Perception and reality

Discuss any topics related to metaphysics (the philosophical study of the principles of reality) or epistemology (the philosophical study of knowledge) in this forum.
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Steve3007
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Re: Perception and reality

Post by Steve3007 »

Present awareness wrote:Regardless of what an electron “IS”, it changes behaviour when observed. It seems to be that the wave of probability is collapsed under observation and yet remains undefined when not observed.
Yes, a good model for describing the collection of possible observations that we refer to as "electron" appears to be a wave function that describes the probability of making a particular type of observation (perhaps a click of a counter or a flash on a fluorescent screen) at a particular point in space. But one problem that some people have is when we start to talk about that "probability wave function" as if it's an object - we are perceived to have reified an abstract piece of mathematics. Then we get into a discussion about what it means for something to be an object, and that's where the "perception versus reality" discussion comes in and maps and territories or use/mention confusions get discussed.
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Re: Perception and reality

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Atla wrote:One doesn't, there are dozens of interpretations and they are probably all wrong.
What do you mean by "wrong"? Do you mean that they're inaccurate descriptions of the things that could potentially be observed? Or do you mean that they're inaccurate models of something that we think is (ontologically) "really happening"? Or a combination of those? Or something else?
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Re: Perception and reality

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Consul wrote:Unfortunately, it contains false statements such as this one:

"Quantum theory tells us that an unobserved small object (for instance, an electron or a photon—a particle of light) exists only in a blurry, unpredictable state, with no well-defined location or motion until the moment it is observed."

No, that's not what quantum theory tells us, but only what a particular theoretical interpretation of quantum mechanics tells us...
I think the trouble is that statement isn't problematic just because it's only a description of one possible interpretation. It's problematic because it's not really a fully accurate description of any interpretation. I understand that frequently short summaries of complex ideas have to be written and them compromises have to be made over the strict accuracy of language. But it's often those short summaries that are pounced on by people who aren't prepared to look any deeper but just want to make sweeping "it's all nonsense" or "they're all morons" or "they're all just obsessed with mathematics" types of statements.

I guess that's also a wider problem with the modern world of mass information, where we often judge a story by its headlines. But I think the rational person, if they don't have time to read beyond the headlines/summaries (and most of us don't on most subjects), makes a mental note that they shouldn't leap to conclusions based only on incomplete and potentially misleading information.
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Re: Perception and reality

Post by Atla »

Steve3007 wrote: February 22nd, 2020, 5:15 am
Atla wrote:One doesn't, there are dozens of interpretations and they are probably all wrong.
What do you mean by "wrong"? Do you mean that they're inaccurate descriptions of the things that could potentially be observed? Or do you mean that they're inaccurate models of something that we think is (ontologically) "really happening"? Or a combination of those? Or something else?
Can't fully separate the predictions and the ontology of an interpretation, so I'd say it's sort of a combination of those. But the main issue is the ontological "what's really happening".

For example the above ideas:
- some aspect of some human consciousness as an example of a 'QM observer' may in fact be deeply interwoven into the QM mistery, but it's not the fundamental issue, nothing to do with idealism (but flat out denying the observer-relative nature of QM is also wrong)
- the Bohmian pilot wave theory doesn't even address the measurement problem, even though it claims to, plus it replaces an unexplained thing (the wavefunction or superposition or whatever) with another unexplained thing (the pilot wave), merely overcomplicating the issue
- 'type' of observation like click of a counter or a flash on a flourescent screen doesn't say anything: the real world has no types, and interaction is not the fundamental issue

(probably)
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Consul
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Re: Perception and reality

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Atla wrote: February 22nd, 2020, 6:04 am
- the Bohmian pilot wave theory doesn't even address the measurement problem, even though it claims to, plus it replaces an unexplained thing (the wavefunction or superposition or whatever) with another unexplained thing (the pilot wave), merely overcomplicating the issue.
You seem to be wrong.

QUOTE>
"Bohmian mechanics accounts for the phenomena predicted by standard nonrelativistic quantum theory. Furthermore, it does so in a way that provides a detailed physical account of what is going on at the microscopic scale in our experiments. Particles move around in accordance with the guidance equation, and the guidance equation employs the wavefunction with pure (noncollapse) linear Schrödinger evolution. The “collapse” of the conditional wavefunction follows from this fundamental physics by analysis. There is also an effective collapse of the wavefunction (we can safely permanently discard parts of it) due to the fragmentation of the universal wavefunction into separated pieces in configuration space, as in the Double Slit with Monitoring experiment. Using the theory, we can even draw specific conclusions for particular experiments. In the Double Slit experiment, for example, if a mark forms on the upper part of the screen, the electron went through the upper slit; if it forms on the lower part, the electron went through the lower slit. No similar claim is true in the GRW theory. In that setting, the electron no more “goes through” one slit rather than the other on any run, no matter what the outcome.

There is no problem accounting for measurements and their outcomes. Measurements are just interactions between one physical system and another, governed by the same universal laws. Sometimes, by virtue of the interaction, the configuration of one system will change in different ways, depending on the interaction. If this system is large enough, and the different possible configurations are distinct enough, we can tell by looking at which way the experiment came out. There is nothing magical about experimental apparatus or measuring devices: they are just physical systems like everything else. And if one asks what, if anything, a particular experiment measures, the answer is determined by pure physical analysis. If the observable outcome depends on some feature of the initial state of the interacting system, then the outcome provides information about that feature. What information it provides depends on the details of the interaction. Such questions are settled by using the theory to analyze the interaction.

So there is no measurement problem in Bohmian mechanics. Nor could there, in principle, be anything like a problem with Schrödinger’s cat (or any other cat). Cats are made of particles, according to this theory, and the particles are always in some exact place moving in some exact way. An evolving configuration of many, many particles can unproblematically correspond to how we think a live cat is behaving, or how a dead cat is behaving (or to neither!). The supposedly problematic Schrödinger cat state is a state of the wavefunction or quantum state of the cat, a superposition of two macroscopically distinct states. According to Bohmian mechanics, the cat always has a quantum state, which never fundamentally collapses. But since the important role of the quantum state is to guide the motions of the particles, it doesn’t matter at all that it doesn’t collapse and that both branches of the wavefunction always exist. The branch that is far in configuration space from the actual configuration of particles in the cat becomes irrelevant for the cat’s behavior.

In a nonrelativistic space- time, Bohmian mechanics provides an uncomplicated physics that accounts for all our experiments. There are particles that move around in accordance with a single, simple, deterministic law of motion. That law itself makes use of a quantum state of the system that always evolves by the familiar linear deterministic dynamics shared by all nonrelativistic quantum theories. The quantum state is a physically real, nonlocal entity in the theory; via its nonlocality, the motions of the particles get coordinated even when they are very far apart. That physical coordination yields violations of Bell’s inequality. This is a nonlocal theory, and obviously so. But we know that we need some nonlocality if we are to recover what we take the phenomena to be: violations of Bell’s inequality for outcomes of experiments performed at great distances from one another.

Since the pilot wave approach is simple, has no conceptual difficulties, and recovers the content of the quantum recipe in the nonrelativistic setting, one might wonder why it is not at least discussed in physics textbooks. This question requires a sociological
answer."

(Maudlin, Tim. Philosophy of Physics: Quantum Theory. Princeton, NJ: Princeton University Press, 2019. pp. 169-71)
<QUOTE
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Re: Perception and reality

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Present awareness wrote: February 21st, 2020, 11:27 am How does one explain the two-slit experiment, which when observed it passes through like a bullet but when unobserved it passes through like a wave?
I think there is rather more than this to the double-slit experiment. But maybe this topic is not the right area to explore it?
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Atla
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Re: Perception and reality

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Consul wrote: February 22nd, 2020, 7:58 am
Atla wrote: February 22nd, 2020, 6:04 am
- the Bohmian pilot wave theory doesn't even address the measurement problem, even though it claims to, plus it replaces an unexplained thing (the wavefunction or superposition or whatever) with another unexplained thing (the pilot wave), merely overcomplicating the issue.
You seem to be wrong.

..
Says the guy who is usually wrong about everything.

The Pilot-wave was mostly ignored in the past because it doesn't actually address the measurement problem, it merely asserts that there is none. But that in no way explains how the 'nature' of what is physically happening changes, when observation happens.

I guess the closest in your quote where this is sort-of addressed, is where it is said that the universal wavefunction gets fragmented. Which is sort of a self-contradiction, because if it gets fragmented, then it's not universal. Also it's not explained how or why it gets fragmented, what fragments it, what does this fragmentation mean.

(Then the quote goes on with the usual 'measurements are just intreactions' quantum woo, that was experimentally refuted decades ago.)
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Consul
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Re: Perception and reality

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Atla wrote: February 22nd, 2020, 8:20 amThe Pilot-wave was mostly ignored in the past because it doesn't actually address the measurement problem, it merely asserts that there is none.
No, Bohmian mechanics also explains why! But this is off-topic here, so…
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Re: Perception and reality

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Terrapin Station wrote: February 21st, 2020, 8:34 pm
Prof Bulani wrote: February 21st, 2020, 8:19 pm
They are different events, yes
Well, and different sorts of things--they have different qualities.

So, we're just naming one "Knowledge by acquaintance" and naming the other "propositional knowledge."
I don't see how they can be considered different kinds of knowledge. Telling someone that I did something isn't a new or different type of knowledge from when I did the thing.
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Re: Perception and reality

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Prof Bulani wrote: February 22nd, 2020, 10:53 am
Terrapin Station wrote: February 21st, 2020, 8:34 pm

Well, and different sorts of things--they have different qualities.

So, we're just naming one "Knowledge by acquaintance" and naming the other "propositional knowledge."
I don't see how they can be considered different kinds of knowledge. Telling someone that I did something isn't a new or different type of knowledge from when I did the thing.
It's easiest to just think of the two terms as names for two different things. It's clear that meeting x and uttering a proposition about x are two different things. We can name them whatever we'd like to name them. Conventional names for them are "knowledge by acquaintance" and "propositional knowledge."
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Re: Perception and reality

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Pattern-chaser wrote:I think there is rather more than this to the double-slit experiment. But maybe this topic is not the right area to explore it?
I think it's a useful way to explore some particular empirical findings that have a bearing on the relationship between perception and reality. But I think you're right that to go into it in detail would probably be a distraction from the central theme of this particular topic.
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Re: Perception and reality

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Terrapin Station wrote: February 22nd, 2020, 11:19 am
Prof Bulani wrote: February 22nd, 2020, 10:53 am
I don't see how they can be considered different kinds of knowledge. Telling someone that I did something isn't a new or different type of knowledge from when I did the thing.
It's easiest to just think of the two terms as names for two different things. It's clear that meeting x and uttering a proposition about x are two different things. We can name them whatever we'd like to name them. Conventional names for them are "knowledge by acquaintance" and "propositional knowledge."
Sorry for being difficult but I can't go with that "convention". If these are two things that are not types of knowledge, then don't refer to them as if they are types of knowledge. Knowledge is a particular thing which can be acquired, memorized, recalled, passed on, etc. This isn't the case for generic things.
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Re: Perception and reality

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Prof Bulani wrote: February 22nd, 2020, 5:40 pm
Terrapin Station wrote: February 22nd, 2020, 11:19 am

It's easiest to just think of the two terms as names for two different things. It's clear that meeting x and uttering a proposition about x are two different things. We can name them whatever we'd like to name them. Conventional names for them are "knowledge by acquaintance" and "propositional knowledge."
Sorry for being difficult but I can't go with that "convention". If these are two things that are not types of knowledge, then don't refer to them as if they are types of knowledge. Knowledge is a particular thing which can be acquired, memorized, recalled, passed on, etc. This isn't the case for generic things.
Okay, I'm just letting you know that these are two of the three types of knowledge per conventional philosophical distinctions. (The third is "how-to" knowledge.)

It's fine if you want to use different terms, though it's wise to be familiar with terms as you might encounter them in a philosophical context. In any event, perception, at least on a direct realist account, involves a simple "meeting" with data from outside of oneself.
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Re: Perception and reality

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Terrapin Station wrote: February 22nd, 2020, 11:19 amIt's easiest to just think of the two terms as names for two different things. It's clear that meeting x and uttering a proposition about x are two different things. We can name them whatever we'd like to name them. Conventional names for them are "knowledge by acquaintance" and "propositional knowledge."
There's a distinction between knowledge-of (to know something/somebody) and knowledge-that (to know that something is the case/true), the latter usually being called propositional knowledge; but knowledge by acquaintance isn't the same as non-propositional knowledge, because it can yield propositional knowledge. For example, I can know that people are drunk by virtue of my acquaintance with their behavior, i.e. my direct perceptual awareness or consciousness of it. No one needs to tell me that Peter is drunk, because I see he is.

Footnote: Those who reject direct perceptual realism will deny that we are acquainted with (the behavior of) persons or nonmental objects. For example, Russell thought the only things we are (perceptually) acquainted with are sense-data.
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Re: Perception and reality

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Consul wrote: February 22nd, 2020, 11:03 pm
Terrapin Station wrote: February 22nd, 2020, 11:19 amIt's easiest to just think of the two terms as names for two different things. It's clear that meeting x and uttering a proposition about x are two different things. We can name them whatever we'd like to name them. Conventional names for them are "knowledge by acquaintance" and "propositional knowledge."
There's a distinction between knowledge-of (to know something/somebody) and knowledge-that (to know that something is the case/true), the latter usually being called propositional knowledge; but knowledge by acquaintance isn't the same as non-propositional knowledge, because it can yield propositional knowledge. For example, I can know that people are drunk by virtue of my acquaintance with their behavior, i.e. my direct perceptual awareness or consciousness of it. No one needs to tell me that Peter is drunk, because I see he is.
I believe you and terrapin are saying the same thing. Propositional knowledge seems to be acquired by secondhand information or indirect inference. Knowledge by acquaintance seems to be direct and first hand acquisition of information. I don't see why Terrapin would argue that the acquisition of the knowledge (i.e., how we come to know something) is irrelevant. Knowledge is something you can either have or not have. And the only way to have knowledge is to acquire it in some form. The way knowledge is acquired is the key to classifying whether it's by acquaintance or propositional.
Footnote: Those who reject direct perceptual realism will deny that we are acquainted with (the behavior of) persons or nonmental objects. For example, Russell thought the only things we are (perceptually) acquainted with are sense-data.
I don't quite follow. We cannot become acquainted with an object in actual reality until we first process the sense data we receive from the object. The sense data processing faculty is the interface that exists between our minds and the outside world. We have no other way of becoming acquainted with anything except AFTER this sense data has been processed and made sense of.
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