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.

What is 'seeing' as a process for you? — Isaac

Along the lines of what is written in Searle's article:
“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.”

The Cambridge Dictionary describes "to see" as:
to be conscious of what is around you by using your eyes
to watch a film, television programme, etc.
to be the time or place when something happens
to understand, know, or realize
to meet or visit someone, or to visit a place
to consider or think about
to imagine someone doing a particular activity
to take someone somewhere by going there with them
to try to discover
to make certain that something happens

I see what you mean, but both the good and bad thing about language is that each word may have several different meanings, and knowing what is meant often depends on context, which is often ambiguous.

so are you seeing two things? One, the tree(indirectly) and two, the model (directly). — Isaac

I think that I am seeing only one thing, a model of a tree in my mind.

Searle wrote:
"The experience of pain does not have pain as an object because the experience of pain is identical with the pain."

Using Searle's words, it is not that the visual experiences has a tree as an object because the visual experience is identical with the tree.

What would it mean to exist 'as a tree'? As opposed to what? — Isaac

"Trees" exist in my mind as concepts. What exists in the world are elementary particles, elementary forces and space-time.

I don't see how you would know what 'treating it like a tree' would entail if no-one has any veridical experience of trees. — Isaac

"Trees" as private concepts didn't exist before being named in a public performative act, which could have been either by social acceptance over a period of time or by an institutional body. Before being publicly named, no one would have had any veridical experience of "trees". For example, in France, trees were named "arbres" and in Germany were named "alberi". This public performative act is available to everyone who uses that language. Therefore an individual's private concept of "tree" has been determined by knowledge of the public performative act of naming a certain set of shapes and colours as a "tree".

For example, no one at this moment has any veridical experience of a squund. However, if I pointed out to you a certain shape that was square at the top and round at its base and said "I name this a "squund"", we would then both have the private knowledge that this particular shape had the name "squund". I could then ask you to pass me the squund, and you could do so, even though your private knowledge of a squund is inaccessible to me, and my private knowledge of a squund is inaccessible to you. The veridical knowledge of squunds is then henceforth stored in the public domain, either in dictionaries or in conversations

Similarly for trees, my concept of tree is different to yours, I can never know your private concept of tree, yet we can both sensibly discuss trees because what a tree is is stored in the public domain.

If to 'know' something is to have sufficient warrant for believing it', and if 'sufficient warrant' is 'having something respond as expected when treating it as if it were what you believe it to be' - then is simply follows, by substitution, that you 'know' you see a tree all the while you treat it as if it were a tree and it responds accordingly. — Isaac

A warrant is a justification. They say knowledge is justified true belief. I may believe that there is a tree in the field and can justify my belief, but a justified belief is not knowledge.

To be knowledge, the justified belief has to be true. There arrives the problem.

A Direct Realist argues that they have direct knowledge of the world, and therefore knows that there is a tree there. An Indirect Realist argues that they only have indirect knowledge of the world, and therefore can only believe that there is a tree there.

You've made a pretty puzzle for yourself. — Banno

A puzzle I have my own solution to, but remains to be accepted by the Direct Realist.

I wrote "Direct Realism's solution to this seeming paradox is by equating the effect with the cause, in that, if the effect is sensing of the colour green, Direct Realism says that the cause is also the colour green. Given a single effect, Direct Realism gives a single cause that is identical with the effect. However, this is an illusion."

As Searle wrote, the experience of pain is identical with the pain
"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"

The Indirect Realist accepts that perceiving a single cause for a single effect is an illusion, but this is not something that the Direct Realist accepts.

Other factors that the the Direct Realist need to take into account are: i) the asymmetry of causal relations, which coincides with temporal asymmetry, whereby effects do not precede their causes, and ii) the over determination problem, where an effect such as perceiving the colour green can have two or more distinct sufficient causes.

Seems you can't tell that this post from me is a post from me - just by seeing this post, "one cannot know, of the several possible causes, which was the actual cause". — Banno

Very true. Who are you. You may be a sixteen year old working as a waiter and living in Lima, you might be Kamala Harris passing her evenings in Washington, you could be a forty year old tax inspector living in Beijing wanting to improve their English, or you may even be a ChatGPT. I don't know. I am responding to the post, not the author of the post who is unknown to me.

Roland Barthes wrote The Death of the Author in 1967, which emphasizes the primacy of each individual reader's interpretation of the work over any "definitive" meaning intended by the author.

Searle sets out with great clarity the difference. When one sees a tree, there is a tree to be seen. When one hallucinates a tree, there is no tree to be seen...........He does take this distinction as granted. — Banno

Searle writes about the mistakes of philosophers of great genius
"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."

As regarding the debate between Indirect and Direct Realism, he writes
"The second mistake almost as bad is the view that we do not directly perceive objects and states of affairs in the world."

I agree that he writes with great clarity about what he perceives as the mistakes of the past, but he is a bit short on giving any reasons or justifications why they were mistaken. As you say, he takes a lot for granted.

You've mixed your intentionality with your causation. Knowing involves intentionality, rather than cause. That is, claiming to know something is adopting a certain intentional attitude towards that state of affairs: that this is true — Banno

There is a direction of information flow in a causal process

Searle writes about perception and direction of fit and causation
"Perception has the mind-to-world direction of fit and the world-to-mind direction of causation. That is just the fancy way of saying that the perception is satisfied or unsatisfied depending on how the world is in fact independently of the perception (mind-to-world direction of fit), but the world being that way has to cause the perception to be that way (world-to-mind direction of causation)."

Searle writes about the intentionality and causation of a visual experience
"A fourth feature of the situation is that the visual experience has intrinsic intentionality. The experience sets conditions of satisfaction, and these conditions are those under which the experience is veridical as opposed to those conditions under which it is not veridical. Confining ourselves to seeing the tree in front of me we can say that the conditions of satisfaction of the visual experience are that there has to be a tree there and the fact that the tree is there is causing in a certain way the current visual experience. So on this account the visual experience in its conditions of satisfaction is causally self-reflexive in that the causal condition refers to the perceptual experience itself. If the perceptual experience could talk it would say, “If I am to be satisfied (veridical) I must be caused by the very object of which I seem to be the seeing."

In order to know that I am seeing a tree, my visual experience must have an intrinsic intentionality about the tree, such that my mind is directed at the tree. But in order to see the tree, there must have been a temporally prior world-to-mind causation, from the tree being the way it is in the world to the tree in my mind.

Therefore, as Searle writes, knowing requires both intentionality and causation, in that the cause of a perception is temporally prior to the perception itself. Between the cause of the perception and the perception itself there may have been several intermediary stages in a long causal chain.

There is only one direction of flow of information in a causal chain, in that, just by seeing a broken window on a walk into town, one cannot know, of the several possible causes, which was the actual cause. If backwards flow of information was possible through a long causal chain, a detective at the scene of a crime would straight away know the identity of the criminal.

The puzzle is, how can the mind, when perceiving an object, know the single cause of its perception, when the cause happened prior to the perception and at the far end of a long causal chain.

The Direct Realist's position is that the perceiver of an object knows a single cause of that perception, yet this would require a backwards flow of information through a causal chain, which is impossible.

If Direct Realism was how reality worked, every detective would be taught Direct Realism in order to give them a 100% success rate in crime solving.

If I come along and find somebody who does not hallucinate, does this mean they don't have "sense data"? — Richard B

Searle, hallucination and the veridical

Searle discusses the ambiguity of the word "see".
"What shall we say about the bad argument in both of its versions? I think in spite of its enormous influence it rests on a simple fallacy of ambiguity over ‘see’ and other perceptual verbs" and "In the ordinary sense of ‘see’ in which I now see the tree, in the hallucinatory case I do not see anything".

Searle repeats a scientific version of the "argument from illusion":
“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.”

Searle says someone could see a tree even if there wasn't one
"but when I see the tree I cannot separate the visual experience from an awareness of the presence of the tree. This is true even if it is a hallucination and even if I know that it is a hallucination. In such a case, I have the experience of the perceptual presentation of an object even though there is no object there."

Generally, one knows something one perceives is not there because its being there would be improbable or anomalous, for example, an airplane divebombing the house, or a spectre of death standing on the edge of the forest. But for a common object as a tree, something that is not out of place, and there is nothing improbable or anomalous about it, and is something that one definitely expects to perceive, how can one know that there is no tree there.

Searle is saying that in the hallucinatory case the observer perceives a tree within sense data but doesn't see the tree, and in the ordinary case the observer doesn't perceive a tree in the sense data but does see the tree. If the observer perceives a tree, and there is nothing anomalous about the tree, there can be no way for the observer to know whether the tree exists or is an hallucination. If the tree exists, then the observer sees the tree. If the tree doesn't exist, then the observer perceives the sense data.

If there is no way for the observer to know whether everyday objects such as trees exist or are hallucinations, how does the observer know whether they are seeing the tree or perceiving the sense data ?

Searle doesn't explain how an observer can know they are hallucinating about an object that is neither improbable or anomalous.

You questioned whether we know what we see is the tree. — Isaac

As an Indirect Realist, I believe that I directly see a model or a representation of a tree in my mind. I don't directly see a tree in the world, but only indirectly.

When I perceive a tree, I don't question that I am perceiving a tree, but I do question that what I am perceiving as a tree exists in the world as a tree.

As a believer in Realism, I believe the world exists, and believe that there is something out there in the world that I perceive as a tree. Even if it not a tree, I can act towards it as if it were. As you rightly said "all the while that interacting with it as if it were a tree yields the results you'd expect of it if it were a tree"

As a Realist, I believe that there is a world out there and I am part of it. In believing that I can transact with a world that is inseparable from my agency within it, my approach is that of a Pragmatist. As originally conceived by Charles Sanders Peirce, the core of pragmatism was the Pragmatic Maxim, a rule for clarifying the meaning of hypotheses by tracing their ‘practical consequences’, their implications for experience in specific situations. I can treat the something I perceive as a tree as a tree in the world, act towards it as tree, and follow the consequences of my actions. If the results are not as I expected, I can adjust my future interactions with the world.

So we can conclude that virtually all the time we know what we see is the tree — Isaac

I agree when you say that "all the while that interacting with it as if it were a tree yields the results you'd expect of it if it were a tree", but don't agree that your conclusion would logically follow "So we can conclude that virtually all the time we know what we see is the tree"

It doesn't necessarily follow that because we treat something as a tree then it is a tree.

Physical properties interacting with each other without perceivers, becomes oddly anthropomorphic in its conception. — schopenhauer1

Exactly. A case of psychological projection, rather than onto other people onto the world around us. As the Wikipedia article on Psychological Projection writes, "Psychological projection is a defence mechanism of alterity concerning "inside" content mistaken to be coming from the "outside".

You have sufficient warrant to believe the tree you see is, in fact, a tree, all the while that interacting with it as if it were a tree yields the results you'd expect of it if it were a tree. — Isaac

I agree with that. This is the position of the Indirect Realist, a pragmatic approach to the world.

Can we really talk about non-perceived events and interactions — schopenhauer1

There is a useful paragraph in the SEP article Nonexistant Objects.

"One of the reasons why there are doubts about the concept of a nonexistent object is this: to be able to say truly of an object that it doesn’t exist, it seems that one has to presuppose that it exists, for doesn’t a thing have to exist if we are to make a true claim about it? In the face of this puzzling situation, one has to be very careful when accepting or formulating the idea that there are nonexistent objects. It turns out that Kant’s view that “exists” is not a “real” predicate and Frege’s view, that “exists” is not a predicate of individuals (i.e., a predicate that yields a well-formed sentence if one puts a singular term in front of it), has to be abandoned if one is to accept the claim that there are nonexistent objects"

In order to talk about a non-perceived event, one first has to presuppose that we are able to perceive it.

If you need that explaining you may want to seek professional help. — Isaac

I wrote that Searle doesn't explain how one knows whether one's visual experience is an hallucination or a veridical visual experience.

Searle 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. For this view famous arguments were advanced, and I am going to argue in this article that the arguments are all variations on a single bad argument, which I will honor with the capital title “The Bad Argument”
"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"

According to Searle, even the great geniuses of philosophy were concerned with The Argument from Illusion, in how to know whether one's visual experience is an hallucination or a veridical visual experience, so I am in good company.

But there's nothing causal here. Not knowing whether A caused B has no bearing on the plausibility of an hypothesis that A causes B. — Isaac

I agree, but I thought the whole point of Direct Realism is that one directly sees the green tree, not hypothesise about it.

Can you elaborate on this, defining instantiation here, and property and why one instantiation of property is not property? — schopenhauer1

By definition, a property is any member of a class of entities that are capable of being attributed to objects, so there must be at least two things before there can be a property. My starting position is that properties don't exist in the world but only exist in the mind as concepts, along the lines of Conceptualism and Nominalism. It follows that if a "tree is green", the properties green and tree only exist in the mind and not the world. So what exists in the world. There is nothing left but space-time, elementary forces and elementary particles, along the lines of Neutral Monism and Panprotopsychism. Everything else exists in the mind, such as tables, mountains, apples, governments, morality, ethics and green trees.

"What is an event that is unperceived.................what does that even mean for space and time to be a placeholder for an event sans perceiver?" — schopenhauer1

In conceptual terms, what is most widely accepted today is the giant-impact theory. It proposes that the Moon formed during a collision between the Earth and another small planet, about the size of Mars. The debris from this impact collected in an orbit around Earth to form the Moon.

In reductionist terms, there were changes to the elementary forces and elementary particles within space-time.

Wasn't this an event in space-time without a perceiver ?

One of the strengths that folk ascribe to this idea that we "directly perceive sense data" is the certainty that they can not be in error. This is the great appeal. However, I don't believe that the veracity of this idea can be proven, and the idea itself incoheren — Richard B

John Searle: The Philosophy of Perception and the Bad Argument

Searle's refutation of The Argument from Illusion is weak

One reason philosophers in the past have rejected Direct Realism is because of The Argument from Illusion, which is obviously a strong argument. It is argued that the hallucination and veridical experience can be type identical, such that if an hallucination can only be explained by seeing sense data, then a veridical visual experience must also be explained by seeing sense data.

John Austin was critical of sense data, and in his 1962 book Sense and Sensibilia took aim at the doctrine that we never directly perceive material objects but only sense data. However, Searle's refutation of the Argument from illusion is more recent, writing about the topic in the article above.

Searle calls his refutation of The Argument from Illusion The Bad Argument. However, his refutation is quite weak, and not persuasive.

He says that when one sees an hallucination and when one sees an object in a veridical visual experience, the word "see" is being used in two different ways.

However, he doesn't explain how one knows whether one's visual experience is an hallucination or a veridical visual experience, and if two visual experiences appear the same, such that we don't know which is an hallucination and which is veridical, then how do we know in which each sense "see" is being used.

Searle makes the statements " In the sense in which I see the tree, I do not see a sense datum." and " in the ordinary sense of ‘see’ in the hallucinatory case, I do not see anything", neither of which he backs up with any justification.

He writes " it is obvious that the argument is fallacious", to which the retort may well be ""it is obvious that the argument is sound", which doesn't get anyone anywhere.

Direct Realism would require backwards causation, causation from mind to world

My key argument against Direct Realism uses part of Searle's own article, where he discusses the hierarchy of perception, the direction of fit and the direction of causation.

He writes "Perception has the mind-to-world direction of fit and the world-to-mind direction of causation. That is just the fancy way of saying that the perception is satisfied or unsatisfied depending on how the world is in fact independently of the perception (mind-to-world direction of fit), but the world being that way has to cause the perception to be that way (world-to-mind direction of causation)"

It is true that an object in the world could cause a perception in the mind, such that an object in the world could cause the perception of a green tree in the mind, in that causation has a world to mind direction.

Searle writes that the direction of causation is from world to mind, not mind to world, in that there is no backwards causation.

One problem with Direct Realism is that it requires backwards causation, from perceiving a green tree to knowing that the cause of this perception was also a green tree.

For Searle, there is only a mind to world direction of fit, not a mind to world direction of causation. As regards mind to world direction of fit, a perception is satisfied or unsatisfied depending on how the world is in fact independently of the perception. The key is whether the perception is satisfied or unsatisfied. If satisfied the perception fits the world, if not satisfied the perception does not fit the world. There is nothing in this statement that the perception has to fit the world.

For the same reason that when seeing a broken window on one's walk to work, it is impossible to know just from the broken window what caused it to break, just by having the perception of a green tree in one's mind it is impossible to know what caused that perception.

As Searle himself writes, for perception, causation is from world to mind, not mind to world.

How do physical properties obtain without a perceiver? — schopenhauer1

I can discover in the world several shapes that are square at the top and round at the base.
I can invent the physical property "squund", which is a shape that is square at the top and round at its base. As a property is a concept, it cannot exist in the world. Although there may be particular instantiations of the property squund in the world, an instantiation of a property is not a property.

Therefore, physical properties cannot obtain without a perceiver.

What is an event without an perceiver? — schopenhauer1

Unperceived.

Is it space-time that becomes the placeholder for the event to obtain? — schopenhauer1

There's nothing else apart from space-time that could be a placeholder.

There are three scenarios, each arguing against Direct Realism.

Scenario one
I just perceive the colour green. As anything could have caused it, this is an argument against Direct Realism which is the position that its cause would be known.

Scenario two
Over the recent past I had seen a tree and perceived the colour green. Today, I just perceive the colour green. I infer that the cause of my perception of green is a tree, but as inferences may be wrong, my knowledge that the cause is a tree can only be indirect. Another argument against Direct Realism which is the position that its cause would be known.

Scenario three
I see light from the sun hitting the leaves of a tree, green light is reflected and enters my eye which I perceive as green. I know the causal chain that started at the sun and ends up with my perception of green. But each stage in the causal chain has the same problem: I perceive white, how do I know that it was caused by the sun, I perceive green, how do I know it was caused by the leaves. If the question is, when I perceive a green tree how do I know it was caused by a green tree, the fact that there are many stages in a causal chain doesn't ensure a solution if each stage suffers from the same problem, how do I know what caused my perception.

The problem of knowing the cause of my perception of the colour green is the same problem as how I know the cause of the broken window seen on my walk into work. Causation is directional from the sun to my perception of green. Backwards causation is impossible. Even though one knows the final stage of a causal chain, it would be impossible to discover how the chain was initiated, in that for each effect there will be several possible causes.

And yet one "knows" that the green tree I perceive in my mind was caused by a green tree in the world. The mind must equate effect with cause. If I perceive green the cause was green, if I perceive a tree the cause was a tree, if I perceive a green tree the cause was a green tree.

For the mind, it seems to me, it is not that we directly attend to objects in the world that are independent of us, as in Direct Realism, rather we directly attend to our sense data which we equate with what exists in the world, as in Indirect Realism.

Direct realism I would say is about knowledge of the world, not mechanism of the knowledge. The mechanism is agnostic — schopenhauer1

I agree that in one sense the Direct Realist is looking at a tree in the world , not at the sense data in the mind. They are "looking through" the sense data to the tree on the other side of it, as one looks through a window to the world outside.

However, if someone somehow removed the sense data from the brain of the Direct Realist, they wouldn't be able to see the tree.

In another sense, the Direct Realist is directly looking at something that is at the same time both sense data and a tree. This could be part of the argument against Direct Realism, in that the Direct Realist is perceiving something which is in fact sense data although they think it is a tree, ie, a psychological illusion.

For direct realism, the perceiver directly perceives the world, and thus we are able to distinguish between the perceiver and the things upon which he is directing this activity. For the indirect realist, the perceiver directly perceives sense data, ideas, impressions, representations, models, sensations—internal flora and fauna indistinguishable from the perceiver himself—leaving us no distinction between perceiver and perceived. So it’s like saying we perceive perceptions, we see seeings, or we feel feelings. In order to answer the question of what we are directly perceiving, one must posit something that is not the perceiver to find it. Since indirect realism is unable to do so, indirect realism is redundant. — NOS4A2

The argument is that as the Indirect Realist directly perceives sense data, this leaves no distinction between perceiver and perceived, meaning that the Indirect Realist would be unable to perceive any external world. However the same argument would apply also to the Direct Realist, who also directly perceives sense data, but claiming that sense data is veridical and coincides with reality.

Sense data exists in the mind and is perceived by the mind. If Direct Realism is able to transcend its perception of sense data to the objects in the world that are its cause, then similarly so could Indirect Realism.

For the Direct Realist:
1) We directly perceive sense data
2) There is an external world
3) Sense data is caused by the external world
4) We directly engage with objects in the world using the perceptual intermediary of sense data.

For the Indirect Realist:
1) We directly perceive sense data.
2) There is an an external world
3) Sense data is caused by the external world
4) We indirectly engage with objects in the world using the perceptual intermediary of sense data.
5) From these sense data we construct an internal representation of objects in the world
6) There is a direct causal link from objects in the world, to our sense data and to our perception of these sense data.
7) The fact there is a direct causal link from object in the world to our perception of it in the mind does not mean that we can necessarily have direct knowledge of what is in the world. For example, from the fact that there is a storm, the wind blows, a tree sways, a branch hits a window and the glass breaks it does not follow that when we see broken glass we know the cause was a storm. There is a direction of causation from storm to broken glass. Knowledge of backward causation from broken glass to storm is not possible.

Since it was so important, we developed machines, more sensitive and accurate than humans, that could detect the green color of objects. So light would come in and the machine would report and answer “green”. Is the machine having a sensation or constructed perception of “green” to detect the color of “green” in order to report “green”? — Richard B

The leaf is green because it does not absorb the green wavelength. If it is not, what color is it? If you say there is no color, well OK feel free to define “what it really is” any way you like, maybe it will have some interesting utility for us. — Richard B

A wavelength does not have an inherent colour, though any set of wavelengths can be given the name of a colour. The wavelength between 570 and 500 nm has been named "green", though it equally well have been named "vert".

A machine may be programmed such that if its input is 570 to 500nm its output is "green", though it could equally well have been programmed such that if its input was 530 to 420 nm its output was "xyz".

Rather than say " The leaf is green because it does not absorb the green wavelength", one could also correctly say "the machine gives the output green because its input was between 570 and 500nm due to that being the wavelength the leaf did not absorb".

As regards language, I would say that the machine is able to sense a wavelength but is not able to perceive it.

I’m not sure a direct realist position entails the argument that just by knowing an effect we are directly able to know its cause. Would you explain? — NOS4A2

Direct Realism requires backwards causation, which is impossible

There is a direction to causation, in that it is not the case that first there is an effect and later there is a cause. For example, first sunlight hits the leaves of a tree, then light travels from the leaf to our eyes which we can then sense as green. It is obviously not the case that we sense green, then light travels backwards from our eye to the leaf. There is a direction of causation as there is an arrow of time.

Causation also requires that there is a direction in which information flows. For example, I know that if I throw a stone at a window there will most likely be one possible effect, the glass will shatter. But if I see a shattered window, I cannot know which of several possible causes was the actual cause, a thrown stone, a broken branch or a flying bird. For the same reason, in just sensing the colour green, I cannot directly know its cause because of the fundamental direction of causation, and the direction of information flow within causation.

But on the other hand, when I sense the colour green I psychologically know beyond doubt that I am looking at a single event, a green tree. So how to explain this seeming paradox, that information has appeared to flow backwards through time, in that, given a single effect, my sensing green, I believe I know a single cause, a green tree, something that is impossible given the arrow of causation.

Direct Realism's solution to this seeming paradox is by equating the effect with the cause, in that, if the effect is sensing of the colour green, Direct Realism says that the cause is also the colour green. Given a single effect, Direct Realism gives a single cause that is identical with the effect. However, this is an illusion.

One of the arguments against Direct Realism is the problem of illusion, in that a stick half in water appears bent. However, this is a different kind of illusion to that of Direct Realism, the psychological illusion that the cause of an effect is identical with the effect, that when we sense the colour green its cause was also the colour green. Direct Realism is a psychological illusion, where the mind a priori believes that an effect, a sensation in the mind, such as sensing the colour green, is also the cause of that sensation, ie, seeing a green tree.

This is also a different argument to the argument that there can often be a long and complex causal sequence between an object and event and the perceiver. Many Direct Realists accept this fact, and still maintain that external physical objects or events can be immediate or direct objects of perception, which is a reasonable position. My argument is that Direct Realism is an illusion because it does not take into account the fundamental restrictions in the direction of information flow. There is an asymmetry in the direction of causation, in that causal indirectness inevitably results in cognitive indirectness.

The "arrow of time" linking causal interconnections is one aspect of Leibniz's Principle of Sufficient Reason, one of the four laws of thought, which states that everything must have a reason or a cause. Our normal understanding of causation is that we can only causally affect the future but not the past. In all cases of causation, the cause and the effect are placed in time such that the cause precedes its effect temporally, to such a degree that we intuitively have great difficulty imagining things otherwise. Whereas David Hume argued that causes are inferred from non-causal observations, Immanuel Kant claimed that people have innate assumptions about causes, and about the temporal ordering of events and "directionality" of time

In our example of sensing the colour green and seeing a green tree, Direct Realism is the position that the green tree is a necessary cause of sensing green, whereas Indirect Realism is the position that the green tree is only one sufficient cause of sensing green.

Direct Realism is an illusion because it equates the cause of an effect with the effect, in that it equates sensing the colour green with its cause, a green tree, which is impossible, as it would require backwards causation.

Direct Realism is not valid, as it requires, just from knowledge of an effect, direct knowledge of its cause, which is impossible.

Direct realism argues we perceive the world directly.

A possible sequence is: sunlight travels from the sun to a tree and hits its leaves. Wavelengths between 415 and 740 nm are absorbed by the Chlorophyll in the leaves, and wavelengths between 520 and 625 nm are reflected off the leaves towards our eyes. Say a wavelength of 550 nm enters my eye. In my sense data is a patch of green, I perceive that I am looking at a green tree, and my cognition tells me to go towards it as there may be edible fruit on it.

Both the Indirect and Direct Realist would agree that we directly sense the colour green. However, it is impossible to directly know just from an effect the cause of that effect, although it may be possible to discover its cause indirectly. Therefore, it is impossible to directly know just from sensing the colour green its cause, although it may be possible to discover 550 nm as its cause indirectly.

For example, if a stationary 1kg object starts to move at 10 ms after being hit by another object, we know from the conservation of momentum that the mass * velocity of the hitting object was 10 kg m/s. However, there are an infinite number of possible combinations of m and v of the hitting object. This means that, even if we did know the mass and velocity of the object that was hit, we cannot directly know just from the behaviour of the hit object the m and v of the hitting object, although it may be possible to discover this information indirectly.

Therefore:
1) Just by knowing an effect, it is impossible to directly know its cause. Just from sensing the colour green, it is impossible to directly know that it was caused by a wavelength of 550 nm, although it may be possible to discover this information indirectly.
2) Similarly, it is impossible to directly know that the 550 nm was caused by a green tree.
3) Therefore, Direct Realism, which argues that from just knowing an effect we are directly able to know its cause, which is impossible, is not a valid position to take.

There really is no logic that can reasonably jump to solipsism. Just because we can’t be “sure” (and to be frank we can’t be sure of anything so that’s not a metric to use) doesn’t mean it’s all in your head or you’re the only conscious thing. That’s not what explains our observations so it doesn’t logically follow. — Darkneos

Epistemological solipsism is the philosophical idea that one can only be sure about the existence of one's own mind. The existence of an external world is not necessarily rejected but one can not be sure of its existence.

You write that "and to be frank we can't be sure of anything", but that is exactly the metric to make the jump to epistemological solipsism.

Your position that "we can't be sure of anything" is the point of epistemological solipsism.

When looking at a green tree, does the Direct Realist directly perceive the colour green or directly perceive the wavelength 500nm ? — RussellA

I suspect that he directly perceives all of the above, and everything else within his periphery. — NOS4A2

Sunlight hits the leaves of a tree, wavelengths from the blue and red spectrum are absorbed by the Chlorophyll in the leaves and green, yellow and orange are reflected off the leaves towards our eyes. A wavelength of, say, 500nm then travels from the tree to our eyes, which we can then perceive as the colour green.
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How is it possible to not only perceive the colour green but also to perceive the cause of our perception of the colour green, ie the wavelength of 500nm ?

Like I said before all arguments for it boil to nonsense since you have to deny solipsism to prove it and rely on things outside of it. — Darkneos

This is the problem of negative singular existence statements, where in order to deny the existence of a given individual, one must assume the existence of that very individual.

Faulty premises — Darkneos

Where is the faulty premise ?

My premise was "Everything I perceive in the world outside my mind happened in the past, whether the position of the moon or a leaf falling from a tree."

It takes time for light to travel from an object to my eyes, whether the 2.54 million years from the Andromeda Galaxy, the 8min 20sec from the Sun, the 1.3 sec from the Moon, as well as the leaf falling from the tree.

The time taken for light to travel from a falling leaf to my eyes may well be small, but it is finite. Pragmatically, it may make no difference to my daily life, but philosophically it does.

Philosophically, it means that it is impossible for me to have any knowledge of what exists in the present outside my mind. I may strongly infer what exists, but it is still an inference, and as only an inference, I can never be sure beyond doubt. I can only ever be sure of what exists in my mind in the present .

As I can only exist in the present, the past no longer exists. Therefore, the only other thing that can exist is the present outside my mind. But as I can only know the present outside my mind by inference, and as an inference is something that I may be wrong about, then is something that I cannot be sure about.

Therefore, the only thing that I can be sure about is the existence of my own mind, which is an argument for Epistemological Solipsism.