All those fruits have a property in common, otherwise we would not see something in common in them. — Lionino

That does not follow, and nor does it follow that if they have a property in common then this common property is the property that they appear to have in common.

This problem isn't one that can be solved by a linguistic analysis of how the word "colour" is used; it requires scientific study of tomatoes, the human body, and phenomenal consciousness.

If someone with normal color vision looks at a tomato in good light, the tomato will appear to have a distinctive property—a property that strawberries and cherries also appear to have, and which we call “red” in English. The problem of color realism is posed by the following two questions. First, do objects like tomatoes, strawberries and radishes really have the distinctive property that they do appear to have? Second, what is this property? (Byrne & Hilbert 2003: 3–4)

These questions are not answered by saying that we sometimes use the term "red light" to refer to 700nm light and that tomatoes and strawberries reflect 700nm light.

@Banno Do you have a digital copy of Searle's Seeing Things as They Are? I seem to recall that you agree with his theory of perception?

I ask because according to this:

Searle presents the example of the color red: for an object to be red, it must be capable of causing subjective experiences of red. At the same time, a person with spectrum inversion might see this object as green, and so unless there is one objectively correct way of seeing (which is largely in doubt), then the object is also green in the sense that it is capable, in certain cases, of causing a perceiver to experience a green object.

This seems consistent with what I have been arguing, and so I want to see for myself if the author of the above is reading Searle correctly.

The percept that occurs when we hallucinate red is the percept that occurs when we dream red is the percept that optical stimulation by 620-750nm light ordinarily causes to occur.

Or if you prefer, the neural activity that is responsible for dreaming red is the neural activity that is responsible for hallucinating red is the neural activity that optical stimulation by 620-750nm light ordinarily causes to occur.

When this neural activity occurs when asleep we call it a dream. When this neural activity occurs when awake but not in response to optical stimulation we call it an hallucination. When this neural activity occurs when awake and in response to optical stimulation we call it a non-hallucinatory waking experience.

I'm not arguing for direct realism because it doesn't need an argument. — frank

It needs the support of physics and the neuroscience of perception, which it doesn't have. It's not the sort of thing that can be proved a priori or just assumed.

The absurdity of this should be plain. How do you tell that you are experiencing red? Well, because you know what "the colour red" is. So what is the colour red? Well, it's the experience of red. And what is the red in your experience? Why, it's the colour red, of course... — Banno

It's no more absurd than saying the same thing about pain. Pain is the experience of pain.

More likely that they had not given consideration to the difference. — Banno

I doubt anyone who would not give consideration to the difference is going to be asking for a linguistic analysis of the word “colour” in a discussion entitled “Perception”.

He’s most likely asking the simple question that I am answering.

That is, it seems to me that the question is about the use of the word "red" rather than about the appearance of red. — Banno

Except he says “the colour ‘red’” and not “the word ‘red’”.

I think it more likely that he is misusing quotation marks than misusing the word “colour”. To give him the benefit of the doubt, he’s saying “the colour referred to by the word ‘red’”, with his use of the word “colour” referring to a type of visual appearance.

On this view you're advocating for, you're clearly stating that there is no difference between seeing, hallucinating, and dreaming. — creativesoul

I didn’t say that. I was only saying that the percepts that occur when dreaming red and hallucinating red are the percepts that ordinarily occur when 700nm light stimulates our eyes. That's why they're all referred to using the word "red".

It's certainly not the case that a red hallucination percept is a blue dream percept is a green waking percept.

Dreams, hallucinations, and non-hallucinatory waking experiences differ in what causes these percepts to occur. With dreams it's internal processes when asleep, with hallucinations it's internal processes when awake, and with non-hallucinatory waking experiences it's sensory stimulation when awake.

Which was what? — frank

We know how things affect the world and so can know about a thing from its effect.

Perhaps a different analogy is more helpful. A blind man can know that he is eating an apple because he knows what apples taste like, but the taste of an apple does not resemble the apple or any of its properties. An apple’s taste is a phenomenological consequence of the apple’s chemicals interacting with the tongue’s sense receptors.

Sight isn’t special. Visual sensations (such as colour) need not resemble their cause.

Oh, I quite agree. Odd that you think this worthy of mention. — Banno

You have previously said that colours are both appearances and something else. Except by this you just mean that the word "colours" can be used to refer to both appearances and something else.

But the use of the word "colours" to refer to this something else is of no relevance to the question asked by the OP. It is clear in context that he is asking about the appearance. And physics and the neuroscience of perception support colour eliminativism over naive colour realism with respect to this question.

Yep. "colour" has different senses. — Banno

And only the sense relevant to the question being asked is relevant, not any other sense. It is clear in context that the OP isn't asking if light or atoms reflecting light is mind-independent, and so any use of the word "colour" or "red" that refers to light or atoms reflecting light is irrelevant.

I am pointing out that "red", in the sense of the colour word, does nto refer to a single thing. — Banno

The single thing is a type, not a token.

You seem to be intentionally misrepresenting my position, so I'll try an even simpler approach.

The term "colour" is also used to refer to the way quarks and gluons interact through the strong force, but that use is irrelevant to the question asked by the OP, and to the philosophy of colour in general.

If your theory does not explain the way we use the word "colour" then what grounds could there be for your claiming it to be about colour? — Banno

I addressed this with the example of the Morning Star, but perhaps you need a simpler example.

If you ask me if bats are blind, and if in context it's clear that you are asking about the flying mammal, then I don't need to talk about anything else that is referred to using the word "bat", e.g. the club used in baseball.

Why shouldn't we use the same word to refer to multiple, different things... indeed this seems to be exactly how colour words are used. They refer to multiple things that are quite different. — Banno

I also addressed this before. The question "is the colour red mind-independent?" is not the question "is anything referred to by the term 'colour red' mind-independent?". Perhaps you need to re-examine the distinction between use and mention.

The question "is the colour red mind-independent?" is using the singular compound noun "colour red" to refer to a single thing, and then asking if that thing is mind-independent. Unless they provide greater clarification, you need to make a reasoned assumption as to what that thing is. It's clear in context that the OP isn't asking if 700nm light is mind-independent, or if a micro-structural surface that reflects 700nm light is mind-independent, but is asking if that sui generis, simple, qualitative appearance named "red" is mind-independent.

In other words, it's clear in context that the OP is asking which (if either) of realist color primitivism and color eliminativism/subjectivism provides a correct account of colour appearances.

I believe in the existence of a Geiger counter despite the fact that experiences might not resemble their cause for the same reason that you believe in the existence of radiation despite the fact that Geiger counters do not resemble radiation.

Your very supposition, that if experiences do not resemble their cause then experiences cannot be "trusted" is a non sequitur and barely coherent.

Is there some reason you can't just answer my question? Why do you trust your senses? — frank

I already have. Why won't you answer my question? Why do you trust a Geiger counter to tell you the local level of radiation? It doesn't resemble radiation at all.

Why do you trust your senses if what they show you may or may not resemble what's in front of you? — frank

Why do you trust a Geiger counter to tell you the local level of radiation?

Conclusion: you have to believe your senses are telling you the truth in order to accept the Standard Model. — frank

I don't even know what you mean by "senses telling the truth". Hanover and I are talking about experiences resembling their causes.

This is what Russell was talking about. It's a conundrum. — frank

Russell said the opposite: if direct realism is true then we must accept physics, but physics tells us that experiences do not resemble their causes, therefore if direct realism is true then indirect realism is true.

But your claim – that if indirect realism is true then we must reject physics – is a non sequitur.

Either way, we have to either a) accept indirect realism or b) reject physics.

Although I don't want get into the entire direct vs indirect realism debate here. I'm just focusing on colour.

Why would you believe you actually have a geiger counter in your hand if your perceptions may or may not resemble the object? — frank

I addressed that with the very question I asked you, and which you conspicuously didn't answer. We don't need our experiences to resemble the things we believe in. The direct realist trusts a Geiger counter even though the numbers on the screen do not resemble the radiation they purport to measure.

And this is especially true of colour. I don't need to believe that the colour red resembles 700nm light to trust that objects that appear red reflect 700nm light. It's certainly not infallible, but it's reasonable enough.

I don't think so. It's more like asking why you accept science of any kind if you can't rely on your senses to tell you the truth. — frank

Do you trust the numbers on a Geiger counter to tell you the amount of radiation in the environment, even though the numbers do not resemble radiation?

The presumption you have that one can trust one's experiences if and only if one's experience "resemble" their causes is a fallacy.

If our perceptions may not bear any resemblance to what's out there, then why believe the science that led you to accept indirect realism? — frank

This is like asking why we accept the Standard Model if we cannot see electrons with the naked eye.

You seem to misunderstand my point. Dreams can be about things but dreams are still mental phenomena, caused by neural activity in the brain.

So your claim that distal objects are the intentional objects of waking experience and so therefore colours are mind-independent properties of these distal objects is a non sequitur.

Intentionality simply has no relevance to the dispute between colour eliminativism and colour realism.

those are experiences evoked by stimulation of the neural connections that your brain developed when you were awake — jkop

And colours are constituents of these experiences.

When you dream or hallucinate seeing a colour, you have the experience, but you don't see anything, and that's why they're called dreams and hallucinations. — jkop

This is a word game. You might not like to use the phrase "the schizophrenic hears voices" because it's an hallucination but it is perfectly acceptable to describe the phenomenon in this way.

Brain stimulation is insufficient for colour-experiences. Stimulation from a sense organ that interacts with light and discriminates between different wavelength components is necessary for colour experiences. Therefore, colours exist outside of the brain. — jkop

That does not follow. Colour experiences might depend on neural connections which only develop in response to optical stimulation by light, but your conclusion that therefore colours are mind-independent properties of light/distal objects is a non sequitur.

One does not see the properties of one's own seeing, but the properties of what the seeing is about, the colour. — jkop

I see colours when I dream and hallucinate on mushrooms. I see white and gold when I look at the photo of the dress. I feel pain. The schizophrenic hears voices.

The intentionality of perception means that there's a difference between the experience that you have, and what that experience is about. — jkop

I know. And colours, as ordinarily understood, are properties of the experience, not properties of what the experience is about. The naive colour realist commits a mistake in thinking these experience properties to be distal object properties.

That's precisely why physicists and neuroscientists say such things as "color is a psychological property of our visual experiences when we look at objects and lights, not a physical property of those objects or lights."

And what's the difference between hallucinating red and the mental percept that 620-750nm light ordinarily causes to occur?

Or between dreaming red and the mental percept that 620-750nm light ordinarily causes to occur? — creativesoul

Nothing.

Hallucinations, dreams, and non-hallucinatory waking experiences all involve neural activity in the visual cortex, producing colour percepts.

What is being rejected here is not the physiology. What is being rejected is a reduction of colour to mere percept, because doing so fails to account for the use of colour terms in our everyday lives. — Banno

But the question under consideration isn't "what are all the ways that we use colour terms in our everyday lives?".

Rather, we are using the word "colour" to refer to something in particular and are asking what that thing is. Both the naive colour realist (which is the "common sense" position) and the colour eliminativist/subjectivist are using the word "colour" to refer to the same thing; that sui generis, simple, qualitative appearance. The naive colour realist just falsely claims that this thing isn't a percept but a mind-independent property of material bodies.

As a comparison, when we ask what the Morning Star is we are referring to a planet and are asking what it is (not knowing that we are referring to a planet and not a star). We don't respond to such a question by arguing that the term "Morning Star" is also used to refer to the archangel Lucifer.

What's the difference between seeing red and the mental percept that 620-750nm light ordinarily causes to occur? — creativesoul

Nothing.

We can, and do, use the phrase "red part of the visible spectrum" to mean "620-750nm light". Pens do reflect 620-750nm light, and so we can, and do, say that pens reflect the red part of the visible spectrum of light.

But this isn't our ordinary conception of the colour red. Our ordinary conception of the colour red is that of the mental percept that 620-750nm light ordinarily causes to occur. This is how we can make sense of coloured dreams and hallucinations, of synesthesia, of variations in colour perception (such as the dress), and of scientific studies like this.

The problem is when someone argues for something like naive colour realism/realist colour primitivism, or that there is a "correct" way for an object that reflects 620-750nm light to look. These views do not accept that the percept is a percept, instead thinking it a mind-independent property of the pen (or at least to resemble such a property). And these views are contradicted by physics and the neuroscience of perception.

I understand what intentionality is. I don't understand what intentionality has to do with the discussion we're having.

A book is about a person, but the properties of the book are not the properties of the person. Experience might be about (or of) some distal object, but the properties of the experience are not the properties of the distal object.

Experience has colour properties. These colour properties might "represent" or "stand for" properties of distal objects (e.g. a surface that reflects light of certain wavelengths), but they are nonetheless distinct entities, and it is the colour properties of experience that constitute our ordinary, everyday understanding of colours. We just often naively assume that the colour properties of the experience are the properties of the distal object. This is what physics and the neuroscience of perception has proven false.

I'm not sure what "aboutness" has to do with anything being discussed here. This history textbook is about Hitler, but it isn't Hitler; it's bound pieces of paper with ink writing.

I just read Myles Burnyeat's, "The sceptic in his place and time," (quoted here). His topic is "insulation": that whereby one insulates philosophical claims from everyday claims and everyday claims from philosophical claims. I think Michael is the premiere representative of insulation on TPF. — Leontiskos

This is no longer a matter of philosophy. Science has solved the problem. All I am doing here is explaining what the science shows to those who persist in committing to armchair theorizing.

Neural representations of perceptual color experience in the human ventral visual pathway

There is no color in light. Color is in the perceiver, not the physical stimulus. This distinction is critical for understanding neural representations, which must transition from a representation of a physical retinal image to a mental construct for what we see. Here, we dissociated the physical stimulus from the color seen by using an approach that causes changes in color without altering the light stimulus. We found a transition from a neural representation for retinal light stimulation, in early stages of the visual pathway (V1 and V2), to a representation corresponding to the color experienced at higher levels (V4 and VO1).

Vision Science: Photons to Phenomenology

People universally believe that objects look colored because they are colored, just as we experience them. The sky looks blue because it is blue, grass looks green because it is green, and blood looks red because it is red. As surprising as it may seem, these beliefs are fundamentally mistaken. Neither objects nor lights are actually “colored” in anything like the way we experience them. Rather, color is a psychological property of our visual experiences when we look at objects and lights, not a physical property of those objects or lights. The colors we see are based on physical properties of objects and lights that cause us to see them as colored, to be sure, but these physical properties are different in important ways from the colors we perceive.

Color

One of the major problems with color has to do with fitting what we seem to know about colors into what science (not only physics but the science of color vision) tells us about physical bodies and their qualities. It is this problem that historically has led the major physicists who have thought about color, to hold the view that physical objects do not actually have the colors we ordinarily and naturally take objects to possess. Oceans and skies are not blue in the way that we naively think, nor are apples red (nor green). Colors of that kind, it is believed, have no place in the physical account of the world that has developed from the sixteenth century to this century.

...

Physicists who have subscribed to this doctrine include the luminaries: Galileo, Boyle, Descartes, Newton, Thomas Young, Maxwell and Hermann von Helmholtz. Maxwell, for example, wrote:

"It seems almost a truism to say that color is a sensation; and yet Young, by honestly recognizing this elementary truth, established the first consistent theory of color. (Maxwell 1871: 13 [1970: 75])"

This combination of eliminativism—the view that physical objects do not have colors, at least in a crucial sense—and subjectivism—the view that color is a subjective quality—is not merely of historical interest. It is held by many contemporary experts and authorities on color, e.g., Zeki 1983, Land 1983, and Kuehni 1997.

We mean that the pen has a property of redness, and the specialist is simply explaining what that property is constituted by (i.e. it is constituted by light reflection of a certain wavelength). — Leontiskos

That's not the sense of redness that is our ordinary, everyday conception of colour. Our ordinary, everyday conception of colour is that of the mental percepts that light stimulating the eyes causes to occur, and that also occurs in dreams and hallucinations and synesthesia, and that allows us to understand what it means for some people to see this dress as white and gold and others as black and blue.

If the information about the damage comes from tactile sensors rather than reflected light in its camera eyes, does that qualify as pain? — Harry Hindu

What do you mean by "information"? Are you referring to the chemical neurotransmitters like glutomate that are released and sent to the brain? They, themselves, are not pain. The experience of pain occurs when there is the appropriate neural activity in the insular and secondary somatosensory cortexes, which usually occurs in response to these neurotransmitters, but direct electrical stimulation of these cortexes without any preceding tactile sensor involvement also causes pain.

See Role of the Prefrontal Cortex in Pain Processing

See also synesthesia, which seems relevant to your questions.

Let's take someone with congenital insensitivity to pain with anhidrosis. They don't feel pain but they can still be injured and can still be made aware of their injury another way, e.g. by seeing their broken leg or by being told by a doctor.

So if you're trying to reduce pain to something as simple as awareness of injury then it doesn't work.

As it happens, there are other brain states associated with the experience of red besides the one produced by red light. — frank

Yes, that's what explains dreams, hallucinations, and variations in colour perception, as I have been arguing. Colours, as ordinarily understood, are the mental phenomena caused by neural processes in the visual cortex, regardless of their cause.

700nm light causes red experiences so often that we call it red light. — frank

And this is the important point. It's not the case that we call this experience a red experience because it is the experience of 700nm light; it's the case that we call 700nm light red light because it is the normal cause of red experiences.

The initial/primary use of the word "red" refers to the type of experience, with it's use to refer to the light normally responsible for it post hoc.

Sure. — frank

Good. Then the claim I have been making since the start of this discussion is that colours-as-mental-phenomena constitute our ordinary, everyday understanding of colours. When we ordinarily think and talk about colours we are thinking and talking about colours-as-mental-phenomena (even if we do not recognize them as mental phenomena); we are not thinking and talking about wavelengths of light.

It's not as simple as: 700nm frequency causes the experience of red. — frank

Then why did you claim that there is a "gross disconnect" between a red experience and a picture that doesn't emit 700nm light? You seemed to be implying that it is "correct" for 700nm light to cause a red experience and "incorrect" for a different wavelength of light to cause a red experience.

Sugar is simply a carbohydrate. Sweet is the taste. — javi2541997

I'm aware. That's the point. Claiming that the colour red is 700nm light is as mistaken as claiming that a sweet taste is sugar.

Rather, eating sugar causes a sweet taste and looking at 700nm light causes a red colour.

I'm guessing you understood me just fine, you're trying to make a point by pretending you didn't? — frank

I want to know if you accept the existence of colours-as-mental-phenomena.

I'm asking you if "experienced as red" means "experienced as emitting 700nm light" given that you defined "red" as "emitting 700nm light".