting them reiterate what they believe. Might join you on that if I can get enought sunshine to charge my laptop!

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Re: You can't prove a negative, and you don't need to do so

#10 Post by Stark » January 13th, 2012, 3:52 pm

Can’t find the reference now, but I did once read that, as ‘You can’t prove a negative’ is itself a negative, you can’t prove you can’t prove a negative. Which statement is also a negative. I got very confused and had to go and lie down...

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animist
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Re: You can't prove a negative, and you don't need to do so

#11 Post by animist » January 14th, 2012, 9:38 pm

Stark wrote:Can’t find the reference now, but I did once read that, as ‘You can’t prove a negative’ is itself a negative, you can’t prove you can’t prove a negative. Which statement is also a negative. I got very confused and had to go and lie down...
thanks, I had not thought of that, and I think you may be right. The statement "there is no negative existential statement that can be proved" is a "higher order" universal negative existential statement or metastatement as it is a statement about statements. The statement is in fact disproved by a narrower universal negative existential statement - the example I gave was about there being no dinosaurs on my hand. But imagine that this was not true, ie that there were no cases where you actually know the non-existence of any entity. It might then seem that this statement was true, but then, we would still not be able to prove or know this! I am not sure about this, but sounds as if it is self-confirming.

For a while I thought it was a bit like Bertrand Russell's paradox, which concerns classes of things which are or are not members of themselves:
http://en.wikipedia.org/wiki/Russell's_paradox
the easiest example to understand here is about barbers. If the barber shaves all and only men who do not shave themselves, does he shave himself? Apparently Russell would worry about such things, or similar ones like "Disobey this order"!

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Re: You can't prove a negative, and you don't need to do so

#12 Post by Dave B » January 14th, 2012, 10:30 pm

"I never tell the truth."
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thundril
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Re: You can't prove a negative, and you don't need to do so

#13 Post by thundril » January 17th, 2012, 5:41 pm

Well, I've read a bit of the article, and here are my thoughts so far.

I wonder if Garvey is constructing a subtle straw-man here? He seems to be presenting the atheist's 'teapot argument' as follows;
Even though I can't prove there isn't a teapot orbiting the sun, we agree it's reasonable to suppose that there isn't one. Therefore even though I can't prove there isn't a God we should agree its reasonable for me to suppose that there isn't one.
But I don't believe Bertrand Russell made such a weak argument in the first place. He merely said he found the Christian God's existence just as unlikely as the existence of the orbiting teapot.. As you say, Animist, analogies are always open to attacks based on the fact that the parallels are approximate.
I really don't think Russell meant that god was unlikely for the same reasons that the orbiting teapot is unlikely. Teapots are familiar, manufactured items; there is no prior suggestion anywhere in human history that a teapot might exist uncreated in empty space; there is no widespread tradition of celebrating or worshipping the orbiting teapot; there is no history of intelligent and wise thinkers professing to believe in interplanetary teapots. There is, in short, no supporting evidence of even the most circumstantial kind. These are some of the reasons why it is sensible to dismiss the orbiting teapot out of hand, and why the inability to disprove its existence its immaterial to any argument except this single one; The fact that I cannot disprove an existential proposition is not, in itself, sufficient reason for me to take that proposition seriously..

Consciousness, OTOH, does appear (to many people)to be capable of existing independent of any material cause. So dismissing God isn’t as immediately reasonable as dismissing interplanetary tableware. We must present some sort of argument. For example, dismissal of the Biblical God is justifiable in terms of its own descriptions. The biblical account doesn't fit at all with the view we now have of the universe : Consider how far beyond the grasp of the human mind is our current estimate of the extent of universal space/time; how far the structure of DNA is beyond our capacity to design things from scratch.. etc. Realise then that a designing mind and imagination of sufficient breadth and depth and subtlety to have created the universe that we now see could not credibly be simultaneously small minded enough to command an act of genocide in response to our unapproved fumbling with each other's naughty bits...
So it is perfectly legitimate, IMO, for an atheist to say, as Russell said 'I find the Christian God just as unlikely' as the orbiting teapot. But it is important for atheists using the teapot analogy (or indeed the invisible unicorn, FSM and other, similar analogies) to point out that although we find the biblical God and the orbiting teapot equally improbable, they are improbable for very different reasons; and that we are using the analogy, for limited purposes: first to demonstrate the principle that it is not necessary to disprove something in order to reject it; and secondly to display the extent of our incredulity.
Having thus set aside any requirement to disprove god, we can consider whether there is an onus on the theist to prove that there is one. My argument here is that if the theists are presenting 'god's law' as an argument for reshaping civil laws,(as in reference to gay rights, abortion rights, children's education, etc) then it is indeed incumbent on them to show why they believe god's laws should be taken into account. Obviously in such cases a failure to demonstrate that their god even exists blows a big hole in their political arguments.
The other situation in which a theist may reasonably be required to prove that God exists is in the process of evangelism, where a theist has lumbered himself or herself with an obligation to persuade others to believe what he or she believes.
but either in the case of the political/religious campaigner, or in the case of evangelistic faith, the argument comes down to whether, and under what circumstances, and to what degree of certainty, it is possible to prove an existential positive. Theists accepting the challenge to prove god's existence are of course entitled to ask 'What would constitute proof?' but they seldom do. Rather they assume that whatever they have accepted as proof should be good enough for everyone else. And it very often isn't. Perhaps the reason evangelists don't often ask 'What would constitute proof?' is because this question, once asked, settles the matter. There is no proof possible, except an event which could not reasonably be ascribed to any other cause but God. Such an event is in itself essentially impossible to demonstrate.
OTOH, if the theist argues that it is reasonable to believe a positive existential proposition that cannot be proven, if enough supporting evidence can be shown, he or she cannot then demand a higher standard from the atheist.
The only sensible response from the atheist then becomes "You think the evidence available is strong enough to justify belief in God; I don't think it is strong enough. End of story." This seems to be the inevitable denouement of this debate, for all practical purposes.
Philosophical blood-sport, however, can be entertaining in itself, for those of us who like that sort of thing, and I wonder if your question, Animist, is posed more in this spirit.
At a glance it seems to me that replacing the 'and' in the OP with a 'therefore' would constitute a non sequitur, but I have an itchy feeling that it might not, given some intermediate steps....
Smarter minds than mine might like to have a go?

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Emma Woolgatherer
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Re: You can't prove a negative, and you don't need to do so

#14 Post by Emma Woolgatherer » January 17th, 2012, 6:41 pm

Arguing about the existence or otherwise of God or gods isn't really my bag, and I'm not sure I fully understand what's been said so far, but I'll make an attempt to answer the question, because one thing jumps out at me.

You can't prove that a particular (named and defined) entity does not exist (anywhere in the universe), but you don't need to.

Emma

P.S. And I'm not posting at this point because I think I have a smarter mind than Thundril's, in case it looks that way!

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Re: You can't prove a negative, and you don't need to do so

#15 Post by animist » January 17th, 2012, 6:53 pm

agree that "but" is better than "and", and I will respond more fully - despite, like Emma, not feeling that I am smarter than Thundril!

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Re: You can't prove a negative, and you don't need to do so

#16 Post by thundril » January 17th, 2012, 7:38 pm

How about 'You can't prove a negative, and it is stupid to demand that anyone perform an act which is generally recognised as impossible. Therefore there is no need to do so?'
Or something like that?

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Re: You can't prove a negative, and you don't need to do so

#17 Post by Dave B » January 17th, 2012, 7:48 pm

thundril wrote:How about 'You can't prove a negative, and it is stupid to demand that anyone perform an act which is generally recognised as impossible. Therefore there is no need to do so?'
Or something like that?
Is there any alternative word to "stupid" there, for some reason that just not work for me.

Illogical?
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Re: You can't prove a negative, and you don't need to do so

#18 Post by animist » January 18th, 2012, 5:47 pm

thundril wrote:How about 'You can't prove a negative, and it is stupid to demand that anyone perform an act which is generally recognised as impossible. Therefore there is no need to do so?'
Or something like that?
this does not quite show that it is up to the believer to prove the existence of God or whatever, though, does it? The theist is not demanding that the atheist disprove God, is he? On the basis of what Plantinga and Garvey both say, the theists seem to want a sort of level playing-field which does not weight the onus of proof onto themselves, and that is just what I don't want them to have. I suppose all I am looking for is really supplied by Occam's Razor, since the simpler belief is one without God. It's then up to theists to make some positive case for God like the Cosmological Proof, which Garvey almost gets into but avoids. But Occam's Razor is an argument in its own right; I kind of feel there is a link between this argument and the unproveable negative phenomenon but cannot quite express it.

A few reactions to the Garvey argument; I agree with Thundril's comments. I think Garvey does show that the teapot is very different from God in various ways, but so what? Russell, I assume mischievously, compared the question of God's existence to something as banal as a teapot in space in order to tease the theists, and more modern-sounding variants like the Flying Spaghetti Monster are again a sort of humorous insult by atheists to theists. The trouble in principle with argument by analogy is that if the two sides don't accept whether it works or not it is hard to know where to go. Garvey seems to think that the analogy fails because God is something which purports to explain the Universe, and the teapot emphatically is not: but does this matter, and if so why? But anyway, we don't need the teapot as such, which, as Garvey says, is like one end of a continuum from God. There are lots of other things which we could think of as being on this continuum which will do as better analogies than the teapot in arguing against putting God's existence on a par conceptually with his non-existence. How about the Greek pantheon, which noone believes in nowadays but which does much the same explanatory job as God? Or, if as humanists we don't want to consider any gods, what about aliens in the Earth's atmosphere (lots of people do believe in these and in their importance to human civilisation) - do theists really want their God to be put on a par with these? I often mention my local friend who believes that aliens from Nibiru are responsible for our homo sapiens race (and indeed feature a lot in the Old Testament) and I imagine that theists like Garvey would be horrified to think that their arguments could be used to make the existence of such aliens at least as likely in principle as their non-existence.

I think, after all, that the teapot argument - which maybe should be renamed the aliens argument - is in fact the logical link between not being to prove a negative and not needing to. We don't need to prove any existential negatives because there are an infinite number of possible entities (active ones like God, or the Great Architect, or Jupiter, or aliens, as well as useless ones like ghosts and celestial teapots) all jostling to be believed by us; we know that they can't all exist, so why should any of them exist? OK, it is easier to believe in some rather than others, and a few might be disprovable, but so what?

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Re: You can't prove a negative, and you don't need to do so

#19 Post by thundril » January 19th, 2012, 4:21 pm

I think I've spotted a hitch, Animist.
The pronoun 'you' has different meanings in the two phrases, and this difference is not just a nitpicking one. "You can't prove a negative" is a general truth, where the pronoun 'you' is a peculiarly English (language) idiom. The sense of this statement is more clearly expressed by using the (slightly posh or archaic) 'one'. That is to say, it really doesn't matter who 'you' are; the suggestion is that an existential negative cannot be proven by anyone.
The second 'you', however, is personal. The question of whether or not 'you' need to prove something depends on what 'you' are trying to achieve.
(Emma, for example, feels no need to prove the non-existence of God. Neither do I.)
An atheist in some situations might feel a 'need' to prove God's nonexistence, but that 'need' does not exist in the way the 'impossibility' exists. The need and the impossibility are different kinds of things. So I don't expect it will be possible to argue from one statement to the other.
I'm sure there are technical ways of saying all this. Maybe 'category error' could be worked into the discussion here, or 'the impossibility of deriving an ought from an is'. Something like that, anyway. :)

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Re: You can't prove a negative, and you don't need to do so

#20 Post by Emma Woolgatherer » January 19th, 2012, 5:18 pm

thundril wrote:The second 'you', however, is personal. The question of whether or not 'you' need to prove something depends on what 'you' are trying to achieve.
I see what you mean. Can't that be solved simply by incorporating whatever it is one might be trying to achieve. I'd go for something quite modest, such as:

One can't prove that a particular (named and defined) entity does not exist (anywhere in the universe), but one doesn't need to do so in order to justify one's lack of belief in such an entity.

Emma

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