Damn complicated.

My guess would be he would go the “natural kind” direction. And that natural kind terms would refer directly to things in the world, not to descriptions or mental contents; basically, world-involving from the start, not mediated by sense-data.

However, his argument against mind-brain identity can make one pause. He seems to find talk of first person private phenomenon intelligible, that pain is privately, directly, and essentially felt. But this is not necessary identical with neuron’s firing. So could he not argue that talk of private, direct awareness of mental images of apples be intelligible but not necessary identical with neuron firing. But what about the mental image of the apple and the apple, do they not refer to the same kind in every possible world (including the actual world)?

I was kind of prodding what you would think a Kripkean analysis of the debate would reveal?

For the indirect realist, does the “mental image of an apple” refer to an apple, a neuron state, or some mental substance, or all three at the same time?

I think any realist would say the term “apple” refers to apple.

What say you?

Cool.

This is clearly what indirect realism argues, as contrasted with their naive realist opponents, hence why it says here that "indirect perceptual realism is broadly equivalent to the scientific view of perception". — Michael

And this assessment that "they are broadly equivalent" is not science but philosophical befuddlement.

In normal perception, the object of awareness is the physical object itself, not a representation of it. We perceive objects and states of affairs in the world, not internal representations. In science, neural processes enable perception; they are not what is perceived. Science provides an alternative description of perception by incorporating ideas of diachronic and constitutive causation. Once the brain's causal powers are are accounted for by physical processes and constitutive structure, there is no explanatory gap left for "representation" to fill, like "sense data", "mental phenomena" or "inner images". If representation is just the function of neural states, your philosophical view stops being indirect and becomes more of scientific direct realism.

This idea that we have to 'colonize other planets' to 'escape Earth' is a sci-fi fantasy. We have a perfect starship, one capable of supporting billions of humans for hundreds of milions of years. But it's dangerously over-heated, resource-depleted, and environmentally threatened. That's where all the technology and political savvy ought to be directed - to maintaining Spaceship Earth. — Wayfarer

Sometimes we humans do things not for any good or bad reason. When humans first figure out a way to handle and tame fire, they likely had not idea the benefits or hazards in developing such a technique. We just did it due to some natural inquisitive impulse. I think that same impulse has and will continue to drive space exploration as well. Rational debate will just be window dressing.

Thanks, just a steady diet of many examples.

Neither theory runs against reality. That's why it's such a tense question. I understand the temptation to say what you're saying, but it just doens't touch anything. You're talking about standards and method. The thing Michael and I are, at the least trying to get you guys to deal with properly, is the fact accepted by both camps that there is no possible way for the apple on my desk to be in my head, and it snot possible that my mind is included in the objects it perceives. So there's gap - simple as. — AmadeusD

Let me provide another example, this one from the biological world. I have read that certain species of snake can detect heat signatures from animals. Biologist have identified a “pit organ” around the eyes that senses infrared radiation. The heat the snake is interested in and detects is the heat emanated from warm bloodied mammals. This is not a private sensations the snake is detecting, it is a property of the mammal. No mental images need to explain what is going on here. So, is the snake a direct or indirect realist when it comes to infrared energy? Do we really need to use either expression?

If neither, cant we do the same with colors and homo sapiens?

Some thoughts,

We don’t go around proving humans have sentience. It is not that we have proven sentience for humans and suddenly started using the term for humans. But it is a sort historical reflection about how we characterize what it is being human.

So much of being human is our interactions with an external world. We developed our language to communicate with others, to predict future occurrences, and to cope and survive in such a world.

I think for AI not having this immediate nexus to reality without the intermediary of humans makes it difficult to talk about sentience. However, if some AI is able to collect this information about the world independent of humans, use this information solely for its own purpose, however it defines it, it begins to walk a similar path as humans. Maybe, down the road, it might define or characterize what it is being AI.

There is a great critique by Norman Malcolm of the thought experiment that there could be Martians who have our "sensation of heat" when exposed to cold and our 'sensation of cold' when exposed to heat. He said,

"What sort of behavior on the part of the Martian would justify us attributing to them "sensation of heat and cold' in this sense? Are we to imagine that when they enter a hot room or stand near a hot fire they begin to massage themselves and to put on more clothing? But this would be unsuitable behavior for the Martians. Massaging one's body and donning more clothing is warming because it increases the heat of the body. If the Martians adopted those measure they would show themselves to sensitive to heat as heat, which they are not supposed to be. This description of the Martians would seem to be contradictory. On the one hand, they are not sensitive to heat; on the other hand, they are sensitive to and grateful for the increase of bodily heat produced by putting on more clothing."

He goes on to show the incoherence of the opposite view as well. The ultimate conclusion Malcolm draws is to show the conceptual connection between a sensation and the natural expression of that sensation in behavior. To sever this connection is to cease to employ the concept of sensation.

I do get the impression you both feel that scientific discoveries demand that we should accept the metaphysical picture that indirect realism seems to draw. However, I have attempted to show science gives little to no support to such a philosophical theory. As indirect realism retreats into private first person experiences, science needs to find consensus in the public realm. Much of the foundation of science starts with basic human agreement. We start to learn color concepts not by private introspection, but by being presented with color standards, community reinforcement of color language, and general consistency in color judgement. If we don't have this general harmony, the whole language game of colors may have never gotten off the ground for us to create alternate descriptions of color like the use of wavelengths. Additionally, I attempted to present a picture of science where we may want to use the word "direct" if we view perception as a biological processes like hydration, digestion, and respiration. If hydration directly processes H2O, why can't we say perception directly processes light?

I like to present one more argument that science does not support indirect realism. In fact it actually ignores it all of the time. Science does not treat observables as private introspection mental phenomena but as public, stable, and law governed. Science manipulates and predicts these observables and does not consider them mental accidents. Hallucinations do not come into play if scientific outcomes result in variance. Others considerations are given weight like, measurement error, experimental set-up, statistics, and theoretical framing. Mental phenomena, like hallucinations, serve no global explanatory role and methodologically irrelevant. You might say, we should keep "realism" and drop "direct/indirect" and understand we are causally embedded biological organisms whose process of perception supports interventions, coordinations, and manipulations of our environment.

Yes.

And what scientists are trying to understand is the color judgment inconsistency with the dress, not demonstrating the accuracy of private color experiences.

Austin, “First of all, it is essential to realize that here the notion of perceiving indirectly wears the trousers - ‘directly’ takes whatever sense it has from the contrast with its opposite…”

But what sense can we make of directly seeing a ship when we are told that we only indirectly see a ship in our minds. What are we supposed to envision so to set up the comparison. Indirect realists describe the same process of perception we all probable admit, yet they insist calling it “indirect”. Don’t we deserve to understand what we are supposed to call “direct” when described as well.

Maybe taking a more naturalist's position could help in the matter. I think you would admit that we are all “direct realist” when it comes to the biological processes of hydration, digestion, and respiration. So, the good news is there are biological processes that have “direct” contact with the external world.

There is no temptation to say such things as:
1. “You are only indirectly digesting food via representations of nutrients.”
2. “You are only indirectly hydrating via representations of cells being hydrated”
3. “You are only indirectly having oxygen enter the lungs via representations of gas exchanges.”

Now the question arises, if perception is a biological process continuous with others, why would it uniquely require a mental veil?

Perception is biological relation to the environment just like other bodily processes. The fact that errors, like illusion and hallucination, occur does not imply mediation by mental objects.

Take this analogy about grasping. You can successfully grasp a cup, but you also can try to grasp when the cup is not present. But we don’t say, “What you really grasp is an inner grasp-image.”
Thus, there is no need to metaphysically isolate perception from other biological processes.

So, as naturalists we are committed to the idea that organisms are directly related to their environment through evolved biological processes. So, perception is how organism process light. But this is not the whole story, this light is structured in such a way that the organism is receiving information about the environment. Processing light does not make perception indirect any more than processing oxygen makes breathing indirect. One proponent of this view of perception is James J. Gibson. In, The Ecological Approach to Visual Perception, he presents his theories of perception as an alternative to mentalism or conditioned-response behaviorism. That light is not just for stimulating receptors but transmitting information that can activate the system of the organism.

“Direct realism” is not a position that emerged from philosophers asking how perception is best understood, so much as a reaction to dialectical pressure created by a certain picture of perception, roughly: the idea that what we are immediately aware of are internal intermediaries, be they sense-data, representations, appearances, mental images, from which the external world is inferred.

Once that picture is in place, a binary seems forced: either we perceive the world indirectly, via inner objects; or we perceive it directly, without intermediaries. “Direct realism” is then coined as the negation of the first horn. It is not so much a positive theory as a reactive label: not that. This already suggests the diagnosis: the term exists because something has gone wrong earlier in the framing. — Banno

This is too good.

Moore took the bait from idealist, but at least he included showing us his hands.

In my book From Testimony to Knowledge I lay out simple criteria for evaluating testimony. Testimony isn’t a weak route to knowledge. Most of what we know comes through the reports of others. The issue isn’t whether testimony can ever justify belief. The issue is what makes testimony good evidence, especially when the claim is weighty. — Sam26

In Chapter 2 I give five criteria that strengthen testimony: number, variety, consistency, corroboration, and firsthand character. — Sam26

For roughly 1500 years humanity believed that the Earth was the center of the universe. Supposedly, some folk named Aristotle and Ptolemy rationally demonstrated this geocentric claim. For 1500 years their knowledge was handled down as gospel. I can’t imagine how many folk, from different areas of the world consistency spreading the same message over and over again that the Earth is the center of the universe, sometimes explaining the rationale argument sometimes just blindly repeating the words. I guess what can be passed down can be what is the case or what is not the case.

My only hope is someone new to this area gets curious and wonders why we say such things. Their curiosity, I believe, will be rewarded.

Are you saying light at 450 nm and 700 nm both will stimulate the same B neuron for John to experience two different colors or one color? Or does John need two different neurons to experience two different colors? You example, #1 and 3, suggest two neurons are needed for two colors. Ok, if so, example #4 then suggests that two wavelengths can stimulated the same neuron. So is it one or two? Or some hidden stimulation?

What I have been trying to show is that science can only assist in helping us understand at a microlevel how humans have consistency in color judgment and how some may have divergent judgments (color blindness). Science relies on shared standards of color, consistency of color judgments, and shared language, not private introspection of sense data. So the metaphysics of indirect realism cannot find support from science.

I think these revisions make it clearer what you are trying to assert.

1. The strawberry reflects 700nm light into John's eye which correlates with the stimulation of A neuron, and John’s report seeing the color red.

2. The strawberry reflects 700nm light into Jane's eye which correlates with the stimulation of the B neuron and Jane’s report seeing the color red

3. The strawberry reflects 700nm light into a visor that emits 450nm light into John's eye which correlates with the stimulation of the B neuron and John’s report seeing color blue.


However, point 4 is a little unclear for revision.

4. The strawberry reflects 700nm light into a visor and the visor bypasses John's eye to stimulate his B neuron, John reports seeing blue.

What is a mystery is the nature of the stimulation of John’s B neuron. What we understand is the emission of 450 nm light which we typically call “Blue” is associated with stimulation of John’s B neuron. And no other color’s wavelength should be stimulating this color. So, if it cannot be no other color wavelength stimulating this color, other than blue, what is the nature of this stimulation? We are alway bombarded with enormous amount of “stimulations” from the external world that can make color judgments difficult to get accurate. Looks like the visor is one of them.

A description close to Davidson's anomalous monism, the view that while thoughts and actions are physically grounded (monism), there are not governed by strict laws. — Banno

I am sympathetic to his idea that there are no strict laws connecting the mental and the physical. I myself am incline to think the casual laws are descriptive and predictive but not so sure we should call them explanatory. If I watching a movie from a movie projector, can I come up with a casual law. Sure, I can cut a strip of film into sequential pieces and label them 1, 2, 3, and so on. The law is the previous number piece causes the next number piece, 1 causes 2, 3 causes 4 and so on. I can get another uncut strip of film of the same movie and make all kinds of predictions on what will follow when one sees any particular scene from the movie. But does this explain what the movie is about? What is the plot of the movie? What are motives of the character? What reasons are there that the story is set in that location?

Quite so. But then one has to explain what a hallucination of a dagger is, if not a mental image. That's not easy, because most people are absolutely sure that, like Macbeth, they see a dagger that is not there. — Ludwig V

If I paint a landscape from memory of a park I visited long ago, do I need to appeal to mental images to explain how I did it? Is it not explanation enough just to say, “I am trained to paint landscapes, I visited that park, and have a good memory, go visit the park and you can see how accurate the painting is.” I don't need to say, “I am good at painting the mental copy of the park I have in my mind.” There need not be any mental copy at all.

I thought it might be interesting to interject here since I see my position as being wedged between Banno's and @Richard B's on the one hand, and @Michael's on the other.

I’m broadly sympathetic to the spirit of Banno's and Richard's replies here, but I wouldn’t go quite as far as saying these inversion scenarios are outright incoherent or fail to be truth-apt. — Esse Quam Videri

The modern camera does a good job of accurately depicting the world. I don't hypothesize metaphysical intermediaries like mental images/sense data for the camera to achieve this success in accuracy. Likewise, I don't need to do it for the human brain, which has about million of years of development behind it, while the camera has about two hundred. When an artist paints a landscape by memory of a visit to a park, the accuracy is judged by comparing it to the actual park, not to some mental picture. If the picture is inaccurate, I don't suppose the camera hallucinated an extra tree when the picture has two when there should have been one. But I will inspect the camera to see if it is working properly. This is not to say the imagination cannot aid in the troubleshooting the problem of the camera, but only if that imagination has some knowledge of its design should we expect a resolution.

We probably can’t, save for perhaps opening their heads and checking to see which neural correlates are active. It stands to reason that if their visual cortices are behaving differently then they are having different experiences, even if they utter the same words when asked to describe the strawberry. — Michael

I don't think science can offer any assistance in principle. Let me illustrate this with a thought experiment. For simplicity sake, let us assume this world has only two color, red and blue. Let us assume they have established wavelengths of 620 to 750 nm for red and 380 to 500 nm for blue. In the advance civilization, they have the technology to isolate brain state correlates (BSC) in the human brain with great precision. One day they decided to perform an experiment, where two subjects are exposed to two colored swatches (with verified wavelengths). With each exposure, the subject's BSC is recorded. When they exposed the red swatch to S1 they captured a BSC reading of 100, and when exposed to the blue swatch the BSC reading was 200. Interestingly, when they exposed the red swatch to S2 they captured a BSC reading 200, and when exposed to the blue swatch the BSC reading was 100, they complete opposite of S1. In both case, S1 and S2 verbalize the correct color of the swatches. What can the scientists conclude from such experiment? Simply, when these two subjects are exposed to the same colored swatch, there is a different associated BSC. What evidence is there they are experiencing different "private colors"? They are able to make the correct color judgment, so that seems to suggest they are experiencing the same color but just have different BSCs. And if they were experiencing different "private colors" how could we ever assign which "private color" to which BSC? You can't they are private. Would adding more subjects to the experiments help in any way? I do not see how. We can add 10 more and all had the same patterns as S1 and make the same correct color judgments, but in the end, it adds no evidence to what the "private color" is for each subject.

Whilst Kripke frames are formally useful, the same cannot be said of Kripke's metaphysics. — sime

Yep, pure logic always searches for purity. Unfortunately, reality and humans are messy.

The question is, are your examples counterexamples to Kripke's metaphysical concept of rigid designation? — sime

1. "Water is H2O" I have shown is problematic because it distorts what science actually discovers, how science actually uses the terms, and finally, how we use these term in ordinary language.

2. What about substances such as gold or diamonds that has microstructure exhibited by a single element. This connection between the word "gold" and atomic number 79 is not pre-existing metaphysical bond, but a stabilization of linguistic practice informed by scientiifc investigation.

3. In Norman Malcom's paper "Kripke on Heat and Sensation of Heat", Malcolm dismantles Kripke's idea the heat is identical with the rapid motion of molecules. In particular, he first focuses on Kripke's idea that it is a contingent property of heat to produce a particular sensation in human being; Kirpke's queer idea of how human's "originally" identified certain sensation we call "heat", and, contrary to Kripke, the idea that science discovers correlations not identities.

4. In another of Malcolm's paper, "Kripke and The Standard Meter", he explores Kripke's idea of the standard meter being a contingent a priori truth and finds it wanting. In summary he says, "To think that this sentence should be characterized as either a contingent statement or as a necessary statement seems to me to be looking at it in a wrong way. The sentence, "One meter is the length of S", is correctly characterized as being, in relation to the institution of metric measurement, the definition of 'one meter' and also as a rule for the use of the term 'one meter'. One can also rightly say that this sentence was used to make a fiat or decree. Kripke says that the term 'one meter' was meant to designate 'a certain length in all possible worlds'(p.275) It seems extravagant to say that the decree was a decree for 'all possible worlds'. Probably, the person or persons who made the decree did not envisage anything whatever about 'all possible worlds'.

5. Kripke say something rather prima facie absurd in N&N, "Just as something may have all the properties by which we originally identified tigers and yet not be a tiger, so we might also find out tigers had none of the properties by which we originally identified them. He suggests that this "tiger kind" is rigidly designated by some internal structure, much like the term "water". Certainty an animal's genetic structure would be a good candidate for such an "internal structure." However, I could imagine domesticating a tiger where its behavior is no longer classified as a carnivore but a herbivore. Can't we say we change the kind based on observable properties and not internal structures. What about genetic structure themselves for more simpler living things such as microorganism. But this is tricky, microorganisms can change behavior radically different depending whether they are a "wild type vs lab grown." Depending on their environment microbes will turn genes on or off resulting in morphology differences and behaviors.

I will end with two Wittgenstein quotes showing my foundation of my thinking:

Form PI 18, "Do not troubled by the fact that language (2) and (8) consist only of orders. If you want to say that this shows them to be incomplete, ask yourself whether our language is complete, - whether it was so before the symbolism of chemistry and the notation of the infinitesimal calculus were incorporated in it; for these are, so to speak, suburbs of our language. (And how many houses or streets does it take before a town begins to be a town?) Our language can be seen as an ancient city: a maze of little streets and squares, of old and new houses, and of houses with additions from various periods; and this surrounded by a multitude of new boroughs with straight regular streets and uniform houses."

From On Certainty, 505, "It is always by favor of Nature that one knows something."

It only appears to us that all the sights, sounds, smells, shades that comprise the world, are the world. They are not, they don't belong to the world at all. — hypericin

But those who advocate for indirect realism like to point out how all of this goes on in the brain. And last I heard the brain is part of this world.

Let's
I can conceive some gold is Au if fool’s gold gets $4500 oz. Do I need guidance from possible world semantics to clarify that my use of “some” needs correction?
— Richard B — sime

This example was to draw attention to what Kripke says in N&N:

"If there were a substance, even actually, which had a 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. We would say instead that just as there is fool's gold there could be a fool's water."

I was told that possible world semantics/rigid designation as a formal language does not perfect our language but can guide it. So, I wanted to know if a community that treated "fool's gold"(FeS2) the same as "regular gold" would we need to correct them when they say "some gold wasn't Au." I did not get an answer, but I would say "no" we do not correct them because we can clearly understand how they are using "some" and what is "essential" to them is not some microscopic atomic structure but similar macroscopic properties they find valuable. Another good example is things we call "diamonds." What has science discovered here? That a diamond is C. But wait I thought science also discovered that graphite is C. I am confused about what is happening in that possible world where they both exist. It reminds me of a favorite passage in Quine's paper from "On what there is":

"Take for instance, the possible fat man in the door way; and, again, the possible bald man in the door way? Are they the same possible man, or two possible men? How do we decide? How many possible men are there in that doorway? Are there more possible thin ones than fat ones? How many of them are alike? Or would their being alike make them one? Are no two possible things alike? Is this the same as saying that it is impossible for two things to be alike? Or, finally, is the concept of identity simply inapplicable to unactualized possibles? But what sense can be found in talking of entities which cannot meaningfully be said to be identical with themselves and distinct from one another?"

Getting back to my "diamond" example. Maybe one would like to say "diamond is C in a structure A" and "Graphite is C in structure B" But I could imagine a community saying "some diamonds are not diamonds." What could that mean? Well, actually in today's world many people do not view diamonds found in nature to be the same as "lab-made" diamonds. "Nature-made" diamonds are more expensive than "lab-made" diamonds, and hold their value better historically, yet they both are composed of the same element and microstructurally the same. The "essential" difference between them is simply the process on how they were made.

I will oppose your position of indirect realism from a different angle. I often argued that there is no need to posit “mental entities”. My other criticism is that indirect realism ends up positing an external world. Specifically, indirect realism has a problem with causality. I would summarize my concern as follows:

If all causal relations that we can observe or describe occur within the mind/brain, then the supposed causal link to external objects is never actually experienced or justified.

To put it more specifically, the external cause is never part of the casual network you can access. Thus, the external world only becomes theoretical, which risk slipping into idealism or radical skepticism, which I think you do not want to assert.

Now we are stuck with an external world doing no epistemic work.

I looks like we both have an uneasiness with possible world semantics. I think your unease is more with the metaphysics, while mine is with the application. The PI sections you had mentions, 253 to 256 are typically associated with Wittgenstein's argument around private language. Should this extend to possible world semantics? At first glance, I would say "no". Possible worlds are not suppose to be a private language. In PI, a private language is about language only a single individual understands that refers to purely private inner experiences.

So Kripke just makes a deceptive use of language, to produce the appearance that the table in his hands could also be in another room. — Metaphysician Undercover

He does not say this in the quote I mentioned from N&N. What he says is "Don't ask: how can I identify this table in another possible world, except by its properties? I have the table in my hands, I can point to it, and when I ask whether it might have been in another room, I am talking, by definition, about it."

He is not saying if the table in my hands is also in another room, but whether it might have been in another room. And, he is talking, by definition, about it.

I have no issue with this plain speak. We use this kind of language all of the time in real life. We sit down with old friends, talk about old times and reminisce about "might have beens."

But sometimes philosophers should live well enough only. In this case, they go and introduce the concept of "possible world". My intuition tells me just because you can imagine something does not mean it is possible. And when I use the word "possible", I mean it in the most general sense. Also, alternatively, just because you can't imagine something does not mean it is impossible. For instance, we have learned that nothing can go faster than the speed of light. But some would like to qualify this and say "This is a physically impossible, but not metaphysically or logically." Yet, these limits were not derive from experiments, but are derived conceptually. While one can imagine numbers greater than the speed of light without contradiction, those numbers conceptually would quickly undermine our notions of time, space, and causality, basically reality itself would become unintelligible.

This discussion reminds me what Wittgenstein said in On Certainty 505, “It is always by favour of Nature that one knows something.”

I can conceive going to a community and asking for a glass of pure H2O and the waiter looking at me with puzzlement. I was thirsty so quickly change my strategy and I ask for a glass of water.

I can also conceive going to a community, maybe too scientifically literate, and asking for a glass of pure H2O, but this time the waiter gives me an incredulous look. The waiter explains that they only have 99.8% H2O, 10ppm Na, 30 ppm Ca, 2 ppm Mg, 5 ppm SO4, 25 ppm Cl, 30 ppm HCO3, 0.1 ppm Fe, 300 ppm HDO, and 20 ppm D2O. He also explains to me that there is some uncertainty in these numbers but can provide those values if requested. I was thirsty so I drank this cornucopia of chemicals, even with this analytical uncertainty.

Back at you

I can conceive some gold is Au if fool’s gold gets $4500 oz. Do I need guidance from possible world semantics to clarify that my use of “some” needs correction?

What say you?

"Water is H2O" is statement without context my friend. If the term "water" is being used like "Dihydrogen monoxide" then it is a stipulation and thus analytically true. There is no difference between "water is H20" and "Dihydrogen Monoxide is H2O". If you are using it as a chemist may use it, then it is about composition, not identity. You can call any liquid you like by the name of"water", but an scientific analysis will tell you the composition. And even if you discover that it is mainly composed on H2O molecule, you can still call that liquid by another name depending on the context of the scientific activity.

If you want a reply on this, you are going to have to explain what you are claiming. Are you trying to say something like: "If 'The cat is on the mat' is false (a proposition with sense), how does this imply anything about 'The cat is on the mat or the cat is not on the mat' (a tautology without sense)?" If so, the answer is straightforward: it doesn't imply it in the usual sense. Rather, the tautology is true independently of whether the contingent proposition is true or false. The relationship isn't one of implication but of logical independence—which is precisely the point about necessary truths being "empty" of empirical content. — Banno

OK, to understand what you are saying here, when Kripke says, "Well, if something is false, it's obviously not necessarily true." he is not saying that when something is contingently false, you can infer that it is not necessary true. But that the relationship has something to do with logical independence. Or is that what the Tractatus says, and Kripke would disagree with? I would think the later, and hence my discomfort.

Rigid designation is for proper names. We can use "water" as a proper name like this:

The water in the pool could have been more alkaline.

that bolded section can serve as a rigid designator because we know which water is being discussed. And here:

Water is H20. — frank

My objections have been more around natural kinds as rigid designators, not proper names. Kripke's example "water is H2O" is about a natural kind.

Well I don't think it addresses my main concern. My discomfort with Kripke is not merely terminological — it’s that he appears to reify necessity as a worldly fact, whereas for early Wittgenstein necessity belongs to logical form, not reality. (And in later Wittgenstein, necessity is a reflection of grammar and language games, and not facts holding in all possible worlds)

More specifically, Kripke’s phrase “this fact about the world is a necessary one” is exactly what Wittgenstein would reject. Your reply implicitly accepts Kripke’s metaphysical framing instead of explaining why it doesn’t violate Tractarian structures. Also, I don't believe you address how a proposition with sense implies something about a proposition without sense? This violates the saying/showing distinction Wittgenstein stressed throughout the Tractatus.

My main point with this example is if "air" can be non-rigid, then so can "water". But I am open to hear why one would think otherwise.

Another passage I could not but wince at from N&N,

"But what I am concerned with here is a notion which is not a notion of epistemology but of metaphysics, in some (I hope) non pejorative sense. We ask something might have been true, or might have been false. Well, if something is false, it's obviously not necessarily true. If it is true, might it have been otherwise? Is it possible that, in this respect, the world should have been different from the way it is? If the answer is 'no', then this fact about the world is a necessary one. If the answer is 'yes', then this fact about the world is a contingent one." This in and of itself has nothing to do with anyone's knowledge of anything."

This passage seems to offend my Tractatus sensibilities along with a dose of Quinian skepticism towards modal logic. But let us put aside Quine for now, and let me express my Tractatus concerns.

When Kripke says something might have been true or something might have been false, I think it fair to say he is talking about a possible state of affairs. In the Tractatus, the sense of a proposition is simply to picture what might be so, a possible state of affairs. And to grasp the proposition's sense is to grasp both on what it would be like to be true and what it would be like to be false. But what sense can we make of necessarily true proportions, true whatever the circumstance. As Wittgenstein points out, it is necessary that to understand proposition's sense one must understand what it would be like to be true and what it would be like to be false, so this implies that a proposition cannot be true whatever circumstances. So, if a proposition is true whatever the circumstances, whatever might occur in the world, then it pictures nothing in particular. To say something with sense is to picture some definite possibility in particular.

So, from Tractatus point of view, I have these concerns with the Kripke passage:

1. Saying that "....then this fact about the world is a necessary one" seems incorrect. A fact about the world is not because of the nature of logical structure, but whether a possible state of affairs is true or false.

2. Saying that, "Well, if something is false, it's obviously not necessary true." How can proposition that that says nothing, follow from a proposition that says something? From a proposition that says something about the world, how is it obvious that it implies a proposition that shows logical form but states nothing about the world.

Let me give a compare and contrast between Kripke and Wittgenstein and let us see where it goes.

From Naming and Necessity,

"Let's call something a rigid designator if in every possible world it designates the same object, a nonrigid or accidental designator if that is not the case. Of course we don't require that the objects exist in all possible worlds"

and

"Don't ask: how can I identify this table in another possible world, except by its properties? I have the table in my hands, I can point to it, and when I ask whether it might have been in another room, I am talking, by definition, about it. I don't have to identify it after seeing it through a telescope. If I am talking about it, I am talking about it, in the same way as when I say that our hands might have been painted green, I have stipulated that am talking about greenness."

From Philosphicaal Investigations,

80. I say "There is a chair". What if I go up to it, meaning to fetch it, and it suddenly disappears from sight? - "So it wasn't a chair, but some kind of illusion". - But in a few moments we see it again and are able to touch it and so on. - "So the chair was there after all and its disappearance was some kind of illusion". - But suppose that after a time it disappears again - or seems to disappear. What are we to say now? Have you rules ready for such cases - rules saying whether one may use the word "chair" to include this kind of thing? But do we miss them when we use the word "chair"; and are we to say that we do not really attach meaning to this word, because we are not equipped with rules for every possible application of it?"

Both philosophical points, I find, are forcefully made. Kripke's example, I like it because it seems rather apropos for everyday conversations we have about everyday objects. However, when we bring in the metaphysical talk of possible worlds and rigid designation, I start to squirm. As Wittgenstein say in the 81. "All this, however, can only appear in the right light when one has attained greater clarity about the concepts of understanding, meaning and thinking. For it will then also become clear what can lead us (and did lead me) to think that if anyone utters a sentence and means or understands it he is operating a calculus according to definite rules." What Wittgenstein is trying to do in 80 is to illustrate that very point. Can Kripke look at Wittgenstein's "chair" and say, "If I am talking about it, I am talking about it"? So, does this object only exist in a possible world when it appears, and is excluded when it disappears? But should we include this object as a "chair" even when it behavior so radically different from typical chairs. And how do we go about saying it is identical every time it appears/disappears/appears? Are we equipped with rules for this possible application?

Am I not also raising a concern about the process of rigid designation as well?

I take it we can agree that hallucinating a ship and perceiving a ship are indistinguishable experiences. So we need to explain why the hallucinating episode and the perceiving the ship episode would be indistinguishable. — Clarendon

Well, it is a good thing we don't learn what an hallucination is by evaluating our private experiences since they are indistinguishable from our veridical experiences. But somehow we actually do learn what they are, the advantages of learning a language in a community with other human beings.

My view does this: they are both perceiving relations, it's just that one has as its object an actual ship, and the other has a mental image of a ship as its object. — Clarendon

Yes, the typical imagery of the private theater that no one else can enter.

But on your view in the hallucinating case there is no object at all - but then that means it is not a perceiving relation and thus is a quite different kind of experience from the perceiving one. So why would it be indistinguishable from it? — Clarendon

Those are your words not mine. In principle, you cannot demonstrate to anybody that the two experiences are indistinguishable. However, what you do present is a metaphysical fiction that tries to explain why someone would claim they are perceiving an "apple" when it is not there.

I simply am stating that when someone is hallucinating they simply did not perceive what they claimed.

But if an explanation is needed, let's look no further than a naturalistic one. First, view the human as a color detecting machine, just like colorimeter. In both case, in order to detect color you need to standardize the machine. For example, when a child is learning colors, we present them with standardized swatches. They practice identifying the colors, learn how to verbalize their names, and with enough practice they are able to demonstrate to the human community their ability. Whether a colorimeter is operating as expected will also need to be check using standardized color solutions or filters.

Unfortunately, machines can break down or not put together well. The human can make incorrect color judgments, or the colorimeter can't make the correct reading. In either case, there is no need to construct metaphysical entities like "mental states" or "sense data" to explain what may be going wrong. I better route would be to understand the physical mechanism in which each machine is able to correctly make the necessary color judgments and repair as needed.

I am interested in your opinion on the following and how you would think Kripke would reply.

Take this two terms, "water" and "air". The claim that water rigidly designated H2O in every possible world in which that substance exists.

OK, what about "air"? So, what has science discovered in the case? Again, depending where you look, the composition may be 78% N2, 21% O2, and 1% Ar. OK, in past posts, someone has replied that it does not rigidly designate anything.

But I am puzzled by this response. In the case of "water", which naturally occurs as a mixture everywhere, we somehow can selectively exclude "impurities" to arrive at a single substance. But with "air", this exercise seems not so simple. What justification is given to keep or exclude any particular substance?

All of this feels rather arbitrarily, picking and choosing examples to make your theory work.

The difference, then, between hallucinations and perceptions of mind-external objects is not that one is a perception and the other not, but that one is a perception of something purely mental (but indistinguishable from a perception of something mind-external), whereas teh other is a percpetion of something mind-external — Clarendon

I think you over complicated this scenario. The essential difference between a hallucination and the perception of a mind-external object is in the case of a hallucination we have the absence of a "mind external object." In one case, the success of calling out an apple when an apple is present shows we perceived an object. In the other case, the error of calling out an apple when none is present shows we may have hallucinated, thus, we did not perceived an object called "apple."