In case it was unclear, I made some concessions to your reading in my previous post. I now agree that a mental image can be a picture, but on the proviso that a private picture/description of one's mental image is not intrinsically private (or private in the same sense as a private language); that it can be made public. However, I sense that you have not gone far enough in your rejection of this "inner picture", which is why I asked: "how is it that we agree that a mental image is not its description?"

On my view, as stated in my previous post, what Wittgenstein means by this "content" is a public picture or public description of what is privately imagined.
— Luke

PPF 10. What is the content of the experience of imagining? The answer is a picture, or a description.

The content of the experience of imagining is what is imagined. The experience itself is a picture or description that occurs in the mind. In order to answer the question of what that is I can draw a picture or describe the content. — Fooloso4

I was referring to the content of the experience. Do you agree that the content of the picture/description is the same regardless of whether it is a public object or whether it is privately imagined?

The mental image is not a picture hanging on the wall of my mind. — Fooloso4

Can you explain how it is different? I note that a moment ago you said:

The experience itself is a picture or description that occurs in the mind. — Fooloso4

The two uses of the term 'picture' belong to different categories. — Fooloso4

Could you please explain the two different uses of the term 'picture'?

It seems to me that W is using 'picture' as a noun at PPF 133 and that he is using 'drawing' as a noun at PPF 134. It also seems that the content of both an imagined picture and a physical picture are the same, even though the "medium" of the pictures is not. Other than that one is imagined and the other is physical, I don't see what different meaning the word "picture" has when used to refer to an imagined picture compared to a physical picture. And I don't see Wittgenstein using the word as a verb here, either, such as "picture this...".

I take PI 280 to be denying that the picture has a double function. The picture he paints to show how he imagines the stage set does not also inform him. It does not tell him what he imagined. — Fooloso4

I also take it this way. But do you consider there to be a single picture here or two different pictures? There is the (physical) picture that was painted but also the (imagined) picture of the stage set in his mind before he painted it. You appeared to be siding with the latter when you said:

The experience itself is a picture or description that occurs in the mind. In order to answer the question of what that is I can draw a picture or describe the content. — Fooloso4

As I noted earlier, this begets a picture of a picture or a description of a description. This is the view that W appears to reject at PI 280.

EDIT: Also, did you have any comment to make about our disagreement over sentence 2?

I believe that Wittgenstein makes a case for sentence 2 of PI 389 - "For however similar I make the picture to what it is supposed to represent, it may still be the picture of something else" - in sections PI 139-141. — Luke

The question is whether a description can be the content of the experience of imagining. Imagining how someone might come to regard a mental image as a superlikeness is to give a description of the steps taken. Isn't that what we are doing when we are figuring out how to respond to each other, imagining how this or that description might be persuasive? Imagining how this or that description might get the other person to see it differently? — Fooloso4

I'm not questioning whether the content of the experience of imagining can be a description. On my view, as stated in my previous post, what Wittgenstein means by this "content" is a public picture or public description of what is privately imagined.

It is your position that the mental image itself can be a picture or description. If a mental image were itself a description, then a description of that mental image (such as per the definition in PI 367) would be a description of a description. Likewise, if the mental image were a picture, then the public version would be a picture of a picture.

At PPF 133, W states:

133. The concept of an ‘inner picture’ is misleading, since the model for this concept is the ‘outer picture’; and yet the uses of these concept-words are no more like one another than the uses of “numeral” and “number”. (Indeed, someone who was inclined to call numbers ‘ideal numerals’ could generate a similar confusion by doing so.) — PI 133

I note that the SEP article on Wittgenstein's Philosophy of Mathematics states (my emphasis):

The core idea of Wittgenstein’s formalism from 1929 (if not 1918) through 1944 is that mathematics is essentially syntactical, devoid of reference and semantics. The most obvious aspect of this view, which has been noted by numerous commentators who do not refer to Wittgenstein as a ‘formalist’ (Kielkopf 1970: 360–38; Klenk 1976: 5, 8, 9; Fogelin 1968: 267; Frascolla 1994: 40; Marion 1998: 13–14), is that, contra Platonism, the signs and propositions of a mathematical calculus do not refer to anything. As Wittgenstein says at (WVC 34, note 1), “[n]umbers are not represented by proxies; numbers are there”. This means not only that numbers are there in the use, it means that the numerals are the numbers, for “[a]rithmetic doesn’t talk about numbers, it works with numbers” (PR §109). — SEP article on Wittgenstein’s Philosophy of Mathematics

The implication is that the inner picture is the outer picture. If there can be any private use of pictures and descriptions as mental images, then such use follows public rules; it treats pictures and descriptions as public objects. There are not two separate descriptions or pictures where one is inner and one is outer; there is only the one description or one picture used for both inner and outer.

Then how is it that we agree that a mental image is not its description?

Perhaps a solution can be found if we agree that a picture or a description is intrinsically public (i.e. derives its meaning/use publicly), but that one can use these public instruments privately, such that one can imagine descriptions or pictures (using their public meanings).

Another way of looking at it could be that I have my private mental image (which is a private picture or description) which I then describe in our public language (or e.g. in a painting, etc). One could worry that something might get lost in translation from the private image to the public description. However, it could also be argued that nothing could possibly get lost because the mental image itself can only be publicly expressed as well as it can be privately imagined. If my private description (e.g. of directions to somewhere) is poor, then so, too, will be my public description. If the picture I imagine is hazy or indistinct, then my public description (or painting, etc) of what I imagine can only be as hazy or indistinct.

This way, a mental image is not a private picture or description (an idea I was keen to reject) and neither do we require two different versions of each picture and description: the public and the private versions (which thus avoids the need for pictures of pictures or descriptions of descriptions).

PI 280 is relevant here:

280. Someone paints a picture in order to show, for example, how he imagines a stage set. And now I say: “This picture has a double function: it informs others, as pictures or words do —– but for the informant it is in addition a representation (or piece of information?) of another kind: for him it is the picture of his image, as it can’t be for anyone else. His private impression of the picture tells him what he imagined, in a sense in which the picture can’t do this for others.” — And what right have I to speak in this second case of a representation or piece of information — if these words were correctly used in the first case? — PI 280

In response to the question of the mental content I might say: "I had a picture in my mind of a man on a horse". This description can be put in the form of a public or physical picture, but a mental picture and a physical picture of that mental picture are two different things. — Fooloso4

I guess that the mental and physical pictures both have the same content, though? In that case, yes, I see what you are saying.

perhaps another way of saying this could be that it is an image of this.
— Luke

The same question: an image of what? What is "this"? — Fooloso4

What I've been trying to say, and how I read sentence 3, is that the content of the mental image can only be this (i.e. whatever one imagines at a particular time) and nothing else. As he is inclined to say at PI 523, "A picture tells me itself".

As I argued earlier, I see no reason why a mental image must represent anything, or be of anything in particular. Maybe the interlocutor errs by thinking sentence 3 is true (when it is false), as you suggest, but I think this reading would make more sense if sentence 2 of PI 389 was also false.

However, I believe that Wittgenstein makes a case for sentence 2 of PI 389 - "For however similar I make the picture to what it is supposed to represent, it may still be the picture of something else" - in sections PI 139-141.

At PI 10 he says:

What is the content of the experience of imagining? The answer is a picture, or a description. — Fooloso4

This is consistent with his defintion of a mental image at PI 367:

367. A mental image is the image which is described when someone describes what he imagines. — PI 367

Note that he distinguishes between a mental image and its description at PI 367. So, there is such a thing as an undescribed mental image. When he speaks of "the content of the experience of imagining" at PI 10, I consider this to be the same as "the image which is described" at PI 367. In other words, the (physical) "picture, or a description" at PI 10 is the described mental image, not the undescribed mental image. Otherwise, why would he include "or a description" at PI 10? The content of the mental image can be physically represented by a picture or description.

If we cannot appeal to a mental image of a color then, with regard to color, we cannot determine that the mental image of a red object is more like the object than a physical picture of the red object. — Fooloso4

Weren't you making these same appeals to a mental image with your examples of the person on the telephone and your siblings' summer house? You claimed that the person on the telephone and the summer house were both unlike your mental images of them. One wonders how you and your siblings were able to show your mental images to each other in order to compare them.

The term picture is used in different ways. At PI 389 he is referring to a physical picture, something that others can see. But we can also picture things to ourselves as in PI 10. These pictures are mental images. — Fooloso4

I don't agree that he is using "picture" as a verb at PI 10. Again, the addition of "or a description" is at odds with that reading.

He says that 1) a mental image must be more like its object than any picture. This is because 2) a picture may be of something other than what it is supposed to represent. But 3) a mental image can only be an image of this. "This" does not mean an image of itself, an image of an image. It is an image of the object that he claims a picture may fail to represent. — Fooloso4

Maybe you're right. I'll try this reading on for size.

You can say that the mental image of a horse is of a horse
— Luke

The mental image of a horse is not a horse, it is an image of a horse. — Fooloso4

I said that the image was of a horse.

A mental image need not represent anything or be of anything, but this does not mean it represents itself or is of itself. It presents itself, it does not re-present itself. — Fooloso4

To make a last gasp argument for my reading, perhaps another way of saying this could be that it is an image of this. Similarly, if someone were to ask what the Mona Lisa is a picture of, one could respond by pointing at it and saying "it's a picture of this".

It is worth noting, however, that a major difference between a mental image and a picture is that, unlike a picture, one cannot point at a mental image. Neither can one point at this object that one is looking at and compare it to one's mental image of the object (that one is having while looking at the object). This is the faulty assumption behind the idea of "superlikeness".

When the interlocutor says at the start of 2: "For ..." the claim is that because a picture may be a picture of something else, the mental image is more like its object than any picture. This is not the same as simply saying a picture may be a picture of something else. Something specific is supposed to follow from the interlocutors claim that need not follow from the observation that a picture may be a picture of something other than what it is supposed to represent. — Fooloso4

The interlocutor might come to believe sentence 1 based (partly) on sentence 2, but I still don't consider PI 389 to be a rejection of sentence 2. It's a non sequitir wherein sentences 2 and 3 are true (and W thinks them true) but the conclusion at sentence 1 does not follow from them.

The point is that one's mental image is not part of the language game; only a description of one's mental image is.
— Luke

And what follows from this? — Fooloso4

For one thing, it follows that a mental image is not a picture.

Many of the surrounding passages of PI 389 are discussing undescribed or unexpressed mental images and questioning how (or whether) these relate to our linguistic abilities. He is trying to steer us away from "an inner ostensive explanation" (PI 380). The distinction between a mental image held only in the mind and a mental image expressed via action or description is crucial to this.

I assume you mean mental image
— Luke

No, I mean a picture, a painting or photograph. — Fooloso4

Wittgenstein maintains a distinction between mental images and pictures at PI 389. On what grounds do you collapse this distinction? Wittgenstein may argue that a mental image does not have a superlikeness to its object, but how do you infer that there is no distinction betweem a mental image and a picture?

3. A mental image cannot be of anything else (but itself).
— Luke

The interlocutor's claim is not a mental image is a mental image of a mental image. It is an image of the object it is an image of. — Fooloso4

I may have expressed that poorly. It is the interlocutor's claim that the mental image is not representative of anything and that it is simply what it is: the image of this.

I can see how you might read it as: the mental image is a representation of the represented particular object. That is, a mental image is a representation of the object that the mental image is of.

To offer an analogy (while trying not to say that pictures are identical to mental images) what is a Jackson Pollock painting the image of; or what does it represent? If I had only the mental image of a Jackson Pollock painting, what would it represent? You can say that the mental image of a horse is of a horse, but what does the mental image of a Jackson Pollock painting represent? My point is that I don't consider it intrinsic to a mental image that it must be of some particular object in the world. I believe that a mental image can also be of something not in the world; that a mental image need not represent anything or be of anything other than what it is: this.

However, I would more readily side with you on this point re: sentence 3 than I would agree with you that a picture is no different to a mental image. That is, I would not agree that a picture is no different to an unexpressed or undescribed mental image.

What is rejected is not that the picture could be of something else. — Fooloso4

Right, but earlier you said:

The point of PI 389 is to reject claims 1 -3 — Fooloso4

Now you are saying that claim 2 is not rejected.

What is rejected is that it follows from the fact that it could be an picture of something else that a mental image must be more like its object than any picture. — Fooloso4

And, as I said earlier:

I believe Wittgenstein disagrees with sentences 1 and 4 but agrees with sentences 2 and 3. — Luke

So I agree with what you say here; that he rejects sentence 4. But I believe he also rejects sentence 1. I believe he does not reject sentence 2 and 3, but that they are misunderstood by the interlocutor to reach the conclusion of sentence 4.

Here's the problem. I describe my mental image of an object, a summer house by the lake. When I am finished by brother tells me that my mental image is not the same as his mental image of that house. We talk to my sister and dig out some old photos. It becomes clear to me that my mental image was not of image of this house and of nothing else, it was a composite image of different houses we stayed in over the years. — Fooloso4

It's not your mental image that your brother tells you is different to his mental image. It's your description of your mental image that your brother tells you is different to his mental image. You might ask him how his mental image is different and he would then describe his mental image. The point is that one's mental image is not part of the language game; only a description of one's mental image is. The description is like a picture that you can use as an object of comparison - to compare against your actual house(s), for example; the mental image is just the (private) mental image.

A picture of X is an image of X. — Fooloso4

I assume you mean mental image, but if that were true, then sentences 2 and 3 of PI 389 would contradict each other, and I don't think that's the point.

For the same reason that we should not conclude from this that it is an intrinsic feature of a picture that it is a picture of this and of nothing else, we should not conclude that a mental image is an image of this and nothing else. — Fooloso4

A reminder of PI 389:

389.
1. A mental image must be more like its object than any picture.
2. For however similar I make the picture to what it is supposed to represent, it may still be the picture of something else.
3. But it is an intrinsic feature of a mental image that it is the image of this and of nothing else.”
4. That is how one might come to regard a mental image as a superlikeness. — Luke

Sentence 3 would be a tautology if it said 'a mental image of X is a mental image of X', but that's not what it says.

If, as you claim, sentence 3 tells us that a mental image is the image of object X and of nothing else, then I don't see how it's any different to sentence 1. The interlocutor would just be repeating himself.

This is how I read it:

1. A mental image must be more like its object (X) than any picture.
2. A picture can be of something else.
3. A mental image cannot be of anything else (but itself).
4. This is how one might come to regard a mental image as most like object (X).

I take it you don't wish (sentence 3) to say that it is an intrinsic feature of a mental image that it is the image of object X and of nothing else, because then all mental images would be of object X. Otherwise, Wittgenstein could have limited sentence 3 to say "it is an intrinsic feature of a mental image that it is the image of its object and of nothing else." But I don't believe it is an intrinsic feature of a mental image that it must be the image of a particular object.

It does not follow from a) the fact that there is not a necessary correspondence between a picture and what it is supposed to represent, that b) there is a necessary connection between a mental image and what it is an image of. — Fooloso4

I agree. That’s not what I said.

I said it follows from the rejection of a) the fact that there is not a necessary correspondence between a picture and what it is supposed to represent, that b) there is a necessary correspondence between a picture and what it is supposed to represent.

If W rejects sentence 2 of PI 389, as you suggest, then his position is that b) there is a necessary correspondence between a picture and what it is supposed to represent.

I don’t believe that is W’s position. Therefore, I don’t believe he does reject sentences 1-3 as you say. (At least, not sentences 2 and 3.)

It is a tautology to say that a mental image of X is an image of X. But this does not mean that my mental image of X is anything like X. If I describe my mental image of X it may become clear that the image as described is nothing like X. It may be that it is an image of something else. — Fooloso4

That’s right. That may explain W’s definition of a mental image at PI 367.

The point of PI 389 is to reject claims 1 -3 — Fooloso4

Sentence 2 states:

2. For however similar I make the picture to what it is supposed to represent, it may still be the picture of something else. — Luke

This tells us that there is not a necessary correspondence between a picture and its object (or “what it is supposed to represent”). If W rejects this, as you say, then it is W’s position that there is a necessary correspondence between a picture and its object. To what object does the picture of the duck-rabbit necessarily correspond?

What does "this" refer to?
— Fooloso4

I was quoting PI 389.
— Luke

Right, but you said:

I don't see why the mental image must correspond to any object.
— Luke

At PI 389 "this" refers to the mental image of a particular object. If you disagree with the interlocutor then we are in agreement.

But you also said:

However, this need not imply that Wittgenstein rejects the interlocutor's statement that "it is an intrinsic feature of a mental image that it is the image of this and of nothing else".
— Luke

He does reject it. He rejects it for the same reason you now seem to be rejecting it. — Fooloso4

Allow me to be more clear. I will number the sentences of PI 389 and state which I think Wittgenstein agrees and disagrees with:

389.
1. A mental image must be more like its object than any picture.
2. For however similar I make the picture to what it is supposed to represent, it may still be the picture of something else.
3. But it is an intrinsic feature of a mental image that it is the image of this and of nothing else.”
4. That is how one might come to regard a mental image as a superlikeness.

Firstly, I don’t read there as being any necessary correspondence with an object in sentence 3. “The image of this” is just whatever is the content of one’s mental image.

I believe Wittgenstein disagrees with sentences 1 and 4 but agrees with sentences 2 and 3. Sentence 4 seems little more than a restatement of sentence 1. Sentence 1 (together with 3) could be a definition of “superlikeness”. Incidentally, Hacker relates this concept to the terms “super-order” and “super-concepts” mentioned at PI 97.

I think PI 380-388 (especially 380 and 382) supports my reading and does not support your reading (where you take the point of PI 389 to be that a picture can equally or more closely resemble an object than does a mental image). I also believe these passages support my position against your assumption/reading that a mental image (like a picture) can be compared with an object for the purpose of determining the image’s resemblance or correspondence to that object.

Take PI 380 for example:

380. How do I recognize that this is red? — “I see that it is this; and then I know that that is what this is called.” This? — What?! What kind of answer to this question makes sense?
(You keep on steering towards an inner ostensive explanation.)
I could not apply any rules to a private transition from what is seen to words. Here the rules really would hang in the air; for the institution of their application is lacking. — PI 380

Or PI 382:

382. How can I justify forming this [mental] image in response to this word?
Has anyone shown me the image of the colour blue and told me that it is the image of blue?
What is the meaning of the words “this image”? How does one point at an image? How does one point twice at the same image?

Or this excerpt from PI 386:

I say without hesitation that I have done this calculation in my head, have imagined this colour. The difficulty is not that I doubt whether I really imagined anything red. But it is this: that we should be able, just like that, to point out or describe the colour we have imagined, that mapping the image into reality presents no difficulty at all. — PI 386

I believe this context shows that the point of PI 389 is not what you seem to think. You read W as saying that a mental image can be compared to an object in order to determine its resemblance to that object, just like a picture can. I see W as attacking this assumption.

"it is an intrinsic feature of a mental image that it is the image of this and of nothing else."
— Luke

I don't see why the mental image must correspond to any object.
— Luke

In general a mental image need not correspond to any object, but we are discussing PI 389:

389. “A mental image must be more like its object than any picture. — Fooloso4

Yes, but you provided a counterexample to this:

The mental image of this refers to the one object it is an image of. Two blurred objects or events is a counterexample. — Fooloso4

Therefore, I take it you disagree with the interlocutor's statement that "A mental image must be more like its object than any picture".

Your requirement that the mental image must be of one object presupposes that it can correspond or be compared to some object.
— Luke

This is not my requirement. This is the interlocutor's claim: — Fooloso4

You appear to agree that a mental image can correspond or be compared to some object, even though you disagree that the mental image must be of one object.

Do you therefore think it follows that a picture has a superlikeness to its object, — Luke

No. As I said:

A photo of X may to varying degrees and in various ways capture a likeness of X. — Fooloso4

Yes, you also said:

So too, our mental images of X may to varying degrees and in various ways capture a likeness of X. — Fooloso4

So, your position is that mental images and pictures/photos can both correspond or be compared to some object.

Is his point simply that there is no distinction between a picture and a mental image?
— Luke

Of course not! — Fooloso4

What do you take to be his point at PI 389?

On my reading, a mental image is unlike a picture because a mental image can only be "the image of this and of nothing else", — Luke

What does
"this"
refer to? — Fooloso4

I was quoting PI 389.

Why can't my mental image be a likeness to the object it is an image of? I do not have to describe that image to myself, I see it. — Fooloso4

I think Wittgenstein might take issue with your use of "see" here. You don't really see or look at your mental image; it is what you imagine.

I talk to someone on the phone who I have never met. I imagine what this person looks like. I form a mental image of them. Later I meet this person and they are very different from my mental image. — Fooloso4

That's an obvious assumption to make (just like the assumption of a private language), but how does it relate to the text or to what Wittgenstein says at PI 389?

The mental image of this refers to the one object it is an image of. Two blurred objects or events is a counterexample. — Fooloso4

I don't see why the mental image must correspond to any object. As I understand it, the mental image is just whatever its content is; whatever the image is. I don't see that it needs to be of any singular thing in particular. To repeat the definition given at PI 367:

367. A mental image is the image which is described when someone describes what he imagines. — PI 367

Your requirement that the mental image must be of one object presupposes that it can correspond or be compared to some object.

Like the private timetable at PI 265, the mental image cannot be tested for correctness. There is no method of projection (PI 366) from the mental image to the object. There are no rules for verifying that the mental image corresponds to its object.

On the other hand, the description of the mental image is a kind of picture and can be compared or correspond to some object, but the description (of the mental image) is not the mental image.

At least, that's how I read it, and how I see it tying in to the rest of the text. I don't see how your reading relates to the rest of the text.

Your reading - where you trust the picture to be like its object more than you trust the mental image to be like its object - could explain how the interlocutor comes to regard a mental image as a sub-likeness instead of a super-likeness. This might make more sense to you but it is not consistent with the text.
— Luke

The interlocutor comes to regard it as a super-likeness because he assumes that it is an intrinsic feature of a mental image that it is the image of this object and of nothing else. I think the interlocutor is wrong and I gave some reasons why. You think Wittgenstein agrees with the interlocutor's assumption, I don't. — Fooloso4

Your takeaway from PI 389, as I understand it, is that the interlocutor has it backwards; that a picture better represents its object than a mental image does. Also, that the interlocutor is incorrect to assume that a mental image can only represent one thing. Do you therefore think it follows that a picture has a superlikeness to its object, or is the idea of a "superlikeness" irrelevant to Wittgenstein's point here? Is his point simply that there is no distinction between a picture and a mental image?

On my reading, a mental image is unlike a picture because a mental image can only be "the image of this and of nothing else", whereas a picture may still represent something else. Consequently, the interlocutor may mistakenly come to regard a mental image as a superlikeness with its object - because a mental image cannot represent anything else, whereas a picture can. I view Wittgenstein as being critical of the interlocutor's inference that the mental image is any sort of likeness; that there can be any correspondence between a private (undescribed) mental image and its object.

Hacker tells us that a mental image is "not a likeness [to its object] at all" since its being a mental image of X "is not determined by its likeness to X".
— Luke

This is like saying a photo of X is not a likeness of X at all since it being a photo of X is not determined by its likeness to X. — Fooloso4

Only if you take a photo to be no different to a mental image. A photo is a picture; a mental image is not.

So too, our mental images of X may to varying degrees and in various ways capture a likeness of X. — Fooloso4

If you were to describe your mental image, then maybe we could compare it to the object and find out how closely it resembles its object, but a mental image cannot be compared to its object; only a description of the mental image can.

it is an intrinsic feature of a mental image that it is the image of this and of nothing else
— Luke

I don't agree. Many things can influence our mental images. Two different events can get blurred in the mind. — Fooloso4

Then the mental image would be an image of the two blurred events and of nothing else. The mental image would be singular even if it was of two blurred events. See the definition at PI 367.

What Wittgenstein criticises is that the interlocutor "might come to regard a mental image as a superlikeness" with an object.
— Luke

How is it that he might come to regard it in this way? As I read it, because he assumes that a mental image must be more like its object than any picture. I think just the opposite is true. My mental picture of the house I used to live differs from photographs of it. I trust the photo to be more like the house. — Fooloso4

I take it he comes to regard it this way for the reasons given at PI 389, namely: "however similar I make the picture to what it is supposed to represent, it may still be the picture of something else. But it is an intrinsic feature of a mental image that it is the image of this and of nothing else."

Your reading - where you trust the picture to be like its object more than you trust the mental image to be like its object - could explain how the interlocutor comes to regard a mental image as a sub-likeness instead of a super-likeness. It might make more sense to you to trust the picture over the mental image, but it is not consistent with the text.

It may make more sense if you bear in mind that Wittgenstein is criticising the interlocutor for thinking that there can be a superlikeness, or even a likeness; for thinking that a mental image can be used as an object of comparison, or compared with an object in the same way that a picture can.

Incidentally, I think there is a similarity here to PI 253 (despite its being about pain). Consider:

I have seen a person in a discussion on this subject strike himself on the breast and say: “But surely another person can’t have THIS pain!” — PI 253

It is the immediate experience of pain or qualia described here ("THIS pain!") that I think is relevant or similar to the idea of a superlikeness (compare: "a mental image...is an image of this and of nothing else" at PI 389). I guess the similarity is simply that it cannot be of anything else, but also that it is private.

Now I remember why I balk when Hacker is mentioned. — Fooloso4

I'll try to limit my references to his exegesis then.

PI 389, which states: "it is an intrinsic feature of a mental image that it is the image of this and of nothing else."
— Luke

It is Wittgenstein's imagined interlocutor who makes this claim in the quotations. W.'s response is:

That is how one might come to regard a mental image as a superlikeness.

One might regard a mental image in this way but a mental image is not a superlikeness. One's mental image can be quite unreliable. — Fooloso4

Wittgenstein defines a mental image at 367:

367. A mental image is the image which is described when someone describes what he imagines. — PI 367

This indicates that a mental image is what one imagines at a particular time, and the description will describe what one imagines at the time.

One might regard a mental image in this way but a mental image is not a superlikeness. One's mental image can be quite unreliable. — Fooloso4

What Wittgenstein criticises is that the interlocutor "might come to regard a mental image as a superlikeness" with an object. However, this need not imply that Wittgenstein rejects the interlocutor's statement that "it is an intrinsic feature of a mental image that it is the image of this and of nothing else". What I see W as rejecting here is the supposed superlikeness of the mental image with its object, not the fact that a picture may still be of something else, or that a mental image may not.

For what it's worth, Hacker tells us that a mental image is "not a likeness [to its object] at all" since its being a mental image of X "is not determined by its likeness to X". He says that "...it neither looks like nor fails to look like its object. It is not a picture at all. How does one know that one’s image is of X and not Y (which looks like X)? One does not know, nor can one be mistaken. One says so, without grounds, as one says what one means or what one thinks."

An image may change over time based on new experiences or the unreliability of memory. — Fooloso4

How would you know that it changes? In other words, why think of it as a single (or as the same) image that undergoes change instead of as different images?

I think that both a picture and what is pictured can be seen in different ways. Consider the duck-rabbit, for example.
— Luke

When the picture itself is an object I agree, but not all pictures are objects.

When Wittgenstein says at PI 1:

These words, it seems to me, give us a particular picture of the essence of human language.

he is talking about a mental image, not an object. — Fooloso4

On your reading, a picture can be synonymous with a mental image. Your reading therefore seems inconsistent with Hacker's reading (who warns against conceiving of mental images as pictures) and with PI 389, which states: "it is an intrinsic feature of a mental image that it is the image of this and of nothing else." I think we both agree that a picture (such as the duck-rabbit) can be seen in more than one way. However, I don't believe Wittgenstein would agree that a mental image "picture" can be seen in more than one way.

My mental image may be at one time of a duck and at another time of a rabbit, but when my mental image is of a duck I cannot see it in any way other than as a duck (i.e. how I see it at the time), and the same for when my mental image is of a rabbit.

When he says:

115. A picture held us captive. And we couldn’t get outside it, for it lay in our language, and language seemed only to repeat it to us inexorably.

he is talking about a mental image, a way in which something is conceived to be. — Fooloso4

It is worth noting that your example at PI 1 is "a particular picture" (my emphasis), and it is presumably also a particular picture at PI 115 that held us captive. We might infer, then, that a particular picture, or a particular way of seeing a picture, may be synonymous with a mental image (which can only be seen in one way), whereas a picture more generally speaking can be seen in more than one way.

When he says at 301:

What is in the imagination is not a picture, but a picture can correspond to it.

This should not be thought of as a general statement about pictures, as something that holds true for all pictures. He is talking specifically about how pain is imagined. Pain in the imagination is about what pain feels like, not about how we might picture it. See 302: — Fooloso4

Perhaps what is in the imagination is not a picture because what is in the imagination (a mental image) can only be seen in one way, unlike a picture which can be seen in more than one way.

In case my reading is correct such that pictures and mental images differ in the number of ways they can be seen, then maybe PI 301 should be viewed as a general statement about pictures. The fact it was given its own number lends credence to it being a more general statement not necessarily related to PI 300.

It is not that the picture can be seen in different ways, but that what is pictured can be seen in different ways. — Fooloso4

I think that both a picture and what is pictured can be seen in different ways. Consider the duck-rabbit, for example.

I don't believe it would be a picture theory per se...
— Luke

In the PI? I think that's right. — Banno

To clarify, you think it's right that it's not a picture theory in the PI?

It's delicate. Consider:

And it is this inner process that one means by the word “remembering”. The impression that we wanted to deny something arises from our setting our face against the picture of an ‘inner process’. What we deny is that the picture of an inner process gives us the correct idea of the use of the word “remember”. Indeed, we’re saying that this picture, with its ramifications, stands in the way of our seeing the use of the word as it is. — 305

This has ramifications for your discussion with schopenhauer1, who is seems is in the thrall of a certain picture. — Banno

I think I understand Hacker's exegesis now as simply saying that we should not confuse mental images with pictures; that a mental image can be pictured but is not itself a picture. I think I got myself confused earlier into thinking he was saying that a mental image could not be pictured.

So "picture" is being used diversely. — Banno

It seemed to me he had used "picture" in a singular way in both the Tractatus and PI. What are the different uses of "picture" you find in PI?

The alternative seems to be that he still harbours a referential picture theory, somehow sitting under his theory of meaning as use. — Banno

I don't believe it would be a picture theory per se, since now "we may not advance any kind of theory. There must not be anything hypothetical in our considerations. All explanation must disappear, and description alone must take its place." (PI 109)

However, I think the question is whether or not Wittgenstein considered pictures as having different applications in the Tractatus, or whether he viewed them as having only a single application. Without having given it much investigation, I would assume it was the latter.

In the Tractatus, we picture facts to ourselves (2.1) and a picture is a model of reality (2.12) [and a model of reality as we imagine it (4.01)]. Also, the metaphysical subject or philosophical self is considered to be "the limit of the world - not a part of it." (5.641) Since a picture is a model of reality and since the metaphysical subject is not part of reality, then the metaphysical subject is not something that is pictured (in the Tractatus). It is interesting to question whether Wittgenstein also carries this view over to the PI.

At PI 300, he appears to indicate that our pictures of pain are not limited to pain-behaviour:

300. It is, one would like to say, not merely the picture of the behaviour that belongs to the language-game with the words “he is in pain”, but also the picture of the pain. Or, not merely the paradigm of the behaviour, but also that of the pain. — It is a misunderstanding to say “The picture of pain enters into the language-game with the word ‘pain’ ”. Pain in the imagination is not a picture, and it is not replaceable in the language-game by anything that we’d call a picture. — Imagined pain certainly enters into the language-game in a sense; only not as a picture. — PI 300

In his exegesis of PI 300, Peter Hacker offers the following clarifying remarks:

The point upon which W. focuses here is a confusion concerning the relationship between the concept of a mental image and that of a picture. Clearly, pictures are objects of comparison, and, equally clearly, mental images can correspond to pictures. So we are inclined to think that mental images are likewise objects of comparison. Indeed, we are prone to conceive of mental images as pictures. They seem to be just like pictures, save for being mental! This is multiply confused. Imagined pain (Die Vorstellung des Schmerzes) is not a picture of pain (ist kein Bild). One can imagine a toothache or remember a headache, but this does not furnish one with a picture; there is nothing here employable as a picture or a paradigm, not even as a picture which only oneself (as it happens) can see. The description of the imagined is not a description of an inner picture, but a description of what one imagines (e.g. the face that launched a thousand ships (cf. PI §367)). Similarly, the description of the recollected is a description of what I remember, perhaps only hazily, not a description of a hazy picture. There is no such thing as using a Vorstellung of pain (as one can use a picture of something) as a sample or paradigm. Even in those cases where one can intelligibly talk of (vivid) images (Vorstellungsbilder), one’s mental image is not a sample or paradigm, for there is no such thing as a method of projection for a mental image. One cannot lay a mental image alongside reality for comparison. But it is important that if, e.g. I imagine a shade of red (and perhaps have a vivid image of it), I can paint what I imagine, and that can be used as a paradigm. ‘That is how I imagined the backcloth to be’, I might say to the scene‐painter, while pointing at a patch of paint. Here the image of red is replaceable by a paradigm (picture) of red. But nothing corresponds to imagined pain (die Vorstellung des Schmerzes) as a red sample corresponds to imagining, having an image of, red. Hence the ‘image’ or ‘representation’ (Vorstellung) of pain is not replaceable by anything that can function as an object of comparison. — P.M.S. Hacker, An Analytical Commentary on the Philosophical Investigations, Vol. 3, Part 2: Exegesis 243-427

Therefore, at least on Hacker's view, a picture is an object of comparison which must be capable of a method of projection or which can be "laid alongside reality" for comparison (by anyone).

The moral here could be that a picture is in the mind but cannot be of the mind, as there is no possibility of comparison.

W follows this with PI 301:

301. What is in the imagination is not a picture, but a picture can correspond to it. — PI 301

In his exegesis of 301, Hacker states:

An image, which one may have when one imagines or remembers something, is not an ‘inner picture’. But a picture may correspond to such an image, for one can often paint a picture of what one imagines and say ‘This is how I imagined it’ (cf. §280). Is this always possible, i.e. does it always make sense? No; for it is clear from §300 that though I can imagine a severe toothache, no picture corresponds here as a picture of someone clutching his swollen jaw corresponds to imagining someone with a bad toothache. — Hacker, ibid

However, confusingly, at PPF 10 (Part II), W states:

What is the content of the experience of imagining? The answer is a picture, or a description. — PPF 10 (Part II)

On the face of it, this appears to contradict PI 301. Perhaps W's comment at 301 is limited only to the context of pain, or perhaps this comment includes imagining everything but pain.

Wittgenstein also distinguishes a mental image from a picture at 389:

389. “A mental image must be more like its object than any picture. For however similar I make the picture to what it is supposed to represent, it may still be the picture of something else. But it is an intrinsic feature of a mental image that it is the image of this and of nothing else.” That is how one might come to regard a mental image as a superlikeness. — PI 389

I also found an interesting overview of W's mention of "picture" throughout his works here.

Oh I wasnt meaning to say “our representation” bit rather “my representation”, however that applies — schopenhauer1

Well, I've answered that. I'll leave you to your private language.

How can one claim one was following it? Verifying by another representation suv. There’s no getting outside representation — schopenhauer1

A second ago you were asking about getting outside of one's own representation. Now you are asking about getting outside of everyone's representations. Which is it?

It's our practices, our rules, our games, our language. Calling all of these "our representations" makes them seem like some communal, shared idea, rather than our practices and actions in the world. I don't see the benefit or truth in calling them all "representations".

How is this outside their own representation? What can that mean? — schopenhauer1

202. That’s why ‘following a rule’ is a practice. And to think one is following a rule is not to follow a rule. And that’s why it’s not possible to follow a rule ‘privately’; otherwise, thinking one was following a rule would be the same thing as following it. — PI 202

If the practice called "following the rule" wasn't outside of one's own representation, then there would be no difference between thinking one was following a rule and following it.

I'm not going to keep going around in circles on this.

Others are verifying…right so no it goes to others verifying. Now, when they verify, is it their own representation of what’s right or wrong, or do they have access to something outside their own representation? — schopenhauer1

I've already answered this. They have access to something outside their own representation:

Individual confirmations of what are the rules and cultural ideas are not hidden and private; they are expressed publicly. One's public expression can be demonstrated to be inconsistent with the accepted practice that is called "following the rule". — Luke

How is anything “external”? — schopenhauer1

What do you mean by "external"? I mean public, open to view, available for others to verify, not limited to one person's private experiences.

It doesn't matter how it is "internalized". That is irrelevant to following the rule.
— Luke

Who decides? :chin: — schopenhauer1

To begin with, those who teach you the rules, the game or the language "decide" - that is, show you what the practice is or how to play. Later, other players/speakers may also correct you or remind you of the rules. Or you might correct or remind them. Maybe a referee or a rule book or an authority will decide. Some may be incapable of learning the game/language. Some might not want to play along.

I don't. What's internalized (or internal) is the beetle, which drops out of consideration as irrelevant. All that matters to following a rule is "what's being conveyed" or one's words and actions.
— Luke

Huh who decides? — schopenhauer1

Nobody decides this. We are unable to verify anyone else's private, internal beetle, so we can only judge whether another has followed the rule based on their ("external") behaviour.

But how is this internalized? — schopenhauer1

It doesn't matter how it is "internalized". That is irrelevant to following the rule.

Publically? — schopenhauer1

What?

How do you know what’s internalized is what’s being conveyed? — schopenhauer1

I don't. What's internalized (or internal) is the beetle, which drops out of consideration as irrelevant. All that matters to following a rule is "what's being conveyed" or one's words and actions.

It’s not my view it’s what Witts anti foundationalism points to. That is to say he wants the inner representation to be always hidden and private yet have “room” for public. Public is always individual confirmations of what are the rules and cultural ideas. So how is it he is getting out of any private version of representation? — schopenhauer1

Individual confirmations of what are the rules and cultural ideas are not hidden and private; they are expressed publicly. One's public expression can be demonstrated to be inconsistent with the accepted practice that is called "following the rule".

You can’t just say common sense or refer to the other person because that can just be an individuals representation. The beetle in the box. — schopenhauer1

201. ...there is a way of grasping a rule which is not an interpretation, but which, from case to case of application, is exhibited in what we call “following the rule” and “going against it”.
That’s why there is an inclination to say: every action according to a rule is an interpretation. But one should speak of interpretation only when one expression of a rule is substituted for another.

202. That’s why ‘following a rule’ is a practice. And to think one is following a rule is not to follow a rule. And that’s why it’s not possible to follow a rule ‘privately’; otherwise, thinking one was following a rule would be the same thing as following it. — PI 201

Although there may occasionally be borderline cases where it is unclear whether a rule has been broken or not, there are the more common, obvious cases where it either has or it hasn't. If there weren't such obvious cases, then we wouldn't be able to learn or to teach any rules or games or language and we wouldn't have them.

Do you feel Wittgenstein can be wrong or everything he said is airtight? I mean this in both his content and in the weird “oh well the way he wrote there is no wrong even” or some such claim. — schopenhauer1

Yes, Wittgenstein can be wrong. Like anyone, he was not infallible.

You haven't sufficiently provided what this public is. Those things you described can simply be representations in individual minds. — schopenhauer1

As I said: other people. Other people such as the parents and teachers and others who taught you many of the rules and the games and the language. If you think that other people are no more than representations, and that you were born with an innate knowledge of all the rules and games and language, and that children don't learn rules and games and language, and that you are actually speaking only to a representation of me (and others) in your private language, and all of this because there are no things or people outside yourself but only your representations of them, then I can't help you with your solipsism.

Solipsism is not possible without a private language, and Wittgenstein showed that the concept of a
private language is incoherent.

There has to be a theory of what this public is — schopenhauer1

Wittgenstein uses the term "public" only once in the PI and that is in the preface. Besides, why does there need to be a theory instead of the common meaning of the word?

The beetle box deigns that you can ignore individual representations of meaning as "functionally" it's all "use". Well, that poses problems due tot he "public" nature of the "functionality of use". That requires a metaphysics of entities such as "public" that goes beyond the individual. — schopenhauer1

It's not a metaphysics of entities. What is public does go beyond the individual. That's what "public" means (as an adjective), or is at least its one of its meanings; one of the ways it can be used..

Something has to obtain in the world called "public". — schopenhauer1

When you said there was a "public nature of the functionality of use", you used "public" as an adjective to describe the nature of the functionality of use. But in your next sentence you reify this adjective into an entity where this public nature requires a "metaphysics of entities such as "public"". You haven't really explained why such an entity is required.

I think that, because you assume there can be nothing but private representations, your complaint is that there must be for Wittgenstein some public representation (or public mind) that is the arbiter of all rules and games and language. And who does that public representation belong to? The short answer to your conundrum is: it belongs to the public. That is, to other people, to accepted authorities, to rule books and other references, to convention, to general agreement; to things that are necessarily outside of one person but not necessarily outside of all people.

I don’t follow why there needs to be either foundationalism or certainty in order for there to be rules.
— Luke

Because it posits a public entity — schopenhauer1

Because what posits a public entity? What "public entity"? I don't see the problem.

Im saying you can’t have both uncertainty, anti foundationalism but then claim that there’s X (rules, games, use) — schopenhauer1

I don’t follow why there needs to be either foundationalism or certainty in order for there to be rules.

That logic makes no sense. Someone else’s beetle may think they understand what I’m doing, find it “normal” or not, but it’s just their beetle reacting to something. That doesn’t confer anything outside of solipsism. How is there a public to Witt if there’s no certainty to ontology? It’s all anti foundational. You can’t start positing an external confirming entity. — schopenhauer1

So there are no rules? No rules of chess or any other game/sport? No road rules?

All of these things are said as if there is a Platonic "public" judging this.. It is just people's internal "beetles" judging this. — schopenhauer1

202. That’s why ‘following a rule’ is a practice. And to think one is following a rule is not to follow a rule. And that’s why it’s not possible to follow a rule ‘privately’; otherwise, thinking one was following a rule would be the same thing as following it. — Wittgenstein, PI 202

Sure, but this language game (the uses) learned from a community is not some Platonic "thing" but is rather the various instantiations of understanding in each individual (internally). Thus the beetle-box actually seems at odds with this, as if internal understanding doesn't count here. — schopenhauer1

Internal understanding counts to the extent that it can be demonstrated externally. We say that a person understands something to the extent that they are able to demonstrate their understanding. In fact, the external demonstration is all that we usually (non-philosophically) mean by "understanding". Whatever internal understanding there is "left over" that cannot be demonstrated, or that is not included in an external demonstration of understanding, is irrelevant to the meaning of "understanding". Like Wittgenstein's beetle, the internal aspect of understanding itself "drops out of consideration as irrelevant" to the meaning of the word "understanding". This is not to say that we don't have an internal understanding or an internal life or any feelings or thoughts or first-person perspective. Only that these private "inner" things do not determine the public meanings of our words.

Use to whom? Surely if you get me a slab, there is nothing beyond me finding it "normal" and you finding it "normal" to do X and X. But it is still just "me" and "you" and nothing beyond that. There is no unifying form of "use". — schopenhauer1

Our finding it "normal" or customary to "do X" is the unifying form of "use". The way "slab" is used in the builder's language game is that one person calls out "slab!" and another person brings them a slab. The same applies to all words, that is, we are trained in their use; we master the (techniques of) language. Whether or not we understand the language is demonstrated by our actions, which may be appropriate/natural or which may demonstrate that we don't understand what was said or that we don't speak the language.

In the same way, anyone can use the word "pain" in language, regardless of anyone's personal sensation of pain. — RussellA

Now you're getting it.

There are also private concepts, such as my personal experience when looking at something in the world having a wavelength of 400nm. — RussellA

I don't see why you would call your personal experience a concept.

I agree, as with the beetle in PI 293, the beetle drops out of consideration in the language game. — RussellA

Yep.

There are different uses of the world "meaning". The absence of pain means a lot to me and "pain" means "a sharp unpleasant sensation usually felt in some specific part of the body". — RussellA

This is why I emphasised the distinction between meaningfulness (significance) and word meaning (definition, sense) in my previous post, where I said: "What the words "pen" or "Eiffel Tower" mean to you are irrelevant to the meaning of "peffel"". That is, the personal significance to you of "pen" and "Eiffel Tower" are irrelevant to the meaning or sense of "peffel", which you defined as "part [your] pen and part Eiffel Tower". The word "peffel" can be used by anyone to mean ""part [your] pen and part Eiffel Tower" regardless of your personal feelings about the words "pen" or "Eiffel Tower".

My concept of "peffel" is inaccessible to others as my concept of violet is inaccessible to others. — RussellA

Violet is not your concept. But your understanding of the concept is accessible to others, depending on how you use it.

Can you describe in words your personal experience of the colour violet to a colour blind person? — RussellA

I don't need to describe my personal experience in order to use the word "violet" appropriately. And neither does a colour blind person.

The point is that our experiences are irrelevant to linguistic meaning; to language use. This is not to say we don't have experiences. Things can still be significant or meaningful to you; but the way it feels or looks or tastes, etc. is irrelevant to the meaning or use of a word.

For example, we don’t know someone is in pain, not because it is “unknowable”, but because when someone seems to be in pain, we don’t: “know” their pain, we react to it, to the person; their pain is a plea, a claim on us—we help them (or not); that’s how pain works. — Antony Nickles

I have to disagree with you here. At PI 246, Wittgenstein says:

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. — PI 246

That's just quibbling over the definition
— Luke

Similar and same mean different things. "The Eiffel Tower is similar to the Blackpool Tower" is true. "The Eiffel Tower is the same as the Blackpool Tower" is false. — RussellA

I have been foolishly following you down this rabbit hole. @Banno has pointed out what's important here:

What matters is that when the builder calls "slab", the assistant brings a suitable piece of stone. — Banno

That is, your individual or private concept of "slab" can be whatever you like; it makes no difference provided that you act/react appropriately in the language-game. Like Wittgenstein's beetle, your individual or private concept "drops out of consideration as irrelevant". As I quoted from PI 199: "To understand a language means to have mastered a technique."

What is the correct use of Form of Life ? — RussellA

As I quoted from the SEP earlier:

What enables language to function and therefore must be accepted as “given” are precisely forms of life. In Wittgenstein’s terms, “It is not only agreement in definitions but also (odd as it may sound) in judgments that is required” (PI 242), and this is “agreement not in opinions, but rather in form of life” (PI 241)...Forms of life can be understood as constantly changing and contingent, dependent on culture, context, history, etc.; or as a background common to humankind, “shared human behavior” which is “the system of reference by means of which we interpret an unknown language” (PI 206); or as a notion which can be read differently in different cases – sometimes as relativistic, in other cases as expressing a more universalistic approach.

I can define the word "peffel" as "part my pen and part the Eiffel Tower", and I can define "pen" and "Eiffel Tower", but I cannot put into words what the words "pen" and "Eiffel Tower" mean to me, as my concepts of "pen" and "Eiffel Tower" have grown and developed over a lifetime of unique multiple experiences. — RussellA

What the words "pen" or "Eiffel Tower" mean to you are irrelevant to the meaning of "peffel", which means "part [your] pen and part the Eiffel Tower". Is this not what "peffel" means?

Even in Wittgenstein's terms, as my personal concept of "peffel" is inaccessible to others, it is part of my private language. — RussellA

In what way is the concept of "peffel" inaccessible to others? You have already defined it for us. Also, in what way is "peffel" a part of any language? Do you ever use the word "peffel" and, if so, how do you use it?

As definition i) is your definition of a slab but not mine, then we don't agree as to the definition of a "slab". For me a "slab" can be "a large or small, thick or thin, flat or uneven piece of stone or concrete, typically square or rectangular in shape". — RussellA

That's just quibbling over the definition. It's not like you meant something entirely different, like a hammer or like definition ii). This is where family resemblance and fuzzy boundaries might enter into it. We could ask how small or thin or uneven it could be before we would no longer consider it a slab. But even then we are still both talking about the same meaning of "slab"; the same "slab" concept.

I find it hard to believe that two people can have the same concept of any word. — RussellA

What about the words in your sentence quoted above? How could anyone else possibly understand what that sentence meant if we didn't have the same concept of those words? Do you think your ordinary use and understanding of the word "two" or "people" or "word" is different to that of any other fluent English speaker?

To follow a rule, to make a report, to give an order, to play a game of chess, are customs (usages, institutions).
To understand a sentence means to understand a language. To understand a language means to have mastered a technique. — PI 199

Even if you have lived a similar form of life to me — RussellA

As I mentioned in my previous post, you are using "form of life" incorrectly.

Each individuals experience of the Form of Life will be different and unique to them. — RussellA

Individuals (humans) don't experience Form of Life differently; it's who we are. It's the shared human
behaviours and judgements that are common to all humans; our human form of life.

For many years, I have had the concept of a "peffel" as well as its name, part my pen and part the Eiffel Tower. This word I have found useful when thinking about the ontology of relations, and has been part of my private language, and so far, unique to me. — RussellA

As @Antony Nickles mentioned recently, what Wittgenstein means by "private" in relation to a private language is that the words of this language can, in principle, be understood by one person only and that nobody else can understand the language. Since you were able to explain the meaning of the "peffel" concept, then I don't believe this qualifies as a private language.

How can you know my concept of Slab? How do you know that our concepts of a "slab" are the same? — RussellA

In the context of this discussion about PI and language-games, I presume that your concept of "slab" is the same as mine, referring to one of the builder's building materials. Did you have something else in mind?

My Form of Life has been unique to me, — RussellA

Form of Life is not relative or unique to individuals.

The SEP article on Wittgenstein gives the following account of Form of Life:

What enables language to function and therefore must be accepted as “given” are precisely forms of life. In Wittgenstein’s terms, “It is not only agreement in definitions but also (odd as it may sound) in judgments that is required” (PI 242), and this is “agreement not in opinions, but rather in form of life” (PI 241)...Forms of life can be understood as constantly changing and contingent, dependent on culture, context, history, etc.; or as a background common to humankind, “shared human behavior” which is “the system of reference by means of which we interpret an unknown language” (PI 206); or as a notion which can be read differently in different cases – sometimes as relativistic, in other cases as expressing a more universalistic approach.

Form of Life may allow for some relativism between different cultures or time periods, depending on your reading, but it does not allow for relativism between individuals. An individual does not have their own unique Form of Life, just as (and for the same reasons that) an individual does not have their own unique language.

We can agree to the dictionary definition of a slab as i) a large, thick, flat piece of stone or concrete, typically square or rectangular in shape ii) a large, thick slice or piece of cake, bread, chocolate, etc, iii) an outer piece of timber sawn from a log, but many don't see the value in definitions. Definitions can end up circular and change with time. — RussellA

Is the first definition, i), your concept of slab (i.e. the concept you claimed ownership of when you asked: "How can you know my concept of Slab?"? If so, then it is the same concept as mine (in this context). This shouldn't come as a surprise.

If concepts didn't exist in the mind, but only in a community, such a community would be a community of zombies, none having a private concept or private sensation.

Cavell in The Later Wittgenstein makes the point that Wittgenstein never denied that we have private thoughts and feelings

Other philosophers, I believe, are under the impression that Wittgenstein denies that we can know what we think and feel, and even that we can know ourselves. This extraordinary idea comes, no doubt, from such remarks of Wittgenstein's as: "I can know what 70 * MUST WE MEAN WHAT WE SAY? someone else is thinking, not what I am thinking" (II, p. 222); "It cannot be said of me at all (except perhaps as a joke) that I know I am in pain" (§5!46). But the "can" and "cannot" in these remarks are grammatical; they mean "it makes no sense to say these things" (in the way we think it does); it would, therefore, equally make no sense to say of me that I do not know what I am thinking, or that I do not know I am in pain. The implication is not that I cannot know myself, but that knowing oneself-though radically different from the way we know others--is not a matter of cognizing (classically, "intuiting") mental acts and particular sensations.

Having private thoughts and feelings is not the same as having what is called "a private language".

As the analogy of the beetle in PI 293 illustrates, private sensations do drop out of consideration within the language game, not that private sensations drop out of consideration. — RussellA

I don't see what any of this has to do with language, or with your earlier suggestion that we each play our own individual language-games rather than partaking in communal ones, namely:

The meaning of the word "slab" derives from its context in the language game being used by the speaker.

When I say "bring me the slab", my concept of "slab" is part of from my language game. When you say "bring me the slab", your concept of "slab" is part of your language game. — RussellA

When I say "bring me the slab", my concept of "slab" is part of from my language game. When you say "bring me the slab", your concept of "slab" is part of your language game. — RussellA

Typically, we don't each play our own individual language-games. It isn't that I have my own concept of slab and you have yours. You either learn to use the word/concept "slab" like others do or else you haven't learned the concept. We both speak English, right? You wouldn't get very far in the builder's language-game if you repeatedly fetched a hammer in response to the command "Slab!".

You are talking about us each having our own private language. Wittgenstein took issue with that idea.

What textual evidence in the PI is there that the PI is not taking the position of Linguistic Idealism?

Linguistic Idealism is the position that language is the ultimate reality. GEM Anscombe in her paper The Question of Linguistic Idealism considered the question whether Wittgenstein was a linguistic idealist.

For the PI , the meaning of a word is its use in language. Within language, a word can be used to describe the appearance of an object, give an order, obey an order, etc as set out in PI 23. But all these things happen within the world of language, not in a world outside language. — RussellA

I think there is abundant evidence in PI that Wittgenstein situates language use within the world among a community of speakers, and so there is definitely "a world outside language". For example, he refers to language use as "part of an activity". Again, at PI 23 (my bolding):

The word “language-game” is used here to emphasize the fact that the speaking of language is part of an activity, or of a form of life. — PI 23

Wittgenstein compares language use to games very deliberately. Games are played in the world (outside our minds), usually with other people, and they often have a set of rules guiding the actions of the players. Once again, they are activities:

66. Consider, for example, the activities that we call “games”. I mean board-games, card-games, ball-games, athletic games, and so on... — PI 66

Wittgenstein is at pains to get us (philosophers) out of our own heads and very much into the "world outside language" (my bolding):

The sense in which philosophy of logic speaks of sentences and words is no different from that in which we speak of them in ordinary life when we say, for example, “What is written here is a Chinese sentence”, or “No, that only looks like writing; it’s actually just ornamental”, and so on. We’re talking about the spatial and temporal phenomenon of language, not about some non-spatial, atemporal non-entity. — PI 108 - boxed section

He also situates philosophical problems or contradictions within the community of speakers, referring to their "status in civic life":

The civic status of a contradiction, or its status in civic life — that is the philosophical problem. — PI 125

Wittgenstein also emphasises that language is something we learn; something that we are taught by others how to use. He speaks of how we learn the names of sensations from others (PI 244). He speaks of a teacher and a pupil and makes references to, e.g., learning language, learning to play chess, learning to calculate, learning rules, learning how to go on, etc.

Not to mention that the majority of the work is focused on trying to break the misconception that meaning is something subjective or mentally determined, and trying to get us to see that the grammar of our language is based in a community of speakers and our publicly observable behaviours (in the world). That's the point of the private language argument.

241. “So you are saying that human agreement decides what is true and what is false?” — What is true or false is what human beings say; and it is in their language that human beings agree. This is agreement not in opinions, but rather in form of life. — PI 241

Form of life is the wider activity surrounding language use; the passing of slabs on command, the smile that accompanies a greeting, the gathering of friends and family to witness a couple say "I do", the facial expression suitable for a question or a sympathetic word. In short, our human life on Earth in which language is embedded.

We only know the "unicorn" by description, not acquaintance. Apart from a few people who have directly seen the fossil of a Tyrannosaurus Rex, most people only know about dinosaurs by description, not acquaintance — RussellA

Technically, you should say that most people only know about dinosaur fossils by description, not by acquaintance. I don't believe anyone knows about dinosaurs by acquaintance; not the extinct ones anyway. You claimed earlier that if a word did not refer to an object then the word would not exist. That's clearly not true in the case of (extinct) dinosaurs.

Totally agree. I have been trying to get across the idea for weeks that Wittgenstein's theory that meaning is use in language is circular, as I wrote before: — RussellA

I know you have, but you're mistaken. As I mentioned, Wittgenstein cites examples of different uses of language at PI 23. He is not saying "the use of a word is meaning is use", as you seem to think. He offers some examples of the different types of uses of language. To quote one of these several examples, a word or sentence could be used for "Requesting, thanking, cursing, greeting," to name just a few. These alternative uses of language alone falsify the assertion that language is only used to refer to objects.