I’m not assuming direct realism in order to know that there is error. What I’m rejecting is the assumption — which I take to be doing a lot of work in the IR picture — that error must be identified by comparing experience with either a mind-independent phenomenal property or an inner experiential surrogate. — Esse Quam Videri

Good charge, but I think misguided. In either theory there can be aberration - and generally, this would be represented by the exact 'error' you're pointing to - in perception precisely because it is indirect. Neither theory branches here - they both predict error with reference to shared experience - not external objects. That was what I took to be the claim for the DRist - error must be as held up to the "real world". Otherwise, we're not looking at error. We're just looking at disparate experience and error with this frame of reference is trivial. It seems you've given an IRist concept in support of rejecting IR. Perhaps not.

To me, the difference comes in where, for DR a mental event of perception could only be labeled an error for practical purposes - which is something I want to avoid. I want to actually know the relationship between my experience and the world - not other people's experiences. I just take it we can't know, or can't be certain. I don't see a problem with that conclusion unless its emotionally unsatisfying.

I think it might be worth dealing with a couple of common objections to IR that I think fail, and are being brought to bear here in complex discussion, instead of just stating them...probably because when stated just so, objection is easy.

Experiential transparency:
We must admit that the an anatomically indirect visual complex is at the base level of our descriptions (seems no one denies this part) and that we should not work backwards from psychological impressions to a theory. We need to work from the ground up to something which also fits our psychological impressions or we should adjust them. This is why experiential transparency is a red herring to me. It does literally nothing but say that humans tend to assume they are directly in touch with the world. So much is trivial. It doesn't help. Simply stating that it feels like that cat you see is "the cat out there" isn't anything so much as a lack of curiosity (or, ignorance).

Phenomenology of acquaintance:
There's no explanation of how this fixes the problems of content or accuracy. It just re-describes the above in a specific domain (felt sensation). It, also, seems to be a mere label in service of a couple other of the concepts below..

Disjunctivism:
In claiming that the object is constitutive of the veridical perception event, it accepts that there is a disjunct and cannot explain commonality in phenomena between minds without regression - which i find far less satisfying that "we can't know". Either way, its immensely underdeterminative and not supported by the neuroscience indicating common proximal causes of phenomenon. Also, what's the criteria for a disjunctive experience? Sort of begs the question..

Action-guidance:
IR predicts this just as well as DR. It seems to confused metaphysical structure with functionality/functional success. IR accepts the latter as well as DR.

Anti-skepticism:
Do I need to? LOL.

These seem to cover most motivations for clinging to DR:

- suspicion of representationalism or similar ruffle. The thing is, IR rejects antirealism, even if it accepts a basic framework from which it springs. Confusing these is poisoning the well I think;
- resistance to epistemic internalism and hte risks it presents;
- preference for ontological parsimony - not always the best answer. In fact, its only usually a good starting point, when we have conflicting data;
- desire to dissolve skepticism rather than answer it - fair, but again, about comfort not what's being argued.

Its just incredibly underdetermined. For me, far, far more questions arise from DR than IR. But more risk arises for IR than DR, epistemically. I understand that impulse, but it seems almost anti-philosophical.

The causal chain remains the same, but our attention(the blanket) can be placed in differing locations. So in one throw we can refer to your wife’s voice, in another to the electronically constructed reproduction, and so on. — Banno

You don't have access to your wife's voice. If you did, you wouldn't need a phone.

Think of your sensory nervous system as technology that allows that grey blob in your skull to gain information it wouldn't otherwise have access to.

You don't have access to your wife's voice. — frank

I'm not sure I know what that might mean; but I do hear my wife's voice, through the telephone. That's indirect, in comparison to when she is in the room, but perhaps more direct than listening to a recording...

I'm not sure I know what that might mean; but I do hear my wife's voice, through the telephone. — Banno

Telephony creates an illusion, and so does television. There's no tiny Donald Trump inside your TV.

Where does your concept of "cup" come from? How does your internal concept of "cup" instantiates in the external world? — Corvus

Suppose on many different occasions I see the same combination of things, such as a square shape being cream in colour. Using my reason I can infer that in the mind-external world something exists that is causing me to see this particular combination of square shape being cream in colour. I don’t know what this something is in the mind-external world, but for convenience I can give it a name, and I name it “cup”. I could have named it anything, but I happen to name it "cup".

Therefore my concept of “cup”, a combination of a square shape being cream in colour has come from regularly seeing the combination of a square shape being cream in colour.

Therefore my concept of “cup”, a combination of a square shape being cream in colour has come from regularly seeing the combination of a square shape being cream in colour. — RussellA

It seems to indicate that you don't need your internal cup in your mind to be able to see the external cup in the external world. At the beginning first time you saw the cup, you didn't have the concept of cup, but you were still seeing it. After having seen the cup many times, you named the object "cup".
Would it be correct?

The fact that there is no sharp, language-independent cutoff for when a Sun becomes a non-Sun, or a seed becomes a tree, shows that our classificatory practices are vague, not that there is nothing mind-external there, or that persistence through change is merely linguistic. — Esse Quam Videri

In Presentism, how can the Sun persist through change, when only the present moment in time exists. The Sun cannot exist in the past when the past does not exist.
In the Block Universe, in the present is a physical state of matter and energy and in the past is a different physical state of matter and energy. But you talk about the Sun persisting through change. If two physical states are different between the past and present, where is the commonality between them?

If the Sun loses one atom, why does it remain the Sun rather than become a different object?=========================

It requires only that there be mind-external continuants with causal powers, and that perception be directly related to those continuants, even though the concepts under which we describe them are supplied by us. — Esse Quam Videri

How can the Sun persist through time?
In Presentism, how can that part of the Sun that existed in the past and no longer exists in the present directly causally affect the present? Indirectly, yes, but directly, no.
In the Block Universe, how can that part of the Sun that exists in the past causally affect anything in the present, when in a Block Universe all moments in time are fixed, and there is no movement between moments in time?

As regards language, in what sense does the past directly (rather than indirectly) affect the present?=====================

On Presentism, what I perceive is a presently existing continuant whose earlier state is made perceptually available by presently arriving light. On a Block Universe view, what I perceive is a temporal part of an extended object. Either way, the object of perception is mind-external, not something that exists only in language or concepts. — Esse Quam Videri

In Presentism, what I see in the present was indirectly caused by something in the past, but that something in the past no longer exists, so I cannot directly perceive it.
In a Block Universe, nothing can move between the past and present because both the past and present are fixed, including perception of the past from the present.

For both the Indirect and Direct Realist, the mind-external exists, and being mind-external, not just something that exists only in language or concepts. =================================================

If temporal mediation or vagueness in classification were sufficient to make perception indirect, then all perception would be indirect—not only perception of mind-external objects, but even the “direct perception” of mental images or sense-data, since those too are temporally extended, causally conditioned, and conceptually classified. — Esse Quam Videri

As regards temporal causal chain:
In Presentism, we infer that there is a temporal causal chain from a mind-external something in the past to a perception in the mind in the present. We can only directly perceive the present as the past no longer exists.
In the Block Universe, both the past and present are fixed, meaning that at each moment in time perception can only be directly of that particular moment in time .

As regards language:
In Presentism, only the present exists, and in the present I have the concept of the Sun, meaning that my perception can only be directly about something in the present.
In a Block Universe, each moment of time is fixed and nothing moves through this Block Universe, meaning that at each moment in time the perception of a concept can only be directly in that particular moment in time.

When I see the Sun, my perception is directly of something that exists in my present. There is no regress if my perception is directly of something.

It seems to indicate that you don't need your internal cup in your mind to be able to see the external cup in the external world. — Corvus

No. I need the concept of a cup in my mind before I know I am looking at a cup. If I don’t know the concept of a cup, I don't know what I am looking at.

At the beginning first time you saw the cup, you didn't have the concept of cup, but you were still seeing it. After having seen the cup many times, you named the object "cup".
Would it be correct? — Corvus

No. I didn't see the cup many times, I saw many combinations of a square shape coloured cream, which I reasoned had been caused by something specific in the mind-external world.

From regularity of observation I learn the concept of a square shape coloured cream. For convenience this concept may be named, such as “cup”, but it could have been given any name.

Ordinary causal media do not introduce a layer whose outputs can succeed or fail as presentations of the environment. — Esse Quam Videri

This is the thing I'm trying to make sense of. What does it mean, for example, for 700nm light to "succeed" as a presentation of a strawberry and 450nm light to "fail" as a presentation of a strawberry?

You appeared to accept before the plausibility of the inverted spectrum, so let's assume that the phenomenal character I experience when my eyes detect 700nm light is the same as the phenomenal character you experience when your eyes detect 450nm light and vice versa. You are wearing a visor that transforms 700nm light into 450nm light and I'm not wearing a visor. When you and I look at a strawberry we now experience the same phenomenal character.

In what sense has your visor "failed" to present the strawberry to you? And why do we not ask if my eyes have "failed" to present the strawberry to me?

No. Humans do not experience neural representations; experience is having neural representations.

You are not separate from your neural processes. — Banno

We experience (are aware of) something when we dream, when we hallucinate, (when we have synaesthesia?), etc., and these things are not distal objects in the world. The indirect realist claims that these things we experience when we dream etc. are mental/neurological phenomena, that we also experience these things when we have ordinary waking experiences, and that these things satisfy the philosophical notion of directness.

So which of these is your counterclaim?

1. We don't experience (are not aware of) anything when dream, when we hallucinate, (when we have synaesthesia?), etc.
2. Those things we experience when we dream etc. are not mental/neurological phenomena
3. We do not experience these things when we have ordinary waking experiences
4. These things do not satisfy the philosophical notion of directness

Note specifically that I haven't yet said that we don't directly perceive distal objects in the world when we have ordinary waking experiences. The above is just to see if we can agree that we do (also?) directly perceive mental/neurological phenomena (even during ordinary waking experiences)

The thing in itself is either "judged", in that its represented meaning is already crystallised as symbol and is a container for pre-existing, values, relationships and meanings. Or the thing in itself is "perceived", taken in as presenting true novelty and is a thing which seeks to bond and affiliate with purpose and meaning, with continued availability to be reassessed or realigned or left in aporia.

Thanks for laying that out so clearly — I think this makes it obvious that we’re no longer talking past one another.

I agree with you on several points up front. I’m not trying to refute indirect realism, and I agree that IR can accommodate error, coordination, and action-guidance without collapsing into skepticism. I also agree that the epistemic situation is deeply underdetermined, and that “we can’t know with certainty” is a live philosophical outcome.

Before responding to your specific objections to experiential transparency, phenomenology of acquaintance, disjunctivism, and action-guidance, I want to flag why I haven’t engaged them directly. I’m not defending any of those positions. My claim is narrower: that the epistemic primacy of experience is itself a substantive theoretical commitment, not a neutral starting point. Whether or not disjunctivism or transparency succeed on their own terms is downstream of that more basic question.

Where I think we part company is over whether that underdetermination should be treated as a neutral default or as a philosophical choice. On the IR picture you’re defending, experience is effectively insulated from normative assessment: it can be causally aberrant, but it is not itself answerable to the world in a way that admits of correctness or incorrectness. Normativity enters only at the level of relations between experiences or theoretical overlays.

My move is to deny that insulation. I don’t think experience itself justifies our judgments, but neither do I think justification requires experiential comparison. The justificatory work is done by the norms governing world-directed judgment — norms shaped by, and answerable to, stable patterns of successful interaction with the world — with experience playing a causal, enabling role rather than an evidential one.

So I take your position to be coherent, but not compulsory. The disagreement, as I see it, is not about whether IR is viable, but about whether experience must be treated as epistemically primary in the first place.

No. I need the concept of a cup in my mind before I know I am looking at a cup. If I don’t know the concept of a cup, I don't know what I am looking at. — RussellA

OK fair enough. But going back the DR or IR, they are both realism. Isn't realism about existence? It is not about concept, or knowing. It is about existence. Even if you don't have concept, you cannot deny what you are seeing in front of you - the cup shaped object, and it is real.

Does existence of cup need concept of cup? What do you mean by existence? Even if, you don't have a concept of cup, you cannot deny the existence of cup shaped object you are seeing.

In what sense has your visor "failed" to present the strawberry to you? And why do we not ask if my eyes have "failed" to present the strawberry to me? — Michael

First I want to say that I agree that it would be a mistake to say that particular wavelengths or phenomenal characters “succeed” or “fail” as presentations of a strawberry. Neither wavelengths nor raw phenomenal character, taken in isolation, have correctness conditions. The notion of success or failure I’m invoking is role-based, not phenomenal: it concerns whether a system’s outputs function as presentations of the environment in a way that is answerable to how things are beyond the subject.

This is where the visor differs from ordinary vision, even allowing for spectrum inversion. In the inversion case, we can grant that you and I have systematically different mappings from wavelength to phenomenal character, and even that we enjoy the same phenomenal character when looking at the strawberry. Still, neither of us is perceiving an image that stands in for the environment. We are perceiving the strawberry itself, through our visual systems, under whatever lawful mapping holds for each of us. That lawful variation does not introduce a further question about whether what is presented corresponds to the environment; it just is how the environment is perceptually available to that subject.

The visor changes this structure. The crucial difference is not that the visor is physical while the eye is biological, or that one is reliable and the other not. It is that we do not perceive the outputs of retinal processing and then perceive the world by way of them; we perceive the world through the eye. By contrast, the visor produces an image that is itself an object of visual experience—something we see, and which purports to show us the scene beyond. Because the visor’s image is experienced as a presentation of the environment, it becomes intelligible to ask whether it corresponds to how things actually are. That is the sense in which its outputs can succeed or fail as presentations.

So the reason we do not ask whether your eyes have “failed” to present the strawberry is not that eyes are infallible, but that they do not introduce a detachable presentational layer whose outputs play the epistemic role of standing in for the world. The visor does. And that difference—between perceiving an object through a medium and perceiving an image that purports to present the object—is what introduces a normative dimension that causal covariance alone cannot supply.

But going back the DR or IR, they are both realism. Isn't realism about existence? — Corvus

Yes, both the DR and IR believe that a mind-external world exists. Even if there were no humans, there would still be a mind-external world.

It is not about concept, or knowing. It is about existence. — Corvus

Yes, even if there were no humans, there would still be a mind-external world. In this mind-external world there would be neither concepts nor knowledge.

Even if you don't have concept, you cannot deny what you are seeing in front of you - the cup shaped object, and it is real. — Corvus

I agree that even if I did not have the concept of “cup” I could not deny that in front of me I would still see shapes and colours.

But if I did not have the concept of “cup”, how could I know that what is in front of me is a “cup”? I would know something was in front of me, but I would not know that it was a “cup”

Both the DR and IR would agree that there is something in the mind-external world causing me to see something in front of me, and that something, whatever it is, is real.

Does existence of cup need concept of cup? — Corvus

That something in the mind-external world causing me to see something in front of me does not need any concept in my mind. That something exists independently of any concept in the mind.

What do you mean by existence? — Corvus

Something that is physical, being either matter or energy. Things in the world.

The neurons of the brain exist as matter and energy. My assumption is that concepts in the mind are no more than arrangements of neurons in the brain. In that sense, concepts also exist.

It is that we do not perceive the outputs of retinal processing and then perceive the world by way of them; we perceive the world through the eye. By contrast, the visor produces an image that is itself an object of visual experience—something we see, and which purports to show us the scene beyond. — Esse Quam Videri

Let's assume that there are just five "things" in the world; my brain, my eye, the visor, light, and a strawberry. The strawberry "moves" the light which "moves" the visor which "moves" the eye which "moves" the brain.

Without begging the question, why is it correct to say that we perceive the strawberry "through" the eye and not that we perceive the strawberry "through" the visor or "through" both the eye and the visor? You said before that it depends on whether or not something "introduces a layer whose outputs can succeed or fail as presentations of the environment". So why is it that the visor's output can "fail" as a presentation of the strawberry but that the eye's output cannot "fail" as a presentation of the visor? Remember; neither the visor nor the eye "purport" to do anything. They just behave according to the deterministic laws of physics. We make true or false judgements that something "succeeds" or "fails", but that's subsequent to perception and phenomenal experience.

@Esse Quam Videri, I'll try to explain this in an even simpler way, using a very simplified account of physics and physiology.

1. The strawberry reflects 700nm light into John's eye and John's eye stimulates his A neuron, causing him to "see red".

2. The strawberry reflects 700nm light into Jane's eye and Jane's eye stimulates her B neuron, causing her to "see blue".

3. The strawberry reflects 700nm light into a visor that emits 450nm light into John's eye and John's eye stimulates his B neuron, causing him to "see blue".

4. The strawberry reflects 700nm light into a visor and the visor bypasses John's eye to stimulate his B neuron, causing him to "see blue".

You count (1) and (2) as direct perception and (3) as indirect perception, but what about (4)?

If the visor's "output" in (4) — i.e. stimulating John's B neuron — can be a "false" presentation of the strawberry then surely the eye's "output" in (2) — i.e. stimulating Jane's B neuron — can also be a "false" presentation of the strawberry. So it seems to me that (2) is direct perception if and only if (4) is direct perception.

But if (4) is direct perception then why isn't (3)? It seems to me that the visor in (3) can "fail" to present the strawberry if and only if the visor in (4) can "fail" to present the strawberry. So it seems to me that (4) is direct perception if and only if (3) is direct perception.

And because (1) is direct perception if and only if (2) is direct perception it seems to me that (1) is direct perception if and only if (3) is direct perception.

But if I did not have the concept of “cup”, how could I know that what is in front of me is a “cup”? I would know something was in front of me, but I would not know that it was a “cup” — RussellA

We are not interested in knowing it was a cup. We are interested in if the cup exists as a real object. It is all what realism is concerned, isn't it? Knowing is not existence, is it?

The neurons of the brain exist as matter and energy. My assumption is that concepts in the mind are no more than arrangements of neurons in the brain. In that sense, concepts also exist. — RussellA

Can you prove and demonstrate the existence of concept as arrangement of neurons in the brain?

I think your equivalence argument is very helpful, because it shows exactly where the disagreement lies. I’m happy to grant that (1) and (2) are on a par: variation in neural mapping or phenomenal character by itself does not make perception indirect. Where I part ways with you is in the move from (2) to (4), and therefore in the further identification of (4) with (3).

Your argument assumes that if two systems produce the same proximal neural outcome—e.g. stimulation of the B neuron—then they must have the same intentional structure, and so must count equally as cases of direct perception. That assumption is precisely what I reject. Intentional content is not fixed by proximal neural causes alone, but by the functional role of the system within a larger perceptual apparatus and its standing relations to the environment.

In (2), Jane’s eye and visual system are her means of perceiving the strawberry. The neural outcome is part of the perceptual process itself, not something she perceives instead of the strawberry. Differences in mapping (including inversion) affect how the strawberry appears, but they do not introduce a new object of awareness or a new question about whether what is presented corresponds to the environment. The system is functionally integrated into perception in such a way that the strawberry itself remains the intentional object.

In (4), by contrast, the visor is not functioning as part of the subject’s perceptual system in that sense. It is an external device that intervenes on the subject’s neural states, fixing the perceptual outcome independently of the normal perceptual linkage between subject and object. Even though there is no intervening “image,” the visor still determines what the perceptual state is of by inserting itself into the causal–functional role that normally belongs to the visual system. That is why (4) is relevantly like (3), not like (2): in both cases, the visor fixes the intentional object of experience rather than merely enabling access to it.

So the difference I’m drawing is not about where in the causal chain neural stimulation occurs, nor about whether phenomenal character matches across cases. It’s about whether the system producing the perceptual state is functioning as the subject’s means of perceiving the object, or as an intervening device whose outputs stand in for the environment. In (2), the eye is part of the perceptual system through which the strawberry is perceived. In (3) and (4), the visor plays a different functional role: it intervenes on perceptual states in a way that makes it intelligible to ask whether its outputs succeed or fail as presentations of the environment.

If one insists that intentional structure must collapse entirely into causal structure, then your equivalence argument goes through. But that insistence is a substantive internalist thesis, not something forced on us by physics or by the bare facts of causal mediation.

We are not interested in knowing it was a cup. We are interested in if the cup exists as a real object. — Corvus

The Indirect Realist does not believe that a cup exists in the mind-external world, but only exists in the mind as a concept. In the mind-external world exists physical matter and energy, which the human mind may interpret as being a cup.

The Direct Realist believes the cup exists both in the mind as a concept and as a real object in the mind-external world.

What makes something an object? Suppose we see an apple on a table. The apple is a single object. The table is a single object. But is the apple on a table a single object? There seems to be no reason to think so. But we could name an apple on a table “apptab”. Is the apptab now a single object just because we have given it a name?

This raises the question, do objects exist in the mind-external world or are they created by the mind?

Can you prove and demonstrate the existence of concept as arrangement of neurons in the brain? — Corvus

No. I assume the mind is no more than the brain, but others disagree.

I think the remaining disagreement comes from running together three different questions:

(1) how persistence through time should be understood,
(2) how causation across time works, and
(3) what “direct” is supposed to contrast with in a theory of perception.

First, about persistence. On Presentism, to say that the Sun persists through change is not to say that past parts of the Sun still exist. It is to say that the present Sun stands in lawful causal continuity with earlier states. Persistence here is not identity-with-the-past, but continuity governed by physical laws. Losing one atom does not generate a new object because nothing in our best physical theories treats that loss as a boundary for objecthood. The absence of a sharp cutoff does not show that persistence is merely linguistic; it shows that persistence is a real-world phenomenon that our concepts track imprecisely.

On a Block Universe view, the Sun is a temporally extended physical process. Different temporal parts are different physical states, but they are unified by belonging to the same continuous spacetime process governed by physical law. The relevant commonality is not qualitative sameness at each moment, but participation in a single causal–spatiotemporal structure.

Second, about causation. You repeatedly say that on Presentism the past “no longer exists” and therefore cannot directly affect the present. But this conflates existence now with having causal efficacy. On Presentism, causal explanations are perfectly coherent: present states are effects of earlier states, even though those earlier states no longer exist. That is not indirect causation; it is just causation across time. Likewise, on a Block Universe view, causal relations are encoded in the spacetime structure itself. Nothing needs to “move” between moments for there to be causal dependence.

Third, and most importantly, about perception. When I say that perception is direct, I am not claiming that the past is perceived as past, or that temporal mediation is eliminated. I am denying that perception proceeds by inference from an inner surrogate. On Presentism, my perception is directly related to a presently existing physical state through which the mind-external object is perceptually available (for example, light now arriving), where that state is itself the lawful causal manifestation of the object. On a Block Universe view, my perception is directly related to a temporal part of a mind-external process. In neither case is the direct object of perception a mental item that stands in need of inference to reach the world.

This is why the regress point still matters. If the mere fact that a causal chain involves time were enough to make perception indirect, then your own claim that perception is “directly of something that exists in my present” would not stop the regress. That present item would itself be temporally conditioned, causally structured, and conceptually articulated, and so—by the same standard—would require a further intermediary. To halt the regress, something must count as non-inferentially present to the mind, and temporal mediation alone cannot disqualify it from playing that role.

So the core issue is not whether only the present exists, or whether time is block-like. It is whether “direct” means non-inferential openness to mind-external reality, or instead absence of temporal structure altogether. I reject the latter requirement, and without it, the arguments you’re pressing don’t force the indirect realist conclusion.

In (4), by contrast, the visor is not functioning as part of the subject’s perceptual system in that sense. — Esse Quam Videri

Why not? It is effectively a bionic eye, and you granted before that a bionic eye is no different in kind to an organic eye. There's nothing privileged about proteins. Both just deterministically react to electromagnetism by sending neurotransmitters up the optic nerve. So to suggest that (4) is different to (2) is special pleading or begging the question. A bionic eye "intervenes" and could "fail to present the environment" if and only if an organic eye "intervenes" and could "fail to present the environment".

I think your question here makes the issue as sharp as it can be. I'll try to clarify where I think the equivalence argument ultimately breaks down.

I’m happy to grant that there is nothing privileged about proteins, and that a genuinely bionic eye could, in principle, count as part of a subject’s perceptual system. Material composition does no work here. What matters is not what the system is made of, but the role the system plays in constituting perception for the subject.

The distinction I’m relying on is not between lawful vs. unlawful mappings, or between covarying vs. non-covarying systems. I agree that in all of your cases—(1) through (4)—there can be lawful, consistent causal mappings from strawberry to neural outcome. So counterfactual covariation by itself cannot mark the difference. The real distinction is this: whether the mapping in question is constitutive of what it is for the subject to perceive at all, or whether it is a substitutable, instrumental mapping that could be altered without redefining perception for that subject.

In (2), Jane’s visual system—eye, retina, and downstream neural processing—constitutes her perceptual capacities. Whatever the mapping from wavelength to neural state happens to be (even under inversion), that mapping is not something that stands in for perception; it is how objects are perceptually available to her. There is no further question of whether this mapping is “doing its job correctly,” because it is not functioning as an intermediary whose output purports to represent the environment. It defines what counts as seeing for Jane.

By contrast, in (4), the visor introduces a mapping that is not constitutive in this sense. Even if it covaries lawfully with the strawberry, it functions as a substitutable system that fixes perceptual outcomes independently of the strawberry’s own role in determining how it is perceived. That mapping could be changed, replaced, recalibrated, or removed without thereby redefining what it is for John to perceive at all. That is why it is intelligible to ask whether the visor is presenting the environment correctly. The mapping is instrumental rather than constitutive, and so its outputs are assessable as succeeding or failing as presentations of the world.

This is also why (4) aligns with (3) rather than with (2), even though (4) bypasses the eye entirely. The difference is not whether an image is interposed, nor where in the causal chain neural stimulation occurs, but whether the system in question defines perceptual access or intervenes by imposing a detachable mapping. A bionic eye could fall on either side of this divide, depending on whether it becomes constitutive of the subject’s perceptual capacities or remains an instrument that determines perceptual outcomes in place of object-governed availability.

So the equivalence argument only goes through if one assumes that any lawful causal mapping to neural states is sufficient to fix intentional structure. That assumption collapses constitutive and substitutable mappings into the same category. I reject that assumption. Once the distinction is in view, it becomes clear why (1) and (2) count as direct perception, while (3) and (4) do not—not because of biology, reliability, or phenomenology, but because of the different roles these systems play in individuating what perception is for the subject.

In (2), Jane’s visual system—eye, retina, and downstream neural processing—constitutes her perceptual capacities. Whatever the mapping from wavelength to neural state happens to be (even under inversion), that mapping is not something that stands in for perception; it is how objects are perceptually available to her. There is no further question of whether this mapping is “doing its job correctly,” because it is not functioning as an intermediary whose output purports to represent the environment. It defines what counts as seeing for Jane.

By contrast, in (4), the visor introduces a mapping that is not constitutive in this sense. Even if it covaries lawfully with the strawberry, it functions as a substitutable system that fixes perceptual outcomes independently of the strawberry’s own role in determining how it is perceived. That mapping could be changed, replaced, recalibrated, or removed without thereby redefining what it is for John to perceive at all. That is why it is intelligible to ask whether the visor is presenting the environment correctly. The mapping is instrumental rather than constitutive, and so its outputs are assessable as succeeding or failing as presentations of the world. — Esse Quam Videri

I'm sorry but this still seems to beg the question. You just assert that Jane's organic eye counts as constituting her perceptual capacities and that John's bionic eye doesn't. I want to know why this is. Why does a bionic eye "function as an intermediary whose output purports to represent the environment and can be assessed as succeeding or failing" but an organic eye doesn't? They both function in identical ways; they react to electromagnetic stimulation by generating neurotransmitters that are sent up the optic nerve. It shouldn't matter whether the eye is one's natural eye, taken from a donor, grown in a lab, built by a mechanical engineer, or is a Boltzmann eye that spontaneously formed from quantum fluctuations. If any one of them can output the "wrong" neurotransmitters given the input then all of them can.

Although it's still not clear to me what would even count as the "wrong" (or the "right") neurotransmitters given your objection to the notion that the phenomenal character of experience can "succeed" or "fail" at representing the mind-independent nature of the world. It seems like your position now depends on the very naive realism that you previously rejected.

I think these revisions make it clearer what you are trying to assert.

1. The strawberry reflects 700nm light into John's eye which correlates with the stimulation of A neuron, and John’s report seeing the color red.

2. The strawberry reflects 700nm light into Jane's eye which correlates with the stimulation of the B neuron and Jane’s report seeing the color red

3. The strawberry reflects 700nm light into a visor that emits 450nm light into John's eye which correlates with the stimulation of the B neuron and John’s report seeing color blue.


However, point 4 is a little unclear for revision.

4. The strawberry reflects 700nm light into a visor and the visor bypasses John's eye to stimulate his B neuron, John reports seeing blue.

What is a mystery is the nature of the stimulation of John’s B neuron. What we understand is the emission of 450 nm light which we typically call “Blue” is associated with stimulation of John’s B neuron. And no other color’s wavelength should be stimulating this color. So, if it cannot be no other color wavelength stimulating this color, other than blue, what is the nature of this stimulation? We are alway bombarded with enormous amount of “stimulations” from the external world that can make color judgments difficult to get accurate. Looks like the visor is one of them.

Why does a bionic eye "function as an intermediary whose output purports to represent the environment and can be assessed as succeeding or failing" but an organic eye doesn't? — Michael

It turns on what kind of standard a system is answerable to. I'll try to explain what I mean by this:

You’re right that Jane’s eye can be assessed against physical and biological standards. We can say that it malfunctions if it fails to transduce wavelengths in the statistically normal way, or relative to how human eyes typically function. But that kind of assessment is not yet an intentional standard of correctness. A biological malfunction is a failure relative to a kind; it is not, by itself, a failure to accurately present the world. Even a normally functioning eye does not answer to some prior specification of how the environment is supposed to look for Jane. Rather, it fixes what “getting it right” means for her perceptually. That is what makes it constitutive.

By contrast, the visor in (4) is assessable as misrepresenting the environment even when it is functioning exactly as designed. That difference matters. The visor’s outputs purport to stand in for how the environment is perceptually available independently of it, which is why it makes sense to ask whether those outputs succeed or fail as presentations of the world. That question does not arise for Jane’s eye, not because it is organic, but because there is no independent intentional standard against which its mapping could be evaluated for her. Its mapping is identity-fixing, not performance-assessable.

This also explains why lawful covariation and consistency are insufficient to erase the distinction. An organic eye with an inverted mapping is not misrepresenting the strawberry; it determines what it is for strawberries to look any way at all for that subject. A visor with an inverted mapping can misrepresent even while covarying perfectly, because its role is instrumental rather than constitutive. The possibility of misrepresentation without malfunction is exactly what marks that difference.

So the asymmetry is not asserted but grounded: Jane’s visual system constitutes her perceptual capacities because it defines the intentional space within which perceptual correctness is possible at all. The visor intervenes on an already defined perceptual capacity, which is why its outputs are assessable as accurate or inaccurate in a way the eye’s are not.

What is a mystery is the nature of the stimulation of John’s B neuron. What we understand is the emission of 450 nm light which we typically call “Blue” is associated with stimulation of John’s B neuron. And no other color’s wavelength should be stimulating this color. So, if it cannot be no other color wavelength stimulating this color, other than blue, what is the nature of this stimulation? We are alway bombarded with enormous amount of “stimulations” from the external world that can make color judgments difficult to get accurate. Looks like the visor is one of them. — Richard B

I don't quite understand your question.

In this simplified account of physics and physiology, when the sense receptors in John's eye detects 450nm light it sends an electrical signal up the optic nerve and into the brain, "activating" neuron B, and when the sensors on the visor detect 700nm light it sends an electrical signal up the optic nerve and into the brain, "activating" neuron B.

The visor’s outputs purport to stand in for how the environment is perceptually available independently of it — Esse Quam Videri

The visor doesn't purport to do anything. It's just a machine that deterministically reacts to light, exactly like an organic eye.

If it helps, the visor was not designed by anyone for any purpose. It spontaneously formed via quantum fluctuations, and those who wear it don't even know that they wear it.

I apologize for the length of my replies. I don't feel I can do justice to your questions without going into detail.

No it doesn't. The visor doesn't purport to do anything. — Michael

I’m not attributing intentions, purposes, or design to the visor. “Purport” here is not a psychological or teleological notion. It doesn’t require anyone to think, intend, or even know that the visor exists. It marks a normative role a system plays relative to perceptual correctness, not an attitude the system has.

To say that a system’s outputs “purport to present the environment” just means this: the outputs are assessable as correct or incorrect relative to how things are, independently of whether the system is functioning normally or as designed. No intentions are required for that assessment to make sense.

That’s the crucial difference.

An organic visual system—even if it arose by chance, even if it were unknown to the subject—does not answer to an independent standard of perceptual correctness. If Jane’s eye maps 700nm light to a certain phenomenal character, that mapping fixes what red looks like for her. If the mapping were different, that would not make her perception false; it would make her a different perceiver. Biological malfunction is possible, but misrepresentation in the intentional sense is not separable from what it is for her to see at all.

By contrast, the visor’s mapping remains assessable as misrepresenting even if it arose spontaneously and even if no one knows it is there. We can coherently say: the visor is causing the subject to see the strawberry as blue even though, absent that device, it would appear red to that very same subject. That counterfactual comparison is what makes the visor’s outputs normatively assessable. No design, intention, or awareness is needed—only the fact that the visor intervenes on a perceptual capacity that is already defined independently of it.

So the distinction is not about what the visor “means to do,” but about whether a system defines perceptual correctness for a subject or is answerable to such correctness. “Purporting” names that answerability, not any inner purpose.

If you deny that distinction, then you are committed to the view that there is no principled difference between a system that constitutes perception and a system that merely alters its outputs—that all such systems are on a par as long as they are causally lawful. That is a coherent position, but it is precisely the internalist thesis at issue, not something forced on us by physics or by the absence of design.

So it's a question of whether perceptual normativity can be reduced entirely to causal covariance, or whether some causal systems fix the space of perceptual correctness while others operate within it. That’s the real fork in the road.

We can coherently say: the visor is causing the subject to see the strawberry as blue even though, absent that device, it would appear red to that very same subject. — Esse Quam Videri

Let's assume that the people who wear the visor don't have eyes, and so absent their visor they don't see anything.

Let's also assume that they are later given eyes, and that rather than their visor bypassing their eyes to stimulate their optic nerve, their eyes bypass their visor. We can coherently say: the eyes are causing the subject to see the strawberry as red even though, absent the eyes, it would appear blue to that very same subject.

So why do eyes count as part of direct perception but the visor doesn't?