The atom used to be the stand-in for 'simple' in that it was 'indivisible', not composed of parts. Regrettably, nature did not oblige, as it turns out atoms are far from simple. — Wayfarer

:up:

Are you not familiar with the depth perception due to parallax? Is there really any such things as a two-dimensional image? Even lines and the paper they are on are really three-dimensional. — Janus

Parallax can be used to determine the distance of an object, as nearby objects show a larger parallax than farther objects, but it doesn't allow us to see the back of a three-dimensional object.

What is parallax doing? Is it giving us information about the distance of an object from us or is it giving us information about the three-dimensional space that the object occupies?

Sorry, but I don't think there is such a thing as a "thought of a cup." — Ciceronianus

In order to write the sentence "Sorry, but I don't think there is such a thing as a "thought of a cup."" you must have had the thought of a cup.

I am still saying that, just the red patch colour visual perception would be more meaningful than the scientific instrument reading of the red patch emission of 700nm to the most ordinary people — Corvus

Yes, as you say, most ordinary people can understand Naïve Realism.

Even if the supposed Atom images are seen in the microscope, how do you know they are atoms? — Corvus

Yes, even the atom is a representation of something deeper, which is why my position is that of Indirect Realism. As the IEP article on Objects of Perception writes:
The indirect realist agrees that the coffee cup exists independently of me. However, through perception I do not directly engage with this cup; there is a perceptual intermediary that comes between it and me. Ordinarily I see myself via an image in a mirror, or a football match via an image on the TV screen. The indirect realist claim is that all perception is mediated in something like this way. When looking at an everyday object it is not that object that we directly see, but rather, a perceptual intermediary. This intermediary has been given various names, depending on the particular version of indirect realism in question, including “sense datum, ” “sensum,” “idea,” “sensibilium,” “percept” and “appearance.”

I think that what you call Indirect and Direct Realism reflect a pseudo-problem.........................We see a cup made up of atoms, then. Does that make it any less a cup? — Ciceronianus

As Bertrand Russell in The Problems of Philosophy wrote:"But the notion of being 'in' the mind is ambiguous. We speak of bearing a person in mind, not meaning that the person is in our minds, but that a thought of him is in our minds."

In the expression "we see a cup made up of atoms", the underlying problem is the inherent ambiguities within language. It is not a cup that is the object of consciousness, but rather the thought of a cup that is the object of consciousness. There is no cup in our minds, only the thought of a cup.

There is the act of apprehending a cup in a mind-independent world, but this does not mean that there is a cup in a mind-independent world that is being apprehended.

The question as to whether cups exist or not in a mind-independent world is certainly not a pseudo-problem, as it is crucial to our understanding of the nature of reality.

Strictly speaking, wouldn't it be the instruments (invented and calibrated for their own convenience by humans) which tells the wave length of 700nm emission, rather than science? — Corvus

Difficult to escape from a metaphorical use of language. I am using "science" is a figure of speech that includes the instruments of science.

See, could be, not necessarily or for definite. "could be" sounds a negativity in disguise here — Corvus

Wholes have parts, which in turn have parts, which in turn have parts. But sooner or later one assumes there are parts which have no parts, ie, simples. In contemporary mereology, a simple is any thing that has no proper parts. Sometimes the term "atom" is used, although in recent years the term "simple" has become the standard.(Wikipedia - Simple (philosophy)). It may be that fundamental forces and fundamental particles are simples, but science may discover it to be something else altogether.

Not sure, if science has to be consulted for that assurance. Wouldn't common sense or intuition do? And we don't really care about a set of atoms unless for some peculiar reason. To me atoms are just an abstract concept, that doesn't exist in the real world. Or if it did, it has nothing to do with me, or daily life. — Corvus

Science can tell us things that intuition cannot, such as when we perceive a red object, such as a post-box, the object may have emitted a wavelength of 700nm.

I only mentioned science to try to distinguish between a subjective mind and objective world. Coming from a position of mereological nihilism, my belief is that the cup as appearance does exist in the mind but the cup as thing-in-itself doesn't exist in a world independent of any mind.

In a sense, "atoms" are a convenient figure of speech for mereological simples, whatever they may be, but could be fundamental forces and fundamental particles existing in time and space.

So you might say Kant says that there are two cups?  That is absurd...............Logic is the engine of how rationality, intuition, perception, understanding and judgement works. — Corvus

When I look at a cup, in my mind is a two-dimensional appearance, but science tells me that what I am actually looking at is a set of atoms in a three-dimensional space.

In one sense there are two cups, the cup as it exists as a two-dimensional appearance in my mind and the cup as it exists as a three-dimensional set of atoms, both of which are very different. But in another sense, there is only one cup, the cup as a thing-in-itself in the world as the cause of the cup as an appearance in my mind.

What is crucial is a logical connection between the thing-in-itself in the world and the appearance in the mind, and this connection is what Kant understands as the Category of Cause. Kant's Category of Cause is what ensures that there is only one cup, even though the cup may exist in different forms, first as a set of atoms in three dimensional space in the world and then as a two-dimensional appearance in the mind.

Kant's Category of Cause is crucial to the viability of his Transcendental Idealism.

But when we talk about the cup, the pot, the cupboard, we are not talking about our private perception-of-cupboard, or the pot in itself, or one's mental image of a cupboard, but about the cup, cupboard and pot. — Banno

Both the Indirect and Direct Realist see a red cup, take it out of the cupboard, boil the kettle and make themselves a cup of tea.

However, the Indirect Realist takes into account the fact that science has told us that the cup we perceive as red is actually emitting a wavelength of 700nm. This causes them to question whether what they perceive as a red object is actually red. They then begin to question the relation between the appearance of an object and the object as a thing-in-itself.

However, Direct Realism turns a blind eye to scientific discoveries and continues to insist that when we perceive an object to be red it is actually red.

The Direct Realist refuses to address Kant's concerns about the ontological nature of objects in the world, and limit themselves to Wittgensteinian Linguistic Idealism, whereby language games are founded on hinge propositions, such as "I see a red cup". Such hinge propositions remain true regardless of the ontological reality of the world .

Part of the problem is that whilst the Direct Realist wilfully ignores Kantian concerns with the ontological nature of reality in favour of Linguistic Idealism, the Indirect Realist is willing to take into account not only Kant's ontological concerns but also Wittgenstein's Linguistic Idealism, acknowledging that language is needed to talk about the non-linguistic.

I think this is a question only if we assume that we or our "minds" are separate from (outside) of the world. That's not an assumption I think we should make. We are a part of the world, not outside it. The chair is a part of the world as well. The chair isn't part of us. We aren't a part of the chair. We are a part of the world. The world isn't inside us, as we're a part of it. We have certain characteristics as human beings. We interact with the world as human beings do. We see as human beings do, hear as they do, etc. There's nothing surprising about this, and it doesn't establish in itself that we can't know what it is we encounter or interact with. — Ciceronianus

As an Indirect Realist, I agree with your paragraph, as would a Direct Realist, but this does not address the topic of the thread "A Case for Transcendental Idealism". In other words, "A case for Indirect Realism".

Both an Indirect and Direct Realist would agree that both us and the chair are part of the same world, but they would disagree as to the nature of this world

You inferred before your support for Direct Realism as opposed to Indirect Realism
To Kant, though, is reserved the claim that there is, e.g., some thing which I call a chair and sit on all the time, which although it is in all respects a chair as I understand a chair to be and I use it as such, cannot be known.

I am persuaded by Bertrand Russell's support for Indirect Realism as he sets it out in the beginning of his book "The Problems of Philosophy"

My question is, how does the Direct Realist answer Indirect Realism's objections to Direct Realism?

. And, if we can't know what "things in themselves" really are, what possible difference would it make? — Ciceronianus

This morning, when making a cup of tea, it didn't pass my mind whether the cup was an appearance or a thing-in-itself. But this is a Philosophy Forum, where such considerations are of interest.

Neither you nor I have minds lurking within us, separate from the rest of us. We think as part of our interaction with the rest of the world. Language as well is a result of that interaction, as are the definitions arrived at in the use of language. — Ciceronianus

I believe in Enactivism, the philosophy of mind that emphasizes the interactions between mind, body, and the environment (Wikipedia - Enactivism). I agree with Dewey's cultural naturalism, where philosophy should be seen as an activity undertaken by inter-dependent organisms-in-environments (SEP - John Dewey)

We agree that we as humans interact with the rest of the world, but the central question remains unanswered, where exactly is this world that we interact with?

For example, this question was never addressed by Wittgenstein in Philosophical Investigations.

There is certainly a world that we interact with, but is this the world of the Direct or Indirect Realist.

Is it the case as the Direct Realist believes that the world as we perceive it exists independently of our perception of it but exactly as we perceive it, or is it the case as the Indirect Realist believes that the world as we perceive it only exists as a representation of something that exists outside our perception of it.

Yes, there is a chair in the world that we interact with, but does this world of chairs exist in our minds or outside our minds?

It's strange to think of the phenomena/noumena distiction in relation to one's own body parts. Is there a nose-in-itself vs the phenomena of it? — Gregory

After an amputation, some people experience pain in the part of the limb that’s no longer there. This sensation is phantom limb pain. The pain is real. The phantom part refers to the location of the pain: the missing limb or part of the limb (such as fingers or toes) (Leveland Clinic - Phantom Limb Pain)

Moore famously put the point into dramatic relief with his 1939 essay Proof of an External World, in which he gave a common sense argument against scepticism by raising his right hand and saying "here is one hand," and then raising his left and saying "and here is another" (Wikipedia - Here is one hand)

Who is to say that Moore hadn't had both his hands amputated after an accident, and only imagined his hands were still there?

Here's a small chance, a chink in the wall of Kant*. What if talk of the cup perceived and of the cup's ding an sich are talk of the very same thing? Perhaps there is just one cup? — Banno

Given your position as a Direct Realist, and assuming Direct Realism, when we look at an object and perceive the colour red, science may tell us that the object has emitted a wavelength of 700nm

How can the Direct Realist justify that a perception of red in the mind and a wavelength of 700nm in the world are the very same thing?

To my understanding Kant became a dualist because of the arguments by Hume that physical "laws" cant be known — Gregory

Yes, empirical knowledge is insufficient by itself for understanding. In today's terms, Innatism is also needed.

Also i'd like to say that if a positivist says he is not an idealist, why won't he just call himself a materialist then? — Gregory

If Positivism is the philosophical theory that holds that the only true knowledge is scientific knowledge, based on data and experience, then Kant was not a Positivist.

I would say there is no "thing" called a concept floating about in a thing called a "mind." — Ciceronianus

We both have the concept of a "thing" in our minds. If our concept of "thing" doesn't exist in our minds, then where does it exist?

Concepts and minds all exist in the same world as chairs — Ciceronianus

It seems that your position is that of Idealism.

First, you have inferred that the chair can be known:
To Kant, though, is reserved the claim that there is, e.g., some thing which I call a chair and sit on all the time, which although it is in all respects a chair as I understand a chair to be and I use it as such, cannot be known

Also, you have said that minds exist in the same world as chairs:
Concepts and minds all exist in the same world as chairs.

Kant was a philosophical Realist. From the Wikipedia article Philosophical Realism
Philosophical realism – usually not treated as a position of its own but as a stance towards other subject matters – is the view that a certain kind of thing (ranging widely from abstract objects like numbers to moral statements to the physical world itself) has mind-independent existence, i.e. that it exists even in the absence of any mind perceiving it or that its existence is not just a mere appearance in the eye of the beholder

From the Wikipedia article on Idealism
Idealism in philosophy, also known as philosophical idealism or metaphysical idealism, is the set of metaphysical perspectives asserting that, most fundamentally, reality is equivalent to mind, spirit, or consciousness; that reality is entirely a mental construct; or that ideas are the highest form of reality or have the greatest claim to being considered "real"

To Kant, though, is reserved the claim that there is, e.g., some thing which I call a chair and sit on all the time, which although it is in all respects a chair as I understand a chair to be and I use it as such, cannot be known. — Ciceronianus

We all have the concept of a chair in our minds, and we only know what a chair is because in our minds is the concept of a chair.

It is true that you can point to something in the world that corresponds with your concept of a chair, but you cannot point to something in the world that is your concept of a chair. IE, concepts exist in the mind, not in a world outside the mind.

Kant is not saying that we have no concept of chair in our minds, but he is saying, as would an Indirect Realist, that concepts only exist in the mind and not in a world outside the mind.

@Bob Ross @J

For every effect there is a cause
We know that one of Kant's Categories was the Category of Cause. There are many passages in the Fourth Paralogism, where the thing-in-itself is declared to be the cause of appearances. For Kant, Knowledge is both formal, a priori through the Category of Cause, and material, a posteriori given empirically through sensations.

I agree with @J who wrote "surely Kant didn't "deny that things exist outside the mind" -- he merely sought to discover the limits of our knowledge of them".

Common sense tells us for every effect there has been a prior cause. EG, a snooker ball on a snooker table doesn't spontaneously move until hit by either a snooker cue or another snooker ball.

Reason tells us that the same effect may have different causes, eg, a broken window could have been caused by either a ball or a bird. Reason also tells us that two different effects have two different causes, eg, perceiving the colour red may be caused by an object emitting a wavelength of 700nm and perceiving the colour green may be caused by an object emitting a wavelength of 530nm.

The perception of the colour of objects in the world
Science tells us if an object emits a wavelength between 620nm and 750nm, all things being equal, we perceive the colour red, and if an object emits a wavelength of between 495nm and 570nm, all things being equal, we perceive the colour green.

For the Indirect Realist, the effect, eg, the perception of the colour red, can have a different kind of existence to its cause, eg, an object emitting a wavelength of 700nm. For the Direct Realist, the effect, eg, the perception of the colour red, has the same kind of existence as its cause, eg, an object emitting the colour red.

For the Indirect Realist, in the absence of any observer, an object emits a wavelength of 700nm. For the Direct Realist, in the absence of any observer, an object emits the colour red.

Does colour exist outside a person's perception of it
When we look at one object emitting a wavelength of 640nm and another object emitting a wavelength of 730nm, all things being equal, we perceive that they are similar in some way, ie, both red. But when we look at one object emitting a wavelength of 640nm and another object emitting a wavelength of 530nm, we perceive that they are different in some way, ie, one is red and the other is green.

The Indirect Realist attributes this to how the wavelengths are perceived in the mind.

Question to Direct Realists
My question to the Direct Realist is, in the absence of anyone perceiving such objects, whilst agreeing that the wavelengths of 640nm and 530nm are different, in what way is it possible for the wavelengths of 640nm and 730nm to be similar?

Whatever the things are in-themselves is entirely impossible to know. — Bob Ross

This is the position of the Indirect Realist. The Direct Realist would say that things-in-themselves are possible to know, as the world we see around us is the real world itself, where things in the world are perceived immediately or directly rather than inferred on the basis of perceptual evidence.

We can talk about things-in-themselves even if we don't know what they are

There are many passages in the Fourth Paralogism of Kant's Critique of Pure Reason where the thing-in-itself is declared to be the cause of appearances.

For example in A199/B244: Now if it is a necessary law of our sensibility, thus a formal condition of all perceptions, that the preceding time necessarily determines the following time (in that I cannot arrive at the following time except by passing through the preceding one), then it is also an indispensable law of the empirical representation of the temporal series that the appearances of the past time determine every existence in the following time, and that these, as occurrences, do not take place except insofar as the former determine their existence in time, i.e., establish it in accordance with a rule. For only in the appearances can we empirically cognize this continuity in the connection of times.

When we perceive the colour red, there is the appearance of the colour red in our sensibilities, which we can reason to have been caused by a particular thing-in-itself. When we perceive the colour green, there is the appearance of the colour green in our sensibilities, which we can reason to have been caused by a different particular thing-in-itself.

It is true that we cannot know the thing-in-itself that has caused our perception of the colour red, but we can reason that it is different to the thing-in-itself that has caused our perception of the colour green.

We may not know what the thing-in-itself that caused our perception of the colour red, but we can reason that it exists, and we can reason that it is a different thing-in-itself to what caused our perception of the colour green. We can name the unknown thing-in-itself that caused our perception of the colour red as R, and and we can name the unknown thing-in-itself that caused our perception of the colour green as G.

The names R and G are not descriptions, as a description of an unknown thing-in-itself would be impossible, but they are, as Wittgenstein says in Philosophical Investigations, replacements for the unknown thing-in-itself. As with the Beetle in the Box, PI 293, this allows us to talk about unknown things-in-themselves.

For the Indirect Realist, thing-in-themselves may be impossible to know, but we can talk about them.

There is experience, therefore something exists. — Bob Ross

As an Indirect Realist, I agree.

As both good philosophy and good science are founded on sound logic, your argument aiming at being logical is as much science as it is philosophy.

Odd, isn't it, that when some folk discover that the chair they are sitting on is composed of atoms, and is overwhelmingly space, they sometimes decide that therefore it's no longer really a chair. — Banno

It depends whether one is an Indirect or Direct Realist

My belief is in Indirect Realism, whereby our ideas of objects existing in a mind-independent world are interpretations of sensory input derived from a mind-independent world that is real. I also believe that Kant and @Bob Ross can be said to be Indirect Realists.

I am sure that your belief is in Direct Realism, whereby objects in a mind-independent world are perceived immediately or directly rather than inferred on the basis of perceptual evidence

Odd, isn't it, that millions of years ago even before there were folks, lakes and seas existed, even though there was no mind present at that time able to judge whether a large stretch of water was a lake or a sea.

Odd, isn't it, that millions of years ago even before there were folks, that the colour red existed, even though there was no mind present at that time able to judge a similarity in the wavelengths of 620nm to 750nm.

Odd, isn't it, that that millions of years ago even before there were folks, there were rocks that could function as either a table or chair, even though there was no mind present at the time able to judge whether the rock functioned as a table or chair.

As lakes, seas, the colour red, rocks, tables and chairs only exist as concepts in the mind and names in language and don't exist in a mind-independent world, they cannot be perceived immediately or directly in a mind-independent world as required by Direct Realism.

Direct Realism is invalid as one cannot perceive something immediately or directly in a mind-independent world if that something doesn't exist in a mind-independent world.

Yes, but not for scientific reasons. — Bob Ross

What non-scientific reasons are there to hold the view of perception that subjects do not experience the external world as it really is, but perceive it through the lens of a conceptual framework.

I am starting to embrace transcendental idealism, — Bob Ross

Am I right in thinking that your position is that of Indirect Realism, as described by the Wikipedia article Direct and Indirect Realism

Indirect realism is broadly equivalent to the scientific view of perception that subjects do not experience the external world as it really is, but perceive it through the lens of a conceptual framework.

When an object changes from existence to non-existence (the book on the table),  the property of the object changes from extension to non-extension. — Corvus

On the desk is a book. One could say that the book exists because the atoms that make it up exist in different locations, for example, atom A and atom B. One could also say that the desk exists because the atoms that make it up exist in different locations, for example, atom C and atom D.

The mind connects atom A and atom B as being part of the object book, and also connects atom C and atom D as being part of the object desk. Therefore, these objects, the book and the desk, exist in the mind.

But outside the mind, what connects atom A to atom B but not to atom C?

If there is nothing outside the mind that preferentially connects atom A to any other particular atom, then objects as we know them don't exist outside the mind.

Outside our minds, atoms exist but not objects (treating the "atom" as a figure of speech for something that does physically exist)

Objects as a concept in the mind don't exist outside the mind, meaning that we can perceive something as existing in the world that in fact doesn't exist in the world.

IE, we perceive something where in fact there is nothing.

You can perceive the essence of the Absolute Nothingness via Husserl's phenomenological method called Bracketing, which is to bracket the distracting details of the perception such as the book, existence, the table ...etc, and just concentrating on the subjective experience of Absolute Nothingness - i.e. {the non-existence} of the book at that moment of your perception. — Corvus

There seems to be a family resemblance between Bracketing and Nominalism.

Wikipedia - Bracketing (Phenomenolgy)
The preliminary step in the philosophical movement of phenomenology is describing an act of suspending judgment about the natural world to instead focus on analysis of experience.

Wikipedia - Nominalism
In metaphysics, nominalism is the view that universals and abstract objects do not actually exist other than being merely names or labels.

But the universe will contain no objects, — universeness

As a Nominalist, rather than a Platonic Realist, that's my present understanding of the universe today, in that there are no such things as objects in the world outside the mind. What we perceive as a book only exists in the mind. What exists in the world outside the mind are elementary particles and elementary forces existing in time and space.

Let's ignore language or communicating with others. Do you think it's possible for an existent to perceive 'nothing?' internally? — universeness

Or if there was a book on the desk this morning. You saw it there lying on the desk. But when you saw the desk when you returned home from the town after few hours of errands, it has gone. There is nothing on the desk....................At that moment, in your mind, you have the feeling or perception of "absolute nothingness" about the existence of the book. — Corvus

A book at one moment in time can only exist in one location. For example, in the morning, it exists on the desk. But in order for it to exist on the desk, it cannot exist anywhere other than on the desk, for example, under the desk or ten metres to the right of the desk.

As I perceive the book existing on the desk, at the same time, I also perceive the book as not existing under the desk.

Generalising, to be able to perceive something somewhere, I must be able to perceive nothing somewhere else.

What are the counterpart words for "car", "book" and "Coca Cola"? — Corvus

For Derrida, the meaning of a word derives from how it contrasts with other related words.

In this instance "car" contrasts with bicycle, train and pedestrian. "Book" contrasts with film, ebook and radio. "Coca Cola" contrasts with orange juice, Pepsi Cola and water.

From the Britannica article on Jacques Derrida
Building on theories of the Swiss linguist Ferdinand de Saussure, Derrida coined the term différance, meaning both a difference and an act of deferring, to characterize the way in which linguistic meaning is created rather than given. For Derrida as for Saussure, the meaning of a word is a function of the distinctive contrasts it displays with other, related meanings. Because each word depends for its meaning on the meanings of other words, it follows that the meaning of a word is never fully “present” to us, as it would be if meanings were the same as ideas or intentions; instead it is endlessly “deferred” in an infinitely long chain of meanings. Derrida expresses this idea by saying that meaning is created by the “play” of differences between words—a play that is “limitless,” “infinite,” and “indefinite.”

There is a table in front of me. On the left there is not a unicorn and on the right there is not something.

As there is no logical necessity that a word such as "unicorn" refers to a thing that exists outside of language, there is also no logical necessity that a word such as "something" also refers to a thing that exists outside of language.

Regarding the question "Why is there something rather than nothing?", as we know that "something" and "nothing" exist in language, but cannot know whether something and nothing exist outside of language, our reply can only be in terms of language and not in terms of what may or may not exist outside language.

Why is there something rather than nothing? — Ø implies everything

"Something" and "nothing" are words. As only words that are part of a pair (more or less) have any use in language - hot/cold, up/down, sense/nonsense, good/bad - the fact that a word exists in language assumes it has a counterpart - something/nothing. If a word had no counterpart, it wouldn't be part of language in the first place.

IE, the reason there is "something" is that it has the counterpart "nothing". In other words, as Derrida might have said "vive la différence".

Could you then please explain how the brain generates the mind? Please explain in detail how can the mental can emerge from the physical. — Corvus

If I could explain that, then I would be world famous.

I feel that self is a special perception (apperception of Kant's term), that looks inwards into the mind, whereas all the standard perceptions look outwards into the external world. — Corvus

But dragging the brain into the Epistemic discussion has been always the same - nothing much in essence and nothing really fruitful to add into the conclusion apart from just muddling up the points. — Corvus

The self is a special form of perception which looks inward into your mind, being conscious of all the mental events taking place in your mind. The self perception would be invisible or unknowable by all your outward perceptions. It can only be intuited via mediation or self introspection. In that sense, it is transcendental in nature. — Corvus

If I correctly understand your position:
1) You distinguish between standard perceptions looking outwards into the external world, and special perceptions that look inwards into the mind
2) Within the mind are both inward and outward looking perceptions
3) The mind is somehow generated by the brain
4) The self is known by inward perception, and the self knows both inward and outward perceptions.

As both inward and outward perceptions are part of the self, then one would expect that the outward perceptions would know the inward perceptions, as they are both part of the same self. Yet you say that the outward perceptions don't know the inward perceptions.

Kant's apperception is not a special kind of perception, but is a unity of apperception that applies to all perceptions, whether inwards or outward looking.

A common epistemological question is the relationship between the mind and brain, the relationship between the mental and the physical, in asking how can the mental emerge from the physical.

If the physical brain is excluded from the epistemological discussion, then Realism is also being excluded from the epistemological discussion, as, in Realism, a material substance such as the brain does exist outside the mind.

The discussion then reduces to that of Idealism, in that there is no material substance outside the mind, no physical brain outside the mind.

When you say "all the standard perceptions look outwards into the external world.", if epistemology has been reduced to Idealism, then the external world would exist in the mind, meaning that all perceptions look inwards into the mind. In that event, any distinction between inward and outward looking perceptions disappears, such that the self does then become available to Kant's unity of apperception.

However, Realism and the physical brain cannot be excluded from the epistemological discussion.

So it is not very fruitful to bring the brain into the epistemological discussion yet until the sciences made some real progress on explaining the hard problems. — Corvus

As you wrote: The mind has two sides, i.e. the inside (self) and outside (perceptions for the external world).

The relationship between the mind and body, and how the mind can emerge from a physical brain, is part of the epistemological debate. To say that the physical brain cannot be brought into the epistemological debate is to take the side of Idealism, thereby excluding the possibility of Realism.

The Direct Realist would say that our perceptions of the external world are directly of the external world, rather than inferred on the basis of perceptual evidence.

The Indirect Realist would say that our perceptions of the external world are not directly of an external world, but are directly of an internal representation in our mind of an external world. Such a representation may or may not directly correspond with the external world that is causing such representations

The Berkelian Idealist would say that the external world exists in the mind of God.

The Solipsist Idealist would say that the external world only exists in the mind of the perceiver.

The Realist would say that the external world exists independently of the mind. They are not Immaterialists, in that there is such as thing as material substance. They can be either a Monist, where there is only one fundamental substance, the mind/body, or a Dualist, where there are two fundamental substances, the mind and the body.

The idealist would say that there is no external world existing independently of any mind, and are Immaterialists in that there is no such thing as material substance

Personally, I am an Indirect Realist, Neutral Monist and Nominalist.

I feel that self is a special perception (apperception of Kant's term), that looks inwards into the mind, whereas all the standard perceptions look outwards into the external world. — Corvus

Light enters the eye from outside, is processed in the brain, and "I" perceive the colour red.

When "I" perceive the colour red, where is what I am perceiving exist.

I am indirectly perceiving light that exists outside in the world

But am I directly perceiving light that exists outside in the world, or am I directly perceiving a process happening inside my brain?

This idea is absurd in that, if all these ideas/concepts/mental objects are the self, then you end up having 1000s of different selfs. — Corvus

You used Kant's concept of Apperception when you wrote:
Idea or concept of self is a type of intuition or Apperception (in Kant's terms), that looks into the Mind.

The Wikipedia article on Transcendental apperception wrote:
Transcendental apperception is the uniting and building of coherent consciousness out of different elementary inner experiences (differing in both time and topic, but all belonging to self-consciousness).
1) All experience is the succession of a variety of contents (an idea taken from David Hume).
2) To be experienced at all, the successive data must be combined or held together in a unity for consciousness.
3) Unity of experience therefore implies a unity of self.
4) The unity of self is as much an object of experience as anything is.
5) Therefore, experience both of the self and its objects rests on acts of synthesis that, because they are the conditions of any experience, are not themselves experienced.
6) These prior syntheses are made possible by the categories. Categories allow us to synthesize the self and the objects.

It seems to me that the whole point of Kant's concept of the unity of apperception is the possibility of the unity in the mind of different experiences.

Is your understanding of Kant's apperception different?

So, the purpose of this thread is to explore those ideas/concepts/mental objects that might be required for the formation and sustenance of the self, assuming the self is contingent on previously formed concepts; — Daniel

At one moment in time, if I am conscious, I must be conscious of something, there must be an intentionality about my consciousness. For example, at one moment in time, I can be conscious of the concept circular shape, the concept of pain, the concept of the colour red and the concept of an acrid smell.

As regards my consciousnesses of the concept circular shape, at the same time not only am I conscious of a simple concept, a circular shape, but also I am conscious of a set of composite concepts, an arc at the top, an arc to the right, an arc at the bottom and an arc to the left.

As for my consciousness of a single concept, it may be the same for my consciousness of a set of concepts

For a single concept, at the same time I am conscious not only of a simple whole but also a set of composite parts. Similarly, for a set of concepts. At the same time I can be conscious of a simple whole, ie, a self, as well as a set of composite parts, ie, the individual concepts making up the whole.

From Kant, Hegel, and the Transcendental Unity of Apperception, by Kourosh Alizadeh, Hegel takes the basic Kantian idea of the original unity of apperception.

It may be that this unity of apperception becomes a single conscious self out of the many different concepts that we are aware of at any one moment in time.

IE, rather than certain ideas/concepts/mental objects pre-existing the self, these ideas/concepts/mental objects are the self.

I don't think this view is supported by the text. The complaints coming from Wittgenstein regarding the excesses of science as culture is expressed as an overindulgence in generalizations. No limits upon what science could actually produce were promulgated therein. — Paine

The Wikipedia article is about the Investigations. In the Investigations, Wittgenstein writes that whilst logic lies at the bottom of science, this is not the case for language and thought. IE, science and language/thought are different.

Where in the Investigations does he write about the excesses of science?

What I'm getting at, is I believe you can create a formal system that, in its axioms, defines the "laws of choice" that act on its fundamental objects, agents. These laws would of course be unchanging, unbreakable, and, in some sense, determine the proceedings of phenomena in this world. If this is indeed a possible world, what I have described is a deterministic world with the concept of free will embedded in the system, at the axiomatic level. — Jerry

I can imagine a world where there was an event yet nothing preceded it, ie, a deterministic world of free will. I can imagine a world where elephants were orange, could run at 100 km/hour and every afternoon would stop for a coffee at Pret A Manger.

Because I can imagine such a world, why would it follow that such a world is possible?

The complexity of 'philosophical' questions, that perhaps could be "shooed out of the bottle" is not the same as recognizing the complexity of the 'ordinary.' — Paine

As regards the Investigations, I read it more as an attack on "bad" philosophy than scientism.

I see the key to the Investigations as PI 43: the meaning of a word is its use in the language, and this is what the Investigations considers.

Scientism is a pejorative word. Scientism is an overconfidence in the power of science, trying to explain all experiences in mechanical terms rather than accepting them as part of the inexplicable wonder and mystery of life. I am sure that the majority of scientists are also opposed to scientism. Though if anti-scientism was taken too far, beliefs such as astrology, witchcraft and aliens in Mexico would be excluded from scientific investigation and blindly accepted as fact by the un-philosophical.

When someone says "I know your pain", Wittgenstein is not attacking the scientist for wanting to carry out experiments on the brains of the speaker and listener, but rather is attacking the "bad" philosopher for questioning such an expression in the first place. A "bad" philosopher being someone who attempts to discoverer something using language that exists outside of language, and is therefore logically outside of the ability of language to discover.

For Wittgenstein the meaning of "I know your pain" in our common sense and ordinary language is given within the context of the language game being used, and cannot be explained other than being part of its language game. In science it will be an axiom of a theory. In On Certainty it will be a hinge proposition, As he wrote in OC 501: 'Am I not getting closer and closer to saying that in the end logic cannot be described? You must look at the practice of language, then you will see it' . In the Investigations it will be what founds language. As he writes in PI 217 If I have exhausted the justifications I have reached bedrock, and my spade is turned. Then I am inclined to say: "This is simply what I do.". These are not concessions to the scepticism of the "bad" philosopher, but are acknowledgements that most of our actions are normative.

In my terms, words such as "know" are figures of speech used in a non-literal sense. They can only be explained by understanding the wider context of the language game existing within a particular form of life. As "the language game" is a figure of speech, the "form of life" is a figure of speech, then also "know" is a figure of speech.

From what I have gathered, not only was Aristotle an advocate for using "theory" in way that Wittgenstein questioned but Aristotle considered himself able to distinguish the inquiries by kind. That endeavor is far removed from the criticism of 'scientism' put forward by Wittgenstein. And it is the matter of 'science' distinguished from philosophy that I directed my comments toward — Paine

The Investigations is not the work of a sceptic, but that of someone confidently expounding the theory that the meaning of a word is its use in the language. An approach more that of common sense than the metaphysical.

As Wikipedia in its article Philophical Investigations wrote:
The Investigations deal largely with the difficulties of language and meaning. Wittgenstein viewed the tools of language as being fundamentally simple, and he believed that philosophers had obscured this simplicity by misusing language and by asking meaningless questions. He attempted in the Investigations to make things clear: "Der Fliege den Ausweg aus dem Fliegenglas zeigen"—to show the fly the way out of the fly bottle.

I read Wittgenstein as being troubled in the vernacular of Plato more than confident in the way of Aristotle...................I don't understand how "common sense" is a given in the text. Many of the examples treat what is given as commonly understood as odd when looked at as general reference. — Paine

Wittgenstein is confident in the Investigations, in the way of Aristotle, that the role of the philosopher is to bring clarity to the ordinary use of language, rather than investigating the nature of reality.

As language is only capable of doing certain things, it is inevitable that outside what language can do there will be mysteries.
PI 38 For philosophical problems arise when language goes on holiday.

For Wittgenstein, the role of philosophy is to be able to think clearly and clear up confusions about words such as know, believe, desire, intend, think as they are ordinarily used, not about the nature of reality, not about the validity of Realism or Anti realism .
PI 126 Philosophy simply puts everything before us, and neither explains nor deduces anything.—Since everything lies open to view there is nothing to explain. For what is hidden, for example, is of no interest to us.

For Wittgenstein, the philosopher starts with language as it is ordinarily used, where the meaning of a word is its agreed use, and where language is grounded in common sense.
PI 122 A main source of our failure to understand is that we do not command a clear view of the use of our words

It is true that he does give many examples, such as imaging people around me as automata, that are much discussed within philosophy, but is making the point that, as there are limits to what language is capable of, such discussions, being outside what language is capable of, become meaningless.
PI 420 But can't I imagine that the people around me are automata, lack consciousness, even though they behave in the same way as usual?................But just try to keep hold of this idea in the midst of your ordinary intercourse with others, in the street, say!............And you will either find these words becoming quite meaningless; or you will produce in yourself some kind of uncanny feeling, or something of the sort.

For Wittgenstein, problems arise when the philosopher tries to use language beyond what it is inherently capable of, and beyond the common sense use of language as it is used in the everyday.
PI 133 For the clarity that we are aiming at is indeed complete clarity. But this simply means that the philosophical problems should completely disappear.

Does the ordinary user make this claim about aliens and Trump? There is nothing ordinary about that claim. — Fooloso4

It is the ordinary user of the language rather than the philosopher who puts demands on the words they use, for example, making extraordinary claims about aliens and Trump.

Assuming that we are both ordinary users of the language, you did write that "The problem is that the Trumpsters do not want to preserve democracy.", and many would say that this is also an extraordinary claim about democracy and Trump.

IE, it is the ordinary user rather than the philosopher who puts demands on our use of words such as "know".