C1. Therefore, the word "headaches" refers to private sensations — Michael

Seems clear.

If people had no private sensations - having a headache, feeling pain, feeling hot, smelling something, seeing something, tasting something, etc - then there would be no public language.

A public language only exists because people have private sensations.

Words, such as "headache", would have no meaning if people had no private sensations, such as headache.

A thermometer is put into water. When the thermometer reads 10deg C, the water is given the public name “cold”. When the thermometer reads 30deg C, the water is given the public name “hot”.

John sits in water, feels a private sensation, sees the thermometer read 30deg C, and says “I feel hot”. Jane sits in water, feels a private sensation, sees the thermometer read 30deg C, and says “I feel hot”.

It may well be that John feels the same private sensation when sitting in “hot” water that Jane feels when sitting in “cold” water.

No one can know, because no one can know another person’s private sensations.

The Indirect Realist accepts that it may well be that John feels the same private sensation when sitting in “hot” water that Jane feels when sitting in “cold” water.

The Direct Realist has the untenable position that i) John cannot possibly feel the same private sensation when sitting in “hot” water that Jane feels when sitting in “cold” water and ii) John must feel the same private sensation when sitting in “hot” water that Jane feels when sitting in “hot” water.

The word “hot” refers to both i) John’s private sensation and ii) the temperature of the water. The word “hot” does not mean that i) John’s private sensation and ii) the temperature of the water are the same thing.

There is no conclusive objective details of proof or demonstration how physical brain relates to the mind yet. — Corvus

:100:

The step you keep taking is from: "the object perceived must in fact be causally responsible if perception is veridical" to "the perceiver must know or believe that the object caused the perception." That step simply does not follow. — Esse Quam Videri

Step 1 - If I perceive the Sun, and my perception is veridical, there must be a Sun in the world
Step 2 - If a DR perceives a Sun, they know that the Sun caused their perception. If an IR perceives a Sun, they don’t know what caused their perception.
As far as I can see, both 1 and 2 are correct.
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Direct Realism requires causal dependence as a metaphysical condition of perception, not causal knowledge as part of perceptual content. — Esse Quam Videri

Both the DR and IR require causal dependence as a metaphysical condition of perception, because they both believe in Realism.
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This is precisely why illusions are possible: one can perceive as of the Sun without knowing what actually caused the perception. So the illusion argument does not show that DR is committed to knowing causal initiation; it presupposes the opposite. — Esse Quam Videri

On the one hand, when the DR perceives a Sun they know that the Sun caused their perception, which is why they are DR’s. On the other hand, the DR accepts that when they perceive a Sun it may be an illusion. DR seems to be a contradictory position to hold.

It is the IR who accepts that what we perceive may not be veridical.
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On inference: I’m not denying that we can infer from regularities in perception. I’m pointing out that inference to the best explanation presupposes some non-inferential constraint by the world in order for explanations to be better or worse at all. Otherwise, the regularities you cite are equally compatible with indefinitely many hypotheses. The regress is not inference-from-inference, but inference with no account of how perceptual appearances are answerable to the world in the first place. — Esse Quam Videri

I regularly perceive a yellow circle. I can infer infinite possible causes, such as an illusion, hallucination, God in the world, Sun in the world, Moon in the world, mind in a vat, etc.

Why choose one possibility rather than another. What constrains one’s choice?

The constraint comes from other perceptions, such that there is a logical coherence in all my perceptions. Perceptual appearances are answerable to the establishment of a coherent set of perceptions from which a logical world can be inferred using reason to the best explanation.

Philosophy is largely about semantics and logic. It doesn't deal with the cells, neurons and brain chemistry how it works with the entered images into it, does it? These are the subject for Neurology and brain science. — Corvus

Philosophy is also about the brain and how it relates to the mind.

Once the image you saw enters into your mind, shouldn't you then consult neurology or brain science in order to find out what is happening with the perceived image in your mind, rather than calling it Indirect Realism? — Corvus

I don’t think that neurologists or brain scientists can currently observe thoughts in the mind.

At the moment it is up to philosophy.

Direct realism says: "the object perceived is the mind-external object itself, not an intermediary". It does not say: "perception includes knowledge that the object caused the perception". That is an extra thesis you keep tacking on. — Esse Quam Videri

DR says that they directly perceive the Sun

If the DR says that they directly perceive the Sun, then it logically follows that it is their belief that the Sun caused their perception.

If the DR directly perceives the Sun, but it is the Moon that caused their perception, then this is one argument the IR makes against DR. The illusion argument.

This is not an extra thesis I keep adding on. It is a logical consequence of what the DR believes.
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Otherwise, the “unknown regularity” is doing all the work with no epistemic access—which collapses into skepticism or instrumentalism. — Esse Quam Videri

The IR avoids scepticism about an external world using inference to the best explanation.
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The inference to a “regularity in the world” must be answerable to something. That “something” cannot be the inferred regularity itself, or the bare perceptual appearances alone (since those are compatible with many worlds). — Esse Quam Videri

Yes, from a regularity in perception one can infer that there is a regularity in the world causing such regularities in perception. The inference that there is a regularity in the world causing regularities in perception is answerable to regularities in perception.

It is not necessary to be in epistemic contact with the world in a non-inferential way in order to make inferences about the world. That is why they are inferences. If one was in epistemic contact with the world in a non-inferential way then it would not be necessary to make inferences about the world, as you would already know about the world.

A person regularly perceives yellow circles.
Person A infers that their regularity of perception was caused by a regularity in the world.
Person A infers that their regularity of perception was caused by random events in the world.
Person C infers that their regularity of perception was caused by a God in the world.
Person D infers that their regularity of perception was caused by hallucinations.
We can then use reason to narrow these down to the best explanation.

All these inferences are answerable to something, a regularity of perception, and none involve any regress.

If I inferred from my inference then that would be a regress. In other words, if I inferred from my inference that my regularities of perception are caused by regularities in the world that there are regularities in the world, then that would be a regress.

Saying, you see a ship directly or indirectly sounds like, if there are any obstacles in the middle of the path of the seeing, rather than seeing the ship itself. It just sounds like it is a statement something unnecessarily confusing. You would only say that when asked - how do you see the ship? Was there anything between you and the ship, not blocking the view? — Corvus

When the IR says “I see the ship indirectly” the word “indirectly” is not referring to the space between the person and the ship but rather is referring to what is happening in the mind of the IR.

Direct Realism does not claim to know what initiated the causal chain. That’s not a weakness of DR; it’s a basic feature of any sane theory of perception. — Esse Quam Videri

As far as I know, DR is exactly the claim that they know what initiated the causal chain. In our example, they claim that they know the Sun initiated the causal chain. That is why it is not a “sane theory of perception.”

From IEP - Objects of perception

1 Direct Realism
Perceptual realism is the common sense view that tables, chairs and cups of coffee exist independently of perceivers. Direct realists also claim that it is with such objects that we directly engage.
2 Indirect Realism
The indirect realist agrees that the coffee cup exists independently of me. However, through perception I do not directly engage with this cup; there is a perceptual intermediary that comes between it and me.

=================

Perception is not an inference from present effects to past causes; it is a current perceptual relation to an existing object.......................The object does not need to be known as initiator in order to be known as perceived......................The inference itself still depends on perceptual contact with something, and that perceptual contact is still not knowledge of causal initiation. — Esse Quam Videri

Totally agree.
===============

IR does not escape the alleged logical impossibility either — it simply relabels perception as inference, which only leads to a regress, as we’ve already identified. — Esse Quam Videri

For the IR, perception is not inference. First there is perception and later there can be inferences made about this perception.

Suppose I regularly perceive a yellow circle. Using my reason I can then infer using best explanation that my regularity of perception was caused by a regularity in the world. For convenience, yellow circles can be named “Sun”, though it could be named anything. The word “Sun” then refers to not only i) perceived yellow circles but also ii) an unknown regularity in the world causing such perceptions.

I don’t see where any regress comes in.

Surely there are no such folks as DRists or IDists from their births, who must see a ship always either directly or indirectly no matter what situation under they see a ship? — Corvus

Yes, I had never heard of Direct and Indirect Realism ten years ago.

So acquaintance works like this: (1) you are perceptually related to an object, (2) that relation does not presuppose propositional knowledge, (3) description, classification, and judgment are subsequent cognitive acts — Esse Quam Videri

As an IR, I agree.

But how does the DR know what initiated a causal chain when such knowledge is a logical impossibility?
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Direct Realism does not claim that we can recover past states from present perception, or that perception gives us epistemic access to past events as such. What it claims is that perception is a present relation to a presently existing object, even though that relation is enabled by a causal history.Recovering the past is a task for inference, science, and explanation — not for perception itself. — Esse Quam Videri

So, DR does not claim we can recover past states from present perception, and recovering the past is a task for inference. As an IR, I agree.

I agree when you say that perception is a present relation to a presently existing object, which is the position of the IR
=======================

The causal chain enables perception; it is not something you reason from.......................Direct Realism says that we know the object we are perceptually related to, not the full causal history by which that relation was produced. — Esse Quam Videri

Totally agree. But how does the DR know the object that initiated the causal chain when logic shows us it is impossible to know what initiated a causal chain?

1 - We can only know about a Sun in the world because of a causal chain from it to us
2 - There is a change in both form and content of each link in this causal chain
3 - We cannot know either the form or content of a prior link even if we knew a present link
4 - All our information about the external world comes through our five senses
5 - The causal chain is temporal, in that what initiated the causal chain is temporally prior to our perception in the mind.
6 - Something in the external world initiated this causal chain
7 - The Indirect Realist believes that we can infer to the best explanation from the final link in this causal chain to what initiated the causal chain. — RussellA

How does DR overcome what is a logical impossibility?

If you say, well because they are DRists and IRists, then it doesn't make any sense, because it is not explaining why they see and understand the ship they are seeing in that way. — Corvus

Yes, Direct and Indirect Realism are just names which need further explanation.

It sounds really confusing when you say that you see a ship directly or indirectly, when you can say you see a ship. Why add those words, and make the statements unclear and muddled? — Corvus

In Ordinary Language, we say “I see a ship”. In Philosophy Language, the Direct Realist says “I see a ship directly” and the Indirect Realist says “I see a ship indirectly”.

Words need to be added because the Direct Realist, Indirect Realist and person in the street understand the world in different ways.
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It is not what you call yourself, which makes you a philosopher. It is how you think, see, understand and explain on the world and mind, which makes you one. — Corvus

:up:

On Direct Realism, the causal chain is a means of acquaintance, not a carrier of descriptive information. The chain enables perceptual contact with the object; it does not transmit a message that must be decoded. — Esse Quam Videri

How does that work? I am acquainted with an apple in the world even if I cannot describe it?
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The laws of physics do not entail a contradiction in the past state having been thus-and-so; they only show that the past is not recoverable from the present state alone. — Esse Quam Videri

If the laws of physics show that the past is not recoverable from the present state alone, then why does the Direct Realist believe that an apple as it existed in the past is recoverable from our present state of perceiving an apple?
======================

Perception is not an inference from present effects to past causes; it is a current perceptual relation to an existing object. — Esse Quam Videri

How can we know about the apple in the world independently of any causal chain from the apple to our perceiving it?
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On Direct Realism, we know the Sun because we see the Sun, not because we infer it from causal data. The causal chain explains how perception occurs, not what is perceived. — Esse Quam Videri

We seem to agree that:

1 - We can only know about a Sun in the world because of a causal chain from it to us
2 - There is a change in both form and content of each link in this causal chain
3 - We cannot know either the form or content of a prior link even if we knew a present link
4 - All our information about the external world comes through our five senses
5 - The causal chain is temporal, in that what initiated the causal chain is temporally prior to our perception in the mind.
6 - Something in the external world initiated this causal chain
7 - The Indirect Realist believes that we can infer to the best explanation from the final link in this causal chain to what initiated the causal chain.

Yet you say that the Direct Realist knows what initiated the causal chain. How?

Some here seem to think that how we speak in ordinary life is the answer to all the questions. They're just burying their heads in the sand. — Michael

:up:

Ordinary language
As the SEP article on Fictionalism points out, ordinary language uses figures of speech, metaphors, exaggerations and fictions in general.

For example “I see a ship directly in front of my eyes, I can smell its anger and feel its pain as it wanders aimlessly across the dark and mysterious ocean”

Ordinary Language Philosophy (OLP)
For example John Searle and the later Wittgenstein. John Seale is a Direct Realist and in his 2015 book “Seeing Things as They Are” argues against the “Bad Argument” of Indirect Realism”. He maintains that humans are able to directly perceive physical objects in the world, such as apples, because “apples” is already a Category within a public “Language Game”. For Searle, as a Direct Realist, such apples exist in the world even if never seen by a human. OLP argues that once everyday expressions are carefully analysed, many so-called philosophical problems disappear. OLP is an inquiry into meaning as use, rather than meaning as truth, whereby the meaning of an expression in language is inseparable to its use in the language game that is part of a Form of Life.

For example “I see a ship directly in front of my eyes”.

Metaphysical philosophy
One problem with OLP as a philosophy is that it does not question its own presuppositions. It does not question its own presupposition that objects such as apples exist in the world even if never observed by a human. Given such a presupposition, OLP can then make a valid case about the relation of language to the world. This is where the metaphysical philosopher comes in, to question such presuppositions.

For example, OLP is presupposing that relations ontologically exist in the world, which is not necessarily the case. There are many reasons why relations cannot ontologically exist in the world, If relations don't exist in the world, then neither can apples, as an apple can only have an identity if there are relations between its parts.

OLP is assuming that apples are discovered in the world, tending to support Direct Realism, whereas apples are invented in the mind supports Indirect Realism.

It is the metaphysical philosopher that thinks about people’s presuppositions.

Really? How do you tell the difference between the two? — Corvus

That is why posts on the Forum get confused when people mix up ordinary language and philosophical language.

The expression “I am a Direct Realist” would mean something different to the person in the street and a philosophy person.

No, but you would have direct contact with the medium through which the waves travelled, the air. The air comes from and is a feature of the mind-independent world. — NOS4A2

I am in a room with the door closed. I hear a sound I infer is from outside the room that sounds like a bark.

You say that hearing this sound means that I am in direct contact with whatever is outside the room.

But how can I be in direct contact with what is outside the room, when I have no idea what is outside the room that made the noise?

For example, the noise could have been made by a dog, wolf, coyote, fox, seal, bird, human, tv program, radio program, truck, car, toy, horn, alarm, cuica percussion instrument or numerous other things..

Even in ordinary language, should we say that we are in direct contact with something when we don't even know what we are in direct contact with?

However, on the other hand, the Indirect Realist would agree with you that we are in direct contact with the sound, regardless of what the cause was outside the room.

Surely what you are seeing is the image of the ship via telescope, not the ship itself? — Corvus

There is ordinary language and philosophical language.

In ordinary language, when looking at a ship in front of them, both the Direct and Indirect Realist could say “I am directly looking at the ship”. When looking at the ship through a telescope, both the Direct and Indirect Realist could say “I am indirectly looking at the ship in front of me”

However, in philosophical language, when looking at a ship in front of them, the Direct Realist could say “I am directly looking at the ship” and the Indirect Realist could say “I am indirectly looking at the ship”. When looking through a telescope, the Direct Realist could say “I am indirectly looking at the ship” and the Indirect Realist could say “I am directly looking at an image of the ship”

It gets difficult when ordinary and philosophical language are mixed up.

Light is of the mind-independent world; it is absorbed by the eyes; and therefore each of us has direct contact with the “mind-independent world”. Since this contact is direct, so is access to the “mind-independent world”, and there is zero room in space and time for any intermediary. — NOS4A2

I am in a room with the door closed, I hear a sound. I infer that the sound came from outside the room. I may be wrong, but I infer it.

In this case, is it the correct use of language to say “I have direct contact with what is outside the room”?

There is ordinary language, “I indirectly see the ship through my telescope and I directly see the ship in front of me”.

There is philosophical language, “I directly perceive phenomenal experiences in my mind enabling me to indirectly infer that there is a ship in the world.”

Things go wrong when in philosophical language a word is used having an ordinary language meaning.

The duality is necessary for evaluation................This is the computational theory of cognition. It's the scientific status quo, so to speak. — frank

The Direct Realist falls into the duality of the Homunculus Strawman problem: “If a homunculus (a little person) is needed inside the mind to process information, then who processes the information for that homunculus?"

The modern Cognitive Revolution overcomes any need for the duality of a homunculus by using the scientific method and treating the mind like a modular computer. Mental processes are handled through algorithms and mechanisms without the need for any central homunculus. (Wikipedia - Cognitive Revolution).

Logically speaking, if I cannot see what is on the other side of the door then I cannot see it. Similarly, if I cannot perceive what is on the other side of my mind, then I cannot perceive it.

It logically follows that as I can only see what is inside the room, I can only perceive what is inside my mind.

It is not the case that there is the duality “I” am separate to my mind, but rather “I” am my mind.

In my mind there is not the duality of a homunculus looking at my mind. As the modern Cognitive Revolution shows, mental processes are handled through algorithms and mechanisms without the need for any central homunculus.

I take this to be a problem for cognitive science. If they end up agreeing with you, they'll at least have to explain the expectation of the duality of perceiver and perceived. I can't really do anything with the mere suggestion that there is no duality. — frank

I perceive my pain. I am the perceiver and my pain is what is perceived.

If there was a duality between perceiver and perceived, a duality between me and my pain, this would suggest that I am separate to or outside my pain, and it is my choice whether to feel my pain or not.

But we know that this is not the case. I am not separate to or outside my pain. I am my pain. There is no duality between me and my pain. There is no duality between me as perceiver of my pain and what is perceived, my pain.

I would add that a mental state isn't really just one thing. There's the "sensory" mental state, but then also the "intellectual" mental state. I think it quite appropriate to say that my intellect is aware of and tries to make sense of the sensations. — Michael

Yes, there is the sensory mental state “I feel pain” and there is the intellectual mental state “I reason that the pain was caused by something mind-external.”

Question one = Is the mind separate from the brain’s neural activity or is the mind the brain’s neural activity?

To avoid the homunculus straw man problem, the mind is the brain’s neural activity.

Question two = Am “I” separate from my mind or am “I” my mind?

Again, to avoid the homunculus straw man problem, “I” am my mind.

Therefore, because “I” am my mind, and my mind is my brain’s neural activity, “I” am my brain’s neural activity.

This means that the brain’s neural activity can process both sensations and reasoning.

This should not be unexpected, as even the most basic of light sensors can detect the intensity of surrounding light and choose whether to turn the light on or not.

Even the basic £10 light sensor can process both sensations and reasoning about what action to take based on these sensations.

The difference between direct and indirect realists as represented in this thread, comes down to how we want to describe that perceptual relation. Is it between perceiver and a mental state? Or is it between perceiver and physical object? — frank

There is a relation between perceiver and physical object.

But there is no relation between perceiver and a mental state if the perceiver IS the mental state.

What does the Indirect Realist believe?

The homunculus infinite regress problem arises when the mind is assumed to be a separate entity to the brain, and the mind is looking at the neural activity in the brain.

When it is agreed that the mind is the neural activity in the brain, then this problem disappears.

John Searle pointed out the nature of identity in The Philosophy of Perception and the Bad Argument

The relation of perception to the experience is one of identity. It is like the pain and the experience of pain. The experience of pain does not have pain as an object because the experience of pain is identical with the pain. Similarly, if the experience of perceiving is an object of perceiving, then it becomes identical with the perceiving. Just as the pain is identical with the experience of pain, so the visual experience is identical with the experience of seeing.

What do words mean?

Wittgenstein’s “meaning is use” suggests that the meaning of a word is determined by how the word is used in language in a language game. Each language game exists within a “form of life”. A “form of life” means human activities within the world and social interactions between humans within this world.

Wittgenstein is presupposing a world. If there was no world then there would be no form of life and no language game.

So what is the meaning of the word “world”. On the one hand, its meaning comes from how it is used in the language game, but on the other hand, its meaning is presupposed in order to have a language game in the first place.

Therefore, its meaning cannot be found within the language game, as its meaning is presupposed in order to have a language game in the first place.

Then how can the meaning of the word “world” be found if not from the language game itself. Only within the philosophy of metaphysics.

Adding my tuppence worth.

I may regularly perceive in my mind a grey circle, which I infer to the best explanation has been caused by a regularity in the mind-external world

Such regularities of perceptions in the mind become concepts in the mind, where a concept is a regularity of perceptions in the mind.

Concepts, because they are regularities in the mind, may for convenience be given a name. The name is not important, but could be “bird”, for example.

The name “bird” therefore refers to not only i) a regularity of perceptions in my mind (aka concept) but also to ii) an unknown regularity in the mind-external world that causes such regularities of perceptions in my mind.

Such is the basic relation between concepts in the mind, naming in language and objects in the mind-external world.

I appreciate your feedback on my thesis.

3. Rejected: I would not claim that “content travels unchanged” through the chain. I would claim that perception is of the object via the chain, not that the chain preserves representational content. — Esse Quam Videri

You agree that the form of each link and the content of each link in the causal chain can change.

But all information about what initiated the causal chain must be contained within each link.

If both the form and content of each link can change, how exactly is this information about what initiated the causal chain expressed within each link?
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5. Rejected: This establishes at most epistemic underdetermination, not logical impossibility; the examples show fallibility, not impossibility.
6. Rejected: Fallibility or inferential uncertainty does not entail logical impossibility; this confuses limits on reconstruction with limits on knowledge. — Esse Quam Videri

As there is an arrow of time, there is an arrow of causation. We can remember the past but not the future.

During a game of snooker, we observe snooker balls at rest on a snooker table. It is logically possible using the laws of physics to determine the position of the snooker balls a moment in the future. However, it is logically impossible to determine the position of the snooker balls a moment in the past.

This is not epistemic undetermination, this is logical impossibility.
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7. Rejected: Non-sequitur. Even if causal origins cannot be reconstructed with certainty, it does not follow that the object of perception is an inner phenomenal item rather than the external object. — Esse Quam Videri

My argument in 1 to 9 is that causal origins cannot be reconstructed at all, not reconstructed with uncertainty.

How can causal originals be reconstructed even with uncertainty when you agree that not only the form but the content also of each link in the causal chain can change, especially when you accept 8.

8 - As an IR, I accept that it is not logically possible to know either the form or content of a prior link in the causal chain.
8. Granted.

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9. Rejected: False attribution. I do not claim we can logically reconstruct prior causal links; I claim that perception is world-involving without requiring such reconstruction. — Esse Quam Videri

How does the Direct Realist know what initiated the causal chain, if we only know about what initiated the casual chain because of the causal chain itself, and you agree that we cannot reconstruct prior causal links.

What else is there?

The capacity to experience colors and shapes is innate for people born with "normal" perceptual systems. But "yellow" and "circle" are more than just names, they are concepts that have to be understood through personal insight and stabilized through social practice. — Esse Quam Videri

We see the colour red when looking at a wavelength of between about 620nm to 750nm. We have the concept of the colour red through personal insight. We learn the word “red” through social practice.

As with the chicken and egg, which came first, i) we have the concept of the colour red through personal insight and then we learn the word “red” through social practice or ii) and we learn the word “red” through social practice and then have the concept of the colour red through personal insight?

I think i) is more reasonable.

John Searle in The Philosophy of Perception and the Bad Argument wrote about the identity between the perception and experience.

The relation of perception to the experience is one of identity. It is like the pain and the experience of pain. The experience of pain does not have pain as an object because the experience of pain is identical with the pain. Similarly, if the experience of perceiving is an object of perceiving, then it becomes identical with the perceiving. Just as the pain is identical with the experience of pain, so the visual experience is identical with the experience of seeing.

What the Direct Realist proposes is a logical impossibility

The bent stick argument is a weak argument against Direct Realism (DR), in that the Semantic Direct Realist (SDR) may sensibly say that although perception is indirect, cognition is direct. We directly cognise a straight stick that appears bent.

A better argument against SDR is that direct cognition is logically impossible.

The SDR agrees with the Indirect Realist (IR) that i) all our information about the mind-external world comes through our senses and ii) there is a temporal causal chain from something in the world initiating a causal chain which eventually causes a perception in the mind.

For example, we can conceptualise that the causal chain was initiated by the stick, followed by a wavelength of light, to an electrical signal in the optic nerve, then neural activity in the brain and finally perception in the mind.

The SDR agrees that the form of the links in the causal chain may change, for example, from a wavelength of light to an electrical signal. However, it is logically impossible for the content of the link not to change if the form of the link changes. From Leibniz’s Law, the Principle of Indiscernibles, two distinct things, such as two links of a causal chain having different forms, cannot share the same content, the same properties.

As the form of these links in the causal chain change, the content of these links must also change. But it is the content of these links that is cognised.

Therefore, the content of the link at initiation cannot be the same as the content of the link when perceived, but as it is the content that is directly cognised, what is cognised in the link at perception cannot be what would be cognised in the link at initiation.

The SDR is saying that in order to directly cognise the stick, even though the form of the links in the causal chain change, the content of the links must remain the same, as it is the contents of the links that is cognised, but this is a logical impossibility.

I don't deny the IR the right to believe these things, I only deny that they are rationally compelling. — Esse Quam Videri

That’s the question, which of IR and DR is more rationally compelling.
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Tensed truths are not only about the present, but about the past and future as well. Presentism doesn't rule out tensed truths about persistent objects. — Esse Quam Videri

I don’t understand how the Sun can persist through different times when in Presentism there is only one time, namely the present.

I can understand, however, that as a concept the Sun persists.
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I think that your account of experience, understanding and judgment is overly simplistic and elides many important distinctions. — Esse Quam Videri

Possibly, but this is a post on the Forum, not a PhD.
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For example, what does it mean to "perceive" the "combination" or "yellow" and "circle"? A "combination" is a relation. Are you saying we can perceive relations directly? — Esse Quam Videri

Are you saying that when you look at a table, you perceive the spatial relation between the table top and table legs indirectly?

Though I believe that there cannot be a relation in the absence of anything being related.
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"Yellow" and "circle" are classifications. Do these just "appear" within consciousness without any effort or learning on the part of the subject? — Esse Quam Videri

We need to learn the names "yellow" and “circle”, but I would have thought that our ability to perceive yellowness and circularity are innate, something we are born with.

This does not follow. You are trying to argue from epistemic limits to an ontological conclusion. Even granting the contestable claim that it is "logically impossible" to know what initiated the causal chain, all that follows is that we can't be certain of what we perceive. Fallibility doesn't imply indirectness. — Esse Quam Videri

A stick in water looks bent. The Semantic Direct Realist’s (SDR) position is that of indirect perception but direct cognition. The SDR is saying that in the mind-external world is a straight stick, and it appears bent. There are many instances of where perception is fallible.

The Indirect Realist (IR) is not saying that fallibility implies indirectness. The IR is saying that i) there is no stick in the mind-external world in the first place, ii) the fact there is no stick in the mind-external world is what implies indirectness, iii) the stick we perceive exists as a concept in the mind, not as a fact in the mind-external world.
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Persistence on Presentism is cashed out in terms of tensed truths and causal continuity, not simultaneous existence at multiple times. — Esse Quam Videri

The persistence of the Sun has a different meaning to the IR and DR.

For the IR, the Sun exists as a concept in the mind, and as a concept persists from the past to the present. This is reasonable.

For the DR, the Sun exists in the mind-external world. Accepting Presentism, an object cannot persist through different times when only one time exists. The tensed truth “The Sun exists now” is true now has no relation to “the Sun persists now”.

For the Sun to persist makes sense for the IR, but not for the DR.
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The causal chain doesn't interpose something between subject and object; it's the means by which the object is perceptually available. — Esse Quam Videri

As I see it:

I would appreciate it if sometime you could find any flaws in my main argument against Direct Realism (both Phenomenological Direct Realism (PDR) and Semantic Direct Realism (SDR)). — RussellA

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Judgment is the movement from sensory data to existential affirmation by way of insight and understanding, whereas inference is a movement from premises to conclusion by way of logical rules. — Esse Quam Videri

Suppose that many times I perceive the combination yellow circle.

Our ideas about the nature of a mind-external world is not subjective judgement alone, such as “we are a mind in a vat” nor objective inference alone, as we are reasoning about the subjective nature of the mind.

I both judge and infer that there must be a regularity in the mind-external world causing these regularities in my phenomenal experiences.

@Michael

I would appreciate it if sometime you could find any flaws in my main argument against Direct Realism (both Phenomenological Direct Realism (PDR) and Semantic Direct Realism (SDR)).

1 - Both the Indirect Realist (IR) and Direct Realist (DR) agree that there is something in the mind-external world that initiates a causal chain that eventually leads to a perception in our mind.
2 - The IR and DR agree that the links of this causal change chain may change in form, ie, from a wavelength of light to an electrical signal in the optic nerve
3 - The DR believes that a change in form of the link does not mean that the content of the link changes. IE, the DR believes that they still directly perceive what initiated the causal chain.
4 - The IR and DR agree that all our information about the mind-external world comes through our senses.

5 - My argument, as an IR, is that even if one knew one link in the causal chain, it is logically impossible to know either the form or content of a prior link. One can, however, infer to the best possible explanation.
For example, seeing a broken window, it is logically impossible to work backwards through a causal chain to know what initiated the causal chain and thereby know what broke the window.
Also, when a detective sees a crime scene, it is logically impossible for the detective to work backwards through a causal chain to know what initiated the causal chain and thereby know who committed the crime.
Also, when seeing snooker balls at rest on a snooker table, it is logically impossible to work backwards through a causal chain to know what initiated the causal chain and thereby know where the snooker balls were a moment earlier.
6 - Therefore, as it is logically impossible to know the form or content of a prior link in a causal chain, it is logically impossible to know what initiated the causal chain.
7 - But we do perceive things such as the Sun and a wavelength of light. As it is logically impossible to know what initiated the causal chain that gave us the information from the mind-external world, we cannot be directly perceiving what initiated the causal chain, whether the Sun or a wavelength. Therefore we can only be perceiving the phenomenal experience itself. From this phenomenal experience we can infer to the best explanation that in the mind-external world there is something we conceptualise as the Sun and wavelength of light.
8 - As an IR, I accept that it is not logically possible to know either the form or content of a prior link in the causal chain.

9 - The Direct Realist (both PDR and SDR) is basing their belief on a logical impossibility, that it is possible to know either the form or content of the prior link in a temporal causal chain.

I don't accept this phrasing "perceiving the Sun in the mind" if it implies that perception is of some sort of mental item.............................Likewise, I didn't accept this. It suggests that what is perceived is a mental item (a Sun-in-the-mind) and that perception involves matching that mental item to a worldly object. — Esse Quam Videri

The DR accepts there is a temporal causal chain from something in the mind-external world to their perception.

For example, we can conceptualise that the causal chain was initiated by the Sun, followed by a wavelength of light, to an electrical signal in the optic nerve, then neural activity in the brain and finally perception in the mind.

However, as all our information about the mind-external world comes through our senses, and as it is logically impossible to know the true nature of any link prior to coming through our senses, it is also logically impossible to know the true nature of what initiated any causal chain.

The DR agrees that they perceive a Sun because of a causal chain, but as it is logically impossible to know what initiated any causal chain arriving at our senses, what the DR is perceiving cannot be something in the mind-external world.

If the DR is not perceiving a “worldly object”, then they can only be perceiving something in their mind.
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Physical systems persist precisely by changing in structured ways. — Esse Quam Videri

I agree that the concept of a Sun is something that persists through time.

But how can something persist in a mind-external world, if persists means exists at different times, and in Presentism only one moment in time exists.
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DR doesn't require this. It requires only that perception be grounded in lawful causal dependence on the world. — Esse Quam Videri

I thought that DR requires that perception is grounded in a mind-external object. This mind-external object may in fact initiate a causal chain, but it is not the causal chain that the perception of the DR is grounded in.
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I think you are missing the point of the regress argument. At some point, something must count as non-inferentially present to the mind, or explanation never begins. — Esse Quam Videri

Do you mean that judgement is non-inferential?

In my sensations is a yellow circle. I judge that in the mind-external world is a Sun.

In what sense is judging that in the mind-external world there is a Sun different to inferring from my sensations that in the mind-external world is a Sun?

I agree that I am missing what other non-inferential thing must be present in the mind.

I think you are seeing two objects, not a single object. — Corvus

When I see a table, am I seeing one object, the table, or five objects, the table top and four legs?
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Objects exist in the external world if we can see and interact with them. — Corvus

I see an apple, touch it and see it move.

Both the IR and DR agree that there is a mind-external world of physical matter and energy that obeys the physical laws.

It is a problem of naming.

Suppose in touching the apple I knock off one atom. The apple has changed. Is it the same apple even though it has changed or should I give it a new name because it has changed.

If I give it a new name then it becomes a new object.

Only a human can decide whether it should keep its name or be given a new name.

Only a human can create new objects.

All this suggests that objects only exist in the mind and language, not in the external world.
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It needs explanation how brain generates mind, how brain is linked to mind or how mind works from brain. — Corvus

Very true.

(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. — Esse Quam Videri

I will stick to Presentism, as this still makes my point.

The Indirect Realist (IR) and Direct Realist (DR) agree
1 - There is a temporal causal chain that follows the laws of physics from a mind-external something to perceiving the Sun in the mind.
2 - There is a mind-external world, and in this mind-external world physical matter and energy follow the laws of nature.
3 - In Presentism, only the present exists.
4 - There are objects such as the Sun

Beliefs of the IR and DR
1 - The Direct Realist believes that there is a one to one correspondence between the Sun we perceive in the mind to a Sun that both exists and persists in the world.
2 - The Indirect Realist believes that we do not perceive the mind-external world as it really is, but perceive it through a conceptual framework. For the Indirect Realist, the Sun is a concept that both exists and persists in the mind.

As there is an arrow of time there is an arrow of causation
1 - In the arrow of time, we can remember the past but not the future
2 - In the arrow of causation, given a present event, we can determine a future event using the laws of physics, but it is logically impossible to determine a past event.

In particular, during a snooker match, when all the balls are at rest, we can determine their immediate future positions using the laws of physics, but it is logically impossible to determine their immediate past positions using the laws of physics.

In general, during a snooker match, when all the balls are moving, we can determine their immediate future positions using the laws of physics, but it is logically impossible to determine their immediate past positions using the laws of physics.

Where does the Sun exist
Suppose what we know as the Sun in the mind-external world with the passage of time loses one atom. On the one hand, in the mind-external world there has been an ontological change. On the other hand, the human observer has the choice whether to keep the same name, the Sun, or change its name. As the Sun is generally accepted as a concept and within language, although there has been an ontological change, we keep the same name.

Suppose there is one object, an apple, and another object, a table, and the apple is on the table. We could name an apple on a table as “apptab”. We have thereby created another object, an apptab. In the same way we created the objects apple, table and Sun. All names are human creations and exist as concepts and within language.

Objects exist and persist through time because objects are names, and names exist and persist in concepts and language.

The IR and DR disagree
1 - The IR believes that objects such as the Sun only exist as concepts and in language, whereas the DR believes that objects such as the Sun exist in the mind-external world.
2 - The IR believes that we cannot know but can only infer a prior event in a temporal causal chain, whereas the DR believes that we can know a prior event in a temporal causal chain

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. — Esse Quam Videri

As the Sun only exists as a concept and in language, it can persist through change both as a concept and in language. Something in the mind-external world that is constantly changing cannot persist.

Treating the Sun as a concept and in language is the position of the IR.

On Presentism, causal explanations are perfectly coherent: present states are effects of earlier states, even though those earlier states no longer exist. — Esse Quam Videri

Both the IR and DR agree that causal explanations are perfectly coherent and present states are effects of earlier states.

However, in a temporal causal chain, a future event can be determined from a past event using the laws of physics, whereas it is logically impossible to determine a past event from a present event using the laws of physics.

For the DR to believe that they can directly know a past event from a present event through a temporal causal chain is a logical impossibility.

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. — Esse Quam Videri

As knowing a past event using a temporal causal chain is logically impossible, only by inference from the present can a past event be hypothesised. This is the position of the IR.

There is no non-inferential means of discovering a past event from the present using a temporal causal chain.

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.

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 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.