I don't think he would accept or reject it. He would say we have no way of definitively answering the question. — frank

A believer in Transcendental Apriosis is a Rationalist who proposes that a solitary thinker using pure reason can understand reality.

Wittgenstein's hinge propositions are part of the language game. The language game is part of a form of life. A form of life is what society does in the world.

The Rationalist using pure reason could never know a form of life where someone asks of another "bring me a slab"

Surely, for this reason, Wittgenstein would reject Transcendental Apriorism?

The term "noesis" has been revived by modern thinkers in a number of ways that are quite different from the term's historical meaning, so perhaps that is a source of confusion here..................................I think it's fairly obvious that Wittgenstein doesn't think such a faculty exists — Count Timothy von Icarus

Not only Wittgenstein, but many modern philosophers don't accept the concept of Transcendental Aprioris, of which noesis is a part.

As described by MR Burgess, noesis is a part of Transcendental Apriorism, a Rationalist doctrine originated by Plato. It proposes that a solitary thinker using pure reason can unlock the deepest mysteries of external reality. This is an epistemological problem, the notion that the pure human intellect, purged of sensory contamination, can transcend the limits of experience to reach a Platonic understanding of reality.

Plato called the highest form of knowing "noesis". In modern terms, insight. Noesis is the highest form of human thought, and allows the mind direct apprehension of universal truths. Noesis is in opposition to dianoia, discursive thinking and analytical explanations. For example, explaining how a car engine works.

Many modern philosophers from Kant onwards, including the Logical Positivists and AJ Ayer, reject Transcendental Apriorism. However, Burgess argues that such rejection has been too cursory, and the theory should begin to be taken more seriously.

Defenders of Transcendental Apriorism will have a difficult task in justifying how a solitary thinker only having access to their sensations and just using pure reason will be able to unlock the mysteries of the reality of an external world. As WH Walsh wrote in Reason and Experience "There seems to be little difficulty in showing that metaphysics in this sense is an impossible undertaking".

(to be continued)

"I think therefore I am" is not an affirmation, but inference. He was still doubting his own existence, and the possibility that he thinks. — Corvus

It is "Cogito, Ergo Sum" or “I think, therefore I am.” There is a comma between "I think" and "therefore I am"

I agree that the sentences "I think that ghosts exists" and "I think that I am" imply doubt that "ghosts exist" and "I am".

But no doubt is implied in "I think, therefore I am", as these are independent thoughts.

At the start of the Second Meditation, Descartes wrote the following:

“I have convinced myself that there is absolutely nothing in the world, no sky, no earth, no minds, no bodies. Does it now follow that I too do not exist? No: if I convinced myself of something then I certainly existed. But there is a deceiver of supreme power and cunning who is deliberately and constantly deceiving me.
In that case I too undoubtedly exist, if he is deceiving me; and let him deceive me as much as he can, he will never bring it about that I am nothing so long as I think that I am something. So after considering everything very thoroughly, I must finally conclude that this proposition, I am, I exist, is necessarily true whenever it is put forward by me or conceived in my mind.”(Cottingham et al, 1984)

I have the thought that nothing exists in the external world
Does it follow that I don't exist?
No, because if I have a thought then I must exist.

Perhaps hinge and ordinary propositions are not two sharply distinguishable entities , but more or less fluid, more or less hardened aspects of the same practical discursive processes. — Joshs

I would agree with that. Sometimes an atheist finds god and sometimes a religious person loses their faith.

Both could come from a discursive engagement with the world. But as different people engage in different ways with the world, some propositions may be hardened into ordinary propositions and some hardened into hinge propositions

For example, it could be accident of birth, in that 93% of the population of Saudis Arabia is Muslim and 2% in South Africa. It could be innate within a person's character. It could be the teaching that they have had. It could be peer pressure. It could be particular life experiences.

Even though there may be a state of flux in a societies hinge proposition, it is still a useful concept and perhaps informative in explaining the undoubted gulf between Christian and atheist, liberal and conservative and Indirect and Direct Realist.

But if noesis is possible his entire analysis is wrong. — Count Timothy von Icarus

Why?

Noesis seems to be the real content of consciousness. For example, the consciousness of the thought that here is one hand.

Wittgenstein's conclusion is that "here is one hand" is a hinge proposition within a language game.

It is the case, however, that Wittgenstein was of the general opinion that thinking and language were the same.

Notebooks 1914-16 - Now it is becoming clear why I thought that thinking and language were the same. For thinking is a kind of language. For a thought too is, of course, a logical picture of the proposition, and therefore it just is a kind of proposition.

Language would be of no use if the meaning of the words couldn't be thought about. Even though "here is one hand" is a hinge proposition, the meaning of the words can still be thought about.

The hinge proposition "here is one hand" doesn't negate the consciousness of thought that here is one hand.

The point would be that people have often held conceptions of truth that would invalidate Wittgenstein's conclusions. — Count Timothy von Icarus

Conceptions of truth don't invalidate Wittgenstein's conclusion.

Wittgenstein proposed that "here is one hand" is a hinge proposition. A hinge proposition is a foundation of the language game within which it is a part. This makes sense, in that "god exists" is a hinge proposition of the Christian language game and "god doesn't exist" is a hinge proposition in the Atheist language game.

As I see it, for Wittgenstein, within a language are hinge propositions and ordinary propositions, and these are different things. IE, not every proposition within a language is a hinge proposition.

There are many definitions of truth. For example, see SEP article on Truth. However, I find the most informative definition to be when a proposition in language corresponds with a fact in the world then that proposition is true.

The hinge proposition "here is one hand" does not engage with the world, and is therefore neither true nor false, whereas the ordinary proposition "the cat sat on the mat playing with the mouse" does engage with the world, and can therefore be either true or false.

Wittgenstein's main conclusion is that "here is one hand" is a hinge proposition. A hinge proposition is a foundation of the language within which it is a part. It is not a demonstration of the existence of the world.

I agree that the hinge proposition "here is one hand" is neither a tautology, axiom or truism. It is the foundation of the language of which it a part, and allows the rest of the language to take place.

In a different language game, "this is a mountain" could be a hinge proposition allowing the rest of the language to take place. Discussion could then be had about mountaineers, snow falling on the mountain tops, the difficulties of skiers, which ski lodge to visit and the best flights for the skier to use from their home country. It would include the truth or falsity of propositions such as "Italy is the best country to visit for the serious skier". But it wouldn't include the truth or falsity of the proposition "this is a mountain".

Being neither true nor false, the hinge proposition cannot be invalidated by conceptions of truth or falsity.

It isn’t independent of any world. On the contrary, it is the product of practical discursive engagement with others and with material circumstances in the actual world in which we live. — Joshs

The hinge proposition

You are conflating two different types of propositions within the language game. There is the hinge proposition and there is the ordinary proposition.

You are right that the ordinary proposition is the product of practical discursive engagement with others, but the hinge proposition is a different thing altogether.

This is why Wittgenstein critiques Moore's "here is one hand". The whole point of Wittgenstein's hinge proposition is that is not the product of practical discursive engagement with others.

"Here is one hand" is the hinge proposition that is a foundation of the language within which it is a part.

"Here is one hand that is slightly larger than the other and is wearing a yellow glove" is the ordinary proposition that does engage with the world.

From the perspective of the Patristics, or say, Thomism, Wittgenstein is simply deluded about the nature of truth, knowledge, and justification — Count Timothy von Icarus

@Sam26 suggested to me that "I don't want this thread to become an argument about the existence of God, and whether belief in God is a hinge."

However, it does seem that Pope Pius X did establish what Wittgenstein would call a hinge proposition about Thomism.

In the 1914 motu proprio Doctoris Angelici, Pope Pius X cautioned that the teachings of the Church cannot be understood without the basic philosophical underpinnings of Thomas's major theses:

The capital theses in the philosophy of St. Thomas are not to be placed in the category of opinions capable of being debated one way or another, but are to be considered as the foundations upon which the whole science of natural and divine things is based; if such principles are once removed or in any way impaired, it must necessarily follow that students of the sacred sciences will ultimately fail to perceive so much as the meaning of the words in which the dogmas of divine revelation are proposed by the magistracy of the Church. (Wikipedia - Thomism)

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For, leaving aside the proper interpretation of Wittgenstein, to say that "God exists" and "God does not exist" can both be simultaneously "tautologically true" obviously requires a view of truth that is likely to differ fundamentally (i.e. in terms of bedrock understanding) from most historical views, under which claims that something is simultaneously both true and not-true, without qualification, is absurd and "senseless." — Count Timothy von Icarus

Yes, the Law of Non-Contradiction states that a proposition cannot be both true and false at the same time.

However, Wittgenstein's hinge propositions are neither true nor false.

There are many definition of "truth", but for me the most informative definition of truth is the correspondence between a proposition in language and a fact in the world.

Wittgenstein's hinge proposition is a foundation of the language of which it is a part, regardless of any correspondence between the hinge proposition and a fact in the world.

Therefore, the fact that the same hinge proposition may have different meanings in different language games does not break the LNC.

On the other side of the argument, “I have hands holds across contexts and language games. Atheists function without belief in God, but how would they function without the belief we have hands? — Sam26

Fair enough, putting God to one side.

One could argue that although the proposition "here is one hand" can be used across different language games, it could have different meanings. For example in the language games of the Direct and Indirect Realist.

For the Direct Realist (1), the proposition "here is one hand" is true, as they believe that the hand exists in the world. For the Indirect Realist (2), the proposition "here is one hand" may or may not be true, as they believe that the hand may or may not exist in the world.

The Indirect Realist is able to function successfully even though they believe that the hand they perceive may or may not exist in the world. For example, the Indirect Realist stops at a traffic light when they perceive the colour red, even though they believe that the colour red may or may not exist in the world.

For Wittgenstein, the hinge proposition "here is one hand" is independent of any world. As a hinge proposition, it is the foundation of the language within which it is a part, regardless of its truth, where truth is a correspondence between language and the world.

Notes
(1) Direct realism is the view that i) the external world exists independently of the mind (hence, realism) and ii) we perceive the external world directly (hence, direct). For the Direct Realist, we directly perceive hands that exist in the world.

(2) Indirect realism is the view that i) the external world exists independently of the mind (hence, realism) but ii) we perceive the external world indirectly, via sense data (hence, indirect). For the Indirect Realist, we also directly perceive hands, but the hands that we perceive may or may not exist in the world.

https://philosophyalevel.com/aqa-philosophy-revision-notes/theories-of-perception/

However, as mentioned above re noesis, the existence of God and of God as "truth itself" would seem to undermine Wittgenstein's conclusions in a rather radical manner. — Count Timothy von Icarus

For those who believe that god exists, then god exists. This is a tautology. It follows that they believe the proposition "god exists" to be true and the proposition "god doesn't exist" to be false. For those who believe that god exists, the proposition "god exists" is a hinge proposition and is a tautological truth.

For those who believe that god doesn't exist, then god doesn't exist. This is a tautology. It follows that they believe the proposition "god doesn't exist" to be true and the proposition "god exists" to be false. For those who believe that god doesn't exist, the proposition "god doesn't exist" is a hinge proposition and is a tautological truth.

For Wittgenstein, a hinge proposition is foundational to the system within which it is foundational. This is a tautology. For Wittgenstein, the proposition "hinge propositions are foundational to the system within which it is foundational" is a hinge proposition and is a tautological truth.

As the hinge propositions of the Christian and Atheist are tautological truths, they do not undermine Wittgenstein's conclusion, which is also a tautological truth.

Propositions can be true or false, but hinges are true as a condition of being a hinge, i.e., it's their foundational role. Moreover, it’s our acting that cements them in place, not any fact that establishes their truth. — Sam26

The Christian in acting their life cements the hinge "God as the ultimate source of all power", which is their truth. The Atheist in acting their life cements the hinge "there is no God", which is their truth. The Agnostic in acting their life cements the hinge "it is impossible to know whether there is a God", which is their truth.

The hinge is absolutely true within the system that it plays a foundational role. However, the truth of a hinge is relative to which system it is playing a foundational role.

The role of the hinge seems to be in ossifying differences between peoples. The hinge doesn't appear to include a mechanism for recognizing its own fallibility. Is this a correct understanding?

Would you reject out of hand the possibility that "God-realization" is a term, however fuzzy and encrusted with doctrines, that tries to answer this question? — J

The "I" here ceases to be entwined with thought, emotion, or perception - but instead is said to become, or else transcend into, pure awareness devoid of any duality. — javra

Pure consciousness. I'll have to mediate on that.

For pure consciousness is said to remain, even in the absence of the "I" and its objects — J

What would this consciousness be conscious of, if not the "I" or object of thought?

Yes, true, but the concept filled with sense data (in the IDR sense) is not synonymous with the concept. — AmadeusD

I agree. I may have the concept of a house in my mind. If I perceive something that I understand as one instantiation of my concept of a house, then I perceive this something as a house.

This, to be honest, because for it seems as though you are reifying the mind and its components (e.g. individual thoughts and percepts) into having similar characteristics to physical things in the external world, which can indeed hold separated givens. — javra

In the mind, there can be the concept of a house and the thought of a particular house. These are different things. I agree that there can be a concrete example of an abstract concept.

Yet to see a house (a percept) is indeed utterly separate from contemplating the concept/thought of "house". — javra

The Indirect Realist would argue that we never directly see the house, but only perceive a representation of a particular house.

Both the concept of a house and the representation of a particular house exist in the mind, and in this sense are not utterly separate, as both exist in the mind.

The "I" for example is not separate from its perceptions in so far as these perceptions are only so because they are perceived by the "I" - being in fact contingent on the "I"s awareness. — javra

As Nietzsche wrote:

What gives me the right to speak of an 'I' as cause, and finally of an 'I' as cause of thought?'

What gives me the right to say that the "I" causes thoughts, as if the "I" is separate to the thoughts it has?

I agree that the "I" is not separate to either its perceptions or thoughts. But what are the implications of this? The implication is that perceptions and thoughts are an intrinsic part of the "I".

In the same way, iron is an intrinsic part of the Eiffel Tower. Remove the iron, and what is left? Nothing.

Remove the perceptions and thoughts, and what is left? Nothing. There is no "I" remaining.

Doesn't this entail that with each change in thought thunk there will then necessarily be an ontological change in the "I" addressed? If so, how can the same "I" be privy to different thoughts? — javra

Yes, for each change in thought there will be an ontological change in the "I". Are you the same person you were ten years ago?

There is the question of identity through time. The "I" is not just the thought being had at the present moment in time, but is the complete set of thoughts stored as memories that stretch back into the distant past.

The problem is, if the "I" is separate to its thoughts, then how can the "I" know about its thoughts? The "I " can only know about the thoughts it has if these thoughts are an intrinsic part of the "I", such that "I" is its thoughts.

If the "I" is separate to its thoughts, the question is, how can the "I" be privy to any thoughts at all?

If I have a conscious thought/belief that I am seeing something, could that thought/belief be doubted? — Kranky

Nietzsche is right to point out that people naturally separate the "I" from the "thought".

What gives me the right to speak of an 'I' as cause, and finally of an 'I' as cause of thought?'

However, this cannot be the case, otherwise it would lead into the homunculus problem of infinite regression.

It is more likely that "I" is the thought rather than it is the "I" that is having the thought.

It still remains the case that a thought cannot doubt itself.

If I have a conscious thought/belief that I am seeing something, could that thought/belief be doubted? — Kranky

No. What could the existence of the thought/belief by doubted by? Only by a thought/belief. Then it would be the case that a thought/belief was doubting its own existence, which is a logical impossibility, as a thought/belief must exist in order for it to doubt its own existence.

"I think therefore I am" is the first principle of Descartes philosophy.

I don't understand how we could replace 1 by 3. — frank

If there is one object in the world, dividing it into three parts does not involve infinities. In our numbering system, dividing 1 by 3 does involve infinities.

This suggests that infinity is an artificial problem of our numbering system. Perhaps a different numbering system would avoid the problem of infinity altogether.

Could you describe what mind-independent world could be? — Corvus

Impossible for the mind to describe a mind-independent world.

What do we do with numbers like pi that go on forever? — frank

One third of 1 is 0.33333...........continuing to infinity.

If we altered our numbering system, such that we replaced 1 by 3, then one third of 3 is 1. This avoids any problem of infinity.

This suggests that the problem of infinity is an artificial problem of our numbering system.

Similarly with pi.

They are subjective mental states, nothing to do with knowledge. — Corvus

Our only knowledge about any mind-independent world, any objective reality, starts with our subjective mental states. This means that knowledge about an objective reality cannot be separated from our subjective mental states.

When there is discrepancies in the claims of knowledge on the same situation or object between different folks, you always have chance to carry out testimonies on the knowledge via repeated observations, experiments, or testing on the claims, and update your false beliefs, or correct the other folks false claim on his knowledge. — Corvus

True, if two people make different claims about the same situation, for example, one says the postbox is red, and the other says the postbox is green, their claims can be judged.

But as regards perception, what a person perceives in their mind cannot be judged by anyone other than that person, as mind reading is impossible.

In exactly the same way, any pain a person experiences cannot be judged by anyone other than that person, as mind reading is impossible.
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What we see is the only world there is. There is no other world. — Corvus

You could only know what another person sees in their mind if you were a mind reader, which is an impossibility.

Only a mind reader could know that what another person sees in their mind is the same as what they see.

Seeing a colour and feeling a pain are both subjective experiences that are unknowable to any one other than a mind reader.
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Mind-independent world is meaningless if you cannot see or know what it is. — Corvus

If you knew something about a mind-independent world then it couldn't be a mind-independent world.

That would be like knowing something that is unknown.

We do have knowledge about the truth of reality, because we have perception and reasoning and inferring on the perception. Not just perception. — Corvus

Ideal Realism is about a relation between the mind and the world: "The universe is just ideas in the head, but real. Matters are only real when accessible and interactable. When not, all matters are just ideas."

If person A was stung by a wasp, only person A would know their particular pain. Person B may know their own particular pain when stung by a wasp, but as mind reading is not possible, it is impossible for person B to know person A's particular pain.

The top light of a traffic light is labelled "red", the middle light is labelled "orange" and the bottom light is labelled "green".

When person A sees the top light of a traffic light, only person A knows the particular colour that they see. Similarly, person B knows the particular colour that they see. As mind reading is not possible, it is impossible for person B to know the particular colour that person A sees.

Therefore person B can never know whether they are seeing the same or different colour to person A

Therefore, it is possible that persons A and B are in fact seeing different colours.

If persons A and B are seeing different colours, then either one of them or both of them are wrong about the reality of the colour of the top light.

If person B is wrong about the true nature of the traffic light, then this means that even though they see a particular colour of the top traffic light, that particular colour may not in reality be the actual colour of the top traffic light. This means that even though person B sees the colour red, the top traffic light may not in reality be red.

If person B is right about the true nature of the top traffic light, it is possible that person A is wrong.

If person A is wrong about the true nature of the top light, then this means that even though they see a particular colour of the top traffic light, that particular colour may not in reality be the actual colour of the top traffic light. Therefore, even though person A sees the colour red, the top traffic light may not in fact be red.

But persons A and B are interchangeable,

Therefore, it is possible that a person may see a colour that in fact doesn't exist in reality in the world

Direct Realism is the theory that all people directly see the colour that exists in reality in the world, but as mind reading is not possible, this is unknowable.

Therefore Direct Realism is not a valid philosophy. The reality of a mind-independent world is inaccessible to the mind.

For empirical cases like seeing colour red, you must go out and investigate further and verify for the truth, if needed. — Corvus

Suppose in reality the truth is that an object in the world is green, but for whatever reason you always perceive green objects as red.

You could look at the green object from all directions and all times of the day and will always see this green object as red.

How is it possible for the human mind to analyse the fact that they always see a red object to discover the truth of reality that the object in the world is actually green?
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Your seeing colour red is not knowledge. — Corvus

Your seeing the colour red is knowledge about what is in the mind, but is not knowledge about what is in the world.

Knowledge is justified true belief.

As regards the mind, the colour you see is the colour you see, regardless of its name. The colour you see is necessarily a justified true belief, and is therefore knowledge.

As regards the world, you may believe the colour of the object is red. You may be able to justify that the colour of the object is red. But if the object is in reality actually green, then you have no knowledge about the truth of reality.

Perception cannot give us knowledge. It can only present with what is perceived in the form of raw data i.e. shapes, colours, sounds, words and motions. That is where it ends. It is our reasoning and inference which give us knowledge on the reality. Hence both DR and IRists are wrong. — Corvus

We perceive the colour red and reason that it was caused by a red object in the world.

Knowledge is justified true belief.

Just because we have reasoned that our perception of the colour red was caused by a red object in the world, suppose we are mistaken, and in fact our perception of the colour red was not caused by a red object in the world.

Suppose it was caused by a green object. We wouldn't then have knowledge about reality in the world.

Why should our perceptions necessarily give us knowledge about the world?

Perception cannot give us knowledge. It can only present with what is perceived in the form of raw data i.e. shapes, colours, sounds, words and motions. That is where it ends. It is our reasoning and inference which give us knowledge on the reality. Hence both DR and IRists are wrong. — Corvus

It depends what is meant by "knowledge".

Knowledge could mean justified true belief. If I believe that the Eiffel Tower is 330m tall and can justify my belief, perhaps I read it in Encyclopedia Britannica, and the Eiffel Tower is actually 330m tall, then I have knowledge about the Eiffel Tower

I agree that we perceive things and can then use our reason on these perceptions in order to give us knowledge about the world, such that the Eiffel Tower is 330m tall.

But in order to reason about my perceptions, I must first know that I am perceiving the colour red, for example. I don't think that I am seeing the colour red. I don't believe that I am seeing the colour red. I don't need to reason that I am seeing the colour red. I know that I am seeing the colour red.

Is knowing something knowledge? Is knowing that I see the colour red knowledge that I see the colour red?

In propositional terms, when I say "I know the Eiffel Tower is 330m tall", the fact "the Eiffel Tower is 330m tall" is knowledge. Similarly, when I say "I know I see the colour red", the fact "I see the colour red" is knowledge.

I would say that I have knowledge that I see colours, shapes, sounds, etc

It seems that knowledge can be about what is in the mind as well as what is outside the mind.

Does it mean that Indirect Realist can only have beliefs? No knowledge at all?
And likewise, Direct Relists can only have knowledge? No beliefs at all? — Corvus

The meaning of the words "direct knowledge" and "indirect knowledge" depends on context.
In ordinary language, I have direct knowledge of The Empire States Building as I have visited it, but I only have indirect knowledge of The Space Needle as I have never been there.

In philosophy, I have direct knowledge of my perceptions of the colour grey and rectangular shape, but I only have indirect knowledge through reasoning of the something in the world that may have caused my perceptions.

The meaning of the words "knowledge" and "belief" depends on context.
In ordinary language, I know that the Eiffel Tower is in Paris, and I believe that the Eiffel Tower was built in 1889.

In philosophy, I know my perception of the colour red, and I believe that there is something in the world that caused this perception.

The Indirect Realist
Not entirely. The Indirect Realist has knowledge about what exists in their mind, such as when they perceive the colour red. But they argue that we can only have beliefs about what exists in the world that may be causing these perceptions in the mind.

The Direct Realist
The Direct Realist argues that they have knowledge about what exists in their mind, such as when they perceive the colour red, and they argue that they also have knowledge about the something in the world that caused these perceptions in the mind.

However, as I see it, Direct Realist is an invalid philosophy. IE, they are wrong.

That seems to imply that they are back to the dualism. — Corvus

Yes, but there is nothing fundamentally wrong with dualism.

If there was no dualism there would be no language. A word on the one hand exists as a shape and on the other hand exists as a representation of something else.

1) What is the significance of direct and indirect knowledge?...........................................3) What are the differences in direct and indirect knowledge compared to knowledge? — Corvus

I have direct knowledge of New York because I have been there, but only have indirect knowledge of Seattle as I have never been there.

I have direct knowledge of my perception of red, but only have indirect knowledge of the something in the world that might have caused it

Indirect knowledge signifies a belief.

I believe that the Space Needle in Seattle was originally sketched on a napkin, but I don't know it for a fact as I wasn't there at the time.
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2) Indirect or direct on relation to what? — Corvus

In relation to something in the world. The relation between what exists in the mind and what exists in the world.

That sounds confusing. Is it not the other way around? Are you sure you haven't put them wrong way around in the definition? What significance the word "indirect" have in the name? Why indirect? — Corvus

I don't believe so.

Suppose someone perceives the colour red. Both the Indirect and Direct Realist would agree that something in the world caused their perception.

The Direct Realist would argue that they are directly seeing the something in the world that caused their perception. They argue that the something in the world is actually red.

The Indirect realist argues that they are directly perceiving the colour red in their mind and only know about the something in the world that caused their perception indirectly through reason. They argue that the something in the world might be red, might be green, might be a wavelength of 700nm or might be something else altogether.

The Direct Realist argues that they have direct knowledge about the something in the world that caused their perception, whereas the Indirect Realist argues that their reasoning can only give them indirect knowledge about the something in the world that caused their perception.

So what is the difference between indirect realism and direct realism? From what you are saying, they sound exactly the same claims. — Corvus

As I wrote on page 2

Suppose someone perceives the colour red. Both the Indirect and Direct Realist would agree that something in the world caused their perception.

The Direct Realist says the person is directly perceiving the cause of their perceiving the colour red. The Indirect realist says that the person is only directly perceiving the colour red.

You seem to be confusing the point that I was trying to point out the fact that transcendental idealism has problem of having dualistic view of the world i.e. phenomenon and noumenon — Corvus

A dualistic view in itself is not necessarily incorrect. For example, a word is an example of dualism. On the one hand it exists as a shape and on the other hand it exists as what it is representing.

This describes Direct Realism:

When the perceiver and the world is in direct physical contact which allows the perceiver to have direct perception, sensation, and interaction with the world or objects in the world, the world presents to the perceiver as physical entity or material objects. — Corvus

This describes the Direct Realist closing their eyes and using their imagination:

When the perceiver is only thinking about the world without direct visual or material sensation or perception, the world is in the mind of the perceiver as ideas only. — Corvus

You haven't answered the key point question. What do you mean by "regardless of any cause"? Why is it relevant to the point? — Corvus

I wrote "When I perceive the colour red, I perceive the colour red regardless of any cause."

It goes back to your two previous statements:

You end up having 2x copies of every object in your perception, and wonder which one is the real object. — Corvus

Indirect realism's problem is using sense data as the medium of perception, which doesn't make sense. — Corvus

I am trying to show that this is a misrepresentation of Indirect Realism. For Indirect Realism, there is only "1x copy of every object in your perception."

This means that when an Indirect Realist perceives the colour red, they are only directly perceiving the colour red. They are only directly perceiving one thing. They are not directly perceiving two things, the colour red and the cause of their perception of the colour red.

As I wrote:

When the Indirect Realist perceives the colour red, for example, they are not perceiving a representation of the colour red, they are directly perceiving the colour red.
Anything otherwise would lead into the homunculus problem of infinite regression.
What the Indirect Realist does believe is that there is something in the world that has caused them to perceive the colour red, but it is unknowable whether this something in the world is actually red or not. The Indirect Realist reasons that it is not, but cannot know for sure.
In a sense, the colour red that is directly perceived is a representation of the unknown something in the world, which may or may not be the colour red.
There is only one object of perception for the Indirect Realist, and that is the direct perception of the colour red.

What are the ultimate reality for these folks in detail? — Corvus

Presumably the same as for the idealists and the materialists.

The point of idealism or materialism is to define what the ultimate reality is in the end. — Corvus

It sounds like a tautological statement, which doesn't convey any knowledge. — Corvus

The statement "When I perceive the colour red, I perceive the colour red" is a tautological statement.

The statement "When I perceive the colour red, I perceive the colour red regardless of any cause" is not a tautological statement.

Suppose someone perceives the colour red. Both the Indirect and Direct Realist would agree that something in the world caused their perception.

The Direct Realist says the person is directly perceiving the cause of their perceiving the colour red. The Indirect realist says that the person is only directly perceiving the colour red.

Saying "When I perceive the colour red, I perceive the colour red regardless of any cause" is distinguishing Indirect from Direct Realism.
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The point of idealism or materialism is to define what the ultimate reality is in the end. But IR and DR seem to just make vague statements on how they perceive via unknown causes or directly. They just end there. So what is the ultimate reality? They don't seem to be interested in it. Hence no point. — Corvus

A bold statement that neither Indirect nor Direct Realism are interested in the nature of ultimate reality.

Indirect Realism is about the limits of knowledge of ultimate reality. Direct Realists do believe that they know ultimate reality.

There would be no cases such that the cause of break is unknown in medical incidents. — Corvus

I doubt that the cause of a medical condition is always known.

Even though the broken leg has a cause, the doctor is treating the broken leg, the doctor is not treating the cause of the broken leg.

When I perceive the colour red, I perceive the colour red regardless of any cause.
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Not really. Their systems are not denied here. Rather, the OP is based on their systems, but seeing the world in a different way like Husserl and Merlou Ponty have done. — Corvus

You may not deny Indirect and Representational Realism, but you infer there is no point in them.

Doesn't sound it has a point in saying that something has cause but they don't know what the cause is. — Corvus

Doesn't sound it has a point in saying that something has cause but they don't know what the cause is. — Corvus

It would be like a doctor refusing to treat someone in pain with a broken leg until they knew the cause of the break.

It is a brave statement that there is no point in Indirect or Representational Realism, and philosophers such as Aristotle, John Locke, Immanuel Kant, Rene Descartes, Baruch Spinoza and Bertrand Russell were mistaken.

Any objects or world unobserved don't exist. They are imagined or believed to exist. — Corvus

Why should I believe in the existence of an object in the world that I have never observed existing?
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Indirect realism's problem is using sense data as the medium of perception, which doesn't make sense. — Corvus

It may be that your problem with Indirect Realism is, as you said on page 1: "You end up having 2x copies of every object in your perception, and wonder which one is the real object."

But this is not the case for the Indirect Realist. There is no medium of perception. There is just perception.

When the Indirect Realist perceives the colour red, for example, they are not perceiving a representation of the colour red, they are directly perceiving the colour red.

Anything otherwise would lead into the homunculus problem of infinite regression.

What the Indirect Realist does believe is that there is something in the world that has caused them to perceive the colour red, but it is unknowable whether this something in the world is actually red or not. The Indirect Realist reasons that it is not, but cannot know for sure.

In a sense, the colour red that is directly perceived is a representation of the unknown something in the world, which may or may not be the colour red.

There is only one object of perception for the Indirect Realist, and that is the direct perception of the colour red.