We have devices that detect colors on a variety objects that will agree with human judgement. These devices are not detecting color in the minds of humans but on objects — Richard B

We have devices that can detect the wavelength of 550nm emitted by a variety of objects. The device doesn't know the name of the wavelength of 550nm prior to it being named green by a human.

Additionally, if you use the device on the human brain you will be getting the color of the brain not what the brain is sensing. — Richard B

Similarly, a device such as a MRI scanner can be used on the human brain. The MRI scanner doesn't know the colours on its screen prior to their being named by a human. Such devices are only capable of recording the external appearance of the physical brain. They are not capable of recording human thoughts and feelings internal to the physical brain.

We have devices that can detect the wavelength of 550nm emitted by a variety of objects. The device doesn't know the name of the wavelength of 550nm prior to it being named green by a human. — RussellA

1. Scientists are not naming the color green "550 nm." Scientists are characterizing the color green with the property of 550 nm based on the latest scientific theories of light. This can only be done if there is general agreement by humans on what they judge to be green. This is done be utilizing standard samples that we all would agree are called "green."

2. The device will be calibrated to detect particular wavelengths of light from a standard object that human beings collectively judge to be green. This shows the device is working as intended. The device is not calibrated by the color that exists in someone's mind. We need the device to detect the color of an object that is independent of a human but will detect and report the color as humans do.

3. If I want to determine a particular color of a swatch, I may send it out to a company who has sensitive device that can provide a very nuance color determination. So I put it in an envelop and mail it in and in a few days get a report on its color. I am not sending a color that exists in my mind in the mail.

4. The human brain is like the device that detects color. It has evolved to sense and discriminate different wavelengths of colors. This is demonstrated by humans collectively judging and naming colors of particular objects. If a human being has a problem with judging color like the community, scientists may take an interest to understand what is happening in the brain. Maybe with this knowledge they may even attempt to help the human harmonize more.

5. If colors exist in the mind, why did scientist study light and color that is independent of the human? Because it exist independent of them. What scientists may want to study is how the brain reacts to color and light. What they do not study is what color the human is "actually' experiencing. And the reason for this is not technological limitations, but what is being expressed in language is incoherent.

What I want to show with this discussion is this philosophical theory that "color exists only in the mind" has no relevance to how humans use color language in the everyday life and in the pursuit of science. But as a story of entertaining fiction, I do get a good laugh.

3. If I want to determine a particular color of a swatch, I may send it out to a company who has sensitive device that can provide a very nuance color determination. So I put it in an envelop and mail it in and in a few days get a report on its color. I am not sending a color that exists in my mind in the mail. — Richard B

I can take a swatch to my local hardware shop and they will mix me a can of paint to match my sample in about 10 minutes. This is because they are mind-readers swatch-readers.

As Wittgenstein wrote in PI 244, pain is different to pain-behaviour

How should "colour" be defined
The Merriam Webster dictionary defines colour as a phenomenon of light (such as red, brown, pink, or grey) or visual perception that enables one to differentiate otherwise identical objects. However this is ambiguous, and does not address the problem as to exactly how does colour enable one to distinguish between otherwise identical objects.

It depends how you are defining the word colour. If you are defining colour as a name, such as "green", as names have been created in the human mind, names cannot exist independently of any human. But if you are defining colour as a wavelength, such that the colour green is the wavelength 495 to 570nm, then in this sense colours can exist independently of any human.

As defining colour as a wavelength introduces the confusion of over-determination, whereby two very different concepts are given the same name, the definition of colour should be limited to that of a name. In this case, colours can only exist in the mind.

1. Scientists are not naming the color green "550 nm — Richard B

I agree that the colour green has not been named 550nm, but rather the wavelength of 550nm has been named green.

A group of humans look at several objects and come to a communal agreement that there is a certain similarity in the objects emitting wavelength of 495 to 570nm, there is a certain similarity in the objects emitting wavelength of 570 to 590nm, and the objects emitting wavelengths of 495 to 570nm are somehow different to the objects emitting wavelengths of 570 to 590nm. In the English speaking world it is agreed that the objects emitting wavelengths of 495 to 570nm are named "green" and the objects emitting wavelengths of 570 to 590nm are named "yellow". In France, they would be named "verte" and "jaune".

2. We need the device to detect the color of an object that is independent of a human but will detect and report the color as humans do. — Richard B

The device detects the wavelength emitted from an object that is independent of a human, but no device can detect the colour of an object independent of a human.

The community has agreed that objects emitting wavelengths of 495 to 570nm are named "green" and objects emitting wavelengths of 570 to 590nm are named "yellow". These humans can then make a device that distinguishes the wavelengths emitted by different objects. The human designer of the device then programs into the device that if the device records a wavelength of 495 to 570nm, then the device gives the output "green".

3. I am not sending a color that exists in my mind in the mail. — Richard B

I agree, you are sending a physical object through the mail that emits a particular wavelength, not a colour that exists in your mind.

4. The human brain is like the device that detects color. — Richard B

The human brain is different to a device. The human brain directly perceives colour and only indirectly knows about wavelength. The device directly detects a wavelength but only indirectly gives this wavelength the name of a colour.

I agree that the human brain has evolved to sense and discriminate different colours. However, if it weren't for science the human would be unaware that they only perceive colour because information has travelled from the object to the eye in the form of a wavelength. Humans know colour directly, and only know about wavelength indirectly.

On the other hand, a human-made device is only able to discriminate between different wavelengths. These wavelengths can then be named by a human programmer in order to give the output "green" when input the wavelength 550nm. A device can directly detect an input wavelength but only has indirect information about its colour.

5. If colors exist in the mind, why did scientist study light and color that is independent of the human? — Richard B

Colour can refer to two different things. In sense one, it can refer to the private subjective feeling within the mind that cannot be described, as explained by Wittgenstein's Beetle in the Box analogy. In sense two, it can refer to the public name "green", "yellow" etc as used in the language game, the physical object, the physical name "green" that you see on the screen in front of you.

In sense one, colour only exists in the mind and not the world. In sense two, wavelengths only exist in the world and not the mind. Sense one and two are linked because the reason that we perceive colour in our mind is due to the fact that wavelengths exist in the world.

Scientists can measure physical things that exist in the world, such as wavelengths and language expressed either verbally or in writing. After all, the word "green" you see on your screen is a physical object that exists in the world. Scientists can measure pain-behaviour, which are physical events in the world, but not the pain itself that caused the pain-behaviour.

Wittgenstein writes in PI 244
A child has hurt himself and he cries; and then adults talk to him and teach him exclamations and, later, sentences. They teach the child new pain-behaviour. "So you are saying that the word 'pain' really means crying?"— On the contrary: the verbal expression of pain replaces crying and does not describe it.

But as a story of entertaining fiction, I do get a good laugh. — Richard B

If philosophy was meant to be fun, it would be being promoted at the Edinburgh Fringe Festival. :smile:

If philosophy was meant to be fun, it would be being promoted at the Edinburgh Fringe Festival. :smile: — RussellA

Well, we always have Monty Python if an ounce of levity is needed.

we always have Monty Python — Richard B

Even Monty Python get Wittgenstein sent off from playing the game.

Colour can only exist in a world outside the mind as a Platonic Form

A group of humans look at several objects and come to a communal agreement that there is a certain similarity in the objects emitting wavelengths of 495 to 570nm, there is a certain similarity in the objects emitting wavelengths of 570 to 590nm, and the objects emitting wavelengths of 495 to 570nm are somehow different to the objects emitting wavelengths of 570 to 590nm. In the English speaking world it is agreed that the objects emitting wavelengths of 495 to 570nm are named "green" and the objects emitting wavelengths of 570 to 590nm are named "yellow". In France, they would be named "verte" and "jaune".

However, if it weren't for science, the human would be unaware that they only perceive colour because information has travelled from the object to the eye in the form of a wavelength.

Where does colour exist, in the mind or in the world. Do we perceive an object as green because the object is green or is this an illusion.

The colour green includes the wavelengths 495 to 570nm. The wavelengths 570 to 590nm are not green.

But what has science discovered in the world outside the mind that relates the wavelength 500nm to 550nm but not to 580nm.

We know that in the mind the wavelength 500nm is related to 550nm but not to 580nm because the mind can distinguish green from yellow.

If green exists in the world independent of the mind, then what exactly has science discovered in such a world that relates 500nm to 550nm but not to 580nm ?

If green exists in the world independent of the mind, then what exactly has science discovered in such a world that relates 500nm to 550nm but not to 580nm ? — RussellA

1. The color of an object is determined by which wavelengths of light it reflects. For example, plants appear green because they contain the pigment chlorophyll. Chlorophyll absorbs all other wavelengths of light. Green is reflected so it is green light that hits our eyes. Science discovers that the green light has a wavelength of 550nm and not 580nm, and yellow light has a wavelength of 580 nm and 550 nm.

2. If you have no problems with a device that detects color by utilizing scientific theories of light and not positing the device having private color sensations, why not humans that have evolved biological apparatuses to do the same without private color sensations?

3. To get poetic, you seem to picture the color experience as if you are in a room with no doors or windows but just a TV set with a wire coming from the wall that you presume is sending signals from an outer-world that you can’t be so sure if it accurately reflects reality. I, on the other hand, have an open window with a clear view. If the is a metaphysical dispute, I like to be optimistic and believe we are seeing the same thing. And maybe that is the more reasonable position because we have similar biologies, judge color the same , use the same words, and inhabit the same world.

Science discovers that the green light has a wavelength of 550nm — Richard B

This sentence may be used to illustrate Wittgenstein's importance to language and philosophy.

The link between linguistic grammatical form and philosophical substantive content

Many philosophers believe that the first task is finding a theory of meaning in language. Given such a theory, they can then turn to the problems of philosophy. However, for Wittgenstein, whose first interest is in philosophy, it is this interest in philosophy that makes him then interested in language, but concludes that there is no theory of meaning in language that will enable the solving of philosophical problems. It is incorrect to say that Wittgenstein is an ordinary language philosopher in the sense that JL Austin is.

Wittgenstein urges throughout his later work that mistaking a grammatical claim for a philosophical one is a common source of philosophical confusion, Wittgenstein says that the philosophical problems that concern him are not empirical problems, but are problems solved by looking into and recognizing the workings of our language.

Wittgenstein often insists that he is not presenting a philosophical argument. In PI 109 he writes "We must do away with all explanation and description alone must take its place", whereby such descriptions get that purpose from philosophical problems.

For Wittgenstein, a standing source of philosophical confusion is the tendency to transpose a remark concerning the grammar of an expression into a substantive claim about the things referred to in the expression. For example, from PI 246 is the sentence “Only I can know that I am really in pain; another person can only surmise it”. This is clearly false, as that on many occasions we can know full well that someone else is in pain, there is no surmising about it. The grammatical difference between the first person "I have a pain" and the third person "he has a pain" wrongly becomes a substantive philosophical problem

For Wittgenstein the first step is to acknowledge the confusion between statements of grammatical fact and the use of them in the search for substantive philosophical meaning.

Science discovers that the green light has a wavelength of 550nm — Richard B

I agree. But to avoid any ambiguity, does the sentence mean i) what appears green to us science has discovered has a wavelength of 550nm or ii) science has discovered that a wavelength of 550nm is green independent of any observer ?

2. If you have no problems with a device that detects color by utilizing scientific theories of light and not positing the device having private color sensations, why not humans that have evolved biological apparatuses to do the same without private color sensations? — Richard B

By the sentence "a device that detects colour", do you mean i) a device that is able to directly detect the colour green independent of any observer or ii) a device that is able to detect the wavelength 550nm, and has been programmed by a human that a wavelength of 550nm is named green ?

I like to be optimistic and believe we are seeing the same thing — Richard B

I am sure we do. I agree that because humans have similar biologies we judge colour the same, and I am sure that your subjective green is the same as my subjective green. I believe this, but I don't know it, as I cannot see into another person's mind

However, even though I believe that we see the same thing, in that we both see the same green plant, our seeing the same thing can be explained by both Direct Realism, looking through a clear window, and Indirect Realism, looking through a TV screen.

It then comes down to arguments for and against Indirect and Direct Realism.

I agree. But to avoid any ambiguity, does the sentence mean i) what appears green to us science has discovered has a wavelength of 550nm or ii) science has discovered that a wavelength of 550nm is green independent of any observer ? — RussellA

What it means is human beings collectively will call the green standard sample "green", and current scientific technology will measure the light reflected off such a standard sample as 550 nm.

By the sentence "a device that detects colour", do you mean i) a device that is able to directly detect the colour green independent of any observer or ii) a device that is able to detect the wavelength 550nm, and has been programmed by a human that a wavelength of 550nm is named green ? — RussellA

What it means is a device that can detect light with a wavelength of 550 nm light, and humans collectively has established that light of such a wavelength is called "green", and the device can be programmed to report out the name of the color.

I am sure we do. I agree that because humans have similar biologies we judge colour the same, and I am sure that your subjective green is the same as my subjective green. I believe this, but I don't know it, as I cannot see into another person's mind — RussellA

I think this is where Wittgenstein would say this philosophical discussion is "going off the rails" so to speak. The language game is learned in a community from color language users that can judge color samples the same, and use the color names in the same way. This is how they know they see the same color of an object. This is all we have and it is all that matters when discussing color.

It then comes down to arguments for and against Indirect and Direct Realism. — RussellA

I would say Wittgenstein is not supporting either Indirect or Direct Realism since both are philosophical theories in which language goes on a holiday.

Many philosophers believe that the first task is finding a theory of meaning in language. Given such a theory, they can then turn to the problems of philosophy. However, for Wittgenstein, whose first interest is in philosophy, it is this interest in philosophy that makes him then interested in language, but concludes that there is no theory of meaning in language that will enable the solving of philosophical problems. It is incorrect to say that Wittgenstein is an ordinary language philosopher in the sense that JL Austin is.

Wittgenstein urges throughout his later work that mistaking a grammatical claim for a philosophical one is a common source of philosophical confusion, Wittgenstein says that the philosophical problems that concern him are not empirical problems, but are problems solved by looking into and recognizing the workings of our language.

Wittgenstein often insists that he is not presenting a philosophical argument. In PI 109 he writes "We must do away with all explanation and description alone must take its place", whereby such descriptions get that purpose from philosophical problems.

For Wittgenstein, a standing source of philosophical confusion is the tendency to transpose a remark concerning the grammar of an expression into a substantive claim about the things referred to in the expression. For example, from PI 246 is the sentence “Only I can know that I am really in pain; another person can only surmise it”. This is clearly false, as that on many occasions we can know full well that someone else is in pain, there is no surmising about it. The grammatical difference between the first person "I have a pain" and the third person "he has a pain" wrongly becomes a substantive philosophical problem

For Wittgenstein the first step is to acknowledge the confusion between statements of grammatical fact and the use of them in the search for substantive philosophical meaning. — RussellA

Please make it clear when you are quoting from a book.

Please make it clear when you are quoting from a book. — Jamal

Point taken. I will be more careful in the future. I'm pleased that someone is actually reading my posts.

:up:

Actually though…

I will be more careful in the future — RussellA

I hope this doesn’t mean you’re just going to plagiarize more skilfully. :wink:

What it means is a device that can detect light with a wavelength of 550 nm light, and humans collectively has established that light of such a wavelength is called "green", and the device can be programmed to report out the name of the color. — Richard B

The Indirect Realist would argue that what we perceive through our senses is only a representation of what exists in the world, in that even though we perceive a green object, the object in the world does not of necessity have a colour. Therefore, the Indirect Realist would say: What it means is a device that can detect light with a wavelength of 550 nm light, and humans collectively has established that light of such a wavelength is called "green", and the device can be programmed to report out the name of the colour.

The Direct Realist would argue that what we perceive through our senses is not a representation of what exists in the world, but gives us direct knowledge of what exists in the world, in that if we perceive a green object then a green object exists in the world. Therefore the Direct Realist would say: What it means is a device that can detect light with a wavelength of 550 nm light, and humans collectively has established that light of such a wavelength is "green", and the device can be programmed to report out the name of the colour.

The difference between the Indirect and Direct Realist is that for the Indirect Realist the object in the world is named green but for the Direct Realist the object in the world is green.

The principle can be extended. For an Indirect Realist, an object in the world can be named "apple", "table", "chair", etc, whereas for the Direct Realist, an object in the world is an "apple", ""table", "chair" , etc

Therefore, for an Indirect Realist, the name of an object is a label for the object and does not describe the object in the world, whereas for a Direct Realist, the name of an object describes the object in the world.

In today's terms, Wittgenstein's approach in PI is that of an Indirect Realist rather than a Direct Realist, whereby a name is a label for an object in the world than rather than a description of it.

Wittgenstein in PI 26 wrote that naming is like attaching a label to a thing
One thinks that learning language consists in giving names to objects. Viz, to human beings, to shapes, to colours, to pains, to moods, to numbers, etc. . To repeat—naming is something like attaching a label to a thing.

He also indicated in PI 244 that a name is in a sense an object in its own right and may replace another object but does not describe it
On the contrary: the verbal expression of pain replaces crying and does not describe it.

I would say Wittgenstein is not supporting either Indirect or Direct Realism since both are philosophical theories in which language goes on a holiday. — Richard B

Yes, Wittgenstein doesn't write in support of either. Only today can we take his writings as being in support for one or the other.

As he wrote in 1917 "And this is how it is: if only you do not try to utter what is unutterable then nothing gets lost. But the unutterable will be unutterably contained in what has been uttered!”

I hope this doesn’t mean you’re just going to plagiarize more skilfully. :wink: — Jamal

Plagiarising is serious.

For example, www.scribbr.com writes:
The consequences of plagiarism vary depending on the type of plagiarism and the context in which it occurs. For example, submitting a whole paper by someone else will have the most severe consequences, while accidental citation errors are considered less serious.
If you’re a student, then you might fail the course, be suspended or expelled, or be obligated to attend a workshop on plagiarism. It depends on whether it’s your first offence or you’ve done it before.
As an academic or professional, plagiarizing seriously damages your reputation. You might also lose your research funding or your job, and you could even face legal consequences for copyright infringement.

The Merriam-Webster dictionary defines plagiarising as: to steal and pass off (the ideas or words of another) as one's own : use (another's production) without crediting the source.

I may use established sources to back up my ideas, to clarify my own ideas, to give me ideas or provide me with sentences I think especially well written, but that is not the same as copying the ideas of established sources. For example, for many years I have held the belief that names are labels not descriptions, and used Wittgenstein's quote in PI 26, where he says - One thinks that learning language consists in giving names to objects. Viz, to human beings, to shapes, to colours, to pains, to moods, to numbers, etc. . To repeat—naming is something like attaching a label to a thing. - to support my belief, not as a replacement for it.

I never plagiarise. All the ideas in my posts are my own, even if they are my ideas about other people's ideas, and am more than willing to justify any post I have ever written. :wink:

I may use established sources to back up my ideas, to clarify my own ideas, to give me ideas or provide me with sentences I think especially well written, but that is not the same as copying the ideas of established sources — RussellA

:100: I do just the same.

I was willing to move on, but now that you’re arguing…

Within the text of yours that I quoted—text that is presented as yours and is at least partly or mostly yours—you did embed sentences and fragments of sentences that you copied from a book. That’s plagiarism. But it’s no problem if you make the quotations obvious in future.

But it’s no problem if you make the quotations obvious in future. — Jamal

As I accepted, point taken, and I will be more careful in the future.

Thanks Russ :up:

am sure we do. I agree that because humans have similar biologies we judge colour the same, and I am sure that your subjective green is the same as my subjective green. I believe this, but I don't know it, as I cannot see into another person's mind — RussellA

Consider On Certainty(OC) 504, "Whether I know something depends on whether the evidence backs me up or contracts me. For to say one knows one has pain means nothing. "

The same goes for private sensations of color, for to say one knows one has the sensation of green means nothing.

Or, OC 548, "A child must learn the use of colour words before it can ask for the name of a colour." Again, the emphasis here is language use, not recognition of color sensations.

In today's terms, Wittgenstein's approach in PI is that of an Indirect Realist rather than a Direct Realist, whereby a name is a label for an object in the world than rather than a description of it. — RussellA

Consider OC 505, "It is always by favor of Nature that one knows something." Notice he is not saying it is by the favor of our awareness of private sensations that one knows something. This is evidence he would not support Indirect Realism.

I will leave this discussion with one more quote from Wittgenstein from "Culture and Value" which suggest the importance of what can and cannot be said, "Couldn't one actually say equally well that the essence of colour guarantees its existence? As opposed, say, to white elephants. Because all that really means is: I cannot explain what 'colour' is, what the word "colour" means, except with the help of a colour sample. So in this case there is no such thing as explaining 'what it would be like if colors were to exist'.

Consider On Certainty (OC) 504, "Whether I know something depends on whether the evidence backs me up or contracts me. For to say one knows one has pain means nothing. " — Richard B

It is true that in a sense to say one has the sensation of green means nothing, as the sensation of green is a private subjective experience and cannot be described in words. For example, how could you describe the colour violet to a person who cannot experience colours. When we do use the word "green" in language, this is a label and not a description.

As Wittgenstein writes in PI 15
The word "to signify" is perhaps used in the most straightforward way when the object signified is marked with the sign. Suppose that the tools A uses in building bear certain marks. When A shews his assistant such a mark, he brings the tool that has that mark on it. It is in this and more or less similar ways that a name means and is given to a thing.—It will often prove useful in philosophy to say to ourselves: naming something is like attaching a label to a thing.

and also in PI 26
One thinks that learning language consists in giving names to objects. Viz, to human beings, to shapes, to colours, to pains, to moods, to numbers, etc. . To repeat—naming is something like attaching a label to a thing.

Or, OC 548, "A child must learn the use of colour words before it can ask for the name of a colour." Again, the emphasis here is language use, not recognition of color sensations. — Richard B

Words labelling inner private sensations are only possible if there is some outward sign of such inner private sensation. As Wittgenstein writes in PI 257:
"What would it be like if human beings shewed no outward signs of pain (did not groan, grimace, etc.)? Then it would be impossible to teach a child the use of the word 'tooth-ache'."

Even when there is an outward sign of an inner experience, such an outward sign does not describe the inner experience but only shows that there has been one. As Wittgenstein writes in PI 244:
"So you are saying that the word 'pain' really means crying?"—On the contrary: the verbal expression of pain replaces crying and does not describe it.

Language labels inner experiences, not describe them.

Consider OC 505, "It is always by favor of Nature that one knows something." Notice he is not saying it is by the favor of our awareness of private sensations that one knows something. This is evidence he would not support Indirect Realism. — Richard B

Indirect Realism is a direct knowledge of the mind and an indirect knowledge of the world.

Wittgenstein in PI 246 writes that we know our private sensations:
In what sense are my sensations private?—Well, only I can know whether I am really in pain; another person can only surmise it.—In one way this is wrong, and in another nonsense. If we are using the word "to know" as it is normally used (and how else are we to use it?), then other people very often know when I am in pain.— Yes, but all the same not with the certainty with which I know it myself I—It can't be said of me at all (except perhaps as a joke) that I know I am in pain. What is it supposed to mean—except perhaps that I am in pain? Other people cannot be said to learn of my sensations only from my behaviour,—for I cannot be said to learn of them. I have them. 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.

It is true that he writes in OC 505 that "It is always by favour of Nature that one knows something", but what does he mean by this. It could mean that we know the private sensation of pain because a heavy object has fallen on our foot.

Taking the example of the Earth as something that exists in nature, throughout On Certainty, Wittgenstein writes about the belief in the existence of the Earth not from direct knowledge but from a coherent set of evidence that points to its existence.

He writes in OC 291 about his belief that the earth is round
We know that the earth is round. We have definitively ascertained that it is round.
We shall stick to this opinion, unless our whole way of seeing nature changes. "How do you know that?" - I believe it.

He writes in OC 231 that his beliefs in the earth are supported by evidence
If someone doubted whether the earth had existed a hundred years ago, I should not understand, for this reason: I would not know what such a person would still allow to be counted as evidence and what not

He writes in OC 165 that a belief in the earth has been learnt
One child might say to another: "I know that the earth is already hundred of years old" and that would mean: I have learnt it.

As Wittgenstein writes that we directly know our sensations and only indirectly believe in the world, this is the position of an Indirect Realist.

I will leave this discussion with one more quote from Wittgenstein from "Culture and Value" which suggest the importance of what can and cannot be said, "Couldn't one actually say equally well that the essence of colour guarantees its existence? — Richard B

Although the private sensation of green cannot be said, the word "green" can be said within the language game. For Wittgenstein, we first know the private sensation green and then use the word "green" as a label for these private sensations, not as descriptions of them.

This is clarified by the Beetle in the Box analogy in PI 293
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.

Wittgenstein in PI 246 writes that we know our private sensations:
In what sense are my sensations private?—Well, only I can know whether I am really in pain; another person can only surmise it.—In one way this is wrong, and in another nonsense. If we are using the word "to know" as it is normally used (and how else are we to use it?), then other people very often know when I am in pain.— Yes, but all the same not with the certainty with which I know it myself I—It can't be said of me at all (except perhaps as a joke) that I know I am in pain. — RussellA

I don’t believe that the quote supports your reading.

I don’t believe that the quote supports your reading. — Luke

In PI 246, Wittgenstein writes that he knows his private sensations with certainty, whereas other people only know his private sensations with less certainty.

He writes that he doesn't doubt that he is in pain, whereas other people may doubt that he is in pain.

Wittgenstein is introducing the concepts of doubt and certainty, which led to his book On Certainty. As AC Grayling said, a book of "serious philosophy".

n PI 246, Wittgenstein writes that he knows his private sensations with certainty, whereas other people only know his private sensations with less certainty. — RussellA

Let me repeat your quote of PI 246 with some emphasis:

In what sense are my sensations private?—Well, only I can know whether I am really in pain; another person can only surmise it.—In one way this is wrong, and in another nonsense. If we are using the word "to know" as it is normally used (and how else are we to use it?), then other people very often know when I am in pain.— Yes, but all the same not with the certainty with which I know it myself I—It can't be said of me at all (except perhaps as a joke) that I know I am in pain. — RussellA

Wittgenstein rejects the idea that we can know our private sensations.

Wittgenstein rejects the idea that we can know our private sensations. — Luke

PI 246 can be considered as having five separate parts.

Part one
In what sense are my sensations private?

He asks the question

Part two
Well, only I can know whether I am really in pain; another person can only surmise it.—In one way this is wrong, and in another nonsense. If we are using the word "to know" as it is normally used (and how else are we to use it?), then other people very often know when I am in pain.— Yes, but all the same not with the certainty with which I know it myself

It is true that it is often said that only I know I am in pain and other people can only surmise it.

But clearly this is in a sense wrong, otherwise it would be socially acceptable to kick dogs, for example, which is obviously not the case. So we do clearly know when other people are in pain, not just that we surmise it .

It comes down to the exact meaning of "know". This often depends on context. In one sense we do know when a loved one is in pain, but in another sense we cannot really know the pain of another person.

The word "know" has different levels of certainty. I know with certainty my own pain, and even though I know others feel pain, I can only know with less certainty their pain.

Part three
It can't be said of me at all (except perhaps as a joke) that I know I am in pain. What is it supposed to mean—except perhaps that I am in pain?

The word "know" seems to be redundant in the two propositions "I know I am in pain" and "I am in pain". Does that mean we can reject the idea that we can know our private sensations.

From PI 293, the thing in the box that has no place in the language-game is the sensation of pain. When he writes "I know what the word "pain" means", he is referring to the word "pain" as a concept in the language-game.

However, in order to say "I am in pain", I must already know the concept "pain". Therefore saying "I am in pain" is shorthand for saying that not only do I know the concept "pain" but also I know that my sensation has the name "pain".

If I know that my private sensation has a name, then it follows that I must also know that I am having a private sensation.

But if I know that I am having a private sensation, then I must know the private sensation that I am having.

IE, I can know a private sensation.

Part four
Other people cannot be said to learn of my sensations only from my behaviour,—for I cannot be said to learn of them. I have them.

He is saying that other people cannot learn his private sensations from his external behaviour as well as saying that I don't learn my sensations, I just have them.

Part five
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 is saying it makes sense to say that he has no doubt that he is in pain, whereas other people may doubt that he is in pain.

It can't be said of me at all (except perhaps as a joke) that I know I am in pain. What is it supposed to mean—except perhaps that I am in pain?

The word "know" seems to be redundant in the two propositions "I know I am in pain" and "I am in pain". Does that mean we can reject the idea that we can know our private sensations. — RussellA

I don’t believe redundancy is the reason why “it can’t be said of me at all (except perhaps as a joke) that I know I am in pain.” What sort of joke would it be to redundantly say “I know I’m in pain”?

The reason one cannot know their private sensations relates to the grammar of the word “know”, which Wittgenstein spends more time examining in On Certainty.

In order for something to be known/knowable, it must be able to be learned, doubted and surmised and we must be able to satisfy ourselves of its truth or falsity. It is because one cannot learn, doubt, surmise, etc. about their own private sensation that it cannot be known.

I don’t believe redundancy is the reason why “it can’t be said of me at all (except perhaps as a joke) that I know I am in pain.” What sort of joke would it be to redundantly say “I know I’m in pain”? — Luke

PI 246 is contradictory in that it doesn't distinguish between sensation and concept

In what sense are my sensations private?—Well, only I can know whether I am really in pain; another person can only surmise it.—In one way this is wrong, and in another nonsense

Wittgenstein is saying that it is said that only I know that I am in pain, whereas others can only surmise it. But he is surely saying that this is wrong because others also know that I am in pain.

If we are using the word "to know" as it is normally used (and how else are we to use it?), then other people very often know when I am in pain.— Yes, but all the same not with the certainty with which I know it myself

Wittgenstein is saying that others know I am in pain, but not with the same certainty that I know when I am in pain. The problem arises that Wittgenstein is not distinguishing between knowing a concept and knowing a sensation.

It can't be said of me at all (except perhaps as a joke) that I know I am in pain. What is it supposed to mean—except perhaps that I am in pain?

Wittgenstein is saying that when others say "he knows he is in pain", this is grammatically incorrect and means no more that "he is in pain". It is possible that someone could use a grammatically incorrect phrase as a joke.

However, in order to say "I am in pain", this presupposes that not only "I am having the sensation of pain" but also "I know the concept of pain". For example, if I didn't know the concept of pain, I wouldn't be able to distinguish between "I am in pain" and "I am hungry". Therefore the proposition "I am in pain" is shorthand for "I am having the sensation of pain and I know the concept of pain".

Other people cannot be said to learn of my sensations only from my behaviour,—for I cannot be said to learn of them. I have them.

The key word is "only". It is true that other people cannot learn of another's sensations purely from that person's behaviour if they didn't have their own sensations that produced the same behaviour in themselves.

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

Wittgenstein is saying that although it makes sense for others to doubt that I am in pain, it makes no sense for me to doubt that I am in pain.

PI 246 is contradictory in that Wittgenstein doesn't distinguish between sensation and concept. On the one hand he uses the word "know" to refer to a concept: If we are using the word "to know" as it is normally used (and how else are we to use it?), then other people very often know when I am in pain.— Yes, but all the same not with the certainty with which I know it myself and on the other hand he uses the word "know" to refer to a sensation: It can't be said of me at all (except perhaps as a joke) that I know I am in pain. What is it supposed to mean—except perhaps that I am in pain?

PI 246 is contradictory in that it doesn't distinguish between sensation and concept — RussellA

It's unclear what distinction you think there should be between sensation and concept, or how you think this distinction would help. However, Wittgenstein does discuss how words might refer to sensations at 244.

If 246 seems contradictory, it may be because Wittgenstein speaks in more than one voice, where he often gives voice to common philosophical assumptions/confusions before giving his corrective responses to them. The voice that expresses common (mistaken) philosophical assumptions is sometimes referred to in the literature as Wittgenstein's interlocutor.

I would say that there are two instances of the interlocutor's voice at 246. I will highlight Wittgenstein's interlocutor in bold (and extra spacing) in the quote below. The other sentences are Wittgenstein's responses:

246. In what sense are my sensations private? —

Well, only I can know whether I am really in pain; another person can only surmise it. —

In one way this is false, and in another nonsense. If we are using the word “know” as it is normally used (and how else are we to use it?), then other people very often know if I’m in pain. —

Yes, but all the same, not with the certainty with which I know it myself! —

It can’t be said of me at all (except perhaps as a joke) that I know I’m in pain. What is it supposed to mean — except perhaps that I am in pain? Other people cannot be said to learn of my sensations only from my behaviour — for I cannot be said to learn of them. I have them. This much is true: it makes sense to say about other people that they doubt whether I am in pain; but not to say it about myself. — Wittgenstein, Philosophical Investigations

Wittgenstein is saying that it is said that only I know that I am in pain, whereas others can only surmise it. But he is surely saying that this is wrong because others also know that I am in pain. — RussellA

He says that others (often) know when he is in pain. He does not say that he (also) knows when he is in pain. As he states later in the passage, it can't be said of him at all that he knows he is in pain.

Wittgenstein is saying that others know I am in pain, but not with the same certainty that I know when I am in pain. — RussellA

This is stated in the interlocutor's voice, giving voice to the mistaken philosophical assumption that only the person in pain can know with any certainty that they are in pain. He immediately provides a correction to this in the following sentence, stating that it can't be said of him at all that he knows he is in pain.

Wittgenstein is saying that when others say "he knows he is in pain", this is grammatically incorrect and means no more that "he is in pain". It is possible that someone could use a grammatically incorrect phrase as a joke. — RussellA

He is making a stronger statement than this. It is not merely that it is redundant to say "I know" (that I am in pain). Wittgenstein tells us (here and in other places) that it is nonsense to say he knows he is in pain; that it does not make sense to say it.

However, in order to say "I am in pain", this presupposes that not only "I am having the sensation of pain" but also "I know the concept of pain". For example, if I didn't know the concept of pain, I wouldn't be able to distinguish between "I am in pain" and "I am hungry". Therefore the proposition "I am in pain" is shorthand for "I am having the sensation of pain and I know the concept of pain". — RussellA

This would suggest that we always append "and I know the concept of x" to every concept we ever talk about, or every word we ever use. However, I don't think that's what "I am in pain" means, and I don't believe we are always talking about our knowledge of concepts in everything we say. I imagine that only a very small percentage of discussion (or language use) is about our knowledge of concepts. Also, sometimes we don't know the concept of x when we talk about or use the word 'x'.

Other people cannot be said to learn of my sensations only from my behaviour,—for I cannot be said to learn of them. I have them.

The key word is "only". It is true that other people cannot learn of another's sensations purely from that person's behaviour if they didn't have their own sensations that produced the same behaviour in themselves. — RussellA

I agree that the key word is "only" here. I also think this is an important part of the Wittgensteinian puzzle. However, I don't see how this supports your assent to the statement: "I know I am in pain."

Wittgenstein is saying that although it makes sense for others to doubt that I am in pain, it makes no sense for me to doubt that I am in pain. — RussellA

If it makes no sense to doubt (that I am in pain), then it makes no sense to know (that I am in pain).

309. “I know what I want, wish, believe, feel, . . .” (and so on through all the psychological verbs) is either philosophers’ nonsense or, at any rate, not a judgement a priori.
310. “I know . . .” may mean “I do not doubt . . .” — but does not mean that the words “I doubt . . .” are senseless, that doubt is logically excluded.
311. One says “I know” where one can also say “I believe” or “I suppose”; where one can satisfy oneself... — Wittgenstein, Philosophical Investigations - PPF/PI II

PI 246 is contradictory in that Wittgenstein doesn't distinguish between sensation and concept. On the one hand he uses the word "know" to refer to a concept: If we are using the word "to know" as it is normally used (and how else are we to use it?), then other people very often know when I am in pain.— Yes, but all the same not with the certainty with which I know it myself and on the other hand he uses the word "know" to refer to a sensation: It can't be said of me at all (except perhaps as a joke) that I know I am in pain. What is it supposed to mean—except perhaps that I am in pain? — RussellA

Wittgenstein doesn't use "know" to refer to a sensation. Knowledge isn't a sensation. The only sensation he refers to here is pain.

A lot to think about.

It's unclear what distinction you think there should be between sensation and concept, or how you think this distinction would help — Luke

A "cube" is an example of a concept. Wittgenstein is saying that we know and understand the word "cube" not from the sensation of seeing a picture of it but rather from how the word is used.
PI 139 When someone says the word "cube" to me, for example, I know what it means.

Wittgenstein is asking how we know the role of the King in a game of chess. In broader terms, how do we know the rules of the language-game. He says that it is not by definition, which leads to the problem of circularity, but rather from observing how other people use the King when playing chess. We learn concepts from how the concept is used over a period of time, rather than from any momentary definition or particular sensation.
PI 31In this case we shall say: the words "This is the king" (or "This is called the 'king' ") are a definition only if the learner already 'knows what a piece in a game is'. That is, if he has already played other games, or has watched other people playing 'and understood'—and similar things.

For Wittgenstein, sensations are particular and immediate events, such as a smell, a touch, a pain.
PI 24 Think how many different kinds of thing are called "description": description of a body's position by means of its co-ordinates; description of a facial expression; description of a sensation of touch; of a mood.

There are two aspects to the word "pain". The general universal concept, as with any concept, such as house, love, government, trees and the particular momentary sensation, such as a biting pain, an acrid smell, a bitter taste. Both aspects of the word must be taken into account to avoid ambiguity in any paragraph.

I imagine that only a very small percentage of discussion (or language use) is about our knowledge of concepts — Luke

I agree that in normal conversation we don't talk about the meaning of the concepts we use, but rather just use them. That being said, as a concept is an abstract idea, I would have said that every word we use in the language-game is a concept. The language game is a game of concepts.

However, in Wittgenstein's terms, our knowledge of the concepts we use in the language game doesn't come from discussing them in a definitional sense, but rather from using them. It is true that definitions are invaluable in helping us gain knowledge of the concepts we use, but only in structuring the relationship between concepts, not in explaining the meaning of an individual concept.

We may not specifically discuss our knowledge of concepts, but concepts are the foundation of any discussion we have.

If 246 seems contradictory, it may be because Wittgenstein speaks in more than one voice — Luke

I agree that his sentence "Well, only I can know whether I am really in pain; another person can only surmise it." is that of the interlocutor.

However, I am not so sure that his sentence"Yes, but all the same, not with the certainty with which I know it myself!" is that of the interlocutor or his own position.

For example, Wittgenstein writes that he has sensations
PI 246 Other people cannot be said to learn of my sensations only from my behaviour,—for I cannot be said to learn of them. I have them

He also writes that he doesn't doubt his sensations
PI 246 - 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 also links indubitability with certainty.
From the SEP article on Certainty: Ludwig Wittgenstein also seems to connect certainty with indubitability.
From OC 115: If you tried to doubt everything you would not get as far as doubting anything. The game of doubting itself presupposes certainty.

In PI 246 he is linking certainty with knowing.
Yes, but all the same not with the certainty with which I know it myself

As the trail leads from his having sensation that he doesn't doubt, to linking indubitability with certainty and then linking certainty with knowing, this suggests that this statement is his own position rather than that of an interlocutor.

He says that others (often) know when he is in pain. He does not say that he (also) knows when he is in pain. As he states later in the passage, it can't be said of him at all that he knows he is in pain. — Luke

If I said "I don't know I am in pain", this means that I don't know the meaning of the concept "pain", and therefore don't know whether my sensation is that of pain or not, For example, my sensation could be that of hunger.

Therefore, to say "I know I am in pain" means that I do know the meaning of the concept "pain", and therefore do know that my sensation is that of pain.

To say "I am in pain" means that I do know the meaning of the concept "pain", and therefore do know that my sensation is that of pain.

The statements "I know I am in pain" and "I am in pain" have an identical meaning, ie, as I know the meaning of the concept "pain", I know that my sensation is that of pain.

Therefore, it is allowable within the language game to say "I know I am in pain", as it has the same meaning as "I am in pain".

I agree that his sentence "Well, only I can know whether I am really in pain; another person can only surmise it." is that of the interlocutor.

However, I am not so sure that his sentence"Yes, but all the same, not with the certainty with which I know it myself!" is that of the interlocutor or his own position. — RussellA

If we revisit the context in which the latter sentence occurs:

Well, only I can know whether I am really in pain; another person can only surmise it. —

In one way this is false, and in another nonsense. If we are using the word “know” as it is normally used (and how else are we to use it?), then other people very often know if I’m in pain. —

Yes, but all the same, not with the certainty with which I know it myself! — — Wittgenstein, Philosophical Investigations

I would consider "Yes, but all the same..." to be a reaction or response to Wittgenstein's unbolded remarks that immediately precede it, which I believe are made in a different voice. I don't think "Yes, but all the same" makes sense other than as a disagreement with what came before it. That is, I don't see that it would make sense for Wittgenstein to say that people very often know that he is in pain and then to follow up with "Yes, but all the same..." This does not sound to me as though it is in agreement with, or a continuation of, his preceding remarks or that these are given in a singular voice. I could not imagine someone speaking and then reacting to their own comment with "Yes, but all the same..."

For example, Wittgenstein writes that he has sensations
PI 246 Other people cannot be said to learn of my sensations only from my behaviour,—for I cannot be said to learn of them. I have them

He also writes that he doesn't doubt his sensations
PI 246 - 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 also links indubitability with certainty.
From the SEP article on Certainty: Ludwig Wittgenstein also seems to connect certainty with indubitability.
From OC 115: If you tried to doubt everything you would not get as far as doubting anything. The game of doubting itself presupposes certainty.

In PI 246 he is linking certainty with knowing.
Yes, but all the same not with the certainty with which I know it myself

As the trail leads from his having sensation that he doesn't doubt, to linking indubitability with certainty and then linking certainty with knowing, this suggests that this statement is his own position rather than that of an interlocutor. — RussellA

This all hangs on your assumption that he is linking certainty with knowing in PI 246. I don't believe that he is. I believe that this line ("Yes, but all the same...") is given in the voice of the interlocutor instead of in Wittgenstein's own voice. I can see that what you've said here all follows if you assume that it isn't given in the voice of the interlocutor. But I disagree, and your mere assumption to the contrary is not an argument for why my reading is incorrect.

If I said "I don't know I am in pain", this means that I don't know the meaning of the concept "pain", — RussellA

If you did not know the meaning of the concept "pain", I think it would be more natural for you to say "I don't know what "pain" means". Alternatively, "I don't know I am in pain" sounds to me like broken English, and I can't make much sense of it.

Therefore, it is allowable within the language game to say "I know I am in pain", as it has the same meaning as "I am in pain". — RussellA

You're allowed to say anything, but whether you make any sense is another matter. Wittgenstein indicates that it does not make any sense to say "I know I am in pain".