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".

It's a range, but yea. — frank

So when you say this:

"check out the strawberries that are experienced as red, when they're really black and white"

You are saying this:

"check out the strawberries that are experienced as red when they're not really emitting 700nm light"

But what does the "red" in "experienced as red" mean/refer to? Does it mean this:

"check out the strawberries that are experienced as emitting 700nm light when they're not really emitting 700nm light"

A pixel that produces the frequency of red. — frank

Do you mean a pixel that emits 700nm light?

All kinds of brain states can produce the same experience. — frank

Perhaps, but there are no experiences without brain states, and I doubt the same brain state can produce different experiences.

No, I mean sugar.

There are no red pixels in that picture. — frank

What's a red pixel?

There is no simple correspondence between stimulus and experience. — frank

I wasn't talking about a correspondence between stimulus and experience. I was talking about a correspondence between brain states and experience.

Frequencies of light are not color... according to those I'm arguing against. — creativesoul

Correct, just as sugar is not taste.

Check out the strawberries that are experienced as red, when they're really black and white. That's an example a gross disconnect. — frank

Gross disconnect between what? What do you even mean by "really" black and white?

Therefore, if we want to talk about it, we'll have to back down into philosophy. — frank

To the extent that one might want to argue for something like idealism or substance dualism or panpsychism, sure. So if that's how you want to defend naive colour realism then commit to one of them.

But as it stands the scientific view is that colour experiences correspond to neural processes (specifically those in the visual cortex) such that there are no colour experiences without corresponding neural processes and that different colour experiences correspond to different neural processes – and so that distal objects and their properties cannot causally influence colour experience except by causally influencing neural processes.

Which is just as selective, unscientific and false as your belief that colour perception is all about neuroscience. — jkop

So you think that this quote from Vision Science: Photons to Phenomenology is unscientific?

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.

Or this from 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).

I'm going to believe what these scientists say over what you say.

But for a science-buff like you they're all "percepts" — jkop

Yes, that’s what neuroscience shows. Human consciousness does not extend beyond the brain. It certainly does not reach out beyond the body to contain distal objects such that they and their properties are constituents of experience. Any qualitative feature of conscious awareness - smell, taste, colour, pain - is either reducible to or a product of brain activity.

Waking sensations differ from dreams and hallucinations only in their cause, consistency, and intensity, but they are fundamentally the same kind of process.

The fact that depth is a qualitative feature of visual sensations has deceived you into thinking that things like colours are mind-independent features of objects outside the brain, like being convinced that your phantom limb is real.

The science is overwhelmingly clear on this, whether you accept it or not. I’ve referenced the studies. To deny them is to commit to a delusion.

A colour is open to view, while its seeing is in the head. The seeing is just the conscious awareness of the colour, while the colour is the bundle of lights and pigments that emerge as a colour when seen under ordinary conditions. It's a way of using light, which is open for anyone who has the ability. It ain't in the head. — jkop

Do you deny that dreams and hallucinations have colour? Because they do. Do you believe that the colours in dreams and hallucinations “emerge” from bundles of light (seen when my eyes are closed in a dark room?). Because they don’t.

These colours are percepts, they occur when the visual cortex is active, and all of this happens when awake as well.

The "naive" belief that the world is coloured, and that colours exist outside the mind, is perfectly compatible with ordinary language and the science. — jkop

It is not compatible with science. I’ve referenced several scientific articles and quoted the SEP summary on the matter.

The noun “red” doesn’t refer to anything — NOS4A2

It does, just as the nouns "colour" and "pain" do. It refers to those things that exist when we dream and hallucinate, that are caused to occur when we use visual cortical prostheses, and which explain variations in colour perception, such as the dress that some see to be white and gold and others as black and blue.

But your general account uses adjectives, not nouns. — NOS4A2

Good catch. I was caught up in the preceding paragraphs. I just meant "word" there rather than "noun". But the point still stands that the word "red" in the phrase "looks red" isn't referring to some mind-independent property of pens. It is referring to the type of experience that the pen causes to occur.

I know we smell, taste, and see our environment, yes. — NOS4A2

I'm not concerned with the verbs "smell" and "taste". I'm concerned with the nouns "smell" and "taste", e.g. a sweet smell and a sour taste. These are not mind-independent properties of flowers or food but mental percepts caused by brain activity in response to sensory stimulation of the nose and tongue.

It’s not clear what we’re experiencing when we use that sort of language, though, leaving unexplained the question of what color is. It’s impossible for me to understand what experiencing an experience is and what that entails. — NOS4A2

Do you understand what pain is? What smells and tastes are? Vision isn't special.

The adjective “red” can only describe a red thing, and it is that thing that absorbs certain wavelengths, and reflect others. There is no reason for me to apply that adjective to any other objects, especially mind-dependent ones. — NOS4A2

I'm not concerned with the adjective "red". I'm concerned with the noun "red". I've been over this with Banno and others.

You can talk about pens as being coloured, just as you can talk about stubbing one's toe as being painful. But colours and pain are not mind-independent properties of pens or stubbing one's toe; they are the mental percepts (which may be reducible to brain states) that pens and stubbing one's toe cause to occur.

Besides, I can dream about red dragons. The adjective "red" is not being applied to some mind-independent dragon that reflects 700nm light.

But if I were to give a general account of the meaning of "the X is red" or "red X" it would be something like "the X looks red" or "red-looking X". The noun "red" in the phrases "looks red" and "red-looking" does not refer to a mind-independent property.

I was speaking of color qua color, not color experiences — NOS4A2

Colour qua colour is the experience; colour isn't light, isn't how atoms reflect light, and isn't some third mind-independent thing that is neither light nor how atoms reflect light.

I don’t doubt that you experience the changes in pigment, but it seems to me the changes in pigment are the result of the changes in the object, not some other mind-dependent property. We can test this by mixing paints. It results in a change in color of the paint. — NOS4A2

Mixing paint changes which wavelengths of light it reflects. The wavelength of the light that stimulates the eyes is what determines which neurons are activated and so which kind of colour experience occurs.

At the moment your reasoning is akin to arguing that because it hurts when I put my hand in boiling water but doesn't when I mix in near-freezing water then pain must be a mind-independent property of boiling water that is then removed by the addition of near-freezing water.

Some of the things we see are complex, context-dependent, dispositional, emergent etc. — jkop

And some of those things, like colour and pain, aren't.

It just bumps against the hard problem again — Harry Hindu

Because you keep asking the hard question. We don't have an answer to it.

All I am explaining is what the science shows; that pain and colour are percepts that occur when there is the appropriate brain activity; they are not mind-independent properties of knives and pens.

How does a colorless process create color? — Harry Hindu

How does a painless process create pain?

Any time you ask me a question like this about colour, just ask the same question about pain. Colour is just like pain, whatever pain is.

What is pain? — Harry Hindu

A percept that occurs when there is the appropriate neurological activity, often in response to electrical signals sent from nociceptors.

See for example Role of the Prefrontal Cortex in Pain Processing:

The main brain areas that are most consistently activated under painful conditions are the insular cortex and secondary somatosensory cortex, bilaterally. Electrical stimulation of these areas, but not in other candidate brain areas, is able to elicit a painful sensation.

In other words, it isn't known whether color experiences require the appropriate neurological activity..., In other words it is possible that colors ain't just in the head. — Harry Hindu

So in other words it isn't known whether pain requires the appropriate neurological activity, and so it is possible that pain just ain't in the head?

Maybe pain really is some mind-independent property of the knife that my body can sense when I'm stabbed with it.

What's so special about neurological activity that causes color? — Harry Hindu

What's so special about neurological activity that causes pain? This is the hard problem of consciousness that is yet to be solved.

It means that the colour ain't in the head. — jkop

No it doesn't. That colour experiences require neural connections ordinarily formed in response to electrical information from the eyes does not entail that colours are mind-independent properties of light or a material surface that reflects such light.

If that was true, then you could make the blind see by merely stimulating parts of their brains. — jkop

We're working on it.

See a narrative review of cortical visual prosthesis systems: the latest progress and significance of nanotechnology for the future.

But since their brains have never recieved the right stimulation (e.g. from the eyes via the optic nerve), then the right neural connections for colour-vision have not been developed,. — jkop

That may also be true, but does not refute anything I have said. It certainly does not entail that colours are mind-independent properties of pens.

If the pen has a surface layer of atoms that reflect light at with a wavelength of ~700nm then there is both red in the pen and the pen is red. — Leontiskos

Except when we say that the pen is red we are not (ordinarily) saying that the pen has a surface layer of atoms that reflects light with a wavelength of ~700nm.

e.g. when we explain variations in colour perception, such that some see a white and gold dress and some see a black and blue dress, we are not explaining that different people are seeing different objects reflecting different wavelengths of light. They are all looking at the same object reflecting the same wavelengths of light but see different colours. The colours they see, and that we are talking about, are not micro-structural properties or reflectances of the computer screen; the colours they see are mental percepts, whether they recognise them as colour percepts or not.

it looks as if you believe that there are mind-independent micro-structural properties that are not responsible for colour — Banno

Then you are not reading what I am writing. So I'll refer you back to the previous post that was directed at you:

The pen just has a surface layer of atoms that reflects light with a wavelength of ~700nm. When light stimulates the eyes it causes the neurological activity responsible for colour percepts, and we name the colour percept ordinarily caused by 700nm light "red".

Your claim that there is red "in" the pen is the naive realist view that science has disproven.

The "common sense" view, before any scientific study, is naive realism:

Naive realism
1. Colours, as ordinarily understood, are sui generis, simple, intrinsic, qualitative, non-relational, non-reducible properties
2. These sui generis properties are mind-independent.

This view contrasts with something like dispositionalism:

Dispositionalism
3. Colours, as ordinarily understood, are micro-structural properties or reflectances.
4. These micro-structural properties are mind-independent.

(1) and (4) are true, (2) and (3) are false.

The fact that people talk about redness as if it is mind-independent does not entail that they are talking about redness as if (3) is true. People tend to talk about redness as if both (1) and (2) are true. People don't tend to think about (3) at all. I suspect many people, especially children, wouldn't even understand (3); but they understand colours.

Those sui generis properties that we ordinarily think about when we think about colours are, in fact, mental phenomena, and not mind-independent properties of pens as some believe.

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). The distinction between these two different neural representations advances our understanding of visual neural coding.

So colour experiences change when the neural activity in V4 and VO1 changes.

Say that a coloring agent is added to a clear pen in order to make it red. Different agents can be added to different pens in order to add different color to the plastic of the pen. Pigments and coloring agents exist out there, in the pen, independent of the mind. I can’t see the color anywhere else, whether beside it, in front of it, or somewhere behind my eyes.

This leads me to believe the color, which is the coloring agent itself, mixed as it is in the plastic in order to produce a singular result, a red pen, is why the color is in the pen.

In scientific terms: the properties of the material in the pen determine the wavelength and efficiency of light absorption, and therefor the color. My question is: what properties in the “color percept”, whether added, removed, or changed, can explain why the pen is red? — NOS4A2

Colour sensations occur when there is neural activity in the visual cortex. These explain dreams, hallucinations, variations in colour perception, and allow for visual cortical prostheses. They also occur in ordinary, everyday experiences, caused by electromagnetism stimulating the eyes. This has all been experimentally verified.

And that is all there is to our ordinary, everyday understanding of colour.

Using the term "colour" in other ways, e.g. as an adjective to describe pens that reflect certain wavelengths of light, or as another term for a colouring agent, does not refute any of the above, and is certainly not the use that is relevant to either the OP's question or the philosophy of colour in general. See for example the SEP summary quoted here.

Yet we both see the red in the pen. — Banno

There is no red "in" the pen. The pen just has a surface layer of atoms that reflects light with a wavelength of ~700nm. When light stimulates the eyes it causes the neurological activity responsible for colour percepts, and we name the colour percept ordinarily caused by 700nm light "red".

You are being deceived by the brain's ability to make it seem as if the qualities of visual experience extend beyond itself, like being convinced that your phantom limb is real. Physics and the neuroscience of perception have proven this naive realism false.