Hume has a nice quote from Enquiry

"It is a question of fact, whether the perceptions of the senses be produced by external objects, resembling them: How shall this question be determined? by experience surely...But here experience is, and must be entirely silent. The mind has never any thing present to it but the perceptions, and cannot possibly reach any experience of their connexion with objects. The supposition of such a connexion is , therefore, without any foundation in reason."

So, indirect realism have is "without foundation in reason" according to Hume. However, I argue that the situation is even more dire because the theory is just incoherent due to the use of "resemblance"

Indirect Realism is incoherent.

The use of the word "indirect" commits us to this idea that there is no resemblance between our "idea/sense data of a tree" and the "material object tree." That we directly perceive the idea/sense data but indirectly perceive the tree.

First, let us recall how we are taught the word "resemblance". Maybe it was done by showing two objects and our teacher says, "See, these two objects resemble each other, while those two objects do not resemble each". With each new encounter we use the word and show that we judge similar to our teachers and thus demonstrate that we understand.

Is the indirect realist use of word "resemble" coherent? This is what indirect realist is asking: see how these objects do not resemble each other:
1. The idea/sense data that is not accessible to us since it is a private object.
2. The tree itself is hidden under the veil of our experience since it is indirectly perceived

So, in principle, both objects are not available to compare on whether they are resembling each other; so, the use of the word "resemblance" in this theory is incoherent. And thus, indirect realism is incoherent.

This sounds just like John Searle’s Chinese Room thought experiment to show computers have syntax but not semantics. In this case, Y is just “moving” symbols around.

I heard a funny story told by Alvin Plantinga, a well know philosopher of religion. One day he visited a surgeon who proclaimed that he was convinced solipsism was indeed true. Upon leaving his office Plantinga asked one of the nurses what they thought of the surgeon, they replied "We make sure we take very good care of him."

Maybe they could re-title the article to “One Logic, Or Many, Or Just talking about something else”

I am sure it is true hallucinations is a rare event, but perhaps a lot of philosophy is based on trying to solve inconsistencies in a theory, such as Frege's puzzles and Russell's paradox. — RussellA

Good point, I just think philosophy tends to start real well rooted in what we all experience, but goes off the deep end when they loose site of the world and get mesmerized by the Eternal Platonic Realm of Ideas. This is where I part ways with Bertrand Russel when he said in "The Problems of Philosophy", "Thus, utility does not belong to philosophy." Maybe if utility was consider a little more, more consensus would be achieved, like in science.

Perhaps illusion would be a better word than hallucination, in that illusions are far more common than hallucinations. For example, I perceive someone 5m away as being taller than the same person 10m away. — RussellA

I have always was puzzled why Bertrand Russel in "Problem of Philosophy" had this expectation that the must be "the height", "the color", or "the shape" of a table. He never presented any argument on why this is the case, but used it as a spring board to start his skepticism of what we can know and cannot know.

True, most of my knowledge comes from the public realm, the Moon Landing, Disney Land, The Large Hadron Collider, Australia etc, ie, Russell's Knowledge by Description. — RussellA

Depending on circumstance on how one uses "I see a tree" and "I know I see a tree" these don't mean the same thing. Furthermore, this starts us down the path where Wittgenstein's in "On Certainty" explores Moore's misuse of "I know" in "I know I have two hands." In summary, both sentences do not make sense,"I know I have two hands" or "I do not know I have two hands", only but in extreme rare circumstances.

Searle wrote about Direct Realism and the problem with hallucinations — RussellA

I appreciate and admire John Searle's ability to critique philosophical theories, and I often find I am in agreement with is final positions. However, John's desire to theorize moves him away from some of the fundamental points Wittgenstein was trying to make in Philosophical Investigations. For example, I have concerns with his distinction between the ontological subjective, and ontological objective. I feel the weight of the private language argument more than he does.

think you are being too harsh on Descartes. He had an intense interest in the sciences, was not a sceptic but used scepticism as a means of philosophical enquiry. — RussellA

I do agree that a healthy dose of skepticism in life is extreme valuable, unfortunately, Descartes takes it too far where I would label it radical skepticism. To doubt whether there is a world or it is just a dream is taking it too far where the only way he saw to rescue the world is to rely on all loving God that would not deceive.

I asked if you see things in your dreams, not if you see dreams.

You asked where a visual representation of a tree appears and I suggested that it appears where all visual representations appear. — praxis

If you are interested, and find it strange when someone might not admit that they see in their dreams, I recommend you read a book called "Dreaming" by Norman Malcolm. In this book, he argues that it is a conceptual confusion to think one judges, reasons, feels, or sees in a dream. Malcolm is a great elucidator of Wittgenstein's later philosophy and uses to its fullest extent to challenge this notion of some mental phenomenon occurs in sleep.

For the Indirect Realist:
1) We directly perceive sense data. — RussellA

This is a problem for two reason:

1. In principle, this claim cannot be verified since it is inaccessible.

2. The indirect realist likes to claim that perceiving the material object is indirect because scientific theory shows this, but do we really think that using a hallucinogen that results in a hallucination is not also plague by a series of intermediary steps in the brain as well. To be consistent, we should also say it is indirect. But this is unfortunate, it seems the word "direct" is dissolving into being senseless, not exemplified by anything, real or conceptual.

Searle writes about the mistakes of philosophers of great genius — RussellA

The moment of "great disaster" is when Descartes decided to retreat to the private world of introspection to look for certainty at the expense of the public realm in which we learn to communicate with words to convey understanding to our fellow humans about a world that can get a bit messy.

As regards language, I would say that the machine is able to sense a wavelength but is not able to perceive it. — RussellA

Let's say I designed some glasses which duplicate an object, so when I put them on I see two objects, I take them off and I see one object. So metaphysically, why am I not committed to the glasses having "sense data" just like when I push one of my eye balls and report I see two of the objects. Can't we just say, "there is nothing to say here metaphysically, just our perception is distorted?"

The puzzle is, how can the mind, when perceiving an object, know the single cause of its perception, when the cause happened prior to the perception and at the far end of a long causal chain. — RussellA

You ask other minds, look at the evidence, and see what is persuasive. In this case, this is done in a public realm, not the private realm of "sense data".

I like to keep challenging this idea of "sense data" derived from the Argument of Illusion. I believe one needs to to assume first that our vertical experiences are the normal background in which we understand and recognize others have hallucinations. Or, we start down the path of radical skepticism in which we believe the whole world is one big hallucination. Additionally, the Argument of Illusion is based on our experience where we identified those who we say are hallucinating. This is not determined by some inward private determination. Given this, human beings who hallucinate are few, and most human beings have never hallucinated, and when hallucinations do occur, it occurs infrequently. So how did something that few humans being will ever experience, may never experience, and, if experienced, will happen infrequently, turn into positing "sense data" that every human being must have when perceiving the world around them. Maybe this shows that a metaphysical explanation that desires universal generality does not apply here. Or maybe it demonstrates a particular absurdity like concluding when I close my eyes and don't perceive anything, the world no longer exist.

One reason philosophers in the past have rejected Direct Realism is because of The Argument from Illusion, which is obviously a strong argument. — RussellA

So, the argument goes that we have hallucinations which seems to be indistinguishable from the veridical experience. To be consistent, whatever we say about the hallucination, we have to say the same thing for the vertical experience. Since the hallucination is not seeing a material object, we need to see something else. And along come "sense data."

But I have many questions here. If I come along and find somebody who does not hallucinate, does this mean they don't have "sense data"? Better yet, if no human being ever hallucinated, would that mean they don't have "sense data"? In this imaginary world, can we say these humans see the tree directly? What if I give two people a hallucinogen, and person #1 is determine to hallucinate, and person #2 is determine not to hallucinate, so does this mean we can conclude one person has "sense data", and the other does not. But if that is the case, we all know that most people don't hallucinate, so why to we talk like "sense data" is something universal to all human beings?

One reason philosophers in the past have rejected Direct Realism is because of The Argument from Illusion, which is obviously a strong argument. It is argued that the hallucination and veridical experience can be type identical, such that if an hallucination can only be explained by seeing sense data, then a veridical visual experience must also be explained by seeing sense data. — RussellA

We understand someone is hallucinating because others have "veridical experiences" and judge the one hallucinating is not acting normally. So how can one establish that someones "sense data" is identical to the other's "veridical experience" when it is inaccessible to verification, testing, or evaluation? How can we even establish if the memory of the hallucination is accurate? Or, if the one hallucinating uses the appropriate words to describe? All of this is not available to us. This undermines the testimony that can be provided by the one who hallucinates. Then what value does positing "sense data" have? None.

I would suggest abandoning such a metaphysical theory, and if you seek an "explanation", maybe look toward scientific theories, such understanding how pharmacological agents impact our the brain. There may be more satisfying explanations to be found.

Yep, for some, finding an answer to the the question is more satisfying, than accepting the question is nonsense or confused and so there is no answer.

We directly perceive sense data. — RussellA

One of the strengths that folk ascribe to this idea that we "directly perceive sense data" is the certainty that they can not be in error. This is the great appeal. However, I don't believe that the veracity of this idea can be proven, and the idea itself incoherent.

1. We all would agree that the truth that we "directly perceive sense data" cannot be verified by anyone because the idea presupposes that sense data is private, inaccessible for anyone to verify.

2. As for the coherency of this idea that you can not be in error, for example, if the sense data is "green" I cannot be in error that it is "green" because I directly perceive that it is "green". Let's take look at this example: the subject of a test is given an object and is asked what is the color of the object. The subject responds "my sense data I perceive is red". All the scientists in the room look at each other with concern. They ask the subject to repeat, and the subject says the same thing "my sense data I perceive is red". The scientists in the room look puzzled because they showed the subject a green object. To verify, they test the object for color and their instrument detects the color "green". What this shows is that what we will appeal to in order to determine if we are in error or not is not our sense data, which was supposedly unquestionable, but humans, in general, on what they agree in calling something "green" and judging that in fact it is a "green" object.

I think the beetle/box language game thing can be parked, but I guess you are saying that although humans 'create' green - it is not out there in reality - what is out there in reality is a particular light frequency that we experience as green. This can be objectively tabulated as a quality of the external world — Tom Storm

First, my response would be, "I perceive trees", "I perceive green leaves", etc. Second, I would not say, "I perceive sense data of trees, green leave" etc. Second, I am not sure if I would use the word "create" unless this means we came up with the word "green" to communicate with our fellow humans about a particular color. Additionally, I think indirect realism and direct realism share a similar problem in that these positions can be concerned with arguing about objects "as they really are". For example, just take these two definitions:

1. direct realism: the idea that the senses provide us with direct awareness of objects as they really are.
2. indirect realism: the idea that we do not perceive the external world as it really is, but know only our ideas of the way the world is

To say, "I directly perceive the tree" sounds redundant to "I perceive the tree", unless you want to set up the comparison with "I indirectly perceive the tree in a mirror." But to say only say "I directly perceive a tree as it really is" seems to have go down the path of philosophical confusion. Could you give it meaning? I suppose you could, and maybe if there is enough agreement in judgment your got agreement in the form of life, for example, scientific theory of color.

Lastly, if what you say, "what is out there in reality is...", means just that our current scientific theory says the color "green" has a particular wavelength and we can talk about the color "green" with each other, OK I am good with that.

I will leave you with what Wittgenstein say in Philosophical investigations, "'So you are saying that human agreement decides what is true and what is false?' It is what human beings say that is true and false; and they agree in the language they use. That is not agreement in opinions but in form of life."

Let us assume we humans evolved to where detecting “green” was so important in that it gave us the necessary energy to live every day. Every time we come across an object that is “green”, we gather it for nourishment by just looking at it. Since it was so important, we developed machines, more sensitive and accurate than humans, that could detect the green color of objects. So light would come in and the machine would report and answer “green”. Is the machine having a sensation or constructed perception of “green” to detect the color of “green” in order to report “green”? Like Wittgenstein’s “beetle in the box”, what is in the box has no place in the language game at all; not even as a something for the box might even be empty (like my machine example?).

There is a direction to causation, in that it is not the case that first there is an effect and later there is a cause. For example, first sunlight hits the leaves of a tree, then light travels from the leaf to our eyes which we can then sense as green. It is obviously not the case that we sense green, then light travels backwards from our eye to the leaf. There is a direction of causation as there is an arrow of time. — RussellA

Let’s clarify something here. What caused us to detected the green coming from the leaves of the tree. Well scientific theory teaches us that chlorophyll gives plants their green color because it does not absorb the green wavelengths of white light. This is a cause. In your example you are asking what causes a human being to sense green in reflected light. This cause is happening in the eye and brain. This cause occurs in the brain and is after the light striking the leaf.

But how does it follow that we do not perceive the external world as it really is. The leaf is green because it does not absorb the green wavelength. If it is not, what color is it? If you say there is no color, well OK feel free to define “what it really is” any way you like, maybe it will have some interesting utility for us.

Pick up a copy of Semantic Relations and the following is the pertinent excerpt of the "two Bruces":

"To this end, let us imagine a universe that is completely symmetric around someone's center of vision. Whatever she sees to her left is and looks qualitatively identical to something she sees on her right(not that she conceptualizes the two sides as "left" and "right" since that would introduce asymmetry) She is now introduced to two identical twins, one to her left and the other to her right, and she simultaneously names each of them "Bruce"; using a left token of "Bruce" for the left twin and a right token of "Bruce" for the right twin. The two tokens of "Bruce" are then always used in tandem so as not to disturb the symmetry. Thus if she uses the left token of "Bruce" to say "Bruce is wearing pink pajama," she simultaneously uses a right token of "Bruce" to utter the same thing. She can even assert the non-identity of the two Bruces by simultaneously uttering the one token of "Bruce" from the left side of her mouth, the other token from the right, and a word for non-identity from the middle of her month.

It seems intuitively clear that she has the use of two names or, at least, the ambiguous use of a single name; and this is something that the Fregean should in any case accept since the name or names can be used to state an informative identity. But what, then, is the difference in sense? By consideration of symmetry, there is no purely descriptive difference in the referents. And this in itself is enough to refute a view that takes sense to be a purely descriptive means of identifying a referent. We can even suppose that she is originally introduced to one person but, seeing him "double," takes him to be two people. Her use of the two names will then not even differ in their reference."

Or, when will we realize that these “puzzles” are not meant to be solved, but to be dissolved away by reflecting on how we use our language.

I can measure the length of a box, but what am I measuring when it comes to time? And so begins the puzzling….

Yeah, I need to find that original. That said, maybe I can have a little fun here. Assuming she lives in a symmetrical universe, her everyday experience would be two Bruces.

It would be completely normal for her to see two Bruces, one on the left, and one on the right. Both moving in the same exact way, like every thing else her world. However, I could imagine her wondering. Wondering why two Bruces move the same way on both sides and two Johns move the same on both sides, but most times, the two Bruces move differently than the two Johns. Would she not wonder why this is the case? Would she not seek an expalnation. Then one day, she comes across a mirror, and see a a reflection of herself on one side, and another reflection on the other side. In this case, this reflection moves exactly as she does, on both sides. Would this experience give her insight into an explanation that all is not what it seems? From this imagination, maybe one day, she becomes a scientist, studies the brain, learns how the brain takes in light and forms visual images, and discovers that her brain(brains?) actually form two images. Would she not be able to determine the "underlying reality"?

Does not this scenario presume one individual since it talks about duplicating the source? And if so, in principle, should be decidable.

“The Finean cluster may be roughly summarized by the following methodological “directives”:

1. Provide a rigorous account of the appearances first before trying to discern the reality underlying them.
2. Focus on the phenomenon itself and not just how we represent or express it in language or thought.
3. Respect what’s at issue by not allowing worries about what we can mean from preventing us from accepting the intelligibility of notions that strike us as intelligible.
4. Be patient with the messy details even when they resist tidying or systematization.
5. Don’t allow epistemic worries about how we know what we seem to know interfere with or distract us from clarifying what it is that we seem to know.”

As one who appreciates and practices later Wittgenstein philosophy, I am particularly suspicious of 1 and 2. And 3 looks like a pill for what some may say is a medication to treat “Wittgensteinian brainwashing”.

↪ — Banno

Nice synopsis.

"Water is H₂O" is another unfortunate example where Kripke takes a "holiday" with language. Consider the following quote from N&N, "Let's consider how this applies to the type of identity statements expressing scientific discoveries that talked about before - say, that water is H₂O. It certainly represents a discovery that water is H₂O. We identified water originally by its characteristic feel, appearance and perhaps, (though the taste may usually be due to impurities). If there were a substance, even actually, which had completely different atomic structure from that of water, but resembled water in these respects, would we say that some water wasn't H₂O? I think not."

In fact, the scientific discovery is not "water is H₂O", but that the substance (whether liquid, solid or gas) we often call "water" we often detect H₂O molecules. Additionally, that substance we call water is not just H₂O molecules, but made up of multitude of compounds, mineral, ion, etc. Not only it is made up of a multitude of different molecules, but that composition can change from thing to thing we call or refer to as "water". So, when any one refers "water", am I referring to only H₂O, or all of molecules that make up any given thing called "water"? Due to multiple uses of "water", and multiple things we use "water" to refer to or could refer to, it is an error to say "water is H₂O" is discover scientically. Lastly, could we say that "some water wasn't H₂O". Yes, in fact we can and do say this, D₂O is called "heavy water" is the scientific community.

So, what is Kripke's error in this example? I believe he ignores the common uses of the word of "water" along with what actually science discovers about "water". What use he has in mind for "water" is how we use the word(symbol) "H₂O"; thus, what he is expressing is "H₂O is H₂O" which is not an a posteriori necessity.

Does this throw some doubt on Kripke's philosophical theory, or just show what he is saying is just trivial, or both?

I would recommend reading Norman Malcolm’s paper on “Kripke on Heat and Sensations of Heat”. Taking a later Wittgenstein approach, Malcolm shows Kripke’s views are not coherent which he also believes sheds doubt on the correctness of his theory. One of the issues Malcolm raises is Kripke’s confusing with the distinction between feeling heat and feeling hot. Also, Malcolm shows how Kripke incorrectly describes how people originally identified heat, specifically, somehow picking out a ‘certain sensation’ instead of learn it from a community of people. Lastly, Malcolm does an forceful job of showing the ‘Martian’ example as incoherent.

I like this quote from Wittgenstein in Culture and Value, “People say again and again that philosophy doesn’t really progress, that we are still occupied with the same philosophical problems as were the Greeks. But the people who say this don’t understand why it has to be so. It is because our language has remained the same and keeps seducing us into asking the same questions. As long as there continues to be a verb ‘to be’ that looks as if it functions in the same way as ‘to eat’ and ‘to drink’, and as long as we still have the adjectives ‘identical’, ‘true’, ‘false’, ‘possible’, as long as we continue to talk of river of time, of an expanse of space, etc. etc., people will keep stumbling over the same puzzling difficulties and find themselves staring at something which no explanation seems capable of clearing up. And what’s more, this satisfies a longing for the transcendent, because in so far as people think they can see the “ limits of human understanding”, they believe of course that they can see beyond these.”

Is it the colours here that are the simples? Or are the colours irrelevant, and the fact that there are squares instead of circles what is important? Or that the grid is three by three, and not two by four? The point is that what is significant here is far from clear until one understands what is at stake. — Banno

Maybe one of the most profound passages in Investigations that seems most do not appreciate. It dissolves away much of philosophy’s pretentious foundations.

Not only do we see this idea in popularized science, but has been firmly imbedded in philosophical circles. Whether D.C. Williams theory of the manifold(“The world manifold of occurrences, each eternally determinate at its own place and date….”), McTaggart’s eternal/nontemporal ordering of events ( C-series), or Quine’s eternally ordered series.

Sometimes a question makes sense, or sometimes a question compels one to give it sense so to continue the dialogue; otherwise, we are talking nonsense.

Determinism could be problematic concept. I would say in three areas, explanatory power, falsification, and rationality.

1. Does determinism explain? Prima facie, it seems so, however, let's look at it a particular way. Many who hold deterministic views propose a "block universe" where past, present, and future exist simultaneously, eternal and unchanging. But if this is so, how does an edge of a block, explain the edge of the other side? What if we introduce an equation, say volume of the block, does that not explain the edges? Or, are we just describing? It seems that the explanation has transformed into a description. If free will is an illusion, is not explanatory causal chains an illusion as well, simply replaced by ordered sequences that are described?

2. Can determinism be falsified? How are we to disprove determinism. What will count against such an idea? If event A is the cause of event B, and I find one instance where event A did not cause event B, would this count? But in practice, would we not appeal to a lack of information with regards to A, something that was missed, somehow we did not define A accurately. It seems we can just ad hoc our way in excusing instances that may falsify determinism. What if event A is the cause of event B one time, and event C another time, and this pattern repeats, ad infinitum. Is this not indeterminism? But who said that could not count as deterministic?

3. Is determinism about what is rational? I would say no, determinism is about what is non-rational. And this is a problem with our notion of being rational. As rational beings we count on our reason and logic to evaluate arguments, positions, views, etc; however, determinism robs us of this intellectual position and reduces us to determined states of affairs following one after another. So, not only is "free will" illusionary but our rationality too.

In conclusion, determinism does not explain, cannot be proved or disproved, and undermines our rationality. So what should we do? Ignore determinism, and continue to utilize the concept of "free will" that has served humanity well for centuries.

You shouldn't raise questions about things you don't really have an interest in. — Constance

“We can never be sure that the opinion we are endeavoring to stifle is a false opinion; and if we were sure, stifling it would be an evil still.” From Mill, On Liberty

It is far more direct and reasonable to posit that abstractions such as property, marriage, and complex numbers are stuff we made up than to imagine them exiting in the way chairs and trees do, but in some parallel reality. — Banno

As an ultimately abstract entity, I enjoy the company of so many numerous abstract entities. We often discuss if there really are concrete objects, but conclude they are just grammatical fictions.

They are in you and in me; they created us, body and mind; and their preservation is the ultimate rationale for our existence. They have come a long way, those replicators. Now they go by the name of genes, and we are their survival machines." — Andrew4Handel

Nice, anthropomorphize DNA, I think I heard this story before

To think, I might be sitting next to unactualized possibles, the conversations to be ……