How Many Blind Men Does It Take To Make An Eyewitness?

TheMadFool

@Samuel Lacrampe started this thread: Principle Of Universal Perception wherein the claim was that the a perception is more likely to be real rather than a hallucination if there are a good number of people reporting that perception. The argument, to my reckoning, employs the well-know Occam's Razor, asserting that a perception being real is much simpler than what the OP calls "collective hallucination", a state of affairs in which a group of people reporting a perception are all hallucinating together.

This belief - that more the people reporting a perception the more likely that that perception is real - is universally accepted (as true) and applied in all occasions that involve perception. In addition to simplicity then, this belief is also justified by the improbability of a perception that is reported by many to be something peculiar to an individual like a hallucination.

It seems then that the rule that more reportings of a particular perception makes that perception more likely to be real and not a hallucination is well-justified by the two reasons I provided above. We should regard as real those things perceived by many people.

That said, what is of concern is this:

1. An individual/one person's report doesn't count as a strong enough foundation to believe that what this person perceives is real. How is it then that a group of people's report of a perception is taken as adequate grounds for believing a given perception is real? After all the group consists of individuals. It's like saying that a group of blind individuals can see even though each and everyone in the group is blind.

2. Let's do a simple mathematical analysis of this principle/rule. Suppose there are 3 individuals X, Y, and Z. They can perceive but they're facing the same difficulty as us in not being able to tell whether what they perceive are hallucinations or are real. We could then say, recognizing our predicament, that the probability that the perceptions of X, Y, and Z being real/hallucinations is 50% = 1/2. To assign any different probability requires justification why, something we lack.

Suppose now that X perceives something, say, P. The probability that X is perceiving something real = 50% = 1/2. The probability that X is hallucinating = 50% = 1/2. If X were now to come to me and report P then I would conclude that P is either a hallucination (50% probability) or P is real (50% probability).

Imagine now that Y and Z inform me that they too perceive P. If that's the case then the probability of X hallucinating and Y hallucinating and Z hallucinating is (1/2)*(1/2)*(1/2) = 1/8 = 12.5% AND the probability of X perceiving something real and Y perceiving something real and Z perceiving something real is (1/2)*(1/2)*(1/2) = 1/8 = 12.5%. In other words, the probability of all three (X, Y, Z) hallucinating is exactly the same as the probability that all three (X, Y, Z) are perceiving something real. This directly contradicts the belief that there's a higher probability that a perception is real just because more people report it.

Comments...

unenlightened

A blind man lacks a common sense. But he presumably has all the other common senses.

TheMadFool

A blind man lacks a common sense. But he presumably has all the other common senses. — unenlightened

I'm particularly concerned about how, for example, when we perceive, let's say see, something odd, we look at our companion, if there's one, and ask, "did you see that?". The question bespeaks that we take the principle/rule, that more people reporting the same perception is a good indication that what's being perceived is real, seriously. But the principle, if I'm correct, is wrong.

unenlightened

Circumstances, dear boy.

Sometimes less is more. https://phys.org/news/2015-11-colour-blindness-aid-efforts.html

It's not a principle at all, but if something leads one to doubt one's senses, one looks for corroboration. I ask whether you saw that flying pig, because it is, as you say, odd. If it were normal, it would arouse no doubt and no comment, unless, 'Did you see that flying pig just now? I'd swear it was smoking a pipe!'

unenlightened

'Did you see that flying pig just now? I'd swear it was smoking a pipe!' — unenlightened

And you think you're the mad fool!

Frank Apisa

My guess is that there was a time when EVERYONE on Earth "perceived" that the sun, moon, and stars traversed the sky around the flat Earth below.

It is not an hallucination, but it is an illusion.

I can bring 10 people to a spot on a roadway during a hot summer day...and they will all "perceive" a reflective body of water way down the other end of the road.

It is not an hallucination, but it is an illusion.

How does that play into the calculation?

Outlander

↪TheMadFool

So what is the remaining 75%?

TheMadFool

It's not a principle at all, but if something leads one to doubt one's senses, one looks for corroboration. I ask whether you saw that flying pig, because it is, as you say, odd. If it were normal, it would arouse no doubt and no comment, unless, 'Did you see that flying pig just now? I'd swear it was smoking a pipe!' — unenlightened

Do you think a person should corroborate what he's perceiving by checking how many other people also perceive the same thing?

Initially I thought this behavior is simply people seeking corroboration but it's not that because corroboration can and does involve stuff other than perception itself. For instance corroborating the perception of a fire includes things like objects near it heating up and catching fire, animals avoiding it (if it's too hot), etc. This is quite different from asking your companions, "do you see that fire?" as the question is specific to visual perception. In that, if my calculations are correct, people are mistaken because the probability of a perception's realness doesn't increase with the number of people reporting the perception.

It is not an hallucination, but it is an illusion.

How does that play into the calculation? — Frank Apisa

An illusion is not the same as hallucination as the former is not a peculiarity of the perceiver/observer like a hallucination is. An illusion is out there just like reality is thought to be but isn't real (confusing) but a hallucination is in here as in something peculiar, "subjective" (?), to the perceiver. A magician can create an illusion but only the person himself/herself is responsible for a hallucination.

So what is the remaining 75%? — Outlander

All different combinations of X, Y, Z hallucinating or perceiving something real.

unenlightened

Do you think a person should corroborate what he's perceiving by checking how many other people also perceive the same thing? — TheMadFool

I asked Mrs un if you were saying what I thought you were saying, and seeking to corroborate what you're thinking with what I'm thinking, and she said "Stop being a twat, Mr un!" or words to that effect.

You'd have to trust your perceptions of what other people are perceiving, so ordinarily no. You need a reason to doubt a particular perception before seeking 'other evidence'. Mainly, things are as plain as the nose on your face, and if you seem to have mislaid the nose on your face, that is the time to consult your nearest and dearest.

Outlander

↪TheMadFool

So that takes us up from 50% to 75%? Was there not already a 100% chance of this with only X? Or perhaps that's your point. Hm.

Well a perception is an observation, inaccurate or not, false witness aside, it is real. Whereas a hallucination... well. Huh. Neat topic to say the least.

How would you differentiate a perception from a hallucination? There seems to be the idea that a perception is a possibly inaccurate or incomplete observation of something actually present vs. something that was not. Of course... wow what a paradox. :D

I guess I'd want to say the normal biological state is to not be hallucinating. So based on that the odds of several people doing so simaltaneously at the same time and place, absent of a hallucinogen, decrease with number.

TheMadFool

You need a reason to doubt a particular perception before seeking 'other evidence'. — unenlightened

But I speak from the bane of philosophy, the skeptic's point of view, someone who merely with three words, "are you sure?" casts everything we think we know - from factoids to facts - into doubt. Everything can be doubted, and in this discussion, doubt about perception is the issue.

How would you differentiate a perception from a hallucination? — Outlander

That is the issue.

unenlightened

But I speak from the bane of philosophy, the skeptic's point of view — TheMadFool

Well from there, you have no more reason to believe any answer you might get, than the original perception. In fact there's no point my talking to you as you will dismiss it as 'mere perception'. In fact you don't even have a point of view, merely a point of perception. In fact... no, there are no facts, only perceptions. The perception that you or I are saying anything at all is... merely ...

TheMadFool

Well from there, you have no more reason to believe any answer you might get, than the original perception. In fact there's no point my talking to you as you will dismiss it as 'mere perception'. In fact you don't even have a point of view, merely a point of perception. In fact... no, there are no facts, only perceptions. The perception that you or I are saying anything at all is... merely ... — unenlightened

Not necessarily. I sought the help of skepticism just to make the point that it isn't necessarily the case that we need a reason to doubt our perceptions. Everything can be doubted and that includes perception as per skepticism. However, skepticism doesn't claim that reality is a hallucination, just that it maybe and so we aren't making a mistake by looking for and evaluating good reasons to believe whether our perceptions are hallucinations or real.

unenlightened

... we aren't making a mistake by looking for and evaluating good reasons to believe whether our perceptions are hallucinations or real. — TheMadFool

And what, pray, does skepticism recommend we use to make this evaluation? Given that even if we find what we are looking for in the way of reasons to believe, they are just as dubitable perceptions as the perceptions we doubt, there seems no reason to do any such thing and that it is indeed a foolish mistake.

TheMadFool

And what, pray, does skepticism recommend we use to make this evaluation? Given that even if we find what we are looking for in the way of reasons to believe, they are just as dubitable perceptions as the perceptions we doubt, there seems no reason to do any such thing and that it is indeed a foolish mistake — unenlightened

Look how we argue (in the logical sense). It reveals what we trust in - logic/reason. Surely then we can rely on logic to come to some agreement on the matter of whether more people perceiving the same thing increases the likelihood of our perceptions being real rather than just a hallucination.

unenlightened

Look how we argue (in the logical sense). It reveals what we trust in - logic/reason — TheMadFool

Just your perception dude. I'm not even here, I'm just an hallucination.

TheMadFool

Just your perception dude. I'm not even here, I'm just an hallucination. — unenlightened

:smile: Nothing in me that could hallucinate a man of such charm, wit, eloquence, and experience as yourself. It's impossible for a fool to hallucinate a sage for the fool simply does not know, and therefore cannot hallucinate, a wise sage.

unenlightened

Totally convincing argument, dude. Your hallucination is convinced by flattery, where logic utterly failed.

Frank Apisa

Everything can be doubted and that includes perception as per skepticism. — TheMadFool

Yeah, the Trump administration tells us this often.

They ask, "What are you gonna believe, you're lyin' eyes or what we tell you is so?"

TheMadFool

Totally convincing argument, dude. Your hallucination is convinced by flattery, where logic utterly failed. — unenlightened

Yes, it was an argument.

unenlightened

↪TheMadFool

Yes it was an argument. Your hallucination agrees with your potent argumentation, and is completely convinced, and this is evidence that you are not hallucinating and and that skepticism, though perfectly reasonable, is in this case disproved. That's right, isn't it?

TheMadFool

Yeah, the Trump administration tells us this often.

They ask, "What are you gonna believe, you're lyin' eyes or what we tell you is so?" — Frank Apisa

This is the broader issue - that of what the truth is, how we may know it to be so - that emerges from my concerns. Note, however, that my probability calculations are specific to perceptions only; I don't know to what extent they apply to other kinds of propositions.

TheMadFool

Yes it was an argument. Your hallucination agrees with your potent argumentation, and is completely convinced, and this is evidence that you are not hallucinating and and that skepticism, though perfectly reasonable, is in this case disproved. That's right, isn't it? — unenlightened

Skepticism is not disprovable or so I hear. All that I wish to show you is our mutual trust in logic and thereby provide a platform for us to work our way to a solution for the issue we're discussing.

prothero

The limitations of our "senses" in combination with the fluidity of our "memory" make eyewitness testimony among the worst forms of "evidence".

TheMadFool

The limitations of our "senses" in combination with the fluidity of our "memory" make eyewitness testimony among the worst forms of "evidence". — prothero

I read that. Seems to agree with my assessment of perception but for a different reason.

unenlightened

I read that too, but I didn't believe my own eyes.

This is the problem with skepticism; the more I believe it, the less believable it is. But I have never met a skeptic yet who could follow this simple logic.

unenlightened

The limitations of our "senses" in combination with the fluidity of our "memory" make eyewitness testimony among the worst forms of "evidence". — prothero

Yes I always rely on my non-senses, for proper evidence.

prothero

↪unenlightened

I suspect you rely more on instrumentation, measurement and science for your evidence i.e DNA vs eyewitness testimony.
I'm not solipist or a skeptic just recognizing the limitations of eyewitness testimony and evidence.

TheMadFool

This is the problem with skepticism; the more I believe it, the less believable it is. — unenlightened

That, you must be able to tell, is a contradiction. Not to be confrontational but just curious, why?

unenlightened

I suspect you rely more on instrumentation, measurement and science for your evidence i.e DNA vs eyewitness testimony.
I'm not solipist or a skeptic just recognizing the limitations of eyewitness testimony and evidence. — prothero

I suspect you rely more on your senses to read those instruments, though you probably don't remember.

Jesus, how hard do I have to press the Non-Sense button before the alarm bells start ringing?

Rely on your senses, or rely on your nonsenses - it's your call folks.

prothero

↪unenlightened

Without engaging in a "idealist" or "solipsism" argument about we don't have any "knowledge" except through our "senses":
Which do you trust more in a murder trial an "eyewitness" or DNA that puts the accused at the scene holding the murder weapon? Just asking?

How Many Blind Men Does It Take To Make An Eyewitness?

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