Absence of Evidence is Evidence of Absence

[MorpheusSandman]

Continued from This thread (http://www.online-literature.com/forums/showthread.php?78538-Shakespeare&p=1255970#post1255970).



(An absence of evidence is not evidence of absence.)Yes it is. (http://lesswrong.com/lw/ih/absence_of_evidence_is_evidence_of_absence/) I'd like to know who came up with that mathematically provable false aphorism.


Nope. You should probably read your own material before posting it incorrectly. From the link: "The absence of an observation may be strong evidence of absence or very weak evidence of absence, depending on how likely the cause is to produce the observation."

False evidence is no evidence at all, but if you want to continue the discussion, I suggest a new thread.I have no clue how you think that contradicts my point, especially when that article's thread title says the exact same thing I did (unless you think Yudkowsky is contradicting his own thread title). The post you quoted says, when you elide the complicating bits: "the absence... may be STRONG evidence... or VERY WEAK evidence..." what he's describing there is the LEVEL of evidence any absence is. I don't know what you mean by "false evidence," and I don't think "false evidence" is what's meant by "absence of evidence."

I used this example on another forum a while back: Imagine that you haven't seen your neighbor for two weeks. Typically, you see him a few times a week just incidentally, such as when you're leaving for work and he's watering his lawn. Now, there are many things that could explain WHY you haven't seen him. One possible explanation is that he's dead. Now, the only evidence you can have of him being dead, without actually seeing his body or being told by a relative, is the ABSENCE of evidence that he's alive, and this absence of evidence IS evidence of his absence (death). It may be very WEAK evidence, given that there are other possibilities that account for your observation (not seeing him) with a higher degree of probability, but this absence of evidence that he's alive is, necessarily, evidence that he's dead according to Bayes' Theorem.

[Lokasenna]

To some extent it must depend on the context of the argument, though broadly speaking I'm more in favour of Atheist's view.

Medievalists like myself are used to scrabbling in the dust of history, trying to discern what meaning we can from the relatively small percentage of literary material that has survived into the modern world. The idea that 'absence of evidence is not evidence of absence' is a key tenet of the medieval scholar - because our absences are so large and glaring, we have to treat them with respect, and not attempt to fill them with baseless conjecture, however much we might like to imagine that the hypothetical evidence (or lack thereof) might support our conclusions.

[MorpheusSandman]

Honestly, this issue really isn't even debatable because Bayes' Theorem--P(A|B) = (P(B|A)*P(A)) / P(B) ...Where P = Probability, A = proposition, B = evidence, and | = given--proves it formally. For someone to continue debating it means either there's a misunderstanding of the term or a lack of understanding of Bayes' Theory, or perhaps both. I'll try to explain with an example from your own field


The idea that 'absence of evidence is not evidence of absence' is a key tenet of the medieval scholar...Let's say it's possible that there was a book written by Julius Caesar that's now lost, but it's also possible that he never wrote such a book. If he never wrote it, there would be an "absence of evidence" 100% of the time because the book doesn't exist. On the other hand, if Caesar HAD written the book, there would only be an "absence of evidence" some percentage of the time less than 100%. We may not know HOW MUCH less than 100%, but it must be less. So any continuing "absence of evidence" would necessarily be evidence in favor of the absence of the book. It may not be STRONG evidence, given how much is irrevocably lost to history for a variety of reasons, but it is evidence nonetheless. If you wanted to fill in some hypothetical numbers:

A = 50% Caesar didn't write the book
B = 90% probability there would be an absence of evidence even if the book was written
B|A= 100% probably there would be an absence of evidence given the book wasn't written

Following Bayes' Theorem you'd end up with a new A of 55.5%. So the absence of evidence, given the above numbers, has increased the likelihood Caesar didn't write the book (the absence) from 50% to almost 56%.

Absence of evidence is evidence absence. The above offers incontrovertible mathematic proof. Any continued use of the phrase means one doesn't understand the phrase or the math. How strong the evidence is is all that's debatable, and it depends upon a variety of factors, including how much absence would be expected even if the something existed. Obviously, we rarely have such precise numbers of these, but knowing the math involved and what it says at least prevents us from making objectively wrong statements like "absence of evidence isn't evidence of absence."

[Lokasenna]

The difficulty with your argument is that you are assuming that ignorance is quantifiable - where do you pick these numbers from, hypothetical or otherwise?

An absence of something, whether it ever existed in the first place or not, is (to use your terminology) 100% - what do you mean by 'there would only be an "absence of evidence" some percentage of the time less than 100%'? Something is either exists, or it does not - and if it does not, then you can't make suppositions about it.

Using your mathematical model as a proof is as flawed as asserting that, thanks to Xeno, the athlete will never the tortoise - which, of course, is nonsense. I could, for example, use your model to argue for the existence of practically anything - for example, that Caesar wrote a first James Bond novel centuries before Fleming appeared on the scene...

[MorpheusSandman]

The difficulty with your argument is that you are assuming that ignorance is quantifiableOur ignorance is quantifiable to a certain extent depending on the subject. I play poker for a living. On every hand I am ignorant of a lot of factors involved in figuring out the best move to make. Yet, the better I am at quantifying the combination of my knowledge and ignorance, the better decision I can make, and the more I will win in the long run. Sometimes our ignorance can be known precisely, such as in a coin flip; our knowledge concerns the coins two equal sides, while our ignorance is our inability to calculate gravity, force of flip, landing surface, etc. that would (all in combination) determine what side the coin landed on. The combination of our knowledge and ignorance makes the flip 50/50, rather than 100/0.


what do you mean by 'there would only be an "absence of evidence" some percentage of the time less than 100%'?Two possibilities: the book exists or it doesn't.

1. If the book doesn't exist, we'd expect there to be an "absence of evidence" for its existence 100% of the time.
2. If the book does exist, we'd expect there to be an "absence of evidence" for its existence some (less than 100%) of the time.

We do not know the probability of 2 precisely, but it must be less than 100% because the book exists. Anything that exists will leave some evidence for itself even if it's only in the form of its actual existence (meaning it would be possible to find the actual book).

Let's use a different example. Instead of a book that may or may not exist, let's take a book you KNOW exist,s but that you've misplaced. You begin by searching your bedroom. The same idea applies: either the book is in your bedroom, or it is not.

1. If the book is not in your bedroom, there will be an absence of evidence 100% of the time.
2. If the book is in your bedroom, there will be an absence of evidence less than 100% of the time.

You may search and search your room and not be able to find it, and for every place you look and don't find it, this "absence of evidence" is "evidence for (the book's) absence" (in that room). While you may not can quantify this evidence in precise numbers, this is one case in which common sense and the math actually gel; or do you continue to search that one room until you die endlessly repeating the phrase "absence of evidence is not evidence of absence" or do you eventually say to yourself "given the absence of evidence, it seems probably the book isn't here"?


Something is either exists, or it does not - and if it does not, then you can't make suppositions about it.Sure we can; if something doesn't exist then it leaves no evidence of its existence.


Using your mathematical model as a proof is as flawed as asserting that, thanks to Xeno, the athlete will never the tortoise - which, of course, is nonsense. I could, for example, use your model to argue for the existence of practically anything - for example, that Caesar wrote a first James Bond novel centuries before Fleming appeared on the scene...Yeah, you're just plain misunderstanding me because there's nothing in my argument that allows for you to "argue for the existence of practically anything," unless there IS evidence for those things. What evidence is there that Caesar wrote the first James Bond novel?

[The Atheist]

I have no clue how you think that contradicts my point, especially when that article's thread title says the exact same thing I did (unless you think Yudkowsky is contradicting his own thread title). The post you quoted says, when you elide the complicating bits: "the absence... may be STRONG evidence... or VERY WEAK evidence..." what he's describing there is the LEVEL of evidence any absence is.

I'm amazed we're having this discussion, because all he missed was "or no evidence at all" after the "VERY WEAK" bit.

The blindingly obvious point is that every new discovery is made in the lack of evidence. Do you really not get that point?

If you can classify the level of evidence for non-existence, then there's obviously some evidence to the contrary, or you wouldn't know it didn't exist! I'll slip in Sasquatch just there.


I don't know what you mean by "false evidence," and I don't think "false evidence" is what's meant by "absence of evidence."

I was referring to you quoting something that does not, in itself, constitute of evidence. It seems to be a conclusion based on false premises, but that's fine, I see it a lot.


I used this example on another forum a while back:

And I'm glad you brought it out here, because it exemplifies my point entirely.

In the case of your neighbour, you start from a position of evidence - your neighbour does actually exist. When you have no evidence at all, you cannot draw any conclusion from it.

In the case of Mr Walter P Smyth, 24 Maple St, Canada, you don't have evidence that he exists, or whether he's been murdered. You can go and find evidence of his existence, but right now, you have no evidence whatsoever. That is exactly the position with the premise in relation to every thing we haven't yet discovered. I should imagine even Galileo would have laughed at you if you'd told him about black holes.

All your premise does is enable a false conclusion to be drawn out of a hat. Russell's teapot.

You may now put your case for the fact that no other forms of life exist in the universe. We've been searching for them - never mind stumbling over evidence, we've been actively searching for them for decades.

[The Atheist]

Our ignorance is quantifiable to a certain extent depending on the subject. I play poker for a living.

You should take up Bingo instead, because that's the answer and you've skipped past it again.

Depending on the subject....

Exactly.

[Ecurb]

One of my friends believes Sasquatches roam the forests of our native Oregon. He points out that there is no "absence of evidence" for his belief -- there are photographs, eye-witness reports, and footprints (casts of which he has made himself).

I don't buy it. That's because there is an absence of the evidence that I expect would have been discovered if Sasquatches exist. No skeletons, bodies, or live specimens have been produced, despite the fact that the Pacific Northwest has been well explored and is filled with people. The only "evidence" I have for the non-existence of Sasquatches is this absence of (a particular kind of) evidence to the contrary. The extent to which such "absence of evidence" is persuasive is our own estimate about the probablility of finding evidence given the nature of the evidence we would expect to find and the intensity of our search for it. If I glanced through my bookshelves for my missing book without finding it, I would have weak evidence that it isn't there. If I scoured the bookshelves meticulously for hours, the absence of evidence would provide stronger evidence that it wasn't there.

This is basic scientific method. My disbelief in Sasquatches is falsifiable. Produce a Sasquatch, living or dead, and I'll alter my beliefs. However, if "absence of evidence is not evidence of absence" I have no evidence whatsoever to support my belief that Sasquatches do NOT exist.

[Volya]

If there is no evidence for something then surely it is just common sense that it is more likely to be false than true.

[MorpheusSandman]

I'm amazed we're having this discussion, because all he missed was "or no evidence at all" after the "VERY WEAK" bit.

The blindingly obvious point is that every new discovery is made in the lack of evidence. Do you really not get that point?

If you can classify the level of evidence for non-existence, then there's obviously some evidence to the contrary, or you wouldn't know it didn't exist! I'll slip in Sasquatch just there.These all sound like non-sequitors. It is never "no evidence at all" even if it sometimes "very weak." It can never, ever be "no evidence" because of how Bayes' works. In the case of absent evidence, B|A will always be 100%, while B will always be less than 100%. If the thing existed, B CAN NEVER BE 100%! And as long as it's less than 100%, absence will always continue to support A more than ¬A.

I don't know what "every new discovery is made in the lack of evidence" means or why/how you think it's relevant to this issue. So, we didn't have evidence for something, discovered it, and then we do. So, even there: it existed, and it eventually provided proof (not just evidence) of its existence. If it didn't exist, we never would've found it!

You can rarely classify the level of evidence of anything precisely, but there are certain abstract statements that can be made about such situations: and the AOEISNEOA is not one of them; it's patently false.


I was referring to you quoting something that does not, in itself, constitute of evidence.I'm still lost: I was quoting something that was false evidence?


That is exactly the position with the premise in relation to every thing we haven't yet discovered.Indeed. But let's consider two categories:

1. Things we imagine to exist, but do not.
2. Things that actually exist, but that we don't have evidence for.

Now in both of these scenarios we are positing knowledge that we actually don't have (for 1. we say we "know" they don't exist, and for 2. we say we "know" they exist), so imagine that we don't have that knowledge. For the things in category 1. there will always, now and forever, be an absence of evidence for them because they don't exist. Yet, for things in category 2. while there may be an absence of evidence NOW, there MAY not be later. So it doesn't really matter if we know something exists or not, the same rules applies for potentially existing things: The continuing absence of evidence is evidence for their absence. Perhaps strong evidence, perhaps weak evidence, but evidence nonetheless. Ecurb's example of Sasquatches is a perfect example: the evidence that exists is far weaker than the absence of evidence that exists for their absence.

Really, there's absolutely no reason why this formula would just stop working or not apply to the potential existence of things. Consider the scenario where you've lost a book. You start searching your bedroom. After 5 minutes, there is an absence of evidence that the book is there. Is this in itself not evidence that book is actually absent in the room? Most would say "yes," and be correct; why would the same thought not apply to the potential existence of something?


You may now put your case for the fact that no other forms of life exist in the universe. We've been searching for them - never mind stumbling over evidence, we've been actively searching for them for decades.The evidence that other life exists in the universe is actually us. We know that life can exist given the right combination of elements and enough trials, and we know (roughly) how many planets there are where life could exist. Now, it's indeed possible to argue endlessly over the numbers, and it's a good example where we recognize our knowledge is far, far outweighed by our ignorance. So while the "absence of evidence" for ET is, indeed "evidence for their absence," it is extremely weak evidence and, indeed, their existence may be more probably given other the other facts involved.

[MorpheusSandman]

This is basic scientific method. My disbelief in Sasquatches is falsifiable. Produce a Sasquatch, living or dead, and I'll alter my beliefs. However, if "absence of evidence is not evidence of absence" I have no evidence whatsoever to support my belief that Sasquatches do NOT exist.Absolutely, and your post does get into some tangentially related subjects like what, exactly, constitutes evidence and absence of evidence and what kind of evidence/non-evidence is stronger/weaker than others. Obviously, I think you're absolutely right regarding Sasquatches for the reasons you've given. Photographs, eye-witnesses, and footprints seem far weaker evidence than actually producing a Sasquatch (given how we know footprints can be faked, like Crop Circles, and that eye-witnesses can lie, be mistaken/confused, etc.), and the fact that nobody has produced one is quite strong evidence they don't exist given how populated and explored the relevant areas have been.

[Emil Miller]

Rummy said it best.

There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns. There are things we don't know we don't know.

http://youtu.be/_RpSv3HjpEw


The hilarious part is the guy at the end.

[AuntShecky]

Julius Caesar didn't write a book? If that's the case, I'm suing my Latin I teacher for foisting upon the class the work of an imposter! This litigation, of course, would entail borrowing the Way Back machine from Sherman and Mr. Peabody.

As far as evidence of absence/absence of evidence: a cable news channel last night featured a side-bar issue concerning the mystifying disappearance of Malaysian Air 370. The gist of that segment centered on the the old dichotomy of supply and demand: the lack of of facts (absence) vs. the world's clamor for answers (evidence.) In this case, there a chasm separates what is actually known about that flight and the pressure by the various media and their audiences to know exactly what happened. Thus, self-appointed "experts" rush to fill that gap with wild speculation and preposterous conspiracy theories, from the somewhat plausible --hi-jacking or an elaborate suicide plot on the part of a crewman or passenger-- to the outlandish and scientifically specious --aliens, black holes, as if a black hole did surgical strikes, sucking in a single aircraft rather than the whole solar system! Supplanting the disturbing mystery with a theory, no matter how unreasonable or irrational, somehow alleviates fear by allowing a small measure of control over the uncontrollable.

If absence of evidence creates a barrier between reality and one's hopeful perception of reality, then there are only two things one can do: drop the whole matter or continue the search for evidence. (Those courses of action would hold through for most cases EXCEPT matters of religious faith, because faith, by definition, is intuitive and thus beyond the scope of "proof." Cf. Douglas "The Hitch-hikers Guide to the the Galaxy" Adams, who said that if your faith depends on evidence, then your faith is nothing. )

[Hawkman]

What seems to me to be a flaw in the argument is that we have no reason to suppose that anything exists without some kind of evidence for it. Even for the debate over whether God exists is based on the primary evidence of the universe and everything in it. God is therefore one of many theoretical explanations for it. Consequently, evidence for the existence of god cannot actually be considered incontrovertible proof that he exists. As for the adventures of James Bond being written by Julius Caesar there is no reason to suppose that such a book ever existed, so why would one look for it? If he had written such a book then it would be possible that we would know of its existence from secondary evidence in the form of contemporary or near contemporary references. If evidence should turn up which stands up to verifiable historical and scientific testing, then it would be reasonable to accept that such a book existed but has subsequently been lost. Whether or not the book is ever found, it is reasonable to accept that it had existed. If the evidence is proved false and a hoax, then there is no evidence for the existence of the book.

[The Atheist]

2. Things that actually exist, but that we don't have evidence for.

....Yet, for things in category 2. while there may be an absence of evidence NOW, there MAY not be later.

There you go - now you understand. We're not talking about the future, or at least you weren't.

I find it strange that you can type that - which completely negates the statement, yet you continue to try to defend it.

Ho hum.

[MorpheusSandman]

As far as evidence of absence/absence of evidence: a cable news channel last night featured a side-bar issue concerning the mystifying disappearance of Malaysian Air 370... Supplanting the disturbing mystery with a theory, no matter how unreasonable or irrational, somehow alleviates fear by allowing a small measure of control over the uncontrollable.
What seems to me to be a flaw in the argument is that we have no reason to suppose that anything exists without some kind of evidence for it.
I wanted to quote these two posts together as I think they're related to each other. AuntShecky hits on the reason WHY there is often such outlandish speculation for the existence of things/causes even in the absence of evidence. The problem with the human mind is that it will sooner invent a possible answer than it will immediately believe it and begin trying to find evidence for it, no matter how specious. As she says, this is directly related to our fear/anxiety at the unknown, the primal need to supplant that mystery with SOME answer, no matter how ludicrous. That instinct makes it easy to suppose the existence of any number of things with no evidence, and then suppose the absence of evidence has no bearing on the likelihood of their existence (when it does). Obviously, what Hawkman says is true, but AuntShecky's post illustrates precisely why we don't live in a world where people believe that "we have no reason to suppose that anything exists without some kind of evidence," and, indeed, people, in general, have a very poor notion of what substitutes real evidence as opposed to false evidence, weak evidence as opposed to strong evidence, or how any kind of evidence affects different possible explanations or existences. The point being that people are not rational, and not being rational leads to nonsense like "absence of evidence is not evidence of absence," even when such a saying is mathematically provably wrong.

[MorpheusSandman]

There you go - now you understand. We're not talking about the future, or at least you weren't.

I find it strange that you can type that - which completely negates the statement, yet you continue to try to defend it.

Ho hum.I still have no idea what you're on about or how it relates to anything I've said. That things that exist CAN provide evidence for their existence some time in the future or COULD HAVE in the past, while things that don't exist CAN NOT or COULD NOT have, feeds directly into the notion that "absence of evidence is evidence for absence." If you understood the math as I've been expressing it you should realize why this is. Math and probability doesn't just stop working because we can't know the future.

[Hawkman]

I wanted to quote these two posts together as I think they're related to each other. AuntShecky hits on the reason WHY there is often such outlandish speculation for the existence of things/causes even in the absence of evidence. The problem with the human mind is that it will sooner invent a possible answer than it will immediately believe it and begin trying to find evidence for it, no matter how specious. As she says, this is directly related to our fear/anxiety at the unknown, the primal need to supplant that mystery with SOME answer, no matter how ludicrous. That instinct makes it easy to suppose the existence of any number of things with no evidence, and then suppose the absence of evidence has no bearing on the likelihood of their existence (when it does). Obviously, what Hawkman says is true, but AuntShecky's post illustrates precisely why we don't live in a world where people believe that "we have no reason to suppose that anything exists without some kind of evidence," and, indeed, people, in general, have a very poor notion of what substitutes real evidence as opposed to false evidence, weak evidence as opposed to strong evidence, or how any kind of evidence affects different possible explanations or existences. The point being that people are not rational, and not being rational leads to nonsense like "absence of evidence is not evidence of absence," even when such a saying is mathematically provably wrong.

Of course, my postulation is rather dependent on the nature of belief. If one believes the crashing of an airliner is evidence for the existence of ET, then as you say, it's rather weak evidence. It is infinitely challengeable and has to be weighed in the scales of probability and likelihood. Likewise, that absence of evidence is not evidence of absence when applied to black holes would be ample proof of the statement, unless, of course, one subscribed to the position that our belief in the possibility of black holes, as first suggested by deduction from a mathematical hypothesis, conjured them into being and subsequently allowed for their detection by the physical observation of their effects. An interesting if solipsistic argument, perhaps, but it is, in my opinion (though I concede that I'm not an astrophysicist or quantum mechanic) unlikely. They almost certainly existed before we even conceived of the idea of them or were able to detect any evidence of their existence.

[YesNo]

Rummy said it best.

There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns. There are things we don't know we don't know.

http://youtu.be/_RpSv3HjpEw


The hilarious part is the guy at the end.

The only case Rummy missed was the one about those unknowns that we know.

I wonder how this would apply to the Emperor's New Clothes.


Absence of evidence (that he's wearing clothes) is or is not evidence of absence (of his clothing).

Of course, we all know he's wearing clothes. Just ask the tailors for the evidence.

[The Atheist]

I still have no idea what you're on about or how it relates to anything I've said.

Yes. I've noticed that.

I suspect that's because it doesn't fit with your flawed idea. The maths is no problem, and I've agreed that it works in cases where we already have some knowledge, and on idiotic premises as to whether Caesar wrote the Bond stories.

It just doesn't work when you can't assign a probability. I'm enjoying watching you come up with ever more-unlikely hypotheses to prove your point though. (Tip: instead of asking whether Julius Caesar wrote Bond, ask whether he wrote an ode to Romulus three weeks before his murder.)

Just carry on - it's not a subject I'm bothered enough about to argue the toss with you on. It seems most people can see the flaws even if you can't.

[Nick Capozzoli]

This "Absence of Evidence is Evidence of Absence" thread makes me think of a joke I heard many years ago. It goes like this:

"An archeologist, who happened to be an avid amateur radio hobbyist, had spent years exploring archeological sites in Peru. He noted that after years of excavations in the Andes, he had never found any sort of metallic wire, such as the type used in wired telegraphy. He concluded that this proved that the ancient Andean societies he was studying must have had "wireless" communications."::eek6:

[MorpheusSandman]

It just doesn't work when you can't assign a probability.Of course it does! This is just an absurdly wrong statement. Yudkowsky uses the example of the possible existence of the Fifth Column during WW2. You can't "assign a probability" to the Fifth Column's possible existence, but you can certainly say that the absence of evidence it exists is evidence of its absence. What you're saying is as silly as saying that if we don't know the numbers involved, we can't know that in adding integers besides zero the sum will always be more than either integer. Of course that's nonsense as well. Just like we can know that adding positive integers will lead to a sum more than either integer without knowing the numbers involved, we can know absence of evidence is evidence of absence because of Bayes' even if we don't know the probabilities.

The only probabilities we need to know to prove the statement are given in the phrase itself: "absence of evidence" means that the probability of B|A (where A is something's "absence," | is "Given," and B is "absence of evidence") is always 100%, while B (absence of evidence even if A exists) is less than 100%. Since B|A is 100% and B is not, the probability of A's ABSENCE WILL ALWAYS INCREASE. If A always increases, then the "absence of evidence" is always "evidence of absence." That deserves repeating: whatever the probability of A's non-existence, any absence of evidence necessarily increases the probability of A's non-existence.

The only FAIR criticism to be made is that we don't (often can't) know precisely how much it increases the probability of A's non-existence, but it must be more than 0, and if it's more than 0, the original phrase is demonstrably wrong.


It seems most people can see the flaws even if you can't. I'm not convinced anyone here actually understands either the phrase or the math. I dare you to explain the math on your own and how it shows my argument is flawed. I've presented my argument in pure mathematical terms, a proof; for you to say it's flawed or not a proof, you need to present your own. Right now all you're doing is blowing hot air.

[MorpheusSandman]

This "Absence of Evidence is Evidence of Absence" thread makes me think of a joke I heard many years ago. It goes like this:

"An archeologist, who happened to be an avid amateur radio hobbyist, had spent years exploring archeological sites in Peru. He noted that after years of excavations in the Andes, he had never found any sort of metallic wire, such as the type used in wired telegraphy. He concluded that this proved that the ancient Andean societies he was studying must have had "wireless" communications."::eek6::lol: At least it's better than concluding that the absence of evidence for Andean wired telegraphy isn't evidence for the absence of Andean wired telegraphy!

[MorpheusSandman]

Of course, my postulation is rather dependent on the nature of belief. If one believes the crashing of an airliner is evidence for the existence of ET, then as you say, it's rather weak evidence.It's not even weak evidence, it's no evidence at all. The problem there is one of fake causality (http://lesswrong.com/lw/is/fake_causality/), like using "phlogiston" to explain "fire." It demonstrates the problem of beliefs that don't depend upon anticipated experience, but rather uses any experience as evidence for said beliefs. Any proper belief should both anticipate and constrain experience, so that, hypothetically, some events would increase the likelihood of the belief while others would decrease the likelihood of the belief.


Likewise, that absence of evidence is not evidence of absence when applied to black holes would be ample proof of the statement...Not quite sure what you mean here as there IS evidence for black holes. EG, when gas reaches millions of degrees it glows in a way that can be detected by X-ray scopes, and looking through such scopes one can see such lights "spiraling" towards a center before it disappears. Hard to explain how that observation would be possible without the existence of black holes.

[Hawkman]

It's not even weak evidence, it's no evidence at all. The problem there is one of fake causality (http://lesswrong.com/lw/is/fake_causality/), like using "phlogiston" to explain "fire." It demonstrates the problem of beliefs that don't depend upon anticipated experience, but rather uses any experience as evidence for said beliefs. Any proper belief should both anticipate and constrain experience, so that, hypothetically, some events would increase the likelihood of the belief while others would decrease the likelihood of the belief.

Well I did say it was dependent on belief.


Not quite sure what you mean here as there IS evidence for black holes. EG, when gas reaches millions of degrees it glows in a way that can be detected by X-ray scopes, and looking through such scopes one can see such lights "spiraling" towards a center before it disappears. Hard to explain how that observation would be possible without the existence of black holes.

Tish Tish and pshaw! Taking a line out of context and building an argument around it is no argument and is the first step on the road to sophistry ;) If you have no evidence then you have an absence of evidence, regardless of whether the evidence exists or not. This was the point I was making, unless of course you subscribe to the position that black holes did not exist until we had the capacity to predict their existence, etc.... It is obviously necessary to define what one means by 'absence'. I use it in the sense of 'not present' in that one does not have it. This does not mean that it does not exist somewhere else or that it cannot be found at some time in the future. Ergo, simply put, an absence of evidence is not evidence of absence. It is, as you say, 'no evidence at all.'

[MorpheusSandman]

Well I did say it was dependent on belief.Real evidence doesn't just depend on belief, it depends on how belief anticipates and constrains experience. If a belief can claim anything that happens (after it happens) as evidence for itself, then nothing is really evidence "for it" because there can't be any evidence "against it."


If you have no evidence then you have an absence of evidence, regardless of whether the evidence exists or not. This was the point I was making, unless of course you subscribe to the position that black holes did not exist until we had the capacity to predict their existence, etc.... It is obviously necessary to define what one means by 'absence'. I use it in the sense of 'not present' in that one does not have it. This does not mean that it does not exist somewhere else or that it cannot be found at some time in the future. Ergo, simply put, an absence of evidence is not evidence of absence. It is, as you say, 'no evidence at all.'Me saying that the crash of a plain isn't evidence for the existence of aliens is completely different than me saying "absence of evidence is evidence for absence." These are two different things: one is about what is and isn't evidence IN GENERAL and the other (absence of evidence is...) assumes we already know what evidence is and that there isn't any.

Where you're going wrong with black holes is in thinking in terms of hindsight bias: "black holes always existed even before we knew they did, so the absence of evidence for black holes before we knew they existed wasn't evidence they didn't exist." This is just plain wrong. We can't know before we find the evidence of something's existence whether or not the something exists, but we do know two things:

1. If the thing doesn't exist the probability of there being a continuing absence of evidence is 100%
2. If the thing exists the probability of there being a continuing absence of evidence is less than 100%

Because of this, a continuing absence of evidence IS evidence that something doesn't exist. Why? Because we'd EXPECT an absence of evidence for something that doesn't exist MORE than we'd expect an absence of evidence for something that exists. The only way for this NOT to be the case is if 2. was also 100%. But 2. CAN'T BE 100% EVER! To suppose that 2. could be 100% is to assume that everything we know exists leaves no evidence of its existence; which is absurd and obviously wrong.

The fact that we found evidence for black holes supports the notion that "absence of evidence is evidence for absence," because the reverse is also true: "existence of evidence is evidence for existence." With black holes, we now have "evidence for existence," not an "absence of evidence."

I think this thread is just another example of how counter-intuitive probabilities are to people, like the Monty Hall Problem (http://en.wikipedia.org/wiki/Monty_Hall_problem) that continues to confuse everyone who hasn't studied probabilities.

[Hawkman]

It seems to me your model of the universe is one of perpetual existence, static,unchanging. See your points 1 & 2. Take the case of the encylopedigazumper. The encylopedigazumper does not exist. Why? Because I haven't built it yet. Ergo there is no evidence for its existence. At least until this moment where the concept of an encylopedigazumper has been postulated, even though I have declared that it does not yet exist. Therefore the potential for it has increased from zero to more than zero. If I actually build it, then it will exist and therefore your point 1 will be unsustainable. It is therefore a false premise. An equation built on a false premise is therefore itself a false premise.

[Hawkman]

"An archeologist, who happened to be an avid amateur radio hobbyist, had spent years exploring archeological sites in Peru. He noted that after years of excavations in the Andes, he had never found any sort of metallic wire, such as the type used in wired telegraphy. He concluded that this proved that the ancient Andean societies he was studying must have had "wireless" communications."::eek6:

Well it's quite true, they did have wireless communications. Communication was by runner with a piece of knotted string or a cleft stick :D

[MorpheusSandman]

It seems to me your model of the universe is one of perpetual existence, static,unchanging. See your points 1 & 2.No.


Take the case of the encylopedigazumper. The encylopedigazumper does not exist. Why? Because I haven't built it yet. Ergo there is no evidence for its existence. At least until this moment where the concept of an encylopedigazumper has been postulated, even though I have declared that it does not yet exist. Therefore the potential for it has increased from zero to more than zero. If I actually build it, then it will exist and therefore your point 1 will be unsustainable. It is therefore a false premise. An equation built on a false premise is therefore itself a false premise.This is just silly: something that doesn't exist but that we have the power to create, like your encylopedigazumper, is quite different than things that may or may not already exist, like Black Holes or God or a book written by Caesar or undiscovered species of frogs in a rain forest, that we can't create; the latter is what's meant by the "absence." I mean, it's apparent in the premise since the phrase deals with the things for which we don't know whether or not they exist; you know your encylopedigazumper doesn't exist so 1. isn't even applicable in that situation. 1. only applies for things in which we DON'T know if they exist.

That said, we can modify the phrase to fit your encylopedigazumper in this way: let's say we don't know if it's possible to create a encylopedigazumper. If it's NOT possible, then we'd to always have no evidence of its existence (ie, it not being created). Yet, if it's possible to create a encylopedigazumper then there is some probability more than 0% for there being evidence of its existence in the form of its invention. The longer you try to invent a encylopedigazumper without success, the more likely it is that it can't be invented, as you'd expect continued failure if it was impossible to create the thing. So Bayes can be applied as much to your encylopedigazumper, to things that may or may not be possible to create, as to things that may or may not already exist.

Here's a better example. You have a coin that may or may not have a tails side. You are not allowed to look at both sides. The coin is always placed on your thumb to flip heads-side up. After 2 flips of heads, is this absence of evidence for a tails-side evidence of the tail sides' absence? What about after 5 straight heads? 10? 100? The answer is fairly obvious, but it feeds directly into the phrase: if the coin has a tails side, we expect to see no evidence for it, the coin coming up heads, only SOME of the time; if the coin DOESN'T have a tails side, if it is "absent," then we expect to see not-tails ALL of the time. The continuing absence of evidence is evidence for the tail-side's absence.

Now, The Atheist would object to the above by saying "but with the coin you KNOW the probabilities precisely, so of course the 'absence of evidence is evidence for absence.'" but The Atheist is wrong because you can phrase the issue this way: you have 5 dice in your hand with an unknown number of sides. These dice may or may not have the number 6 on them. They are not loaded. Even without knowing how many sides there are on the dice, if you continue rolling them, the absence of 6 becomes more likely with each roll where no 6 appears. Even if we say we don't know HOW MUCH more likely the absence of 6 becomes with each roll, the probability of its non-existence must increase by more than 0. The only ways in which it wouldn't increase by more than 0 was if:

1. The number of sides on the dice were infinite (impossible)
2. The dice had a 6 which couldn't be rolled (impossible if the dice aren't loaded, which they aren't).

[Emil Miller]

The only case Rummy missed was the one about those unknowns that we know.

You haven't been paying attention to what Rummy was saying. He distinctly mentions known unknowns just before he refers to unknown unknowns. Now if he had said there are known unknowns that we know are known or unknown knowns that we don't know are unknown that would have answered all queries relating to the problem; except for those unknown unknowns that we don't know are known.

[MorpheusSandman]

The only case Rummy missed was the one about those unknowns that we know.He actually mentioned that (as Emil said). Zizek suggested one Rummy missed though, the unknown known: "If Rumsfeld thinks that the main dangers in the confrontation with Iraq were the "unknown unknowns", that is, the threats from Saddam whose nature we cannot even suspect, then the Abu Ghraib scandal shows that the main dangers lie in the "unknown knowns" – the disavowed beliefs, suppositions and obscene practices we pretend not to know about, even though they form the background of our public values."

[MorpheusSandman]

Sorry, double post (moderator can delete).

[YesNo]

You haven't been paying attention to what Rummy was saying. He distinctly mentions known unknowns just before he refers to unknown unknowns. Now if he had said there are known unknowns that we know are known or unknown knowns that we don't know are unknown that would have answered all queries relating to the problem; except for those unknown unknowns that we don't know are known.

Thanks for setting me straight, Emil Miller and MorpheusSandman.

Actually, Rummy doesn't make any more sense to me today than he did a decade ago, but that could be related to my pigheaded inability to see WMDs where there weren't any.

[Emil Miller]

Thanks for setting me straight, Emil Miller and MorpheusSandman.

Actually, Rummy doesn't make any more sense to me today than he did a decade ago, but that could be related to my pigheaded inability to see WMDs where there weren't any.

Well, you know what they say: Absence of evidence isn't evidence of absence. Or in the case of WMDs, really was evidence of absence.

[Delta40]

So Morph is this a valid argument for the existence of god?

[MorpheusSandman]

So Morph is this a valid argument for the existence of god?If absence of evidence is evidence of absence then it's a valid argument AGAINST the existence of God, since there's no (valid) evidence for his/its existence. The opposite phrase, EOA IS NOT AOE is usually used by believers to argue that the AOE for their God isn't evidence of his/its absence.

[Delta40]

Thank god for that!

[MorpheusSandman]

Thank God I'm an atheist. -- Luis Bunuel

[YesNo]

1. If the thing doesn't exist the probability of there being a continuing absence of evidence is 100%
2. If the thing exists the probability of there being a continuing absence of evidence is less than 100%


(1) is incorrect. That is what I thought the WMDs in Iraq illustrated (or the existence of nonexistent clothes on the Emperor). We have a history of finding evidence for the existence of stuff that doesn't exist if we want to bad enough. So (1) should be less than 100% for some nonexistence stuff.

(2) is even incorrect. The existence of specific creatures in other universes (coming from other big bangs which I assume happened since our big bang happened) is something we will never know at least by currently acceptable means. So there exist things for which we will never have evidence of their existence and (2) will stay at 100% for them.

[Ecurb]

Good points, YesNo. In my previous Sasquatch example there is an absence of certain kinds of evidence (which is sufficient to persuade me that there are no Sasquatches), but there is plenty of evidence supporting the notion that Sasquatches exist. If we think of facts about the past (to return to the Julius Caesar example) there are a great many things that happened in the past for which no evidence exists, or ever will exist. What did Joe Blow have for dinner on May 19, 1211? In this case, the absence of evidence does not persuade me that Joe went hungry, because we would not expect to have any evidence about such a trivial fact.

So although absence of evidence CAN BE evidence of absence, it is not NECESSARILY evidence of absence. I suppose morpheus could argue that there is a infinitesimal possiblity that we might some day discover what Joe Blow (or some individual T-rex 100 million years ago) had for dinner in the distant past, if he ate dinner, so the absence of evidence constitutes infinitely weak evidence for fasting. But this seems like a distinction without a difference.

[Paulclem]

I reckon this thread should be called "The Emperor's New Absence".

[YesNo]

Taking the example of what Joe Blow had for dinner in 1211 is better than my other universe example, Ecurb. Unless we invent a time machine (which I highly doubt), we shouldn't be able to find this out.

I was thinking about Sasquatch when you mentioned him or her earlier in this thread. It all depends on how one defines "Sasquatch" as to whether examples exist or not. For example, Wikipedia says (http://en.wikipedia.org/wiki/Sasquatch) Bigfoot is "large, hairy, bipedal humanoid". Well, a human is a humanoid by default and most of us are bipedal. Some of us are hairier than others and some of us can get quite large. So maybe Sasquatch is a subset of the human species who likes to walk through the woods and is larger than most of us get.

[Nick Capozzoli]

Well it's quite true, they did have wireless communications. Communication was by runner with a piece of knotted string or a cleft stick :D

And that was part of the point I was trying to make with the joke... "Wireless" communication is a broad term, but we take it to mean "radio" communication, though of course that would include every other form of communication that doesn't involve sending and receiving electrical signals over conductive wires.... The joke was a bit off topic, but not entirely... To be on-topic, the archeologist should not conclude that the absence of found wires indicates anything more than that the ancient Peruvians (probably) did not use electrical wires. It was just a joke meant to illustrate sloppy reasoning. In fact, the archeologist would have more logically concluded that the lack of evidence for wires indicated that the ancient Peruvians had no electrical technology whatsoever, let alone radio technology. Would it still be possible that they did have some electrical technology? Perhaps, though the burden of proof would be on the one making that assertion.

[MorpheusSandman]

(1) is incorrect. That is what I thought the WMDs in Iraq illustrated (or the existence of nonexistent clothes on the Emperor). We have a history of finding evidence for the existence of stuff that doesn't exist if we want to bad enough. So (1) should be less than 100% for some nonexistence stuff.

(2) is even incorrect. The existence of specific creatures in other universes (coming from other big bangs which I assume happened since our big bang happened) is something we will never know at least by currently acceptable means. So there exist things for which we will never have evidence of their existence and (2) will stay at 100% for them.(1) Incorrect. What you're talking about gets into the nature of "what is evidence?" rather than if evidence exists for non-existing things. It's true that certain information can LOOK like evidence for non-existing things, but because these things are non-existent, it's our interpretation of the information that's at fault, because it's not really evidence for the thing we think it is. That's why it's important to have a good grasp/understanding of what evidence is before one starts talking about whether such-and-such piece of evidence is evidence at all. To go back to Ecurb's Sasquatch example, one hidden assumption behind the "absence of evidence" phrase is that people aren't faking evidence to begin with, and when it comes to things like Sasquatch, that's not necessarily true. This relates to one Yudkowsky article that nicely summarizes this by saying "we'd expect UFO cults whether UFOs existed or not, so the existence of UFO cults are not evidence UFOs exist." Same with Sasquatch footprints; we expect them because we know certain people believe they exist and want to convince others.

(2) Incorrect again, because you're making multiple assumptions that you can not be 100% sure of:

a) other universes exist
b) other creatures exist in these universes
c) we will never have any evidence about the nature of these other universes

So even when you consider the probabilities of these three things you can't set 2. at 100%, because then you'd just be assuming things you have no reason to assume. But, even if I was to grant your assumption, I think it's safe to say that we're most always only concerned about things that exist within our universe OR things that may exist outside our universe but affect our universe in some way or another. In both cases there would be evidence of their existence.

[MorpheusSandman]

So although absence of evidence CAN BE evidence of absence, it is not NECESSARILY evidence of absence. I suppose morpheus could argue that there is a infinitesimal possiblity that we might some day discover what Joe Blow had for dinner in the distant past...
Taking the example of what Joe Blow had for dinner in 1211 is better than my other universe example, Ecurb. Unless we invent a time machine (which I highly doubt), we shouldn't be able to find this out. Now you guys are having the same difficulty Hawkman had in coming up with examples that aren't even relevant to the phrase itself. "Evidence of absence" means "evidence that something exists/existed," not "evidence that someone once ate something" or "evidence that someone will eat something" or (to use Hawkman's example) "evidence that something can be invented that doesn't currently exist." You guys need to think about examples of things that exist NOW or DID for which there COULD be evidence for. Obviously people eat and the "evidence" of what they eat gets digested and disappears; obviously we can't have evidence NOW for what someone will eat; obviously there would be no evidence now for what someone might invent in the future; all of these things have nothing to do with the phrase itself or what it pertains to. My dice example, or coin example, or book example, et al. pertains to things that potentially exist now and would potentially leave evidence for itself existing.

Just as I said in my last post that one hidden assumption in the phrase is that people aren't faking the evidence, another assumption is that there would/could be some kind of evidence for the thing that exists/existed. Instead of what someone ate 30 years ago, consider, instead something like a global flood, a myth present in many cultures in texts; if such a thing happened, we'd expect certain Geological evidence for it; yet, not only is there no evidence for such a flood, there is evidence of erosion at varying rates in different parts of the world, which is what you WOULDN'T expect if such a catastrophic event happened on a global scale. That's a legitimate example from something in the past because it's something that we would expect to leave evidence were it true. Things people ate or might eat or things we can invent don't leave evidence for itself now, so the phrase is rather irrelevant.

I guess it's my fault for not clarifying this in the OP, but I thought these assumptions were rather implicit. So, for full disclosure, here are the relevant details:

1. Something potentially exists now, or existed/happened in the past.
2. Something that would/could leave evidence for itself

Any talk of "future" events/things is not relevant, nor are things that we know leave no evidence for their existence, like what Joe Blow ate 30 years ago.

[The Atheist]

My dice example, or coin example, or book example, et al. pertains to things that potentially exist now and would potentially leave evidence for itself existing.

You're getting there. That is another admission that the hypothesis only works with concrete examples where there is already knowledge. It is therefore an almost-useless axiom.

You show that again here:


I guess it's my fault for not clarifying this in the OP, but I thought these assumptions were rather implicit. So, for full disclosure, here are the relevant details:

1. Something potentially exists now, or existed/happened in the past.
2. Something that would/could leave evidence for itself

Any talk of "future" events/things is not relevant, nor are things that we know leave no evidence for their existence,...

Nice moving of the goalposts. If you'd said that at the start, I probably would have agreed with you.

[MorpheusSandman]

You're getting there. That is another admission that the hypothesis only works with concrete examples where there is already knowledge.As opposed to abstract examples where there is no knowledge? Such as?


It is therefore an almost-useless axiom.Well, there's two different axioms being discussed: one insists AOE IS EOA, and the other insists that AOE IS NOT EOA. The former is a useful axiom in that it aligns itself with Bayes' Theorem and can teach people how to think in terms of expectations given their beliefs or hypotheses; the latter is useless in that the only things it pertains to are things we don't fuss about to begin with.

Elaborating further:


Nice moving of the goalposts. If you'd said that at the start, I probably would have agreed with you.It's not INTENTIONALLY moving the goalposts. If you want to blame me for not stating those things explicitly, then fine, I'm guilty as charged; but I figured that those elements were already implicit in the phrase since it would patently obvious that for things we KNOW leave no evidence the absence of evidence wouldn't matter one way or another. Yet, I've never heard anyone use the phrase as it pertains to things for which we KNOW leave no evidence, like what Joe Blow ate 30 years ago. Rather, the phrase is always used pertaining to things for which we would EXPECT there to be evidence for (or, at least, potential evidence) if they existed; then, after finding no evidence, instead of people admitting that such absence of evidence is evidence of the thing's absence, they insist that it's not.

[YesNo]

(1) Incorrect. What you're talking about gets into the nature of "what is evidence?" rather than if evidence exists for non-existing things. It's true that certain information can LOOK like evidence for non-existing things, but because these things are non-existent, it's our interpretation of the information that's at fault, because it's not really evidence for the thing we think it is. That's why it's important to have a good grasp/understanding of what evidence is before one starts talking about whether such-and-such piece of evidence is evidence at all.

As I recall, the evidence for the existence of WMDs was satellite images. That seems like valid evidence for the existence of WMDs, however, when confronted with on the ground inspections that satellite evidence should have been dismissed.

In general, I don't think it makes sense to use something like "absence of evidence is (or is not) evidence of absence" too strictly. If you do, you should reject many worlds since there is no evidence for it. All this phrase is is a reminder that we could get things wrong if we don't have adequate evidence.

I do think it is useful to use Bayesian analysis where appropriate, but I don't think it is very useful if we can't determine those probabilities with much confidence.

[MorpheusSandman]

As I recall, the evidence for the existence of WMDs was satellite images.It's been too long and my memory is too fuzzy to get into too deep of a debate, but, IIRC, most all experts at the time said that the satellite photos were not even decent evidence that there were WMDs in Iraq because there were simply far too many other possible explanations behind what the images were. This is in contrast with, eg, the data that was built-up/developed about Bin Ladin's whereabouts when Seal Team 6 went in; even then, the experts could only say it was maybe a 66/33 chance he was there, which was far higher than the likelihood of those images being evidence of WMDs.


If you do, you should reject many worlds since there is no evidence for it.You mean there's no evidence for Copenhagen, since it's the interp making extra assumptions present nowhere in the math. MW is just taking the math at face value, so the math IS the evidence for MW.


I do think it is useful to use Bayesian analysis where appropriate, but I don't think it is very useful if we can't determine those probabilities with much confidence.Really, the essence of Bayes is how to properly reason. We have beliefs, we experience new evidence; how should this new evidence effect our beliefs? Bayes gives us a formula for how evidence affects beliefs. Yet we all believe things for which we can't determine the probabilities of our confidence level, and we all experience new evidence with which we can't influence our confidence levels; so, what is one to do? You might as well apply what you've said to reasoning, in general, because if we can't determine such probabilities with confidence to our beliefs or evidence, we can't really reason at all except in extremely nebulous ways.

I think Bayes can be used practically. As I've repeated many times, I use it in my profession of poker. I don't have EXACT probabilities of how often players make plays with certain hands. Yet, I can always remind myself that the question "given they just did this, what is the probability they have that?" is best answered with two others: "given they have that, what is the probability they would've done this; and given that they don't have that, what is the probability they would've done this." Online, most sites give you 30 seconds for each decision, so you can't do high level math in your head; you basically just have to learn how to intuitively ask these questions and come to rough answers based on very rough data. Yet... it works. Despite the inevitable inaccuracies due to my limited human brain, Bayes can work even without being able to determine probabilities with a high level of confidence. It's much better than nothing at all.

[Ecurb]

There’s really no difference between “someone ate something” and “something existed in the past”. It seems that one is a statement about an activity, and the other is a statement about the existence of something, but someone ate something could (obviously) be translated into a statement about existence (“Joe Blow’s stomach contained partially digested food at 12:00 noon on May 12, 1211.”)

In any event, I think we are in basic agreement that an absence of the evidence that one would suspect could be found if something existed constitutes evidence of its absence. Medical studies, for example, involve falsifying the “null hypothesis” (the notion that a drug has the same effect as a placebo). The null hypothesis is equivalent to the notion that something (Sasquatches, for example) does not exist. It can be falsified by certain kinds of evidence, but not by others (because of the problems previously outlined).

The further question of what constitutes “evidence” is a touchy one. If we find Joe Blow’s fingerprints on the murder weapon, that has evidentiary value – although it hardly proves that Joe is the murderer. There could be any number of reasons his fingerprints are on the blunt object.

The same is true for “evidence” about Sasquatch (or about God, for that matter). We need not claim that the eye witness reports, the footprints and the photographs have no evidentiary value to find them unpersuasive. To return to the notion of probability – it is, in my opinion, highly unlikely that any giant, hairy, non-human hominids roam the Pacific Northwest. However, given the evidence that they do, it’s MORE likely that Sasquatches roam Oregon than that giant bipedal crocodiles wearing top-hats and spats roam Oregon. That’s because we DO have evidence (albeit unpersuasive) for one, but not for the other. Similarly, it’s more likely that Lazarus rose from the dead than that Joe Blow did (although I find both highly, highly unlikely).

[Emil Miller]

... it’s MORE likely that Sasquatches roam Oregon than that giant bipedal crocodiles wearing top-hats and spats roam Oregon. That’s because we DO have evidence (albeit unpersuasive) for one, but not for the other. Similarly, it’s more likely that Lazarus rose from the dead than that Joe Blow did (although I find both highly, highly unlikely).

The American crocodile is a declining species that is only found on mainland USA in small numbers in the south of Florida. While it might be reasonable to assume that they are not bipedal or wear top-hats and spats, absence of evidence isn't evidence of absence.

[Nick Capozzoli]

This "Absence of Evidence is Evidence of Absence" thread makes me think of a joke I heard many years ago. It goes like this:

"An archeologist, who happened to be an avid amateur radio hobbyist, had spent years exploring archeological sites in Peru. He noted that after years of excavations in the Andes, he had never found any sort of metallic wire, such as the type used in wired telegraphy. He concluded that this proved that the ancient Andean societies he was studying must have had "wireless" communications."::eek6:

This was actually a two-part joke, and I omitted the first half. For completeness, here's the whole joke:

An archeologist published a report of his many-years excavation of ancient Egyptian burial sites, in which he found artifacts made of copper wire. He concluded that this meant that the ancient Egyptians understood electricity and used it to "communicate" over wires, as in telegraphy or telephonic communication.

Another archeologist, who had conducted "digs" in ancient Andean sites noted that he had never found any sort of metallic wire, such as the type used in wired telegraphy. He concluded that this proved that the ancient Andean societies he was studying must have had "wireless" communications."

[YesNo]

You mean there's no evidence for Copenhagen, since it's the interp making extra assumptions present nowhere in the math. MW is just taking the math at face value, so the math IS the evidence for MW.


Which is more likely the existence of Sasquatch or the existence of Many Worlds?

[AuntShecky]

The further question of what constitutes “evidence” is a touchy one. The same is true for “evidence” about Sasquatch (or about God, for that matter).

I'll say! Let me give you some examples from the animal kingdom. We live in an area that is partly suburban, partly wildly rural. Couple of years ago my bitter half and yours fooly spotted a mountain lion in a field adjacent to a supermarket parking lot. When we got home, we checked the Internet, only to be informed that no mountain lions exist in the area of the U.S. where we live. But the feline we saw could have posed for the photos on the Web; that's how strong the resemblance was.

Similarly, this morning about 4:30 am, when I looked out the window onto the brightly-lit front lawn I saw a creature I'd never seen before. It was extremely fat, between 2 and 3 feet long, and covered from snout to tail with gray fur, with a few black and white markings. It didn't look at all like a skunk or a ferret or anything other than a badger. I went online to look up "badgers" and the photos depicting that mammal looked exactly like the creature I'd seen early this morning, but various websites insist that badgers are found in the Mid- and far-west of the U.S., and not in my state.

On both occasions, I didn't have a camera. Both times, I was completely sober.

Well, I know what I saw. As far as I'm concerned, that's "evidence" that both mountain lions and badgers can be found this far east. To quote the Marx Brothers --"Who are you gonna believe --me or your lying eyes?" The state wildlife department wouldn't even let me email them!

In the end, people are only going to believe what they want to believe. (But I still know what I saw.)

[Hawkman]

I recommend always carrying a camera and bottle of booze :D

[MorpheusSandman]

Which is more likely the existence of Sasquatch or the existence of Many Worlds?They aren't really comparable; the idea that there are these giant harry ape-like things roaming the forests of certain parts of the US that nobody has been able to capture either alive or dead is just preposterous; on the other hand, like I say, MW is what you get when you take the math that models QM as real and add nothing else. MW doesn't "exist" in our world except in the QM mathematical models, so it's hardly similar to a possibly living being.

[Ecurb]

ICouple of years ago my bitter half and yours fooly spotted a mountain lion in a field adjacent to a supermarket parking lot.... .)

Where do you live? Cougar sightings are becoming more common east of the Mississippi. Cougars have always lived in Florida (The Florida Panther). I've heard about well-confirmed cougar sightings in Illinois, Georgia, and some other states (I can't remember which, but some cougars have been captured or killed in these states). However, there are no sustainable populations of cougars in the East; the cougars that have been killed or captured are all young males, driven out of their birth-lands and roaming after food. Cougars are famous for traveling as much as 30-50 miles in a day, prowling for food. Increased deer populations in urban areas have led to more cougars in towns.

Here in Eugene, cougars killed two goats and several chickens within the last two weeks, right in town. Two cougars (a mother and her year-old cub) were trapped and killed (the local newspaper reported that the cougars had been "euthanized", but it seems to me they were simply killed). In any event, if a lone, young male cougar is prowling about in Eastern states that does not mean cougar populations have returned to the area -- breeding pairs have NOT been found east of the Mississippi. (How the cougars cross the Mississippi is another question, for which I do not have the answer.)

[YesNo]

They aren't really comparable; the idea that there are these giant harry ape-like things roaming the forests of certain parts of the US that nobody has been able to capture either alive or dead is just preposterous; on the other hand, like I say, MW is what you get when you take the math that models QM as real and add nothing else. MW doesn't "exist" in our world except in the QM mathematical models, so it's hardly similar to a possibly living being.

All I was comparing was their likelihood, not Sasquatch and Many Worlds. What do you say P(S), the probability of Sasquatch is? What is P(MW), the probability of Many Worlds. Those numbers are comparable. My view is the following: P(S) > 0; P(MW) = 0. Unlike Sasquatch there really is no evidence for MW.

As we've argued in the past, my position is when "you take the math that models QM as real and add nothing else" you no longer get an interpretation of QM. What you get is an interpretation of a deterministic fantasy land that might have made some minor sense in the 19th century, but is obsolete today. So the "math" is not evidence that I would accept any more than you would accept the sightings of Sasquatch.

[Gilliatt Gurgle]

....I saw a creature I'd never seen before. It was extremely fat, between 2 and 3 feet long, and covered from snout to tail with gray fur, with a few black and white markings...I went online to look up "badgers" and the photos depicting that mammal looked exactly like the creature I'd seen early this morning, but various websites insist that badgers are found in the Mid- and far-west of the U.S., and not in my state.

On both occasions, I didn't have a camera. Both times, I was completely sober...

Aunty, that sounds very much like the notorious Badgecabra the result of cross breeding gone bad between a Badger and Chupacabra. http://en.wikipedia.org/wiki/Chupacabra

Around these parts, its the wood ape aka Big Foot that I keep an eye out for.
Absence of evidence=I just haven't run across it yet. Evidence of absence= he just ain't passed through my creek yet
but when he does I'll be ready for him with my Sasquatch Field Guide signed by Dr. Jeff Meldrum-something I picked up at the 2013 Texas Bigfoot Convention.

http://i963.photobucket.com/albums/ae114/tabuka1/Texas%20BFCon%202013/IMGP2980_zps940c5bb1.jpg (http://s963.photobucket.com/user/tabuka1/media/Texas%20BFCon%202013/IMGP2980_zps940c5bb1.jpg.html)

[Calidore]

Where do you live? Cougar sightings are becoming more common east of the Mississippi. Cougars have always lived in Florida (The Florida Panther). I've heard about well-confirmed cougar sightings in Illinois, Georgia, and some other states (I can't remember which, but some cougars have been captured or killed in these states).

Just a few years ago, police killed a cougar here on the North Side of Chicago in the Roscoe Village neighborhood. That's an upper-middle class yuppie neighborhood well inside the city and nowhere near any forest preserves or anything. The location the cougar was killed was about a mile from Wrigley Field, less than half a mile from Lane Tech High School, and just a block away from a grade school.

Sightings are reported occasionally in the northern suburbs, but having one appear in the city itself, especially a heavily populated neighborhood soon after evening rush, was pretty startling.

[MorpheusSandman]

What do you say P(S), the probability of Sasquatch is? What is P(MW), the probability of Many Worlds. Those numbers are comparable. I'd say P(S) is less than 1% (I don't give anything a 0%), while P(MW) is true is 90% or so.


Unlike Sasquatch there really is no evidence for MW.The math is the evidence. The fact that every test has yet to find any split between the quantum and macro world is the evidence. Occam's Razor is the evidence. Every empirical test we have points towards MW and not anything else.


my position is when "you take the math that models QM as real and add nothing else" you no longer get an interpretation of QM. You can vehemently disagree with MW all you want, but to call it "not an interpretation" is just egregiously ignorant and does nothing but show your bias. I think Copenhagen is equally stupid and wrong, but I don't call it "not an interpretation" because it is. You don't get to redefine scientific terms to fit your tastes.

Also, you have no rational reason for rejecting the math of QM or for stating that it's unreal except your deification of our sense-experience, which has proven so fallible and limited over the course of centuries I have no idea why you'd feel it's more reliable than a mathematical model that has withstood every test science has thrown at it for almost 100 years now. MW explains both the objective determinism of Shrodinger and the subjective indeterminism of Heisenberg; you have presented absolutely no substantial logical (much less mathematical or scientific) arguments against either of these.

[YesNo]

I'd say P(S) is less than 1% (I don't give anything a 0%), while P(MW) is true is 90% or so.


How are we going to argue using probabilities if our assessment of the probability of something existing is so different? You say P(MW) = 90 and I say P(MW) = 0.

Don't worry. I don't want to change your mind.

My problem with Sasquatch, on the other hand, is cultural. When I think of him (or her--I suppose there should be a female version), I think of a humanoid with three characteristics: (1) big, (2) hairy, and (3) nonexistent.

So, if I should happen to see Hagrid coming out of his cottage behind Hogwarts, I wouldn't call him Sasquatch because he exists. In the same way, when I see Uncle Fred on his monthly trip back to town for supplies, I wouldn't (dare) call him Sasquatch because he exists. Culturally built into the very definition of Sasquatch for many people (and I'm trying not to be one of them) is his nonexistence. No wonder they don't go looking for him.

That's why I put P(S) > 0.

[The Atheist]

My problem with Sasquatch, on the other hand, is cultural. When I think of him (or her--I suppose there should be a female version),...

There is definitely at least one female; pretty sure she's named Penny.

[MorpheusSandman]

How are we going to argue using probabilities if our assessment of the probability of something existing is so different?There's a famous Bayesian saying that true Bayesians cannot agree to disagree because any difference in their priors indicate a difference in knowledge that, if they both possessed the same knowledge, would not be different (their priors I mean). In our case, the difference is clearly in your desire to believe in indeterminism and choice, and how this bias has lead you repeatedly to misunderstand QM or what MW actually is; I have no such bias. My only desire is to believe the truth. If a scientific experiment came out tomorrow that proved Copenhagen right I would believe it instantly and drop MW. I only think MW is true based on the available evidence.


My problem with Sasquatch, on the other hand, is cultural. When I think of him (or her--I suppose there should be a female version), I think of a humanoid with three characteristics: (1) big, (2) hairy, and (3) nonexistent. Well, it's a bit silly to think of nonexistence as being a quality of thing. I mean, we DO discover new species rather frequently, and there are still parts of the Earth that are quite hard for us to access and study, so there's always the possibility that there's something out there that is LIKE a bigfoot we still haven't found. It's unlikely, given its size and how much myth has been built up around it (most of the strange creatures near the bottom of the ocean are stranger than any man-made fiction; see the Basking Shark (http://img1.wikia.nocookie.net/__cb20131116143359/twobestfriendsplay/images/1/1e/Basking-shark1.jpg) or Goblin Shark (http://d2tq98mqfjyz2l.cloudfront.net/image_cache/137136057092856.jpg)).

[MorpheusSandman]

There is definitely at least one female; pretty sure she's named Penny.https://www.youtube.com/watch?v=EJDeZIMoEUw

[YesNo]

https://www.youtube.com/watch?v=EJDeZIMoEUw

If that is the Penny one is likely to find when looking for Sasquatch, I don't see why more people aren't looking for her.

I plan on calling mine Betsy Bigfoot assuming I can find her and she doesn't feed me to the little Sasquatches.

[YesNo]

There's a famous Bayesian saying that true Bayesians cannot agree to disagree because any difference in their priors indicate a difference in knowledge that, if they both possessed the same knowledge, would not be different (their priors I mean). In our case, the difference is clearly in your desire to believe in indeterminism and choice, and how this bias has lead you repeatedly to misunderstand QM or what MW actually is; I have no such bias. My only desire is to believe the truth. If a scientific experiment came out tomorrow that proved Copenhagen right I would believe it instantly and drop MW. I only think MW is true based on the available evidence.


The scientific experiments that validate Copenhagen as an interpretation for QM are the various double slit experiments.

One problem with MW is that it removes the Born assumption and so it can't calculate the coefficients of the Schrodinger wave equation. That is not an asset for an interpretation but a liability. Because of that MW doesn't even reach the level of an interpretation for QM. In effect, it is false. That is why I have assessed P(MW) to be zero.

The Heisenberg principle requires "uncertainty" and this is a mathematical consequence of the Schrodinger wave function. This is in conflict with both "randomness" and "determinism". This is not to say that the Schrodinger equation itself is not deterministic. It is. But what does it determine? It determines a set of probabilities that an individual particle might have based on the group of particles. In this case the group of particles is primary, not the individual particle. Because MW can't see that and insists on preserving an obsolete billiard ball model of reality, its grasp on reality is weak. This is another reason for P(MW) = 0.

Bohm and Hiley brought up other unacknowledged assumptions related to Hilbert space that the various MW proponents make. From their perspective, MW loses the Occam Razor's argument on MW's own terms.

The only way one might bring determinism back into QM is to add assumptions, such as Bohm has done, not remove them. However, the cost of these added assumptions based on Bell's inequality is accepting non-locality.

EDIT:

To bring this back to the OP. I don't understand how anyone who believes in MW can also believe in the strict validity of the saying that "absence of evidence is evidence of absence". MW has no empirical evidence supporting it, nor even a rational foundation. Using that maxim as a guide is another way to see that P(MW) = 0.

[MorpheusSandman]

The scientific experiments that validate Copenhagen as an interpretation for QM are the various double slit experiments.Absolutely false. There is nothing in a double slit that confirms a collapse postulate. MW explains the double slit results better than CI.


One problem with MW is that it removes the Born assumption and so it can't calculate the coefficients of the Schrodinger wave equation. That is not an asset for an interpretation but a liability. Because of that MW doesn't even reach the level of an interpretation for QM.Yeah, I'm the one that pointed you toward this problem and admitted it as such. But as a problem it's no more severe (I'd say much less so) than those facing Copenhagen. However, it's ridiculously wrong to state that without Born MW doesn't count as an interpretation. I explained this in another thread that even theories being incomplete (like gravity or evolution) don't invalidate them. Being inconsistent, like CI, is worse than being incomplete, like MW).


The Heisenberg principle requires "uncertainty" and this is a mathematical consequence of the Schrodinger wave function. The HUP requires subjective/observer uncertainty, not objective uncertainty since, as you said, Shrodinger (SWE) itself is deterministic. Trying to say that SWE is deterministic of indeterminism is an oxymoron and is only reoncilible via MW. I have no idea what you mean by "set of probabilities... based on the group of particles." WHAT "group of particles?" The double slit experiments were done both with groups and individual particles with the same results.


Bohm and Hiley brought up other unacknowledged assumptions related to Hilbert space that the various MW proponents make. From their perspective, MW loses the Occam Razor's argument on MW's own terms. Well, you'd have to clarify what these assumptions are rather than just assert they exist.


MW has no empirical evidence supporting it, nor even a rational foundation.Yes it does. Every QM experiment done so far is evidence for MW since every one confirms that the math, which MW takes as real and sufficient in itself, is accurate, while none have supported any of the assumptions present in CI or anything else.

If you could ever get past all these falsities you insist on repeating, maybe you could see this issue with some clarity.

[MorpheusSandman]

If that is the Penny one is likely to find when looking for Sasquatch, I don't see why more people aren't looking for her. :lol: