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Onus of proof

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Consider this hypothetical conversation between guy A and guy B (this probably isn’t the best example, but I hope you get the idea):

A: Animals are not rational beings.

B: Well, prove that they’re not.

A: I’m sorry, but you have to prove that they’re rational.

Now, what if it would’ve happened differently?

B: Animals are not irrational beings.

A: Well, prove that they’re not.

B: I’m sorry, but you have to prove that they’re irrational.

Or maybe this other example:

A: God isn’t real.

B: Well, prove that he isn’t.

A: I’m sorry, but you have to prove that he is.

B: God isn’t false.

A: Well, prove that he isn’t.

B: I’m sorry, but you have to prove that he is.

Who has the onus of proof? How does it work? Is it that easy to fool the procedure, or am I just getting it all wrong?

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You can't prove the absence of something, by gathering evidence and showing it. The statement "Animals are not rational" (or they are irrational=they don't have reason) is about the absence of reason in animals. The absence of reason (or anything for that matter) leaves no traces you can detect and show as evidence. The absence of something is nothingness.

However, the presence of reason leaves traces, which can easily be detected, with a simple experiment. (for instance the presence of reason in me resulted in this post, as evidence of its existence)

Same with God, if God exists, he leaves traces you can find and show people. If it doesn't exist, the absence of traces is all the proof there could be that it doesn't exist.

The best proof there can be that something doesn't exist is the absence of any evidence that it does exist. There can never be more proof than that. Therefor, the onus of proof lies with those who state that something exists.

Edited by Jake_Ellison
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The best proof there can be that something doesn't exist is the absence of any evidence that it does exist. There can never be more proof than that. Therefor, the onus of proof lies with those who state that something exists.
Suppose I agree to buy your house on the condition that you demonstrate that there do not exist termites on the property. If you agree, then the burden is on you to demonstrate that there do not exist termites on the property, and so you call a termite inspector whose empirical testing is taken as grounds for concluding (hopefully) that there are no termites on the property.

I'm not saying this is analogous to any of the scenarios the original poster mentioned; but only that demonstrating a negative of an existence claim or taking a burden to demonstrate one is not always ruled out. Yet, I don't opine as to your claim that absence of evidence is the best proof that can be had; With the termite inspector I would imagine that his method is that of finding either evidence to confirm that termites exist on the property or, indeed, as you mention the notion, absence of evidence to confirm that termites do not exist on the property.

Edited by Hodges'sPodges
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The onus of proof lies with he who asserts the positive proposition not merely the first to assert, for the reasons Jake described.

A: Animals are not rational beings.

B: Well, prove that they’re not.

A: I’m sorry, but you have to prove that they’re rational.

B is effectively asserting animals are rational beings by means of a double negative. Onus on B.

B: Animals are not irrational beings.

A: Well, prove that they’re not.

B: I’m sorry, but you have to prove that they’re irrational.

B is asserting animals are rational beings by means of a double negative. Onus on B.

A: God isn’t real.

B: Well, prove that he isn’t.

A: I’m sorry, but you have to prove that he is.

B is effectively asserting God is real by means of a double negative. ("It is't true that God isn't real until proven" is the same as assuming God is real without proof.) Onus on B.

B: God isn’t false.

A: Well, prove that he isn’t.

B: I’m sorry, but you have to prove that he is.

B is effectively asserting God is real by means of a double negative. ("Isn't false" means true.) Onus on B.

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Who has the onus of proof? How does it work? Is it that easy to fool the procedure, or am I just getting it all wrong?
The basic problem is that your examples are poorly chosen (sorry, but that's the way it is), so I don't know if you will learn much from the question, just because of how you asked it. There is nothing in the syntactic structure of a proposition that tells you who must prove the proposition. The simplest rule is that whoever advances a claim must prove the claim. The problem is that very often people advance claims (call it claim A) and provide evidence for a different claim (claim B). So people assert A but only prove B; and yet, unfortunately, the population thinks that A has been proven (since that is what the proponent asserted). We could talk extensively about why this happens, but the point is that often, proof of a weaker claim is given and understood to show something stronger.

Burden of proof questions reduce to the question of whether a claim has been improperly taken to be shown, when it has not in fact been shown. No claims about god have actually been proven but some people believe that god-claims have been proven, thus the goddites invoke silliness about burden of proof. Animal-geniusologists similar pretend that there is evidence for animals having a rational faculty, when there is no such evidence, and then they occasionally get to play the BOP card.

I think it's relatively easy to evaluate these claims, at least in the realm of popular science (or "not even science"). Look at the evidence for the claim and determine "what does this really show -- are they laying claim to results that are not supported?". My belief is that if you are interested in understanding the logic of BOP, you should only look at scientific questions, because that way you will minimize the volume of irrationality that surrounds the question. Minimize, but of course not eliminate.

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Onus on B.
I don't consider a request for proof of the negation of a propostion P to be in itself an assertion of the truth of the P, no matter what double negatives are involved.

If I'm considering buying your house and you claim "there do not exist termites on the property" then I very well may ask you to prove your claim and by making that request I am not asserting that there are termites on the property.

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Suppose I agree to buy your house on the condition that you demonstrate that there do not exist termites on the property. If you agree, then the burden is on you to demonstrate that there do not exist termites on the property, and so you call a termite inspector whose empirical testing is taken as grounds for concluding (hopefully) that there are no termites on the property.

I'm not saying this is analogous to any of the scenarios the original poster mentioned; but only that demonstrating a negative of an existence claim or taking a burden to demonstrate one is not always ruled out. Yet, I don't opine as to your claim that absence of evidence is the best proof that can be had; With the termite inspector I would imagine that his method is that of finding either evidence to confirm that termites exist on the property or, indeed, as you mention the notion, absence of evidence to confirm that termites do not exist on the property.

Onus of proof in debate is not the same as negotiated terms of sale.

The termite argument in syllogism form is:

If there were termites then there would be evidence of termites.

There is no evidence of termites.

Therefore, there are no termites.

This is called modus tollens or denying the consequent and is valid argument. The burden of proof still lies on he who would assert the positive proposition that there is evidence of termites.

If I'm considering buying your house and you claim "there do not exist termites on the property" then I very well may ask you to prove your claim and by making that request I am not asserting that there are termites on the property.

If it were just a debate the burden would be on you to prove there were termites. But since you have the money and I have the house, it is up to me to provide the evidence in this case.

Edited by Grames
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Onus of proof in debate is not the same as negotiated terms of sale.
I didn't say it was. The context was of a "conversation". I take that it in a sense that might include a conversation between people negotiating the sale of a house. As to debates, particularly formal debates, such rules as to burden are determined by whatever is agreed upon. Anyway, in a formal debate, one side has to take the denial. But you'd hardly score many points by saying merely saying the burden is on the affirmative even IF the affirmative side didn't itself do a good job of supporting the proposition.

The termite argument in syllogism form is:

If there were termites then there would be evidence of termites.

There is no evidence of termites.

Therefore, there are no termites.

This is called or denying the consequent and is valid argument. The burden of proof still lies on he who would assert the positive proposition that there is evidence of termites.

I think it is a valid form of argument (though I'd change 'were' to 'are' and 'would be' to 'is'). (But, as an aside, do you do you know of an Objectivist writing that states that such forms as modus tollens, modus ponens, and others, are valid or even that Objectivism allows that there are arguments that can be determined valid just by form?)

But as to burden, suppose I'm paying for the termite inspector's services. If the termite inspector walked in, sat down, drank a couple of beers, then told me that there are no termites and that he has no burden to prove that there are no termites, then I would say that I have no burden to pay him. If the inspector claims there are no termites, like hell if he doesn't have a burden to prove it (even if by means of modus tollens after some process of looking for but not finding evidence of the critters).

If it were just a debate the burden would be on you to prove there were termites.
No, actually in an ordinary debate, both sides take a burden to demonstrate their position, whether that of affirming or denying the proposition.

But since you have the money and I have the house, it is up to me to provide the evidence in this case.
Right. You take the burden of proving that there are no termites.

Moreover, another context is mathematics. In that field, if one asserts a denial, then it is one's burden to prove it. There is no sense that one may say, for example, "there does not exist an even number greater than two that is not the sum of two primes" by merely resting on a challenge for it to be proven that there does exist an even number greater than two that is not the sum of two primes.

Edited by Hodges'sPodges
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I didn't say it was. The context was of a "conversation". I take that it in a sense that might include a conversation between people negotiating the sale of a house. As to debates, particularly formal debates, such rules as to burden are determined by whatever is agreed upon. Anyway, in a formal debate, one side has to take the denial. But you'd hardly score many points by saying merely saying the burden is on the affirmative even IF the affirmative side didn't itself do a good job of supporting the proposition.

I don't mean formal debates where scoring the technique is the point, but legitimate debates where the goal is to find the truth. Arbitrary claims for which it cannot be determined if they are true or false, are treated as if they are false when it comes time to act. Proposing that my house has termites is not arbitrary. I know nothing of debating contests but I would guess dismissing your opponent's position as arbitrary displays no special skill so would be deprecated as practice in that context even if it were the best course to take.

I think it is a valid form of argument (though I'd change 'were' to 'are' and 'would be' to 'is'). (But, as an aside, do you do you know of an Objectivist writing that states that such forms as modus tollens, modus ponens, and others, are valid or even that Objectivism allows that there are arguments that can be determined valid just by form?)

Valid form should not be taken as validated in the sense of reduced to reality. Objectivism accepts Aristotle's formulation of the law of identity and the principle of non-contradiction as well as the syllogism. It adds hierarchy to epistemology by its theory of concepts and insists nothing is fully validated until it is reduced to concretes or axiomatic primaries. But assuming the premises are true, a valid form of deduction via syllogism results in a true conclusion. I haven't got any Objectivist course on logic, and there is no such thing as "Objectivist logic". There are logic courses by Objectivists and I would be shocked if they came up with anything different.

But as to burden, suppose I'm paying for the termite inspector's services. If the termite inspector walked in, sat down, drank a couple of beers, then told me that there are no termites and that he has no burden to prove that there are no termites, then I would say that I have no burden to pay him. If the inspector claims there are no termites, like hell if he doesn't have a burden to prove it (even if by means of modus tollens after some process of looking for but not finding evidence of the critters).

He voluntarily investigates in order to get paid, and if he claims that you do have termites he has the burden of proof and you should insist on seeing the evidence.

Moreover, another context is mathematics. In that field, if one asserts a denial, then it is one's burden to prove it. There is no sense that one may say, for example, "there does not exist an even number greater than two that is not the sum of two primes" by merely resting on a challenge for it to be proven that there does exist an even number greater than two that is not the sum of two primes.

Denials aren't asserted in that context, they are implied by the requirement to come up with a proof in the first place. In math it is not possible to make the ultimate appeal to reality so there is no distinction between positive and negative statements in the sense of existence and nonexistence. There is only consistency or inconsistency which can be shown for any theorem.

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Moreover, another context is mathematics. In that field, if one asserts a denial, then it is one's burden to prove it. There is no sense that one may say, for example, "there does not exist an even number greater than two that is not the sum of two primes" by merely resting on a challenge for it to be proven that there does exist an even number greater than two that is not the sum of two primes.

True, you can prove that there is no such number (I'm assuming, I don't have it worked out). You can also prove that there isn't an omniscient, omnipotent God, by the way, as Kendall explains in this post. When something is impossible, because it contradicts the laws of reality (or mathematics), then a claim that such a thing exists can be shown to be false, through reductio ad absurdum. (there may be a different term for that, outside mathematics)

But there are other claims, that are possible but false. My previous post is about those claims. (with God in the OP being a limited yet powerful creature)

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All you have to do is say this: "There is no evidence that God exists. That proves he does not exist."

That automatically puts the burden on them to produce the evidence. If they say that there is no evidence for his existence, but that he exists anyway, then you can ask them how they came to believe in him if there was no evidence to support him. Then when they tell you what convinced them, you can argue that that is their evidence, and it will probably be weak evidence at that.

I imagine this concept can be applied for anything you know does not exist.

Edited by Amaroq
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But there are other claims, that are possible but false. My previous post is about those claims. (with God in the OP being a limited yet powerful creature)

Same difference, although the objective truth has to be carefully worded.

Even assuming that one is claiming that there is a physically-provable entity which could be "God", such as some fantastically-advanced alien life form, the onus of proof is still on the one making the claim. The objective truth is: Nothing has been proven to exist that meets the qualifications of "God". Until such proof is provided -- i.e. scientific evidence that it cannot be anything else -- it's safe to conclude that no such entity actually exists.

But, it's wasteful speculation to think there could be a "God" that isn't "supernatural".

God is by definition supernatural. Yet everything that exists exists in nature. Since there is nothing "supernatural" (which is the logical corollary of "everything that exists exists in nature"), "God" as defined as a "supernatural being" can't exist. To claim some newly-discovered and unique entity is "God" would be to automatically invalidate that being as "God", and identify is as something else ... such as a fantastically-advanced alien life form.

Edited by Lemuel
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I don't mean formal debates where scoring the technique is the point, but legitimate debates where the goal is to find the truth. Arbitrary claims for which it cannot be determined if they are true or false, are treated as if they are false when it comes time to act.
My impression is that that is the Objectivist position. And it surely is a good convention to have in the law in the sense of presumed innocence. However, other than in the legal context of presumed innocence, I've given reasons why I don't think it holds as a universal generalization.

I wrote:

"Moreover, another context is mathematics. In that field, if one asserts a denial, then it is one's burden to prove it. There is no sense that one may say, for example, "there does not exist an even number greater than two that is not the sum of two primes" by merely resting on a challenge for it to be proven that there does exist an even number greater than two that is not the sum of two primes."

Denials aren't asserted in that context, they are implied by the requirement to come up with a proof in the first place.
Dnials are commonly asserted in mathematics. That is, one commonly asserts certain negations of propositions, including negations of existence claims. One commonly asserts things of the form "there does not exist a number having such and such a property". And the burden of proof is on one who makes that claim. It is not the case that a proposition such as "there exists a number having such a such property" is "treated as false" unless proven. Rather, it is treated as unproven, and a burden of proof goes to whomever asserts it AND to whomever asserts its negation.

In math it is not possible to make the ultimate appeal to reality so there is no distinction between positive and negative statements in the sense of existence and nonexistence. There is only consistency or inconsistency which can be shown for any theorem.
In mathematics, at least since about the last hundred years, ordinarily, a theorem, by definition, is a sentence provable from some given set of formulas. Consistency is a related but different matter. Propositions of mathematics may come as either negations or not negations (and in constructive mathematics, by the way, it is not the case that every proposition has an equivalent in negation form), and no matter whether one is asserting a proposition that is not a negation or one that is a negation, the burden or proof is on the one who makes the assertion. When a proposition has no known proof nor known proof of its negation, then it is "treated" as "unknown as to its provability", or "unsolved", or "an open problem", and it is not "treated" as false merely for lack of proof. Of course, in classical mathematics, this does not contradict the law of excluded middle: every sentence is either true or false (in a given structure, if more formal); but until we've proven the sentence or proven its negation we don't just "treat" the sentence as false merely for our lack of a proof of it.

Also, contrary to you claim, mathematics may easily distinguish between negations of existence statements and existence statements. An existence statement is of the form "there exists an object having such and such property". The negation of an existence statement is of the form "There does not exist an object having such and such property".

Edited by Hodges'sPodges
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If I'm considering buying your house and you claim "there do not exist termites on the property" then I very well may ask you to prove your claim and by making that request I am not asserting that there are termites on the property.

Actually when purchasing a house the burden is on you (the purchaser) to hire an inspector to discover if there are termites or not.

The seller is bound by decency to be honest but the burden of proof is on the buyer.

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Actually when purchasing a house the burden is on you (the purchaser) to hire an inspector to discover if there are termites or not.

The seller is bound by decency to be honest but the burden of proof is on the buyer.

That may depend on the jurisdiction. (If I recall correctly, I've seen instances in which it is part of the seller's disclosure to attest that there are no termites.) Anyway, I wasn't referring to whatever the particular disclosure laws or conventions are in real estate . Rather, I'm just referring to a situation in which a person claims that there do not exist termites on the property, no matter the relationship of seller or buyer or whatever laws or conventions exist regarding real estate transactions. Even if there is no buying or selling involved, if a termite inspector claims that there are no termites on the property, it is not my onus to prove that there are termites on the property; and I don't regard as false the claim that there are termites on the property based only on lack of proof that there are not termites on the property, but rather, I regard it as undetermined, which again does not contradict the law of excluded middle that it is either true or false that there are termites on the property, since I recognize it is either true or false while also recognizing that I don't know which it is until one or the other is proven (in whatever sense of 'proof' - empirical, in this case, which may include the modus tollens argument about lack of evidence mentioned by another poster earlier). If the inspector asserts that there are no termites, then he needs to prove that there are no termites; he can't just say, "Well, it's a negative statement, so you need to prove that there ARE termites." Edited by Hodges'sPodges
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Without reading the entire thread:

If you claim something that isn't self-evident or well-known and documented, then the burden of proof lies on you.

If I say "The sky is blue," that's self-evident and needs no proof. If I say "e=mc^2" that is well-known and documented (or in other words it's proven) and I don't have to prove it. If I say "There is a God," well it's neither self-evident nor proven. I'd have to supply proof. That means positive proof, not simply demand that you prove there is no God.

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No, I get what you're saying.. . So lets say the seller doesn't know that termites have in fact invaded and in good faith, not realizing they exist tells you no termites. I've lived in many places and the burden of proof in this matter has always been on the buyer to get an inspection- so long as it can not be proven that the owner knowingly lied. Basically the burden of proof is alwys on the person who has the most interest in the matter.. which would presumably be the buyer.

The Priest doesn't have to prove to you that "god" exists just because you ask. It is up to you, as the asker to find your own proof though you can certainly ask questions of that person to try to find your own conclusions.

In business, in philosophy, in every aspect of life it is always caveat emptor.

Expecting anything from anyone else is a fool's game. So when asking on whom the burden of proof lies I would say it lies on the person who wants to know the truth of the matter.. which could be the asker or the questioner. A person who is happy with delusions or lies can't be burdened with proof so why pretend they can be?

Edited by QuoVadis
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No, I get what you're saying.. . So lets say the seller doesn't know that termites have in fact invaded and in good faith, not realizing they exist tells you no termites. I've lived in many places and the burden of proof in this matter has always been on the buyer to get an inspection- so long as it can not be proven that the owner knowingly lied. Basically the burden of proof is alwys on the person who has the most interest in the matter.. which would presumably be the buyer.
As to the legal or civil matter I think it would depend on whatever the law (or lack of one) is in a given jurisdiction. But again, I just posted that the legal or civil or even buyer/seller transaction issue is not what I'm referring to.

The Priest doesn't have to prove to you that "god" exists just because you ask. It is up to you, as the asker to find your own proof though you can certainly ask questions of that person to try to find your own conclusions.
Questions about existence of god come also with their own problems. To begin with, there is the problem of whether (or possibly in what sense) a meaningful proposition is even at hand. I mean, such questions as to what empirical, deductive, or other grounds would be considered adequate to settle the proposition. My own "standard response" to assertions of the existence of god is along the lines of, "I don't deny that you may have whatever personal spiritual experiences you have, but I won't get caught up in a debate over a proposition that you can't tell me the means, empirical or deductive, or even some broad sense, by which it could be settled." Then, supposing we do have some basis upon which to argue the matter, it is up to whomever says "God exists" to prove it and (again assuming, which is a stretch anyway, that there is a basis for determination of the question) it is up to whomever says "God does not exist" to prove it. But of course, I would heartily agree that lack of a submitted disproof of existence is NOT proof of existence. I only disagree that lack of proof of existence is proof of non-existence (again, given the caveat that it's been established in just what sense the proposition 'God exists' is meaningful in terms of public enquiry).

In business, in philosophy, in every aspect of life it is always caveat emptor.

Expecting anything from anyone else is a fool's game. So when asking on whom the burden of proof lies I would say it lies on the person who wants to know the truth of the matter.. which could be the asker or the questioner. A person who is happy with delusions or lies can't be burdened with proof so why pretend they can be.

The point about caveat emptor and fool's game is beside the point. I'm not asking what is a wise policy to have in buying a house or a used car. Rather, my concern is epistemological and as to methodology in inquiry, whether as informal an inquiry.

Again, whoever says there are no termites (whether buyer, seller, disinterested third party, whatever) has the burden of proof, and if there's no evidence yet given, then I don't conclude that I have knowledge that there are no termites, but rather I take it that I don't have knowledge that there are and I don't have knowledge that there are not.

Edited by Hodges'sPodges
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