Except your explanation of what indirect realists believe is that our perceptions of material objects are not mediated by the perception of some other entity, which is therefore not indirect realism. — Luke

What indirect realists mean by "perception of some other entity" isn't what you mean by "perception of some other entity". You're equivocating.

Indirect realists do not and never have believed or claimed that our eyes respond to light reflected by sense data.

That our perceptions of material objects are mediated by the perception of some other entity, such as sense-data. — Luke

Except by this you mean "our eyes respond to light reflected by sense data" which isn't what indirect realists believe.

It's something I do not accept.

According to what I mean by it, it is that we have sensory perceptions of sense-data. but you have been telling me that that's not what you mean by it. — Luke

By "we do not perceive some other entity, such as sense-data" you mean "our eyes do not respond to light reflected by some other entity, such as sense-data".

Indirect realists agree with you that our eyes do not respond to light reflected by some other entity, such as sense-data.

So what is it that indirect realists believe that you do not?

As I've stated several times now, it is over part (2) of Fish's definition: — Luke

Except according to what you mean by "perceive some other entity, such as sense-data", (2) is something that indirect realists accept.

Otherwise, I don't know what indirect realists mean by indirect perception. — Luke

I have spent 70 pages explaining it.

I don't think there's much point in continuing since you refuse to acknowledge that my position is even possible: that one can reject naive realism without being an indirect realist. — Luke

As has been established, your position misunderstands indirect realism. You think that by "we perceive mental phenomena" the indirect realist means "our eyes respond to light reflected by mental phenomena". They don't.

So given that neither non-naive direct realism nor indirect realism believe that our eyes respond to light reflected by mental phenomena; given that both groups believe that some distal object reflects light, that this light stimulates the sense receptors in our eyes, that this then triggers activity in the visual cortex, and that distal objects and their properties are not literal constituents of the resulting conscious experience, where is it that non-naive direct realism and indirect realism diverge?

Some things can be dismissed on logical grounds, like the notion of continuous motion and the infinitely divisible half-way points an object in motion must then move through.

But one cannot use armchair philosophy to determine the smallest unit of space/time/movement.

Light is color. — creativesoul

No it's not. Light often causes us to see colours, but they are not the same thing, as evidenced by the obvious fact that I can see colours when I dream and my eyes are closed in a dark room.

Arguing for them both results in saying incompatible things when compared to one another. Have you been arguing for both throughout this thread, at different times arguing for one, and then the other later? — creativesoul

I have only been arguing that distal objects are not constituents of conscious experience given that conscious experience does not extend beyond the head. This is impartial to which of property dualism and eliminative materialism is correct.

How is Russellian acquaintance with mental representations of external objects an indirect perception? Russellian acquaintance is not a perception, so it cannot be an indirect perception of an external object. — Luke

This is where you're getting confused by grammar. The words "see" and "experience" and "perceive" and "aware" are all being used ambiguously and interchangeably.

Naive realists claim that distal objects and their properties are literal constituents of conscious experience and that as such we are acquainted with distal objects and their properties, and so our knowledge of them is direct and there is no epistemological problem of perception. The external world just is as it appears. They call this "direct perception of distal objects".

Indirect realists claim that distal objects and their properties are not literal constituents of conscious experience – that the constituents of conscious experience are something like sense data/qualia/mental representations – and so that we are not acquainted with distal objects and their properties – only this sense data/qualia/mental representations – and so our knowledge of them is indirect and there is an epistemological problem of perception. The external world might not be as it appears. They call this "indirect perception of distal objects".

That's all there is to it. You're misunderstanding indirect realism if you think it's saying something else, e.g. that our eyes respond to light reflected by mental phenomena and that our ears respond to sound emitted by mental phenomena.

Are you asking if I'm aware that eliminative materialism and property dualism are incompatible? Yes, I'm aware. I'm undecided between them, but my inclination favours property dualism although I'm open to eliminative materialism.

Either way, distal objects and their properties are not constituents of experience. Naive realism would seem to require some sort of substance dualism, as only that would seem to allow for experience to "literally extend beyond the subject's head, to encompass what the experience is of".

Have you abandoned the eliminative materialist approach in favor of a sense data theorist one? — creativesoul

As I've said before, I'm undecided between eliminative materialism and property dualism. If eliminative materialism is true then experience and its constituent properties (e.g. smells, tastes, colours) are reducible to physical phenomena like certain brain states. If property dualism is true then experience and its constituent properties are non-physical emergent phenomena.

Are those constituents of experience? — creativesoul

Yes.

Hence, we've arrived at incoherency/self-contradiction. — creativesoul

How so?

How much time elapses from travel to point a to point b and where is the object located during that time lapse?

Does the object leave existence between a and b and if it does, what maintains its identity during that interval? — Hanover

That’s a question for physicists to answer.

What is color again? — creativesoul

Qualia/sense-data/mental phenomena.

Yes, I think something along these lines is required when talking about perceiving something, especially since the main point of contention in this debate is whether our sensory perception of external objects is direct or indirect. — Luke

Indirect realists don't believe or claim that our eyes respond to light reflected by mental phenomena and that our ears respond to sound emitted by mental phenomena, so you clearly misunderstand indirect realism and are arguing against a strawman.

Who did that? Are they in the room with us right now? — fishfry

See here:

As Salmon (1998) has pointed out, much of the mystery of Zeno’s walk is dissolved given the modern definition of a limit. This provides a precise sense in which the following sum converges:

$\frac{1}{2} + \frac{1}{4} + \frac{1}{8} + \frac{1}{16} + \ldots$

Although it has infinitely many terms, this sum is a geometric series that converges to 1 in the standard topology of the real numbers. A discussion of the philosophy underpinning this fact can be found in Salmon (1998), and the mathematics of convergence in any real analysis textbook that deals with infinite series. From this perspective, Achilles actually does complete all of the supertask steps in the limit as the number of steps goes to infinity.

...

Suppose we switch off a lamp. After 1 minute we switch it on. After ½ a minute more we switch it off again, ¼ on, ⅛ off, and so on. Summing each of these times gives rise to an infinite geometric series that converges to 2 minutes, after which time the entire supertask has been completed.

I have been arguing that it is a non sequitur to argue that because the sum of an infinite series can be finite then supertasks are metaphysically possible. The lack of a final or a first task entails that supertasks are metaphysically impossible. I think this is obvious if we consider the supertask of having counted down from infinity, and this is true of having counted up to infinity as well.

We can also consider a regressive version of Thomson's lamp; the lamp was off after 2 minutes, on after 1 minute, off after 30 seconds, on after 15 seconds, etc. We can sum such an infinite series, but such a supertask is metaphysically impossible to even start.

Do you hold the view that we must perceive mental phenomena in order to perceive real objects? If so, then this is where our positions differ and we have more than a grammatical dispute, since it is not my position that we must perceive mental phenomena in order to perceive real objects. If not, then you are not an indirect realist. — Luke

What do you think "perceive mental phenomena" means? Do you think it means that my eyes respond to light reflected by mental phenomena? Do you think it means that my ears respond to sound emitted by mental phenomena?

I think you're reading something into the meaning of "perceive mental phenomena" that just isn't there. Indirect realists probably aren't saying what you think they're saying when they say that we perceive mental phenomena. Acquaintance with mental phenomena is the appropriate interpretation. This is how to interpret the meaning of "feel" in "I feel pain" and the meaning of "hear" in "the schizophrenic hears voice" and the meaning of "see" in "I see colours".

This sense of acquaintance with mental phenomena occurs also in veridical perception, and this is all that is meant when the indirect realist says that awareness of distal objects is mediated by awareness of mental phenomena. The former sense of "awareness" is the sense of intention and the latter sense of "awareness" is the sense of acquaintance. And it is for precisely this reason that, as argued in Semantic Direct Realism, the intentional theory of perception (a non-naive direct realism) is consistent with the sense datum theory of perception (an indirect realism).

But if we admit that time is infinitely divisible, counting to infinity doesn't seem to amount to a logical impossibility, and so we reverse the time of the task. — Lionino

And that's where you're being deceived by maths. We can't have counted down from infinity because there is no first number and so we can't have counted up to infinity because there is no last number.

The fact that an infinite series can have a finite sum is a red herring in both cases.

But to talk about what the brain is doing when presented with a cow... — Mww

Brains aren't presented with cows. Brains respond to signals sent by the body's sense organs. But most importantly, the phenomenal character of conscious experience – which as a property dualist I take to be a non-physical emergent phenomenon – is ontologically distinct from the cow.

So what’s your third-person account of belief and what it seems like?

Maybe it’s relevant for indirect realists and dualists of all types, no doubt, but my relevant concern is why they’re begging the question, why they proliferate unobservables into a menagerie of ineffable terms and concepts, and why they’d eschew the 3rd-person perspective in favor of one that cannot even see his own ears, let alone what is occurring in the skull. — NOS4A2

It’s not begging the question to accept the reality of a first-person perspective with phenomenal character; it’s the foundation upon which the dispute between naive and indirect realism rests.

Their argument is over whether or not distal objects are constituents of this first-person experience.

But given that experience is an act involving a practical relationship between oneself and the rest of the world (and never a space located in the body with area and volume), it follows that objects are often participants of that act. — NOS4A2

The relevant concern is the phenomenal character of conscious experience. Everyone agrees that veridical perception involves the body responding to and interacting with objects in the wider environment. You're equivocating.

I don't understand your question.

It is simply the case that I'm acquainted with the phenomenal character of my experience, and that this phenomenal character is some sort of mental phenomena, whatever mental phenomena turn out to be (e.g. property dualism or eliminative materialism).

Given that conscious experience doesn't "literally extend beyond the subject's head, to encompass what the experience is of", the naïve realist's claim that distal objects and their properties are literal, non-representational constituents of conscious experience is false, and so the indirect realist account above is true.

Try reading more of the article.

Russell thus characterizes acquaintance as a relation of direct awareness, a relation in which, as Russell and some others have put it, something is “presented” or simply “given” to the subject.

...

Acquaintance with something does not consist in forming any judgment or thought about it, or in having any concept or representation of it.

...

We have already seen that for Russell acquaintance is nonjudgmental or nonpropositional; to be acquainted with something is to be aware of it in a way that does not essentially involve being aware that it is so-and-so. Russell seems to be extending this to knowledge by acquaintance: it is knowledge of something, and logically independent of knowledge that something is so-and-so.

I am simply, irreducibly, aware of my pain. I don't know what my pain is or what causes it; it's just there in awareness.

Maybe read up on the linked article on acquaintance. I'll start you off with this quote:

I say that I am acquainted with an object when I have a direct cognitive relation to that object, i.e., when I am directly aware of the object itself. When I speak of a cognitive relation here, I do not mean the sort of relation which constitutes judgment, but the sort which constitutes presentation. (Russell 1910/11: 108)

So which is it? — NOS4A2

We don't know; the hard problem of consciousness hasn't been resolved. All I know is that I am acquainted with pain and that I can't describe this pain in any simpler terms; pain is just pain.

Is a quale a property of experience or of mental objects? — NOS4A2

Qualia:

(1) Qualia as phenomenal character...
(2) Qualia as properties of sense data...
(3) Qualia as intrinsic non-representational properties...
(4) Qualia as intrinsic, nonphysical, ineffable properties...

If you are you ought be able to describe a property or two of each. — NOS4A2

This doesn't follow. It is properties with which I am acquainted. You're asking for a property of a property.

I'll quote from the SEP article on Acquaintance:

Most philosophers wedded to some notion of acquaintance end up rejecting the idea that we have acquaintance even with bread-box sized objects, immediately before us, under ideal conditions of perception. The test to determine with what we are acquainted is often reminiscent of the method Descartes recommended for finding secure foundations of knowledge—the method of doubt (see Russell 1912: 74; Price 1932: 3). If you are considering whether you are acquainted with something, ask yourself whether you can conceive of being in this very state when the putative object does not exist. If you can, you should reject the suggestion that you are directly acquainted with the item in question. Based on possibilities of error about physical objects from illusion, hallucination and dreams, it seemed to most that we could rule out acquaintance with physical objects, future events, other minds, and facts that involve any of these as constituents. Consider, for example, physical objects. It seems that the evidence that my experiences give me right now for supposing that there is a computer before me is perfectly consistent with the hypothesis that I am now having a vivid dream or a vivid hallucination. If this is right, then the experiential evidence I possess cannot be the computer or any of its constituents. Neither the computer, nor any of its constituents, need be present in that vivid dream or hallucination. Even when our evidence for the presence of physical objects seems as good as we can get, then, we are not acquainted with physical objects or their constituents. (However, some have recently defended the view that we can be acquainted with physical objects in perception. See, for example, Johnston 2004.) Traditionally, acquaintance theorists have taken the most promising candidates for entities with which we can be acquainted to be conscious states of mind (e.g., an experience of pain, a sensation of red) and their properties (e.g., painfulness, redness). Russell and many other acquaintance theorists also take themselves to be acquainted with facts, i.e., with something’s having some property—at least mental facts (e.g., my being in pain, my desiring food, my experiencing red).

I’m just saying that you’re not acquainted with mental phenomena. We’re so unacquainted with mental phenomena that we cannot even describe one. If we were acquainted with mental phenomena this whole issue wouldn’t be such a struggle. — NOS4A2

I'm definitely acquainted with the pain I feel when I stub my toe, and the cold I feel when it's winter, and the blue I see when I look to the sky.

You treat them and speak about them like they are objects. — NOS4A2

I don't know what you mean by "object".

I'm only saying that in perception I am acquainted with mental phenomena.

You can name them. — NOS4A2

Yes. They're primitives, so can't be explained further. I am simply acquainted with them.

Yet we are unable to describe a single quale — NOS4A2

Pain, cold, red, sour, etc.

A simple summation:

P1. We are acquainted with the phenomenal character of experience.
P2. According to the naive realist, the phenomenal character of experience is constituted of distal objects and their properties.
C1. Therefore, according to the naive realist, we are acquainted with distal objects and their properties.
P3. According to the indirect realist, the phenomenal character of experience is constituted of mental phenomena.
C2. Therefore, according to the indirect realist, we are acquainted with mental phenomena.

Note that the term "mental phenomena" is impartial to property dualism and eliminative materialism.

Note also the technical term "acquainted", as described here.

And as explained above, for the phenomenal character of experience to be constituted of distal objects and their properties it requires that perceptual experiences "literally extend beyond the subject's head, to encompass what the experience is of".

Visual experience occurs when the visual cortex is active. We don't need to talk about what a cow is doing to talk about what the brain is doing.

Naïve Realism, Seeing Stars, and Perceiving the Past provides a good account of what "constituent" means for naive realism:

[N]aïve realists have to accept what might be called a radically non-Galilean ontology – i.e. an ontology that, far from kicking the sensible qualities upstairs, into our minds, rather locates those sensible qualities within the external world we see and sense. As Campbell (2010, p. 206) puts it, naïve realism ‘depends on the idea that qualitative properties are in fact characteristics of the world we observe’, whereby this is because, according to naïve realism, ‘our experiences have the qualitative characters … they do in virtue of the fact that they are relations to those aspects of the world’.

Naïve realism is thus a radically externalistic view about the nature of perceptual experience. For it implies that our perceptual experiences, rather than being ‘narrow’ mental events which occur just inside the head, instead reach all the way out to the external things they are of and thereby ‘literately include the world’ (Martin, 1997, p. 84). As Logue (2009, p. 25) observes, on naïve realism, our perceptual experiences ‘literally extend beyond the subject's head, to encompass what the experience is of’.

It also provides a good account of indirect realism, avoiding to frame it in the misleading way that others have:

On the sense datum view, seeing an object, O, is a matter of having some visual experience, E, that has been caused by O in the appropriate way (whereby E's intrinsic nature can be characterised independently of O).

Such visual experiences have phenomenal character, and we are acquainted with this phenomenal character. This is all that is meant by "seeing sense-data/qualia/mental representations".

What do you think "constituent" means?

Then where is the mediation of our perception of visual objects by the perception of some other entities such as sense-data? — Luke

We feel pain – a mental phenomenon – and it is in feeling this pain that we feel the fire. We taste a sweet taste – a mental phenomenon – and it is in tasting this sweet taste that we taste the sugar. We see shapes and colours – mental phenomena – and it is in seeing these shapes and colours that we see the cow.

If you agree with this, then you are arguing for direct realism. If you want to argue for indirect realism, then you must hold the view that our visual perception of material object is mediated by the perception of some other entities, such as sense-data (or mental representations). — Luke

You misinterpret what "perceive mental phenomena" means. I feel pain, and pain is a mental phenomenon. The schizophrenic hears voices, and these voices are a mental phenomenon. I see colours, and colours are a mental phenomenon. This is all that is meant.

And this is where you're reading something into the grammar that just isn't there. I feel pain, and pain is a mental phenomenon. The schizophrenic hears voices, and these voices are a mental phenomenon. I see colours, and colours are a mental phenomenon.

This is all is that is meant by saying that we feel and hear and see mental phenomena.

This is precisely why, as I have repeated ad nauseam, that trying to frame the issue in such terms as "either I see distal objects or I see sense data" is a confusion and a red herring.

The only thing that matters is whether or not distal objects and their mind-independent properties are non-representational, more-than-causal, literal constituents of conscious experience. If they are then direct realism is true and if they're not then indirect realism is true.

The existence of something like a mental representation is what it means for our perception of distal objects to be mediated.

I addressed this before when I asked you to explain the difference between "seeing" a mental representation and perception "being" a mental representation. You were unable to do so. And that is precisely because there is no difference.