I don’t think so because Berkley’s objection to indirect realism still stands, and the direct realist can raise it without himself believing in idealism.

Given that any evidence of the external world lies beyond the veil of perception, or experience, is the realism regarding the external world a leap of faith?

Given that any evidence of the external world lies beyond the veil of perception, or experience, is the realism regarding the external world a leap of faith? — NOS4A2

In a sense, hence why indirect realists claim that there is an epistemological problem of perception, entailing the viability of scepticism.

But the term "faith" is a bit strong. It's no more "faith" than our belief in something like the Big Bang or the Higgs boson is "faith". We have good reasons to believe in them given that they seem to best explain the evidence available to us. The indirect realist claims that we have good reasons to believe in the existence of an external world as it seems to best explain the existence and regularity and predictability of experience.

I’m not sure there is any good reason for the indirect realist to believe in any of them, since any evidence regarding anything about the external world lies beyond his knowledge. He doesn’t know what he is experiencing indirectly. Hell, he can’t even know that his perception or knowledge is indirect.

I’m not sure there is any good reason for the indirect realist to believe in any of them, since any evidence regarding anything about the external world lies beyond his knowledge. He doesn’t know what he is experiencing indirectly. Hell, he can’t even know that his perception or knowledge is indirect. — NOS4A2

His experience is the evidence. He has direct knowledge of his experiences. What best explains the existence of such experiences and their regularity and predictability? Being embodied within a greater external world, with his experiences being a causal consequence of his interaction with that greater external world.

This is the reasoning that leads one to believe in realism (and so for some direct realism) over idealism.

In any case, it’s unfalsifiable and cannot be proven, except when it comes to the science of perception.

In any case, it’s unfalsifiable and cannot be proven — NOS4A2

I might agree; realism, idealism, atheism, pantheism, and the many-worlds interpretation of quantum mechanics are all unfalsifiable and cannot be proven.

except when it comes to the science of perception. — NOS4A2

We can look at what follows if we are scientific realists and accept the literal truth of something like the Standard Model and the science of perception. If true, indirect realism follows.

Of course, you can be a scientific instrumentalist and reject the literal truth of the Standard Model and the science of perception if you wish to maintain direct realism, although there may be some conflict in rejecting the literal truth of something that you claim to have direct knowledge of.

So given that both indirect realists and non-naive direct realists believe that "distal objects are causally responsible for my experience" is true, what is the difference between being a non-naive direct realist and being an indirect realist? — Michael

I've already answered this:

Non-naive realists believe that our perceptions can be of distal objects, whereas indirect realists believe that our perceptions are only of mental representations or sense data. Likewise, non-naive realists believe that our perceptual content can be about distal objects, whereas indirect realists believe that our perceptual content is only about mental representations or sense data. — Luke

Do you deny that indirect realists believe that our perceptions are only of mental representations or sense data? Or do you refuse to accept that non-naive direct realists believe that our perceptions can be of distal objects?

Do you deny that indirect realists believe that our perceptual content is only about mental representations or sense data? Or do you refuse to accept that non-naive direct realists believe that our perceptual content can be about distal objects?

It seems to be that their only disagreement is over what the phrase "my experience is of distal objects" means. — Michael

Does it? You have not at all addressed my comment regarding perceptual content and you continue to avoid discussing intermediaries.

Given that any evidence of the external world lies beyond the veil of perception, or experience, is the realism regarding the external world a leap of faith? — NOS4A2

There is the distinction between what are facts about the (external) world and what is true about it. My argument here would be that science in consideration of facts about the world can determine - wrt to chosen criteria - what is true about it. Of course criteria are a whole other topic.

Do you deny that indirect realists believe that our perceptions are only of mental representations or sense data? Or do you refuse to accept that non-naive direct realists believe that our perceptions can be of distal objects? — Luke

What does "our perceptions are of distal objects" mean?

Given that indirect realists believe that "our perceptions are of distal objects" is false but believe that "our perceptions are caused by distal objects" is true, it must be that "our perceptions are of distal objects" doesn't mean "our perceptions are caused by distal objects".

If what indirect realists mean by "our perceptions are of distal objects" isn't what non-naive direct realists mean by "our perceptions are of distal objects" then you are equivocating.

Assume that by "our perceptions are of distal objects" non-naive direct realists mean "our perceptions are ABC".

Assume that by "our perceptions are of distal objects" indirect realists mean "our perceptions are XYZ".

Non-naive direct realists believe that "our perceptions are ABC" is true. Indirect realists believe that "our perceptions are XYZ" is false.

Where is the disagreement?

And if non-naive direct realists agree with indirect realists that "our perceptions are XYZ" is false and if indirect realists agree with non-naive direct realists that "our perceptions are ABC" is true, then non-naive direct realism and indirect realism are the same.

What does "our perceptions are of distal objects" mean?

Given that indirect realists believe that "our perceptions are of distal objects" is false but believe that "our perceptions are caused by distal objects" is true, it must be that "our perceptions are of distal objects" doesn't mean "our perceptions are caused by distal objects". — Michael

What do you mean by "our perceptions are of distal objects" when you say it is false?

If what indirect realists mean by "our perceptions are of distal objects" isn't what non-naive direct realists mean by "our perceptions are of distal objects" then you are equivocating. — Michael

How does that follow?

Assume that by "our perceptions are of distal objects" non-naive direct realists mean "our perceptions are ABC".

Assume that by "our perceptions are of distal objects" indirect realists mean "our perceptions are XYZ". — Michael

It is not a dispute over different meanings of the phrase "of distal objects", is it? Also, indirect realists do not believe that our perceptions are of distal objects; they believe that our perceptions are of mental representations or sense data.

Where is the disagreement? — Michael

Even if there were no substantive dispute over whether our perceptions are of distal objects, you have still not addressed the other difference that I noted between the two parties: their different beliefs regarding perceptual content.

What do you mean by "our perceptions are of distal objects" when you say it is false? — Luke

I don't say that it's false. I have been at pains in this discussion (and others over the past few years) to explain that trying to address the epistemological problem of perception in these terms is a conceptual confusion. It's an irrelevant argument about grammar.

"I experience X" doesn't just mean one thing. I can say that I feel pain, I can say that I feel my hand burning, or I can say that I feel the fire. I can say that the schizophrenic hears voices. I can say that some people see a white and gold dress and others see a black and blue dress when looking at the same photo.

These are all perfectly appropriate phrases in the English language, none of which address the philosophical issue that gave rise to the dispute between direct and indirect realism (as explained here).

How does that follow? — Luke

If A is true and B is false then A and B do not mean the same thing.

If indirect realists believe that "our perceptions are of distal objects" is false but believe that "our perceptions are caused by distal objects" is true then when they say "our perceptions are not of distal objects" they are not saying "our perceptions are not caused by distal objects."

It is not a dispute over different meanings of the phrase "of distal objects", is it? — Luke

The dispute between naive realists and indirect realists is not a semantic dispute. Their dispute is a legitimate philosophical dispute over the epistemological problem of perception.

The dispute between non-naive direct realists and indirect realists is an irrelevant semantic dispute. They agree on the philosophical issue regarding the epistemological problem of perception.

Even if there were no substantive dispute over whether our perceptions are of distal objects, you have still not addressed the other difference that I noted between the two parties: their different beliefs regarding perceptual content. — Luke

What does it mean to say that something is the content of perception? Perhaps you'll find that what indirect realists mean by "X is the content of perception" isn't what non-naive direct realists mean by "X is the content of perception", and so once again it's an irrelevant dispute about language.

I'll refer you again to Howard Robinson's Semantic Direct Realism.

I like the examples you (and Claude) have been giving, but I don't seem to draw the same conclusion.

I don't think indirect realism presupposes or requires that phenomenal experience is somehow a passive reflection of sensory inputs. Rather the opposite, a passive brain reflecting its environment seems to be a direct realist conception. These examples seem to emphasize the active role the brain plays in constructing the sensory panoply we experience, which is perfectly in line with indirect realism.

For instance, in the very striking cube illusion you presented, we only experience the square faces as brown and orange because the brain is constructing an experience that reflects its prediction about the physical state of the cube: that the faces must in fact have different surface properties, in spite of the same wavelengths hitting the retina at the two corresponding retinal regions.

That such a thing could happen at all is only possible if our sensory experience is an interpretive construction. And if it our experience of the world is via an interpretive construction, our experience of the world is surely not "direct".

And none of these examples demonstrate that phenomenological experience does not supervene on brain states. Rather, we can be sure that the brain states corresponding to the two perceived colors are different from that induced by the same scene without the shadow. That is because brain states don't dumbly correspond to raw sensory inputs but are reflections of the brain's active, predictive powers.

What do you mean by "our perceptions are of distal objects" when you say it is false?
— Luke

I don't say that it's false. — Michael

You said:

Given that indirect realists believe that "our perceptions are of distal objects" is false... — Michael

You said that indirect realists believe it is false. Since you are an indirect realist, then you believe it is false. So, what meaning do you give to this false statement?

"I experience X" doesn't just mean one thing. I can say that I feel pain, I can say that I feel my hand burning, or I can say that I feel the fire. I can say that the schizophrenic hears voices. I can say that some people see a white and gold dress and others see a black and blue dress when looking at the same photo.

These are all perfectly appropriate phrases in the English language, none of which address the philosophical issue that gave rise to the dispute between direct and indirect realism (as explained here). — Michael

I agree that none of this addresses the relevant philosophical issue. Direct realists believe that we perceive external objects whereas indirect realists believe that we perceive internal objects. You continue to avoid this difference between the two views by claiming that they are the same view.

If indirect realists believe that "our perceptions are of distal objects" is false but believe that "our perceptions are caused by distal objects" is true then when they say "our perceptions are not of distal objects" they are not saying "our perceptions are not caused by distal objects." — Michael

I acknowledge that it was a mistake to give a causal explanation to account for the "of" in "our perceptions are of distal objects". My causal explanation was an attempt to account for why we might say that "our perceptions are of distal objects". This was not intended as a statement of synonymy.

To correct my earlier statement, what direct realists mean by "of" in "our perceptions are of distal objects" is the same as what we mean by "this photograph is of Big Ben" or "this painting is of Mr Smith". Just as photographs or paintings represent their subjects, perceptions represents distal objects. However, this is not to say that we have perceptions of perceptions. Similarly, we would not say that a photograph of Big Ben is a photograph of a photograph.

The dispute between non-naive direct realists and indirect realists is an irrelevant semantic dispute. They agree on the philosophical issue regarding the epistemological problem of perception. — Michael

This is mere assertion.

What does it mean to say that something is the content of perception? — Michael

Perceptual content includes the sensory information of the perception and the quality of the subjective experience. Direct realists say that the perceptual content represents external objects. Indirect realists say that the perceptual content represents internal objects.

Perhaps you'll find that what indirect realists mean by "X is the content of perception" isn't what non-naive direct realists mean by "X is the content of perception", and so once again it's an irrelevant dispute about language. — Michael

I do not find that they mean the same thing. Direct realists say that we perceive external objects. Indirect realists say that we perceive internal objects.

Perhaps seeing the coloured squares as different is not inferential or predictive, but a case of the locations of the squares in different tonal contexts producing the apparent differences simply due to contrast.

What do you mean by "our perceptions are of distal objects" when you say it is false?
— Luke

I don't say that it's false. I have been at pains in this discussion (and others over the past few years) to explain that trying to address the epistemological problem of perception in these terms is a conceptual confusion. It's an irrelevant argument about grammar. — Michael

Saying that distal objects are not constituents of perception or experience is potentially semantically ambiguous, so it cannot unambiguously be framed as a purely epistemological problem, as though there could be a determinate fact of the matter.

And yet you argue that we can never know if the smell of smoke indicates that there is smoke (or that one perceives smoke), due to the possibility of illusion, hallucination or error. — Luke

If we know it, to "know" must accommodate a degree of uncertainty. If it does not, we don't know it.

Naive realism and indirect realism are both based on the presupposition that there is a “correct” way to perceive the world, which is to perceive the world as it is in itself. Naive realism supposes that we do perceive the world as it is in itself. Indirect realists oppose naive realism based on the possibility of illusion, hallucination or error. — Luke

No, indirect realism does not presuppose a correct way of seeing the world. There is no such thing as correctly perceiving the world as it is in itself. Rather, the best we can do is derive true propositional content about the state of the world. via perception.

Indirect realism opposes direct realism based on the fundamental meditative role brain-produced phenomenal experience plays in our contact with the world. Illusion, hallucinations, and error are consequences of, and are only possible because of, this mediation.

If this presupposition is rejected, then it is no longer a question of whether or not we perceive the world as it is in itself directly, but a question of whether or not we perceive the world directly. The latter does not require a superhuman form of perception that can infallibly see "behind" the appearance of the world, but simply a form of perception that provides an appearance of the world, fallible or not. — Luke

That contact with the world is mediated by an appearance that is itself not the world can only mean that contact with the world is indirect. The fact that direct contact with the world is not possible does not constitute an argument against this.

You seem want to argue that because direct, immediate experiential contact with the world is impossible and even incoherent, therefore, there is direct, immediate experiential contact with the world. No, if unmediated experience of the world is impossible, experience of the world is therefore mediated.

Direct realists believe that we perceive external objects whereas indirect realists believe that we perceive internal objects. You continue to avoid this difference between the two views by claiming that they are the same view. — Luke

Again, if we do not perceive/experience/have awarenesw of internal objects, what are we perceiving/experiencing/aware of when we hallucinate? External objects?

One question: why did the brain adjust for color constancy in the cube picture but not the snow pictures?

One question: why did the brain adjust for color constancy in the cube picture but not the snow pictures? — hypericin

That's an excellent question that demonstrates that you have been paying attention!

My guess is that, in both cases, the internal cues provided in the picture regarding the spectrum of the ambient light conflict with the external cues regarding the background illumination in the room you occupy while looking at the picture. In the cube case, the image has been designed to maximise the illusion by providing an abundance of internal cues (such as the color of the "white" background and shadows indicating what face of the cube falls under them) that make them predominant. When looking at pictures of shadows on the snow, the internal cues regarding the spectral qualities of the ambient light may be less obvious and so the external cues predominate. All I know for sure is that in real life conditions, our visual system isn't easily fooled.

To correct my earlier statement, what direct realists mean by "of" in "our perceptions are of distal objects" is the same as what we mean by "this photograph is of Big Ben" or "this painting is of Mr Smith". Just as photographs or paintings represent their subjects, perceptions represents distal objects. — Luke

Direct realists say that the perceptual content represents external objects. — Luke

The representational theory of perception that claims that perceptual content is some mental phenomenon (e.g. sense data or qualia) that represents the external world is indirect realism, not direct realism.

Direct realism, in being direct realism, rejects the claim that perception involves anything like mental representations (which would count as an intermediary).

If by "the experience is of distal objects" you only mean something like "the painting is of Big Ben" then indirect realists can agree. The relevant philosophical issue is that we only have direct knowledge of the experience/painting and only indirect knowledge of distal objects/Big Ben, hence the epistemological problem of perception.

This is vaguely inspired by Fodor's criticisms of meaning holism. As appealing as Wittgenstein-inspired meaning holism is, it doesn't work out on the ground. It's not clear how a human could learn a language if meaning is holistic. Likewise, the student of biology must start with atomic concepts like the nervous system (which has two halves). Eventually it will be revealed that you can't separate the nervous system from the endocrine system. It's one entity. But by the time this news is broken to you, you have enough understanding of the mechanics to see what they're saying. And honestly, once this has happened a few times, you're not at all surprised that you can't separate the lungs from the heart. You can't separate either of those from the kidneys, and so on.

This isn't new. As I mentioned, the boundary between organism and world can easily fall away. Organisms and their environments function as a unit. If you want to kill a species, don't attack the organisms, attack their environment. It's one thing. And this leads to my second point: you said that philosophy is the right domain for talking about this issue, but philosophy won't help you when there are no non-arbitrary ways to divide up the universe. Your biases divide it up. All you can do is become somewhat aware of what your biases are. Robert Rosen hammers this home in Life Itself, in which he examines issues associated with the fact that life has no scientific definition. The bias at the heart of it is the concept of purpose. He doesn't advise dispensing with the concept of purpose because there would be no biology without it. What he does is advise a Kantian approach. — frank

I think the idea that one must start with "atomic" concepts isn't wholly inconsistent with the sort of holism Wittgenstein advocated. My former philosophy teacher, Michel Seymour, proposed molecularism in the philosophy of language as an alternative to both atomism and holism. I may not be getting his idea completely right, because I haven't read what he wrote about it, but we can acknowledge that understanding concepts necessitates mastering some part of their conceptual neighborhood without there being a requirement that we master a whole conceptual scheme all at once. Children learn to recognise that an apple is red before they learn that something can look red without being red. Mastering the grammar of "looks" enriches their conceptual understanding of "red". As a child gets acculturated, the growing number of inferential constitutive relationships between neighboring concepts increases their intellectual grasp on their individual meanings (and so is it with students of any science of nature). "Light dawns gradually over the whole." (Wittgenstein, On Certainty, §141). It doesn't make sense to say of anyone that they understand what the physical concept of an electron signifies independently of their ability to make correct (material) inferences from the claim that something is an electron.

The result from this process isn't just to disclose constitutive conceptual connections between the terms that refer to different objects and properties, but also to disclose finer-grained ways in which they are individuated. Hence, getting back to our topic, the involvement of the body and of the world in the process of perception doesn't erase the boundary between the human subject and the objects that they perceive. It rather empowers them to better understand their objective affordances.

The representational theory of perception that claims that perceptual content is some mental phenomena (e.g. sense data or qualia) that represents the external world is indirect realism, not direct realism.

Direct realism, in being direct realism, rejects the claim that perception involves anything like representations. — Michael

This is the distinction between non-naive realism and indirect realism. Indirect realists holds that we perceive perceptions or mental representations, whereas non-naive realists holds that perceptions are mental representations and that they represent external objects. Returning to the photograph analogy, a non-naive realist would say that the photograph (perception) is a representation of a real object, whereas (I imagine) an indirect realist would say that the photograph (perception) is a representation of a representation. A naive realist, on the other hand, might say that there is no representation involved at all. This demonstrates how non-naive realism differs from both naive realism and indirect realism, refuting your claim that non-naive realism is the same view as indirect realism.

Indirect realism opposes direct realism based on the fundamental meditative role brain-produced phenomenal experience plays in our contact with the world. Illusion, hallucinations, and error are consequences of, and are only possible because of, this mediation. — hypericin

I would say that illusions and hallucinations are phenomenal experiences, instead of saying that they are the consequences of phenomenal experiences. It is worth noting that illusions require the perception of an external object, whereas hallucinations are phenomenal experiences in which the external object/stimulus is absent, by definition.

That contact with the world is mediated by an appearance that is itself not the world can only mean that contact with the world is indirect. The fact that direct contact with the world is not possible does not constitute an argument against this. — hypericin

What do you mean by "direct contact with the world"?

You say that our contact with the world is indirect because it "is mediated by an appearance that is itself not the world". Firstly, the mediation is the perception/representation that provides the appearance of the world to us. Secondly, I don't expect a perception of the world to be the world, just as I don't expect a photograph of a lion to be a lion. You are implying that a mental representation must become the external object that it represents (i.e. a representation must become the represented) in order for us to have direct contact with the world. This makes no sense to me.

You seem want to argue that because direct, immediate experiential contact with the world is impossible and even incoherent, therefore, there is direct, immediate experiential contact with the world. No, if unmediated experience of the world is impossible, experience of the world is therefore mediated. — hypericin

The world as it is in itself is the unperceived world. It is incoherent to perceive the unperceived world for then it would no longer be unperceived. The way our perceptions represent the world to us may not reflect the true nature of the unperceived world, but they nevertheless represent the world to us. There is no such thing as perceiving the unperceived world, but this needn't imply that we can only perceive perceptions. We can still perceive the perceived world; the world as it is represented by our perceptions.

Or, as I asked ChatGPT to re-word the above for clarity:

The world in its unperceived state exists independently of our perception. It's logically impossible to perceive this unperceived world, as doing so would contradict its unperceived nature. While our perceptions may not perfectly mirror the true essence of the unperceived world, they still offer us a representation of it. We cannot directly perceive the unperceived world, but this doesn't mean we're confined to perceiving only our perceptions. Instead, we perceive the perceived world— the world as it's presented to us through our perceptions.

Again, if we do not perceive/experience/have awarenesw of internal objects, what are we perceiving/experiencing/aware of when we hallucinate? External objects? — hypericin

The lack of external stimulus is what marks it as a hallucination. Hallucinations are distortions of perception, which can be contrasted with undistorted perceptions that involve an external stimulus.

This is the distinction between non-naive realism and indirect realism. Indirect realists holds that we perceive perceptions or mental representations, whereas non-naive realists holds that perceptions are mental representations and that they represent external objects. — Luke

Both indirect and non-naive direct realists believe that colours are a mental representation of some distal object's surface properties. Both indirect and non-naive direct realists believe that we see colours. Therefore, both indirect and non-naive direct realists believe that we see mental representations.

Experiencing a mental representation and experiencing a distal object are not mutually exclusive. "I feel pain" and "I feel my skin burning" are both true. The grammar of "I experience X" is not restricted to a single meaning.

The relevant philosophical issue is that distal objects are not constituents of experience and so that our experience only provides us with indirect knowledge of distal objects. Everything else is a red herring.

The relevant philosophical dispute is that distal objects are not constituents of experience and so that our experience only provides us with indirect knowledge of distal objects. — Michael

Therefore, Big Ben is not a constituent of a photograph of Big Ben? Surely Big Ben is a component of the photograph. It's the subject of the photograph.

Therefore, Big Ben is not a constituent of a photograph of Big Ben? — Luke

Correct. The photograph is in my drawer. Big Ben is not in my drawer. The only things that constitute the photo are its physical materials.

Surely Big Ben is a component of the photograph. It's the subject of the photograph.

What does it mean for something to be the subject of the photograph? What does it mean for something to be the subject of a book? It's entirely conceptual. The conceptual connection between a photograph or book and their subject does not allow for direct knowledge of their subject. Photographs and books only provide us with indirect knowledge of their subject.

Indirect realists describe this as "seeing representations" and non-naive direct realists describe this as "seeing distal objects". This is the irrelevant semantic disagreement that amounts to nothing. — Michael

How is the dispute between indirect realists and naive realists any different? As you describe it:

Indirect realists claim that perceptions involve mental representations, e.g qualia and sense-data, as contrasted with naive realists who don't. That's the substantive philosophical issue, — Michael

Naive realists and non-naive realists both claim that we see distal objects. Indirect realists say instead that we see representations.

Naive realists and non-naive realists both claim that we see distal objects. Indirect realists say instead that we see representations. — Luke

Which is an irrelevant argument about grammar. From my previous post:

Both indirect and non-naive direct realists believe that colours are a mental representation of some distal object's surface properties. Both indirect and non-naive direct realists believe that we see colours. Therefore, both indirect and non-naive direct realists believe that we see mental representations.

Experiencing a mental representation and experiencing a distal object are not mutually exclusive. "I feel pain" and "I feel my skin burning" are both true. The grammar of "I experience X" is not restricted to a single meaning.

The relevant philosophical issue is that distal objects are not constituents of experience and so that our experience only provides us with indirect knowledge of distal objects. Everything else is a red herring.

Which is an irrelevant argument about grammar. — Michael

Is the dispute between naive realists and indirect realists also "an irrelevant argument about grammar"? Non-naive realists and indirect realists have the same dispute.

Experiencing a mental representation and experiencing a distal object are not mutually exclusive. "I feel pain" and "I feel my skin burning" are both true. The grammar of "I experience X" is not restricted to a single meaning.

I don't see how this example is related to distal objects.

Is the dispute between naive realists and indirect realists also "an irrelevant argument about grammar"? — Luke

No. Naive realists believe that distal objects are constituents of experience and so that experience provides us with direct knowledge of distal objects. That's a substantive philosophical dispute.

I don't see how this example is related to distal objects. — Luke

In this case I'm being imprecise with the term "distal object" to mean anything outside the experience, and so including body parts, such that my skin is a distal object.

Naive realists believe that distal objects are constituents of experience and so that experience provides us with direct knowledge of distal objects. — Michael

I also believe that distal objects are constituents of experience in the sense that you could not have an experience of a distal object without them. I think that naive and non-naive direct realists would agree on this point. I don't see why it must be restricted only to physical constituents, especially since an experience does not have physical constituents.

The grammar of "I experience X" is not restricted to a single meaning.

Why wouldn't you use the same argument against naive realists?