Why would touching be considered impossible? Touching is by many considered an object coming into contact with another, which perhaps requires the objects occupying the same space. And occupying the same space is considered impossible by nearly everyone. — elucid

Let's try these examples of occupying the same space:

1. Consider Matryoshka dolls. This is a good example of each smaller doll occupying the same space of the prior larger doll.

2. Take a 1 cubic meter container and add an equal mixture of two inert gases and close it. Wait a moment and I have two gases occupying the same space in the container.

3. I draw a square object and overlap it with a circle object, then color in the space where they overlap. Conclusion: The colored space where the two shapes overlap occurs in the same space.

It seems occupying the same space is not impossible.

As opposed to how well philosophy doing right now at being relevant? Every time I go into a book store I check out the philosophy section and it invariably is tiny and has just a few copies of books by the same 4-6 authors. Philosophy has become so scared of error that it's afraid to be relevant. Sometimes I even think the arcane vocabulary becomes a hiding mechanism. — Count Timothy von Icarus

Thank Descartes for telling us it is all a dream but don't worry God would not want to fool us.

The Age of Enlightenment at its best.

Oh for sure. But when someone say's "does touch really exist," I assume they mean: "from the standpoint of fundemental physics or metaphysics," simply because the question is silly in any other context.

This is an example where the understanding wrought by the linguistic turn seems to backfire. "Take language the way it is commonly used," is all well and good advice in some cases, but it missteps when it assumes that people don't ever think about metaphysics in their day to day lives. This just doesn't seem to be the case. Books on this sort of thing wouldn't sell millions of copies and churches wouldn't be packed each weekend if these sorts of questions only interested a few egg heads. In our ordinary, everyday lives we still sometimes ask deep metaphysical questions of this sort. — Count Timothy von Icarus

Maybe, but then philosophy flirts with the risk of being viewed as irrelevant, a joke, a psychological disorder, a fictitious narrative, a new religion, etc.

Of course, just because we can't disprove an idea it does not make it true. It does not make it false either. It is an untestable idea. — Truth Seeker

This is what we call an imagination producing a fiction. For example, I can enjoy a novel of fiction where the author has a rich history of some made up land. But there is no proving that this fictional history is true or false.

It is possible that what I perceive is either a dream or a hallucination or an illusion or a simulation and not objectively real. — Truth Seeker

I would disagree with this assertion. In order for one to understand what is a dream, hallucination, illusion, or simulation, one must contrast this with what it is not. This is the world in which we interact with, talk about, act on, born into, communicate with others, learn from others; basically, the background in which we accept and act in. For example, one typically learns the concept of "dreaming" from their parent when upon waking up from sleeping they begin to report strange accounts that never happened with a subsequent reassuring from the parent that all was a dream.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

As the colour of the wavelength 550nm can only be determined by the mind, the colour green can only exist in the mind. — RussellA

We have devices that detect colors on a variety objects that will agree with human judgement. These devices are not detecting color in the minds of humans but on objects. Additionally, if you use the device on the human brain you will be getting the color of the brain not what the brain is sensing.

This simply shows this view colors only existing in the mind is confused and unfruitful.

I like to suggest a different view on "What is Truth." Instead of appealing to Platonic Essences, psychologism, or analytical formulations, I like to take a roughly thought-out Naturalistic position. Truth is just a manifestation of the brain's interaction with its environment through language, to put it as general as I can. It is not a property of propositions, sentences, the world, the mind etc... The human brain has the ability to recognize stimuli "as true" because it has evolved over many eons the innate ability to condition itself to respond to environmental stimuli in ways that have proven valuable for the host. The brain recognizes its conditioning in particular ways, which in turn, we get a manifestation of this recognition in language by saying, "that's true." From this recognition, the host may act as it sees fit.

Let's look at the example, "1 + 1 = 2". All of us who have learned mathematics would say, yep this is a true statement. But not because we all have some strange ability to look into the Platonic realm of Ideas and see that it is true. But because we have conditioned ourselves to react to the symbols "as true". A child has no idea before learning mathematic what these symbols mean, but after proper conditioning, the recognition of it "as true" happens.

Could the brain mess-up, of course. Could the brain set-up conditionings that are not useful, of course. And that is what we exactly see in humanity.

The expression "Truth" may be as primitive as the expression "Ouch".

I disagree that Wittgenstein would agree that words, such as, right, accurate, judgment, etc lose their sense, if that's what you're indeed saying. — Sam26

They lose their sense in terms of talking about private sensations like they are public objects. For example, “I correctly recognize my past sensation is the same one as my current sensation” vs “I correctly recognize the person in the picture is my neighbor.”

another.

Wittgenstein's Beetle in the Box is an argument against Direct Realism. — RussellA

The Beetle in the Box is not to put forward a philosophical theory or to show support for indirect realism theory but to show that the model of “object and designation” is irrelevant to the meaning of the terms expressed in the language game of pain.

In fact he does not even support indirect realism, consider PI 304, “The conclusion was only that nothing would serve just as well as a something about which nothing could be said.”

An indirect realist would not say this. They would say that there are “somethings” and these somethings are private sensations and we have much to say.

Again, recognising the private sensation will help one to use the language appropriately, but language does not describe one person's private sensation. — Luke

I think Wittgenstein would say that recognizing a private sensation does not assist in using a word appropriately. Think of PI 265, the train time-table example. He might say using language correctly shows we recognize the private sensation (or maybe ….we experience the private sensation).

Notice that it's trivially true that feeling just is not concept. — plaque flag

Agreed, feelings are not concepts, but if you want to talk about feelings to your fellow human being there is a lot of set up that needs to take place. We simply do not take a literal picture of what is going on inside and give it to another person and say “see this is how I feel.” We need words associated with particular circumstances; we need a common language to understand those circumstances; we need our fellow human being to react similarly to those circumstances, or at least imagine how they would react, etc… with any luck we get understanding and empathy.

What accurately means depends on context. So if we give people the same color patches and they describe them using the same I words I use, then what more is needed to say they've described the colors accurately, and that they are seeing what I see? For all practical purposed their descriptions are accurate. There's no good reason to think they are seeing different colors. It's a problem without a difference. — Sam26

As Wittgenstein pointed out in PI 258, there is a problem talking about the accuracy of private sensations, he says towards the end, “But in the present case I have no criterion of correctness. One would like to say: whatever is going to seem right to me is right. And that only means that here we can’t talk about ‘right’.

What goes wrong with some much talk of private sensations is it borrows so much from the language of the public shared reality that words begin to loose their sense, like “right” “accurate”, “judgment”, “remember”, “something” etc… How much do you cut off a tree where it is no longer a tree but a stump?

At the very least I can say they are private experiences/sensations, and we often do describe such sensations accurately. — Sam26

What could “accurately” mean in such a case of private experiences/sensations. One, no one, in principle, can verify the truth of such an assertion, so why even call it is an assertion. Two, we learn what “accuracy” means by learning the techniques of determining the accuracy of whatever is under examination. Thus, no one can teach another how to determine the accuracy of a private experience/sensation. Lastly, Wittgenstein does not deny one have these experiences but only what can be said, which is not much at all. Just like if someone is in a completely dark room and someone ask “what do you see?” And one replies, “It is dark.”

When you see a "red" object your private subjective experience may be of the colour blue. — RussellA

I think this idea is confused based on the very idea on how we learn the language of color and language is general. Please consider this example:

For simplicity sake let us assume we are in a world with just two colors, red and blue. In my tribe, we learned when we see a red object we call it “red” and when we see a blue object, we call it “blue”. One day we travel to an island and we meet another tribe that surprisingly has a very similar language like ours with the exception that when they see a red object they call it “blue” and when they see a blue object they call it “red”. What are we to think in this situation? That they actually see a blue object where we see a red object, or that they simply call a red object “blue” in their language? We can easily ask for the red object by saying “Can you fetch me that blue object” in which they bring me the red object. Would it not be more reasonable to believe our words for “blue” and “red” are “inverted” not how we experience those objects? If this is so, how is this any different when someone says to me, I see that red object but I really see it as “blue.” It is not that we will never know what one actually experiences, but that we are going beyond what the language of color can express.

I understand why someone would claim this, and I readily agree that the social aspect is necessary. But I don't think it's exhaustive. Ought we deny our experience of intending an object ? Or intending a state of affairs ? Something like the direct experience of meaning ? I think training is crucial for the linguistic version of this, but once trained we have a certain independence and ability to introspect. — plaque flag

To reiterate what Wittgenstein says in PI 305, "But you surely cannot deny that, for example, in remembering, an inner process takes place." What gives the impression that we want to deny anything? When one says "Still, an inner processes take place here"-one wants to go on: "After all, you see it." And it is this inner process that one means by the word "remembering".-The impression that we wanted to deny something arises from setting our faces against the picture of the 'inner process'. What we deny is that the picture of the inner process gives us the correct idea of the use of the word "to remember".

In terms of "introspection", the idea of "introspection" is shown when we share are ideas with other language users, develop ideas with argument, listen to clarifying questions, see if others can apply our ideas, act on them, and even expand on them. What give "introspection" meanings is not what lies hidden within the self, but what is expressed and understood between others.

perceptual psychology indicating that what you are calling primitive reactions is in fact complex conceptual understanding. — Joshs

Long live theorizing, may you find some pragmatic benefit.

What about pre-linguistic perceptual meanings? Do pre-verbal infants not construct meaning from their surroundings through the use of perceptual-motor schemes? — Joshs

As human being, we have many primitive reactions that serve us well, like thirst, hunger, pain to name a few. But would we say that an infant has the meaning or the concept of “thirst”, “hunger”, or “pain” before they even learn these words from an adult. No, but they do experience these things and later, adults teach the infant to replace this behavior with language.

Private meaning is not made possible by public meaning. — RussellA

Do not agree. Public meaning makes private meaning incomprehensible.

We learn what “red” is by being expose to red objects and judging similarly. What goes on inside is irrelevant to the meaning of the concept “red”.
You ask someone to imagine a red object that is experienced by one person as “blue”, another “green”, and another “yellow”. For example, if I experience a red object as “blue” and blue object as “red” and another person experiences a red object as “red” and a blue object as “blue”, what has established the use of “red object” and “blue object” amongst language users? Private experiences of “blue” and “red”? No. Common color judgments of objects with other language users? Yes. In this example, everyone could be experiencing something different, but what holds it together is the shared judgment when exposed to a particular colored object.

Could it be that I have no experience of what we would call “color” but some other experience of a “private” kind? But what could that be and could it ever be communicated? Just saying it is different is not saying anything at all. This idea of “private meaning” is tempting but ultimately vacuous compared to where that idea of “meaning” has its life, among a group of language users talking about a shared reality.

There's a book I've noticed, Jerrold Katz, The Metaphysics of Meaning. (Reviews here and here). This book, and indeed most of Katz' career, was dedicated to critiquing Wittgenstein, Quine, and 'naturalised epistemology' generally. He also studied under Chomsky, but I think the basic drift is Platonist, i.e. meaning has to be anchored in recognition of universals as constitutive elements of reason - not simply conventions or habits of speech. — Wayfarer

I finally have had a chance to read this book. Thanks for mentioning it. I have not seen many sophisticated attempts that try to argue against later Wittgenstein, but this is one of them. On the positive side, Katz does a great job of elucidating both Wittgenstein’s and Quine’s philosophy. In fact, most of the time he agrees with Wittgenstein’s investigation into meaning and language. However, he believes, Wittgenstein’s criticism does not touch certain linguistic attempts at discovering the underlying structure of language. Additionally, he believes Platonic versions of philosophical theories can explain those linguistic proto-theories better than the naturalistic positions that Wittgenstein and Quine offer.

In the end, he believes he has shown that his vision is a justifiable alternative to the naturalism positions he attempt to critique.

Obviously Av~A is true and A&~A is false. — A Realist

Well that depends.Take A&~A is false. How so? There is a symbol A and there is a symbol ~A thus it is true. Or substitute for A “I am in pain”, in the case Av~A is false because ~A is not sensical so the “or” cannot function if utter in the situation of expressing pain.

Wittgenstein doesn't make this distinction, at least not clearly, but I do. We act in the world with a certain conviction that things are the way they are, and it's not a matter of justification as W. points out in PI 325. And, it's through these actions that these very basic beliefs (other philosophers refer to them animalistic beliefs) are seen. — Sam26

I find it strange to say a basic belief is “I have two hands”. Not only is absurd to say “I doubt I have two hands”, but also “I believe I have two hands” or “I am convince I have two hands”, when, in fact, I have two hands. If other people would start challenging me on this, I would think they have gone mad, or psychologically manipulating me for some reason. Additionally, if one would say, “Well I could imagine that you have been drug and your hands have been amputated, yet you feel certain that you have hands.” My response could be, So what, just because you could imagine such a thing does not make it possible, it could be that I am immune to such drugs and hallucinations. Lastly, why are we calling something “knowledge” as something that excludes possible doubt. This seems too unnecessary of a high bar for a concept that is use in everyday life. It seems Wittgenstein could not cure himself of this philosophical view of “knowledge.”

No, we don't justify that we have hands through sensory experience. Is that how you came to believe you have hands. — Sam26

But we justify orange juice is sweet by our taste? You seem to be inconsistent here.

In my example, I am not speaking in front of skeptical philosophers who are doubting the external world. I am a job applicant who is being ask if I have two hands because the job requires two hands to operate the machinery. I can answer yes or no. If one of my hands was amputated due to an injury the answer is"no". In this circumstance, this can be counted as a statement of knowledge.

The statement that "I know I have hands" is just epistemologically wrong — Sam26

.

Not in general, it depends on the circumstance.

What would it mean to doubt that you have hands in Moore's context? — Sam26

Agree here that the use of "doubt" is questionable in Moore's context. But why could we not say that Moore is justified in saying "I know I have two hands." by just showing the audience such objects.

In PI 325, Wittgenstein says the following, 'The certainty that I shall be able to go after I have had this experience-seen the formula, for instance,-is simply based on induction.' What does this mean?- 'The certainty that the fire will burn me is based on induction.' Does that mean that I argue to myself: 'Fire has always burned me, so it will happen now too?' Or is the previous experience the cause of my certainty, not its ground? Whether the earlier experience is the cause of the certainty depends on the system of hypotheses, of natural laws, in which we are considering the phenomenon of certainty. Is our confidence justified? - What people accept as a justification is shown by how they think and live."

Is not this the case with Moore when he shows the skeptical philosopher his hands thus demonstrating the absurdity of doubting such a thing?

Why would you ask this? — Sam26

I have a job that requires someone to have two hands to operate a piece of machinery; so on the job application I declare “I have two hands.” Is this not providing my knowledge of my biological state to someone who can confirm my assertion?
— Richard B

No, and this Wittgenstein's point, i.e., it's not a matter of epistemology, generally speaking. — Sam26

So is this not

We justify knowledge claims based on sensory experiences. — Sam26

?

So what is a “statement of knowledge”? Can you provide an example?

If you can’t, what distinction can one be making between “ a conviction” and “a statement of knowledge”

One of the problems with Moore enumerating what he knows, is that it seems to amount to more of a conviction of what he believes, than a statement of what he knows. How does this happen? — Sam26

OK, a distinction is being made here, a “conviction” vs “a statement of knowledge”? Declaring “I have two hands” falls under the category of “conviction” But Wittgenstein finds this odd to say this in front of a bunch of philosophers rather than saying it after, say, a car crash. Should it even be called a “conviction” when our concepts have been removed from its common use? What about whether this is an example of a “statement of knowledge”? Again, what circumstances would this become knowledge? I have a job that requires someone to have two hands to operate a piece of machinery; so on the job application I declare “I have two hands.” Is this not providing my knowledge of my biological state to someone who can confirm my assertion?

Why? Because if you add to the concept existing in reality you would still just have a concept existing in reality, not the being itself.

Finally, many find the argument dubious for other reasons, viz., trying to prove the existence of something from the concept alone, which others have pointed out in this thread, is very problematic to say the least. — Sam26

I believe Anselm is trying to distinguish between two different ideas, "understanding that something exists in reality" and "experiencing that something exists in reality." As he says in Chapter 2 "And so. O lord, since thou givest understanding to faith, give me to understand-as far as thou knows it to be good for me-that thou exist, as we believe, and that thou art what we believe thee to be."

Unlike the painter and painting example, where producing a painting is the reason he understands the painting exists in reality, it is the idea of "a being than which none greater can be thought" and its deductive implication that Anselm understands such a concept of a being "exists in reality." So, when you say, "....you would still just have a concept exist in reality, not the being itself.", what is this idea trying to express? That the deductive argument should produce some experience of "the being of God"? Demonstrate some experience we had corresponds to this idea of "a being than which none greater can be thought."? It is a deductive argument, it is about ideas. Geometric proofs are about ideas, which does not mean it will have any successful application in reality.

Whether the argument is sound, how can we fairly access this? How does one evaluate the "truth" of "God is a being than which no greater can be thought", and "Existing in reality" is greater than "existing in understanding" in order to determine soundness. What should we do, take a poll on how many people agree with these premises?

Maybe what this argument ultimately demonstrates is the vacuousness of using general concepts and deductive reasoning whether one thinks something exist or not.

That experience is the final arbiter.

Without assuming some underlying logic behind the language used by Anselm, what could Anslem be showing us with this argument, and why is it so unsatisfying to some. I think the passage before the main argument can shine some light.

“When a painter considers beforehand what he is going to paint, he has it in his understanding…” What is Anslem trying to say here, or how should one understand this? I think he would demonstrate that it is in his understanding by articulating or describing what he plans to paint. This shows what is “in his understanding”. If he was unable to articulate, this would demonstrate that nothing was “in his understanding.”

“But when he has painted it, he both has it in his understanding and understands that what he has now produced exists.” I do not think Anslem is saying that the painter is reporting on what he is perceiving (though it is implied that it happened), but more reflecting on what he has produced, and that he can say “it exists” whether he is perceiving it or not.

How did Anselm demonstrate his understanding of God. He provided us with definition, “God is a being than which none greater can be thought.” It must be accepted to get one started in the deductive reasoning like one does with geometric proofs (consider Euclid’s Elements, "A point is that which has position but not dimensions.") From a definition, Anselm concludes that “God exists” because to exist “in reality” is greater than just “existing in understanding.” Unlike the painting example, Anselm is not reflecting on an experience of God “in reality” like the painter did with his painting, but reflecting on the "ideas of God" that makes him understand "God exists." And this is where, to some, the argument is not satisfying. Anselm gets to “God exists” not by the example most would agree they understand by “to exist in reality” like the painting example.

So we are left with:

Chapter 2 (Proslogion)

“What exists exactly?” Answer, “A being than which none greater can be thought.”

“And what is that?” Answer, “a being that exists “in reality” as well as “in understanding.” This is greater than just "in understanding."

“And what being is that” Answer, “A being than which none greater can be thought.”

Chapter 3 (Proslogion)

“What exists exactly?” Answer, “A being than which none greater can be thought.”

“And what is that?” Answer, "A being that necessarily exists" This is greater than a being that contingently exists."

“And what being is that” Answer, “A being than which none greater can be thought.”

do think this relies on empirical evidence so we don't need to believe everything a person says. But our experiences keep us alive and have allowed us to rigorously manipulate the world so I do not believe our sense have a huge scope for misleading us. So I don't think occasional illusions or false beliefs are grounds to undermine some notion of truth. — Andrew4Handel

There is a sort of intellectual laziness that is pervasive in philosophy. It goes something like this, I can imagine I am being deceive by my senses that there is a real world out there but what it could be is [insert what you can imagine] like a dream, brain-in-vat, simulation, etc. Then the philosopher goes on to say because this is possible will have no reason to believe we know anything. Radical skepticism is born.

I believe one mistake that occurs in the debate is the radical skeptic not distinguishing between what can be imagine and what is possible.

directly see the apple, and you directly see the apple, but the apple I see is different to the apple you see. My private experience of the apple is different to yours. — RussellA

How have (or could) you establish “my private experience of apple is different to yours”?

What evidence do you have that external stimuli, when not being seen, are accurately described by our description of how they appear to us when seen? — Michael

We will have “begging the question” again if you define “evidence” as only counting as how they appear to us when seen.

Only one accurately describes the independent nature of the external stimulus. — Michael

Sounds like you are begging the question now.

The Indirect Realist would say that "something caused the idea of a rock". — RussellA

One could reword as "something in the external world caused an idea of a rock in the mind" — RussellA

To be consistent, the indirect realist cannot say “rock”. The only meaning this term could mean by this theory is “some object” or “something”.

Which reduces to say “something caused an idea of something. Again this is trivial and does not say much of anything”. I don't see adding “external” and “mind” as adding much to the significance to the statement.

But please solicit the help of scientific theories to help give the metaphysical theory some creditability as I expect. Sometimes if you intermingle the two theories enough you can fool folk into believing they are saying the same thing.

That's precisely why the indirect realist says that there is an epistemological problem of perception. You seem to be arguing that because we don't like the conclusion we should reject the premise, which is question-begging. — Michael

Well, if I ask you what is causing your headache, and you tell me “Everything”. This answer does not have much value or any value at all other than maybe expressing frustration.

I would argue that our modern scientific understanding of the world, such as that of quantum mechanics, the Standard Model, string theory etc. support that conclusion above. There's just a mass of fundamental wave-particles, bouncing around, interacting with each another, and when the right stuff interacts in the right way, there's the conscious experience of seeing a red apple. — Michael

Whether you describe a rock “ordinarily” or “scientifically”, neither is more fundamental than the other. Each serves it own purpose to adequately and accurately described our experiences.

In perception, external objects such as rocks and cats causally affect our sense organs. The sense organs in turn affect the (probably, non-material) mind, and their effect is to produce a certain type of entity in the mind, an 'idea.' These ideas, and not external objects, are what we immediately perceive when we look out at the world. The ideas may or may not resemble the objects that caused them in us, but their causal relation to the objects makes it the case that we can immediately perceive the objects by perceiving the ideas. — RussellA

This quote highlights the problem with indirect realism. First, specific terms the community of language users all understand is used like “rocks” and “cats”. Second, the metaphysical theory is introduce, sometimes obfuscated with current scientific theories of perception (probably to give it credibility). Third, these ideas are perceived directly that are claimed to be certain which cannot be doubted. The next step is where a lot of confusion is introduced. Those initial terms we all understood are now in doubt, the external objects may or may not resemble the ideas. So, all the indirect realist can say is “some object caused an idea of rock” and “some object caused an idea of cat.” Which then reduces to “some object caused an idea of some object.” We are left with some trivial generality that does not say much.

Welcome to metaphysics!

Is it socially acceptable to hit a machine that is providing medical assistance to a human being?

Probably not, and it would be nonsense to assume the machine has a concept of human pain.