But for indirect realism, what everyone sees is some private mental image, and hence what you see and what the other person sees are quite different. — Banno

Almost, in that my private perception of a tree may or may not be the same as anyone else's, but it is impossible to know, as it is a private mental image.

Wittgenstein Philosophical Investigations may be used to give insights into Indirect Realism, including his strong case against the possibility of a private language and his arguing that nobody knows another person's private sensations.

The Indirect realist accepts Wittgenstein's conclusion that one's private perception of an object, such as a tree, is forever unknown to anyone else.

The Direct Realist doesn't accept Wittgenstein's conclusion. The Direct Realist argues that we perceive objects in the world as they really are, immediately and directly. Therefore, if two people are looking at the same object in the world, such as a tree, as both will be perceiving the same object in the world immediately and directly, their private mental images will be the same, meaning that each will know the others private sensations.

Therefore, whether one is an Indirect or Direct Realist depends in part of whether one accepts Wittgenstein's Philosophical Investigations

If indirect realism were taken at face value, two people cannot both look at the same thing — Banno

Wittgenstein's para 293 in Philosophical Investigations about a beetle in a box provides a solution to the problem raised about Indirect Realism, ie, how is communication possible between people using a public language when nobody can know another person's private sensations.

For example, as an Indirect Realist, my private mental image of a tree may be different to everyone else's, yet I can use use the word "tree" in a social language game with others. Within the language game, the word "tree" isn't describing my mental image, as each particular mental image has dropped out of consideration within a language game as irrelevant.

Wittgenstein's beetle in the box explains the connection within Indirect Realism between private mental images and a public language.

The indirect realist says what one sees is the model of the tree — Banno

As an Indirect Realist, I am not saying that I see a model of a tree, I am saying that I directly see a tree, though the tree I see is an indirect representation, image or model of something that exists in the actual world.

A key concept is intentionality, in that my mind is directed at the tree that I perceive, not in virtue of the tree representing another object, another tree, as this would lead into an infinite regression and the homunculus problem.

In terms of intentionality I'm talking to (and seeing) my parents, but given the physics and mechanics of external objects and light and sound and the central nervous system, the phenomenology of experience is indirect. — Michael

Yes, intentionality is closely associated with phenomenology.

Taken from the article What Is Intentionality, and Why Is It Important? by Robert Sokolowski:

"The term most closely associated with phenomenology is “intentionality.” The core doctrine in phenomenology is the teaching that every act of consciousness we perform, every experience that we have, is intentional: it is essentially “consciousness of” or an “experience of” something or other. All our awareness is directed toward objects. If I see, I see some visual object, such as a tree or a lake; if I imagine, my imagining presents an imaginary object, such as a car that I visualize coming down a road; if I am involved in remembering, I remember a past object; if I am engaged in judging, I intend a state of affairs or a fact. Every act of consciousness, every experience, is correlated with an object. Every intending has its intended object."

Intentionality is common to both Indirect and Direct Realists.

As an Indirect Realist, when I see a tree, there are two aspects. First, intellectually, I know that my mind is directed onto a representation of a tree. Second, viscerally, I know that my mind is directed onto a tree, not a representation of a tree.

After all, even as an Indirect Realist, if I was standing in the middle of the road and saw a truck approaching me, I wouldn't think "just a representation of a truck" and remain where I was.

This is the exact red herring that is almost always brought up in the debate between direct and indirect realism. — Michael

I am sure that we both agree with Indirect Realism.

Searle definitely supports Direct Realism, and within Direct Realism, as also discussed by Pierre Le Morvan in his article Arguments against Direct Realism and how to counter them, there is causal indirectness (PDR) and cognitive indirectness (SDR).

I would assume Searle agrees with the cognitive indirectness version of Direct Realism, as he must well know the bent stick problem.

What do you mean by red herring ?

Yeah, but what Searle is suggesting is not what you are criticising. — Banno

I think I am criticising what Searle is suggesting.

I don't agree with Searle in his support of naive realism (direct realism), as it seems to me that only Indirect Realism can satisfactorily explain how we interact with the world.

As Searle said "I think the rejection of naive realism was the single greatest disaster that happened in philosophy after Descartes...................but the idea that you can't ever perceive the real world but only a picture in your mind that creates a disaster, because the question that arises is what is the relationship between the idea you do perceive or the sense datum of the impression that you do perceive and the real world, and there is no answer to that which is satisfactory once you make once you make the decisive move of rejecting Naive Realism"

I don't agree with Searle's solution to the epistemological problem of how we can gain knowledge of objects in the real world from private sense data, how we can know the public objective from the private subjective and how we avoid scepticism, subjectivism and solipsism.

Searle proposes the "intentionality of perception". Whereas I agree that we are shaped by evolution, and the object causes the visual experience, I don't agree that the intentional content of our minds (intentional state) is causally self-referential. IE, I may perceive a car, but it is the car that has caused me to have that very perception. Such self-referential causality is inadequate to ensure a condition of satisfaction between the intentional content and object in the world, whether a veridical perception or an hallucination.

Searle tries to avoid Kant's transcendental link between intentional content and actual world by attempting to naturalize intentionality, ie, treating intentionality as just another biological function using a self-referential intentional causation.

Searle attempts to show that a self-referential causation between intentional content and world will ensure that any link between intentional content and world will be logical rather than empirical, and therefore directly observable, avoiding Hume's problem of inference using regularity of observation.

Searle's approach fails because he ignores the asymmetry of cause and effect, and incorrectly assumes a symmetry in the direction of fit from world to mind and from mind to world.

Such asymmetry between cause and effect and effect and cause means that the link between intentional content and actual world cannot be self-referential, as is required by Searle in his support for naive realism.

Who said that there's such a thing as "direct realism"? — Alexander Hine

From Wikipedia Direct and indirect realism

"In contemporary philosophy, indirect realism has been defended by Edmund Husserl[17] and Bertrand Russell.[9] Direct realism has been defended by Hilary Putnam,[18] John McDowell,[19][20] Galen Strawson,[21] and John R. Searle.[22]"

From John R. Searle The Philosophy of Perception and the Bad Argument

"I realize that the great geniuses of our tradition were vastly better philosophers than any of us alive and that they created the framework within which we work. But it seems to me they made horrendous mistakes."

"The second mistake almost as bad is the view that we do not directly perceive objects and states of affairs in the world."

I may be absolutely certain of what I am seeing, whether a tree or snooker balls on a snooker table, but knowing the present effect doesn't allow me to know the preceding cause.

As I cannot know from the position of the snooker balls in the image the preceding state of affairs, I cannot know from seeing an image of a tree the preceding cause of that image.

A Direct Realist would need to explain how the cause of an effect may be unambiguously known just from knowing the effect.

The onus is on direct realists to explain, if only broadly and superficially, how direct realism is supposed to work. Thoughts? — frank

Pierre Le Morvan wrote an article Arguments against Direct Realism and how to counter them

A major problem with Direct Realism is the belief that because one knows an effect, such as the image of a tree, the cause of that effect can be directly and unambiguously known.

The guy on the left is an image of direct realism. He doesn't get a cloud. He just directly sees the tree — frank

You say the Direct Realist is not seeing an image of the tree, which is what the Indirect Realist would say, but is directly seeing the tree.

An Indirect Realist would say that they are looking at an image of the tree, and therefore don't know, just from the image, whether the tree is 5m tall 10m away or is 10m tall 20m away.

If the Direct Realist is directly seeing the tree and not an image of the tree, how does the Direct Realist know, just from the image, whether they are looking at a 5m tall tree 10m away or a 10m tall tree 20m away ?

How can the Direct Realist justify that they are not looking an an image of the tree ?

@Eugen In Physicalism, everything is physical. But the question remains, is a protoconsciousness an intrinsic part of the physical.

What's the difference between protoconsciousness and matter? — Eugen

I would use the term Physicalism rather than Materialism. Physicalism is closely related to Materialism, but Physicalism grew out of Materialism with advances in knowledge about the physical sciences. In the world of space-time there is more than just elementary particles but also elementary forces.

Therefore, an understanding of consciousness needs more than an understanding of matter but also the forces between this matter. The question with the mind-body problem is how consciousness is grounded in broadly physical systems, how the property of feeling pain could be instantiated by an entirely physical object, such as the nervous system.

Referring to the SEP article Russellian Monism, according to Bertrand Russell, fundamental physical entities are intrinsically qualitatively special such that they necessitate conscious states in macro structures, such as humans, but as yet, our understanding outstrips current knowledge. Russellian monism comes in two varieties: panpsychist and panprotopsychist. The former holds that the special intrinsic properties are themselves consciousness properties, and the latter denies this.

I find it hard to believe in panpsychism, in that electrons are conscious, but panprotopsychism seems a more sensible approach, whereby elementary particles and forces have certain intrinsic properties that enable the realization of consciousness in certain circumstances. For example, the property of movement cannot be observed in a system consisting of a single magnet, yet can be observed in a system consisting of several magnets in close proximity. It is also the case the the property of momentum of an objects exists neither in its mass or velocity, but is a product of the two. The property of volume of an object doesn't exist in its parts but in the relation of the parts making up the whole. Perhaps in the same way, the property of consciousness cannot be discovered in an individual element, but only emerges when several individual elements are combined in certain particular ways.

Perhaps protoconsciousness is an intrinsic feature of elementary particles and forces that only emerges as the property of consciousness when these elementary particles and forces are in certain combinations.

Ok... elaborate a bit please, it looks like you're saying something there — Eugen

Intellectually, my belief is that of Neutral Monism, where reality consists of elementary particles and elementary forces in space-time. Consciousness may be explained by Panprotopsychism. However, the unity of consciousness, the neural binding problem, Kant's unity of apperception remains beyond comprehension, and must remain what McGinn called Mysterianism.

On the one hand I cannot believe in Conceptualism but on the other hand I know Conceptualism is true.

As an "experience" is a concept, and therefore a type, perhaps the wording should be "there are no experiences, only tokens of experiences", though I know what you meant, which is the main thing.

But, if I were a materialist, I would go further and eliminate the notion of Type altogether. — Eugen

If I started as a Materialist, this would lead me into becoming a Physicalist, and eventually a Panprotopsychist.

I would have thought that to be a Materialist means rejecting the notion of a type. A Conceptualist would accept the existence of types in the mind, but I don't think that a Materialist would be a Conceptualist.

There are no types of experiences, only experiences. — Eugen

As an aside, an "experience" as a concept is a type.

I referenced cognition because the most popular models of how the brain works are computational — Count Timothy von Icarus

Numbers are computed in language

If asked the question "what is one plus one", as the answer is not contained in either number, I need to carry out a computation in my mind.

If I put one pebble on a table, and then put another pebble next to it, I can see two pebbles.
I don't need any mental computation to know that I see two pebbles, in the same way that I don't need to compute that I see the colour green. Seeing the colour green is the direct effect of the cause of a wavelength of 550nm entering the eye.

Regarding causation, if Bertrand Russell was correct that the notion of causality is objectively redundant, there would be no work for the National Transportation Safety Board which investigates every civil aviation accident in the United States, for example.

Therefore, I only need to carry out a computation if presented with a problem expressed in language, ie, in the computation of numbers where language and naming cannot be ignored. In language, one object is named "one". When another object is added, the set of objects is named "two". When another object is added, the set of objects is named "three", etc. Therefore, when I see one pebble on the table, I can say "I see one pebble". When I see another pebble added I can say "I see two pebbles". I can then answer the question "what is one plus one" as "two".

Therefore, the computation of numbers within the mind can only occur within language.

In terms of grouping rocks together, it's probably easier to conceptualize how the cognition of "there are two rocks over there," and "there are 12 rocks over there," requires some sort of computational process to produce the thought "there are 14 rocks in total." — Count Timothy von Icarus

If I see two rocks on the left, I know that two objects has the name "two".
If I see twelve rocks on the right, I know that twelve objects has the name "twelve".
If I see fourteen rocks in total, I know that fourteen objects has the name "fourteen".

IE, I know there are fourteen rocks in total not from any computational process but from how objects are named.

What is computation? — Count Timothy von Icarus

As a non-mathematician, I am curious about the following:

Question one: if I put one pebble on a table and alongside it put another pebble, has a computation been carried out ? Because, whatever has happened has proceeded in a series of steps, within the system there has been a change in information, something has caused the pebbles to move, time and energy have been needed, two has been instantiated in the physical world as two pebbles but also two exists as the abstract object two and two pebbles existing as a single whole is different to two pebbles existing as two separate parts.

Question two: if in the absence of any observer, a pebble moves alongside another pebble
under natural forces, has a computation happened ?

If the mind, the brain, or the little man can perceive sense-data, representation, idea, both the perceiver and the perceived ought to be able to stand in direct relation to one another, where one perceives and the other is perceived. — NOS4A2

If the mind is the perceiver and the idea is the perceived, and the perceiver and perceived are separate entities, how can the mind ever have knowledge of the idea if the idea is forever separate from the mind?

The point is, perceivers have most if not all of the above. Therefor perceivers are not brains, minds, or homunculi. — NOS4A2

If the perceiver cannot be found in either the mind or the brain, where exactly is the perceiver?

The mind-mediated reality is also determined in pre-cognitive ways by a mind-independent actuality that cannot be real for us, even though we cannot but think of it as being real in itself. — Janus

Are you referring to Innatism, Enactivism, Kant's a priori intuition, etc, in that life has evolved in synergy with the world for at least 3.5 billion years. I agree, if you are.

This is incorrect. Wittgenstein is saying that this picture of naming something private drops out as inconsequential in terms of how we understand what is being communicated. — Richard B

According to Wittgenstein, in addition to the fact that no one can ever never know the private perception of another, but can only infer it from their behaviour, the object can play no part in the language game. The name "pain" may have a use in a language game, but not as a name for a particular thing existing in the world.

This is incorrect. See above. Both are perceiving, talking about a publicly shared object. Not providing proof of what they are supposedly perceiving privately. — Richard B

From Wikipedia - Naive Realism: Things in the world are perceived immediately or directly rather than inferred on the basis of perceptual evidence. According to the naïve realist, the objects of perception are not representations of external objects, but are in fact those external objects themselves.

An Indirect Realist would need proof, but a Direct Realist wouldn't, otherwise they wouldn't be a Direct Realist. To be a Direct Realist is to subscribe to the idea that their private perception is directly of the public object.

But they cannot distinguish between the two “sense datum” of the picture, they are the same. The positing of “sense datum” does not explain why they report a rabbit one time and a duck another. So, “sense datum” has no explanatory power in this case. — Richard B

Someone may first see a duck and later see a rabbit, but they cannot see a duck and a rabbit at the same time. At one moment in time there can only be one intentional object.

I draw a stick figure of a person from my imagination. I show this picture to a child and ask her "what to you see?" The child may reply, "I perceive a stick figure of a person." Can we not claim that the child directly perceives a picture of a stick figure? — Richard B

Wittgenstein's Beetle in the Box argument can be used against Direct Realism

Wittgenstein uses the beetle in a box to argue that a language understandable by only a single individual is incoherent, ie, his private language argument. Para 293 of PI: "Suppose everyone had a box with something in it: we call it a "beetle". No one can look into anyone else's box, and everyone says he knows what a beetle is only by looking at his beetle." He argues that no one can ever never know the private perception of another, but can only infer it from their behaviour.

If Direct Realism was correct, given a picture of a stick figure in the external world, I would directly perceive the stick figure, and the child would directly perceive the stick figure. This would mean that I would know that my private perception was the same as the child's private perception, and vice versa. But this would contradict Wittgenstein's private language argument.

The famous picture of the "duck-rabbit" is an illusion. If presented to someone, they could see the picture as a rabbit, or, another time, see the picture as a duck. However, could we not say the what we perceive is the same figure in both cases? If so, the positing of sense data has no explanatory power in this case to explain this illusion. — Richard B

The Argument from Illusion can be used against Direct Realism

Searle refers to a similar argument used by the Indirect Realists to argue for the existence of sense data. If you hold up one finger and look into the distance past the finger, you will not see one object but will see two sense datum. This means that it is not the object you are directly looking at but the sense datum. Then, when you look at your finger, it may appear that you are directly looking at an object, but in fact you are are directly looking at sense datum.

When someone looks at a duck-rabbit they can only see either a duck or a rabbit, they cannot see both a duck and rabbit at the same time.

Imagine they see a duck. As before, they look into the distance past the picture and will see not one object but two sense datum. This means that it is not the object they are directly looking at but the sense datum. Then, when they look at the picture, it may appear that they are directly looking at an object, but in fact they are directly looking at sense datum.

And this is suppose to turn me into indirect realist because of the causal train of events. — Richard B

Pierre Le Morvan in his article Arguments against Direct Realism and how to counter them is making the valid point that a Direct Realist can accept causal indirectness without accepting cognitive indirectness.

But I do not think the direct realist should be concerned about how we perceive, but how we learn and use the word “perceive”, how we make judgements about what we perceive, or how we gain knowledge from what we perceive. — Richard B

Surely a Direct Realist doesn't need to make any judgement when perceiving the colour green, for example, as they directly perceive the colour green. It is the Indirect Realist who needs to make a judgement when perceiving the colour green.

For the indirect realist, though, something within the man (the mind, the brain, a little man) directly perceives something else within the man (sense data, representation, idea). But the boundaries between both X and Y are so unclear and amorphous that it could rather be the case that X is directly perceiving X. — NOS4A2

I also said “the boundaries between both X and Y are so unclear and amorphous that it could rather be the case that X is directly perceiving X.” — NOS4A2

The perceiver and what is directly perceived by the perceiver must be one and the same

There is X, the mind, the brain, the little man and there is Y, sense data, representation, idea. X is the perceiver and Y is what is perceived.

As Searle said, pain cannot be removed from the experience of pain. Similarly, what is directly perceived cannot be removed from the perceiver.

As Brentano said about intentionality, mental states are an incomplete essence, in that they cannot exist unless they are completed by something other than themselves. The relation between the intentionality of the mind and the intentional object cannot be a causal relation.

For the mind to understand an object it is perceiving, the mind must have ideas about the object. The ability to have ideas must be part of the essence of the mind. The mind, distinguished by the ability to have ideas, is then able to perceive ideas.

But if the mind is X, and Y is ideas, and if the mind is distinguished by its ability to have ideas, then X must by Y.

How can we perceive a concept that exists only in mind if our eyes point outward, not inward? — NOS4A2

The whole concept may only exist in the mind but the parts on which the concepts are based exist in the external world

When we look at a green tree with three branches, we are looking at one particular instantiation of the concept "tree". When we are looking at a particular set of colours and shapes, we perceive it as being one instantiation of the concept "tree". The concept "tree" does not exist in the world, only in the mind. The instantiation of the concept exists in the world. So we are perceiving two things at the same time, the instantiation of the concept "tree" existing in the external world and the concept "tree" existing in the mind.

But the instantiation of the "tree" that we perceive is made up of parts, consisting of a set of colours and shapes. For example, the colour green, a vertical line, three and a horizontal line.

Searle when discussing the science argument against Direct Realism comments that colours such as red don't exist in the world but only in our own mind. The colour green we perceive doesn't exist in the external world but only in our mind.

When looking at a vertical line, we are again perceiving two things at the same time, a particular instantiation of the concept "vertical line" as a set of points existing in the world and the concept "vertical line" existing in the mind.

Similarly when looking at a horizontal line.

As regards the number three, I would argue that numbers only exist as concepts in the mind, though others would disagree. Though if colours and shapes are concepts, then why not numbers also.

The end result is that when we perceive a green tree with three branches, we are in fact perceiving two things at the same time, a set of points existing in the external world which we determine as a green tree with three branches using concepts existing in the mind.

As Searle writes about intentionality and causality, in belief, validity is achieved when the mind matches the world, and in a valid desire the world must come to match the world. The conditions of satisfaction for an intentional state is self-referential, in that perception has a part of its very meaning that it be a state caused by the object represented in it. Searle would say that I have a visual experience with mind to world fit whose intentional content is that there is a green tree with three branches before me and that there is a green tree before me causing this visual experience.

When the Direct Realist says that they are directly looking at a green tree with three branches in the external world, what this means is that they are perceiving on the one hand a set of point in the external world and on the other hand perceiving concepts existing in the mind.

As Searle asks, how do we avoid scepticism, subjectivism or solipsism if our understanding is through concepts which only exist in the mind. Our knowledge of the world derives from the causal connection between points in the external world existing in time and space and our experience of them, and making sense of these experiences using concepts that exist in the mind perceiving these experiences.

Even if it was true that trees are concepts that exist only in the mind — NOS4A2

You wrote: "For the direct realist, the man directly perceives a tree............For the indirect realist, though, something within the man (the mind, the brain, a little man) directly perceives something else within the man (sense data, representation, idea).

If the man directly perceives a tree, and the tree is a concept that exists only in the mind, doesn't this mean that the man is an Indirect Realist ?

I would agree with that.

And what is the nature of this chain? — Wayfarer

There is an article Arguments against Direct Realism and how to counter them by Pierre Le Morvan, where he writes, when discussing the causal argument against Direct Realism:

"It’s wise for Direct Realists to concede that for humans, and for percipients physiologically
like us in the actual world, perception involves a long and complex causal series of events, and that perception is indeed dependent upon the condition of the eyes, of the optic nerve, and of the brain, upon the nature of the intervening medium, and so on."

"But perception involves a long and complex causal series of events. For instance, light quanta are reflected or emitted from an external object, the light quanta then travel through an intervening medium (e.g., air and/or water), they then hyperpolarize retinal cells by bleaching rhodopsin photopigment molecules, and then a very complex series of physiological processes takes place in the eye and in the brain eventuating in perception."

Light travelling from the something in the external world that we perceive as a green tree with three branches to the eye of the perceiver is part of this causal chain.

Part of the nature of this causal chain is that causal relations are generally understood to be asymmetric. This asymmetry is often assumed to coincide with a temporal asymmetry according to which effects do not precede their causes.

As Searle wrote in The Philosophy of Perception and the Bad Argument, perception has the mind-to-world direction of fit and the world-to-mind direction of causation.

The perceiver cannot stand in the way of himself and the outer world, or be his own intermediary, or placed before himself in the causal chain of perception. — NOS4A2

That's how I see it. The perceiver is at one end of a causal chain of intermediaries that links the perceiver to what the perceiver is perceiving. At one end of the causal chain with intermediaries is someone who perceives a green tree with three branches. At the other end is something in the world that the perceiver perceives as a green tree with three branches.

As green, trees, branches, etc are concepts that exist only in the mind, what is being perceived can therefore only exist in the mind.

You’ve inserted another element or space within the perceiver called “the world inside the mind”. — NOS4A2

The Indirect Realist believes they are perceiving a world that exists in their mind. The Direct Realist believes they are perceiving a world than exists outside their mind. Whether or not another element has been inserted within the perceiver depends on one's belief in Indirect or Direct Realism.

If one believes in Indirect Realism, then "the world inside the mind" isn't an element that is additional to the perceiver.

I suggested in the original post that we ought to remove this element from the rest of the man like we can any other part of the man (like any organ), put it on a table beside a perceiver (like we’ve been doing with a perceiver and a tree) for the purpose of analysis. — NOS4A2

I agree with what you wrote before: "If perceiving is an act of a perceiving agent, the act and the agent are one and the same". For the Indirect Realist, the act of perceiving a world and the perceiving agent are one and the same. Therefore, for the Indirect Realist, the act of perceiving a world inside their mind cannot be removed from the perceiving agent, even for the purpose of analysis.

It would be the same problem that Searle wrote about, that of removing pain from the experience of pain.

If perceiving is an act of a perceiving agent, the act and the agent are one and the same — NOS4A2

Both the Indirect and Direct Realist would agree that there is a world outside the mind. The Direct Realist would argue that we directly perceive the world outside the mind. The Indirect Realist would argue that we directly perceive a world inside the mind and only indirectly perceive the world outside the mind.

Is the discussion about direct and indirect inconsequential ? I don't think so. It is true it is not something we need to be concerned about when shopping for lamb, but then again, the lamb didn't question what was going on when approached by a friendly farmer and shepherded into a truck with the word abattoir on the side. It does make a difference to our fundamental understanding of reality whether we directly perceive the world as it is or what we perceive is an illusion that we have to pragmatically work through.

Item 3 doesn't follow from items 1 and 2.

1. If perceiving is an act of a perceiving agent, the act and the agent are one and the same.
I agree with item 1. It is not as if there is a homunculus in the mind that is perceiving an act of perception, but rather, the perceiver is the act of perception. The perceiver and the act of perception are one and the same. As Searle wrote "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".

2. If they are one and the same, we can remove perception as some kind of intermediary between knower and the external world.
I agree with item 2 that perception is not an intermediary between the perceiving agent and the external world, as the perceiving agent and their perception are one and the same.

3. If there is no intermediary, direct access to the external world is not only possible, but a brute fact.
Item 3 doesn't follow from items 1 and 2. I agree that there is direct access by the perceiving agent to their perception of the world, as they are one and the same, which is a brute fact. However, it has not yet been shown that the world the perceiving agent is perceiving exists within the mind or outside the mind.

4. If we are able to directly access the external world, it means we are in the world, a part of the world.
It depends what one means by "world". I agree that both the Indirect and Direct Realist believe they are part of The World, where The World consists of both the world inside the mind and the world outside the mind.

5. If we are a part of the world the knowledge is not circular, but open and relational.
It depends again on what is meant by "world". I agree that the Direct Realist believes that the perceiving agent has direct knowledge of The World. However, the Indirect Realist believes that the perceiving agent has direct knowledge of the world in their mind, only indirect knowledge of the world outside their mind and therefore only indirect knowledge of The World.

It remains to be shown how direct knowledge of a world in one's mind can lead to direct knowledge of the world outside one's mind.

I think later Wittgenstein resist being labeled an Idealist or Realist, or anything in-between — Richard B

We can label Wittgenstein, even if he wouldn't have done so himself

I agree that Wittgenstein would resist being labelled, as that does not seem to be in his character. Although I definately disagree with your position that "Indirect Realism is incoherent", I appreciate your reasoned arguments.

However, I do think we can label Wittgenstein's position, even if he himself would object to being so labelled, not that he can do anything about it. As Wikipedia's article about The Death of the Author writes: "Barthes's essay argues against traditional literary criticism's practice of relying on the intentions and biography of an author to definitively explain the "ultimate meaning" of a text. Instead, the essay emphasizes the primacy of each individual reader's interpretation of the work over any "definitive" meaning intended by the author, a process in which subtle or unnoticed characteristics may be drawn out for new insight"

For example, I am sure it could strongly be argued that Wittgenstein was definitely not an Idealist, in that he argued that a language understandable by only a single individual was incoherent. He wrote in para 256 of PI:
"Now, what about the language which describes my inner experiences and which only I myself can understand? How do I use words to stand for my sensations?—As we ordinarily do? Then are my words for sensations tied up with my natural expressions of sensation? In that case my language is not a 'private' one. Someone else might understand it as well as 1.—But suppose I didn't have any natural expression for the sensation, but only had the sensation? And now I simply associate names with sensations and use these names in descriptions."

As regarding paras 116, 124 and 402 from PI and para 24 from On Certainty, I agree that there is the tendency to attack the words being used rather than what the words mean, but that doesn't mean, as Wittgenstein is seeming to suggest, that words should be taken at their common sense face value, ie, as used by the pedestrian in the street. This is clearly impractical. If a physicist at CERN could only use the word accelerator as understood in everyday language, I doubt future scientific breakthroughs would be possible. Similarly, if we could only use the words direct and indirect as commonly used in everyday situations, such as shopping, our understanding of the true nature of reality would be very much diminished.

The beetle in the box story is incompatible with Direct Realism

Similarly, I would argue that his story about a beetle in a box, para 293, can be used as an argument against Direct Realism, even if he didn't do so himself.

I will use your definitions of Direct Realism as the idea that the senses provide us with direct awareness of objects as they really are and Indirect Realism as the idea that we do not perceive the external world as it really is, but know only our ideas of the way the world is. Therefore, if I perceive a tree with three branches, the Direct Realist would argue that I am directly perceiving a tree with tree branches in the external world and the Indirect Realist would argue that I am directly perceiving a model or a representation of something that is in the external world.

Wittgenstein's private language argument argues that my private perception of a tree with three branches may not correspond with anyone else's private perception of a tree with three branches, in that my own beetle in a box must remain a mystery to anyone else. I can never know the private perception of another, but may only infer it from their behaviour.

Therefore, if "a tree with three branches" has a use within the language of a community, it cannot be the name of something. Either it is entirely possible that each person had a different private perception, or even that an individuals private perception continually changed or there was in fact no private perception. The private perception is irrelevant to whatever language game it is used in, as all we can discuss is what is available within a public language.

But if Direct Realism is correct, when I perceive a tree with three branches, this would mean that in the external world there is in fact a tree with three branches. Then given there is in fact a tree with three branches in the external world, someone else, assuming that Direct Realism is correct, would also directly perceive a tree with three branches.

Therefore, both myself and the other person would be having the exact same perception, that of a tree with three branches. But Wittgenstein's private language argument says that this is impossible. Therefore, Direct Realism and Wittgenstein's private language argument are incompatible.

Therefore, Wittgenstein's beetle in the box story may be used as an argument against Direct Realism.

Let me repeat, this is an absurdity derived from a grammatical fiction. What is the fiction? Directly perceived sense data. — Richard B

I agree that, in a sense, "sense data" is a linguistic fiction, in that, for me, the term is metaphorical rather than literal.

As @NOS4A2 wrote: "For the direct realist, the man directly perceives a tree. For the indirect realist, though, something within the man (the mind, the brain, a little man) directly perceives something else within the man (sense data, representation, idea)."

As Searle wrote: "But the something is not a material object. Give it a name, call it a “sense
datum”."

My conscious mind does perceive something, and there is a long causal chain between this conscious perception and an object in the external world. Exactly what happens in the brain is still mysterious, but the mind does perceive something. The term "sense data" may be a metaphor, but it is still useful, as are the metaphors Evolution by Natural Selection, Laws of Nature, Gravity, General Relativity, etc.

I wasn't intending to push Wittgenstein as taking any sides in this rather silly debate — Banno

It cannot be such a silly debate without philosophic substance if some modern philosophers believe that the great genius philosophers of the past were mistaken.

In Searle's words: "I realize that the great geniuses of our tradition were vastly better philosophers than any of us alive...........The second mistake almost as bad is the view that we do not directly perceive objects and states of affairs in the world."

It is interesting that Searle in his article The Philosophy of Perception and the Bad Argument doesn't logically justify his belief in Direct Realism.

You have an image of a causal chain with you at one end and the tree at the other, and have convinced yourself that you cannot see the tree at the other end of the causal chain. — Banno

From the IEP article Objects of Perception, both the Indirect and Direct Realist would agree with "the common sense view that tables, chairs and cups of coffee exist independently of perceivers". However, "Direct realists also claim that it is with such objects that we directly engage." and for the Indirect Realist, "through perception I do not directly engage with this cup; there is a perceptual intermediary that comes between it and me."

The IEP also notes "There are, however, two versions of direct realism: naïve direct realism and scientific direct realism."

The article Arguments Against Direct Realism and How to Counter Them by Pierre Le Morvan addresses the "causal argument".

He suggests that the Direct Realist should accept that perception is indirect, in that it involves a long, complex causal series of events. However, he argues that accepting causal indirectness does not require rejecting cognitive directness, in that the perceiver is still cognitively directly aware of the external object.

However, this doesn't answer my two fundamental problems with Direct Realism:
1) When we perceive the world, how can we directly know the cause of what we have perceived when our only knowledge of any external world has come from the perceptions themselves.
2) How is it possible to know from knowing an effect the cause of that effect, when every effect is overdetermined by more than one sufficient causes.

"The tree has three branches" is very different from "I perceive the tree to have three branches". Idealism is the conflation of the two. — Banno

Just elaborating:

The Idealist, Indirect Realist and Direct Realist agree that they perceive the tree to have three branches.

For the Idealist, as reality is a mental construct, both the tree and the perception of the tree exist in the mind and are therefore the same.

For both the Indirect and Direct Realist, there is something in a mind independent external world. The Direct Realist knows that this something is a tree with three branches. The Indirect Realist knows that they perceive a tree with three branches, but doesn't know what this something is in the external world.

But see 308 and 309. — Banno

Wittgenstein in PI is more an Indirect Realist than a Direct Realist

It is clear that Wittgenstein is not an Idealist treating the world as a mental construct because of the importance he places on the public language game.
Para 21. "Imagine a language-game in which A asks and B reports the number of slabs or blocks in a pile, or the colours and shapes of the building-stones that are stacked in such-and-such a place.—Such a report might run: "Five slabs". Now what is the difference between the report or statement "Five slabs" and the order "Five slabs!"?"

Para 246 suggests Indirect Realism rather than Direct Realism
"The truth is: it makes sense to say about other people that they doubt whether I am in pain; but not to say it about myself."
He writes that I cannot doubt that I am in pain but I can doubt that others are in pain. Similarly, it must follow that although I cannot doubt that I perceive a tree with three branches, I can doubt that others perceive the same tree with three branches. And if that is the case, this casts doubt on there being a tree with three branches in an external world able to be perceived in the first place.

Para 293 also suggests Indirect Realism rather than Direct Realism
"If I say of myself that it is only from my own case that I know what the word "pain" means—must I not say the same of other people too? And how can I generalize the one case so irresponsibly? Now someone tells me that he knows what pain is only from his own case!——Suppose everyone had a box with something in it: we call it a "beetle". No one can look into anyone else's box, and everyone says he knows what a beetle is only by looking at his beetle.—Here it would be quite possible for everyone to have something different in his box. One might even imagine such a thing constantly changing.—But suppose the word "beetle" had a use in these people's language?—If so it would not be used as the name of a thing. The thing in the box has no place in the language-game at all; not even as a something: for the box might even be empty.—No, one can 'divide through' by the thing in the box; it cancels out, whatever it is. That is to say: if we construe the grammar of the expression of sensation on the model of 'object and designation' the object drops out of consideration as irrelevant."

He writes that the object in my box, my pain, my beetle, may be different to everyone else's object in their box, their pain, their beetle, and therefore the object can play no part in the language game. The name "pain" or "beetle" has a use in a language game, but not as a name for a particular thing existing in the world. Similarly, the object that I perceive in my box, a tree with three branches, may be different to what everyone else perceives in their box. Therefore, the object. my perception of a tree with three branches, can play no part in the language game. The name "a tree with three branches" has a use in a language game but not as a name for a particular thing existing in the world.

This is not the position of the Direct Realist for whom there exists a tree with three branches in the world. This is more the position of the Indirect Realist, where "a tree with three branches" does not refer to something existing in the world but rather refers to a representation in the mind being used within a language game.

I think you are saying not only "the scientist perceives an event in their laboratory" as an inference, but "the laboratory" itself can only ever be an inference. This is an absurdity derived from a grammatical fiction. — Richard B

Two fundamental problems with Direct Realism

In my opinion, there are two fundamental problems with Direct Realism:
1) When we perceive the world, how can we directly know the cause of what we have perceived when our only knowledge of any external world has come from the perceptions themselves.
2) How is it possible to know from knowing an effect the cause of that effect, when every effect is overdetermined by more than one sufficient causes.

Item 2) suffers from the same problem as anomalous monism, that of over determination. If there was an explanation as to how the problem of over determination could be negated in anomalous monism, then perhaps the same argument could be used for item 2).

John Searle in The Philosophy of Perception and the Bad Argument wrote
"I realize that the great geniuses of our tradition were vastly better philosophers than any of us alive and that they created the framework within which we work. But it seems to me they made horrendous mistakes..............The second mistake almost as bad is the view that we do not directly perceive objects and states of affairs in the world."

Whether a scientist or an artist, all humans start off by perceiving the world. The question is, is the Idealist correct that the world is a mental construct, or is the Direct Realist correct that they directly perceive an external world, or is the Indirect Realist correct that they directly perceive sense data (metaphorically speaking) and only indirectly perceive the external world.

I think you will need a stronger argument against Indirect Realism than it is absurd, as, as Searle writes, Direct Realism was not supported by the great geniuses of philosophy.

Neither indirect or direct realism is needed to metaphysically explain, "I perceive a tree" — Richard B

I agree that I don't need to be a philosopher in order to prune a tree. But this is what sets a human using their reason and intellect apart from an animal using their instinct. A pigeon may instinctively peck at grain thrown on the ground, whilst a human invents philosophy to ponder the question, am I looking at this tree directly or indirectly.

I agree that neither indirect or direct realism is needed to explain, "I perceive a tree", though I do disagree that neither indirect or direct realism is needed to metaphysically explain, "I perceive a tree". How else can indirect and direct realism be considered other than metaphysically.

However, reason and intellect are needed to be able to successfully prune a tree, rather than just hacking away at its branches causing irreparable damage. I would recommend the book Philosophy for Gardeners: Ideas and paradoxes to ponder in the garden by Kate Collyns, where she explores ideas and considers the big questions from working in the garden. She describes growers by their nature as philosophers, existentialists who try to live and work by their own rules in a garden, stoics who put up with slug damage again and again, and try to work in harmony with nature and practical quantum scientists who witness incredible processes going on in plant cells beneath the ground.

What I am attempting to argue is that it does not even make sense to say "that they cannot know whether there is or isn't a resemblance between...." because the position is incoherent — Richard B

The problem is, how can I know if there is the resemblance between my perception and the cause of my perception if all I know is my perception. I agree that knowing an effect one may be able to indirectly discover its cause, but is there a philosophical explanation that knowing an effect one has direct knowledge to its cause, taking into account the problem of over determination of sufficient causes ?

. My philosophical position is utilizing Wittgenstein's concept of a grammatical fiction (see Philosophical Investigation section 304 to 307). — Richard B

Mine also. As with Wittgenstein, there is no doubt in my mind that I perceive a tree, you perceive a tree, and everyone else perceives a tree. As Wittgenstein says, the problem begins when someone says "I perceive a tree". What do these words mean ?

We learn words like "perceive" and "resemblance" from our fellow human beings and looking at trees and tables aids in this endeavor, not by introspection of "sense data of trees" and "sense data of tables" — Richard B

I agree. The meaning of words are fixed in performative public situations.

When we asked scientist to study why tree leaves have the color green, they did not start by studying the brain because all we can perceive "directly" is our sense data of the green leaves — Richard B

When a scientist starts to study why leaves are green, the first thing they use is their brain.
I agree they don't need to study their own brain, but they do need to use their own brain. If they didn't use their own brain, they wouldn't be able to do any studying. And using their brain means they are using their own perceptions of the world around them. One cannot get away from the fact that even scientists start from the position of perceiving the world around them.

Let me assure you the scientist perceives the the lab, instruments, and reagents they might use to determine how leaves are green; the lab, instruments, and reagents are not inferred experiences, internal representations, or replicas. — Richard B

You say that for a scientist the laboratory is not an inferred experience. But this statement in itself is making an inference.

But this is the whole debate, how do we know whether or not the scientist's perception of the laboratory is or isn't an inferred experience. The indirect Realist is arguing that what the scientist perceives as a laboratory is an inferred experience. The Direct Realist is arguing that what the scientist perceives as a laboratory isn't an inferred experience.

You included a reference to Hume's An Enquiry Concerning Human Understanding in a previous post. Hume wrote:

"But philosophers, who carry their scrutiny a little farther, immediately perceive, that, even in the most familiar events, the energy of the cause is as unintelligible as in the most unusual, and that we only learn by experience the frequent Conjunction of objects, without being ever able to comprehend any thing like Connection between them."

"When we say, therefore, that one object is connected with another, we mean only, that they have acquired a connexion in our thought, and give rise to this inference, by which they become proofs of each other's existence: A conclusion, which is somewhat extraordinary; but which seems founded on sufficient evidence."

The question is, when the scientist perceives an event in their laboratory, as Hume asks, can this only ever be an inference ?

The use of the word "indirect" commits us to this idea that there is no resemblance between our "idea/sense data of a tree" and the "material object tree." — Richard B

The Indirect Realist is not saying that there is no resemblance between what they perceive in their sense data and the cause of that perception, they are saying that they cannot know whether there is or isn't a resemblance between what they perceive in their sense data and the cause of that perception.

An effect is always overdetermined by sufficient causes

The problem is the same for both the Direct and Indirect Realist, given the effect, the perception in our sense data of a tree, how can one know the cause of that perception, how can one know the cause of that perception is a tree or not. The Indirect Realist argues that it is not possible to know the cause, whilst the Direct Realist argues that it is possible to know the cause.

I think that the term "sense data" should be treated more as a metaphor than literally, as Searle said "Give it a name, call it a “sense datum”.

The fundamental problem is that any effect is always overdetermined by sufficient causes. For example, when seeing a broken window, I cannot know the single cause, a stone, branch, or bird, when visiting the scene of a crime, the detective cannot know just from what they see the criminal responsible, when reading a post on the Forum, I cannot know just from the post whether the author was a 20 year old from Peru or a 80 year old from New Zealand. Similarly I cannot know just from my perception of a tree the cause of that perception, as the effect is overdetermined by more than one sufficient cause.

The mind has evolved to equate effect with cause, such that when perceiving the colour green, the mind assumes that the cause was the colour green, when perceiving a tree, the cause was a tree. As Searle wrote "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".

The Indirect Realist accepts that the mind equates effect with cause, in that the relation of effect to perceived cause is one of identity, the Direct Realist doesn't.

So, indirect realism is "without foundation in reason" according to Hume. — Richard B

I would argue the opposite, that Direct Realism is "without foundation in reason" according to Hume.

Hume wrote: i) "The mind has never any thing present to it but the perceptions, and cannot possibly reach any experience of their connexion with objects" and ii) "The supposition of such a connexion is, therefore, without any foundation of reason".

Item i) is not the position of the Direct Realist, where things in the world are perceived immediately or directly rather than inferred on the basis of perceptual evidence. This is more the position of the Indirect Realist, where our conscious experience is not of the real world itself but of an internal representation, a miniature virtual-reality replica of the world. Knowledge is always via some means, and our ideas of the world are interpretations of sensory input derived from an external world that is real.

Item ii) reconfirms Hume's position that the mind only has knowledge of its perceptions, and that it is not possible to know just from these perceptions their cause in the world, a position again in agreement with that of the Indirect Realist.

In modern terms, Hume's position has been described as realist, anti-realist and projective.

For Hume, Realism about the external world is vindicated, defensible, endorsed or justified, not supported by reason but from our propensity to believe in our senses and experience through inference about what we observe rather than from direct knowledge of what we observe.

Anti-realist is a term coined by Michael Dummett against realism which he saw as a "colourless reductionism". An external reality is assumed rather than hypothetical, and the truth of a statement rests on its demonstrability through internal logic rather than any correspondence to an external, independent reality, A position not that of Direct Realism.

Projective may be a) feature projection, the attribution of features of minds to other objects and has "spatial connotations" of throwing forward features of the mind, something 'in here', onto something 'out there' in the world or b) explanatory projection, where there is an "appearance whose explanation lies not in the world being the way that it seems but because of the mentality of the thinker". A belief in causal necessity is a feature of both feature and explanatory projection, in that as genuine causal necessity is not possible as this would require acquaintance with some a priori knowledge of the object's causal consequences, this motivates a projective explanation of how we can determine a necessary connection that we cannot detect. Hume should be read as a realist about causal power, in that unknowable but real causal powers exist in nature. This means that although perceptions cannot be necessarily connected to their causes in the world, this bundle of casually related perceptions becomes the foundation for the self of the perceiver. Hume rejects that one idea is tied to another, necessarily conjoined, since that would mean we knew something prior to experience. But rather the source of our knowledge of necessary connections arises out of the observation of constant conjunction of certain impressions across many instances. People know of necessity through rigorous custom or habit and not from any immediate or direct knowledge. None of this is that of Direct Realism, whose position is that things in the world are perceived immediately or directly rather than inferred on the basis of perceptual evidence.

Although the terms Direct Realism and Indirect Realism may not have been used at his time of writing, Hume's An Enquiry Concerning Human Understanding indicates a support for Indirect Realism rather than Direct Realism.

Descartes proved he was here with "I think--therefore I am," but how would he have proved that he wasn't alone? — MikeB

I start by assuming that there is nothing external to my mind.
I have read and appreciated the greatness of Don Quijote, but cannot write a sequel of equal greatness.
As I was able to write Don Quijote in the past, but am not able to write a sequel, something must have changed.
My first supposition is that something has changed in my mind.
But then I read Great Expectations, which I know I must have written, appreciate its greatness but am still not able to write a sequel.
As it seems that nothing has changed in my mind, I can only conclude that something has changed outside my mind, concluding that I am not alone.

@Richard B

It will take a while to work through your subtle ideas, though I will do what I can. A proper answer would involve a better understanding of Searle's Thinking about the Real World, Wittgenstein's Philosophical Investigations, Wittgenstein's On Certainty, Russell's Problems of Philosophy and how all these relate to the question posed in the OP, "who perceives what?". The "who" being the Direct Realist and the Indirect Realist. The "what" being do they directly perceive the world or indirectly perceive the world by means of a representation of the world in their mind.

He's certainly not saying models and that which they model are identical — Isaac

I never said he did. I said that using the concept of identity, such as that between the experience of pain and pain, the model and what the model is of are one and the same.

So your eyes are not even involved in seeing? If you don't see the tree, then how do you know what it is your model is a model of? — Isaac

Searle wrote:
"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."

Using Searle's concept of identity between the experience of pain and pain, the model and what the model is of are one and the same, therefore knowing one means knowing both.

A Direct Realist argues that they have direct knowledge of the world, and therefore knows that there is a tree there — RussellA

No direct realist I've ever read claims this. Do you have a quote or reference to work from? — Isaac

IEP article on Objects of Perception
The objects of perception are the entities we attend to when we perceive the world. Perception lies at the root of all our empirical knowledge. We may have acquired much of what we know about the world through testimony, but originally such knowledge relies on the world having been perceived by others or ourselves using our five senses: sight, hearing, touch, taste, and smell.
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. The objects of perception include such familiar items as paper clips, suns and olive oil tins. It is these things themselves that we see, smell, touch, taste and listen to.

If Perceptual Realism claims that we directly engage with objects such as paper clips, and such objects exist independently of the perceiver, and the perception of these objects lies at the root of all our empirical knowledge, then doesn't this suggest that the Direct Realist's perception gives direct knowledge of the world.

Wikipedia article on Direct and indirect realism
Naïve realism is known as direct realism, which was developed to counter indirect or representative realism.
The representational realist would deny that "first-hand knowledge" is a coherent concept, since knowledge is always via some means, and argue instead that our ideas of the world are interpretations of sensory input derived from an external world that is real.

If Direct Realism is a counter to Representative Realism, and the Representational Realist denies that "first-hand knowledge" is a coherent concept, then doesn't that presuppose that the Direct Realist believes that "first-hand knowledge" is a coherent concept.

If the Direct Realist doesn't claim that have they have direct knowledge of the world, what do they claim ?

Given this, human beings who hallucinate are few, and most human beings have never hallucinated, and when hallucinations do occur, it occurs infrequently. So how did something that few humans being will ever experience, may never experience, and, if experienced, will happen infrequently, turn into positing "sense data" that every human being must have when perceiving the world around them. — Richard B

I am sure it is true hallucinations is a rare event, but perhaps a lot of philosophy is based on trying to solve inconsistencies in a theory, such as Frege's puzzles and Russell's paradox.

Searle wrote about Direct Realism and the problem with hallucinations
"I think the great philosophers of the past rejected Direct Realism because of an argument which was, until recently, quite commonly accepted among members of the profession. Some of them thought Direct Realism was so obviously false as not to be worth arguing against. There are different versions of it but the most common is called ‘the argument from illusion’ and here is how it goes. “You said that you directly perceive the tree, but suppose it is a hallucination. And suppose the hallucination is type identical with the veridical experience. What do you see then? It is obvious that you do not see the tree but only the visual experience itself, what the traditional philosophers called an idea, an impression, or a sense datum."

Perhaps illusion would be a better word than hallucination, in that illusions are far more common than hallucinations. For example, I perceive someone 5m away as being taller than the same person 10m away. Perhaps this would also be a route into the discussion as to whether we see the person directly or indirectly.

However, even within Direct Realism there are two versions, naive realism and scientific realism. For naive realism, objects continue to have all the properties that we usually perceive them to have, properties such as yellowness, warmth, and mass, whilst for scientific realism, some of the properties an object is perceived as having are dependent on the perceiver.

You ask other minds, look at the evidence, and see what is persuasive. In this case, this is done in a public realm, not the private realm of "sense data". — Richard B

True, most of my knowledge comes from the public realm, the Moon Landing, Disney Land, The Large Hadron Collider, Australia etc, ie, Russell's Knowledge by Description.

But this knowledge is indirect, more along the lines of Indirect Realism than Direct Realism.

The indirect realist likes to claim that perceiving the material object is indirect because scientific theory shows this, but do we really think that using a hallucinogen that results in a hallucination is not also plague by a series of intermediary steps in the brain as well. — Richard B

So metaphysically, why am I not committed to the glasses having "sense data" just like when I push one of my eye balls and report I see two of the objects — Richard B

As Searle writes, we might as well have a name for our visual experiences, which we may as well call "sense data"
“You told us earlier that visual experience takes place when photons strike the photoreceptor cells and set up a series of causal events that eventually results in a visual experience in the cortex. But it is of that visual experience that we are visually aware. The science of vision has proven that the only thing you can actually see, literally, scientifically is the visual experience going on in your head. We might as well have a name for these visual experiences. Call them ‘sense data’. All you ever perceive are sense data, and by way of vision all you can ever perceive are visual sense data."

I think the term "sense data" should be taken metaphorically rather than literally, as with many other scientific terms, such as The Laws of Nature, Natural Selection, gravity, etc. From the object in the world to our perception of it, there may be be a long chain of intermediary events, meaning that it would be impossible to pinpoint exactly where these sense data are, even if they exist at all

Sense data has the metaphorical meaning in that we don't perceive the object in the world directly, but only indirectly through a chain of intermediary events. It means that we are not perceiving the object as it is in the world, only as to how we perceive it to be in the world.

The moment of "great disaster" is when Descartes decided to retreat to the private world of introspection to look for certainty at the expense of the public realm in which we learn to communicate with words to convey understanding to our fellow humans about a world that can get a bit messy. — Richard B

I think you are being too harsh on Descartes. He had an intense interest in the sciences, was not a sceptic but used scepticism as a means of philosophical enquiry.