And also that humans are designated ‘beings’.

That's interesting, do you have any names I could look into?

Although there are no immediate visual or audible cues as to gravity's disappearance, the occupants will nevertheless be instantly filled with alarm, as they are suddenly struck by that stomach-in-throat, I just jumped off the diving platform, feeling. They will perceive the disappearance viscerally. — andrewk

But this feeling that the diver has is one which he has as a result of falling. The idea of falling obviously assumes that there is somewhere to fall to, and that would assume that there is somewhere that exists while unperceived by the train passengers.

IOW, you ditch inference, and with it, explanations of any sort that aren't strictly deductive. You just have one experience following another for no rhyme or reason. — Marchesk

Indeed. Is there something wrong with that theory. What is it?

Then a partition is put between you and the fire that blocks your from seeing, hearing or smelling the fire. It ceases to exist as a perception. Furthermore, there is a timer that will let you out before your run out of air, but only if the fire on the other side of the partition is no longer consuming air.

What happens? Do you survive or does your air run out? How would Stace answer that? — Marchesk

Presumably he would say: First there is me and the experience of the room and the fire. Then there is just me and the experience of the room. The fire no longer exists since it is no longer perceived. After some time I cease having experiences and die. If I were told that there is this timer in the room which will let me free only if the fire doesn't exist, and I observe until the point where it is pretty clear that the timer is not going to let me out, perhaps I could infer that the fire still exists while unperceived. But I am not sure of the point of this thought experiment, because it is so contrived. If the experiment had been performed in reality, which it hasn't, that might prove the existence of the fire in those contrived circumstances, but the existence of regular objects in regular circumstances would remain unproven.

And really, why would the question of needing air come up at all? Why would you die of needing something (oxygen) you can't perceive? — Marchesk

I can feel the oxygen as I inhale it, can I not? If you say "no. You cannot tell from inhaling that what you inhale is oxygen molecules", then fair enough, but the existence of the molecules can be securely inferred from the perceptible properties of air.

You are being misled by your slideshow treatment of the world. It would indeed be strange if, when the paper ceased to exist, there were just this weird black space, as though the universe is literally a canvas and the piece of paper was literally rubbed out leaving a gap in the line work. But that wouldn't be what the Idealist imagines to happen. When he says that the paper ceases to exist when no one perceives it, what he imagines to happen is that the space where the paper was is replaced with empty space - not some strange erased nothingness, just ordinary empty space. Except, this wouldn't be quite right, since the Idealist holds that nothing exists when unperceived, and so he would have to maintain that the empty space inside the drawer doesn't exist either. But again, he need not be committed to this strange picture of the inside of the drawer being literally erased. He can maintain that the limits of existence are the limits of perception. Where perception stops, there is nothing. No empty space. No strange erased spaces with borders. Nothing.

I think a whole generation of philosophers, and an increasing number of those considering themselves scientists, would question in what way verifiable testing produces truths that are categorically more rigorous from truths detemined through other discourses, such as philosophical. — Joshs

Great point.

So I see the paper, right? But it's not that simple. What if I glance in the direction of the paper but don't process it as a piece of paper. We do that all the time. Our minds are preoccupied with other thoughts and we look right through something, not identifying it conceptually as 'this object'. And the act of identifying the paper as a thing is a protracted process. At first our visual system will process edges and then move on to a more encompassing recognition of the object. And our intentions and presuppositions enter into the perception in complex ways. — Joshs

Now, if instead of a human perceiving thepaper, we take a snake, the perceptual mapping of the works will look quite different, since perception is about interacting with an environment adaptively in relation to one's needs, rather than representing, mirroring or copying something. The idea of object would be, to say the least , wry different for a snake, if in fact a sense of persisting thing was necessary at all for it.
We could demonstrate how different the perceptual mapping of a world would be if we used a human infant, also, one who had not yet established object permanency, and for whom a piece of paper would likely not exist as a coherent object yet. — Joshs

It should be stressed that these two facts are about perception construed very differently. Animals perceive the world differently to humans in the sense that what they literally see - what is given to their conscious awareness - is different because they have different sense organs. Humans don't see the world differently in that sense. What humans literally see is for the most part the same or incredibly similar. What is different is their interpretation of what they see, in accord with their beliefs desires and needs. It is true that infants don't interpret what they see as a 'piece of paper' which exists permanently. But it isn't true that the infants don't literally see the paper. If they didn't see it, there would be nothing for them to later interpret when they pick up the relevant concepts. Its also true that usually I don't pay attention to every object which is part of my visual field. There is a television in the background of my visual field right now which has gone unnoticed by me for about half an hour. But what is all of this supposed to show?

what exactly would be appearing and disappearing in our world as our attentive processing shifted from moment to moment would not only be relative person to person, or creature to creature, or developmental stage to developmental stage, but also moment to moment. — Joshs

This seems to me a fallacious inference. As I said, it is true that people interpret the world differently, but it doesn't follow from this that what exists is person relative. This mistake is perhaps masked by your conflation between the given and interpretation of the given. If there really were nothing given at all, it would seem to follow that humans could only know about their own interpretations of the world, and never about an independent world. And from that one might conclude, ala Richard Rorty, that the idea of 'the word' independent of interpretation is a useless fiction. But as I pointed out, this would rest on confusing the given and the interpretation of the given.

Some difficulties are raised by the fact that different things are given for different creatures. That might put pressure on the idea that humans can know what the world is like in itself, and not just as it is for humans. But this is the point of a scientific account of things. In a scientific account, one is supposed to move beyond the features of a thing which are merely relative to human modes of perception, and seek a more objective characterization of the thing which explains why it appears a certain way to humans. Whether this really works seems to fall outside of the scope of what I wanted to discuss in the thread.

I suppose you would object to the idea of the given on the grounds that it is an 'impoverished abstraction':

Classical logic would say these are peripheral and irrelevant issues to defining the paper as physical entity, but classical logic is content tomsubstitute an impoverished abstraction for the more fundamental interactively determined meanings of how we interact with a world. — Joshs

As I see it, the idea of the given is that it is supposed to be an abstraction. In framing the notion of the given, we are trying to characterize perceptual experience solely by reference to the element which is common across all of us. We abstract away all of the person relative elements and call them the 'interpretation of' the given. What we are left with is the common element of experience, which is to serve as a reliable guide to the nature of the objective world.

Thanks for this, it got me thinking in an interesting direction.

I agree with you. I am only suggesting that the word 'know' needs further explication before the question is well-defined enough for a rigorous answer. Otherwise, the question admits of too many different interpretations. I think Kant failed to see this, but as did many before and after him.

"How can I alone, out of my own resources, know that things exist unperceived?" - then there is no answer, and I am led inevitably to solipsism. — gurugeorge

There is no reliable way for me to know that things exist unperceived at all? But I thought you said:

the hypothesis that the unperceived object exists, is a reasonable explanation for present experience's being the way it is. — gurugeorge

This argument sounds like an argument I could make using my own resources, doesn't it? And what about what other people tell me? Why can't what other people tell me count as part of my resources?

I suppose you might think that this would require that I first know, out of my own resources, that other people exist. That would be right, but couldn't I know this out of my own resources? If I couldn't, what sense does it make for me to enjoy the company of anyone else, given that it is mere guess work whether or not there is anyone else? This last paragraph is only speculation on what you might be thinking. Forgive me if I have gone off on the wrong tracks.

, you employ the same tactic sometimes employed by Marchesk. That is, to answer my question by asking other questions in the hope that my original question then sounds ridiculous. But your raising these questions does not answer my original question, so far as I can tell. It doesn't follow from the facts that (a) the paper is there when I look at T1 and (b) it is there when I look at T3, that it was there when I wasn't looking at T2.

Thanks again for the replies,
PA

It doesn't follow from the facts that (a) the paper is there when I look at T1 and (b) it is there when I look at T3, that it was there when I wasn't looking at T2. — PossibleAaran

I don't think the claim is that it follows. I think the claim is either that it being there when you weren't looking (best) explains why you see it when you look at T3 or that it is more parsimonious for it to still have been there.

However, I think both misunderstand the idealist position. There seems to be this implicit interpretation of it materially popping into and out of existence, which would be a misplaced interpretation. Rather compare it with our experiences when dreaming; I see a tree, I turn around, I no longer see a tree. Is it right to think of the tree as still being in the dream, albeit unseen? No. Is it right to think of the tree "popping" out of existence until you turn back, when it "pops" back in? No. It is just the case that either there is the experience or there isn't, and talk of the tree existing or not existing (as something else) is a category error.

you employ the same tactic sometimes employed by Marchesk. That is, to answer my question by asking other questions in the hope that my original question then sounds ridiculous. — PossibleAaran

Well, it is ridiculous when taken to it's logical conclusion. If the paper in your drawer no longer exists unperceived, then the piano falling toward you no longer exists when you look away.

Because how can the unperceived world be of any threat?

If the experiment had been performed in reality, which it hasn't, that might prove the existence of the fire in those contrived circumstances, but the existence of regular objects in regular circumstances would remain unproven. — PossibleAaran

Thought experiments are used in philosophy. And this one can be performed in the real world. But you can change it to an actual situation where there was a fire but nobody was aware of it, because they were asleep or it was in another part of the building, and they suffocated.

I can feel the oxygen as I inhale it, can I not? If you say "no. You cannot tell from inhaling that what you inhale is oxygen molecules", then fair enough, but the existence of the molecules can be securely inferred from the perceptible properties of air. — PossibleAaran

There's a thousand different variants of this. Someone slips an odorless, tasteless poison into your drink when nobody else is looking. They leave the room.

Now the poison should cease to exist just like the paper, right? You drink from the chalice and next thing you know you're vomiting blood and being rushed to the emergency room where the doctor figures out what poison was used and counters it to save your life. So somehow that unperceived poison came back into existence.

Now if you can do away with experiences being causally connected to one another, and say that you there was no reason you went to the emergency room, then you can maintain your doubt.

I can't do that. I find it to be a reductio. Of course the poison, the paper, the piano, the train wheels, etc. all exist unperceived. That makes sense of why our experiences do seem to be causally connected in a way that papers remain in drawers when nobody's looking.

This argument sounds like an argument I could make using my own resources, doesn't it? — PossibleAaran

No, the idea that the existence of some unperceived object is a reasonable explanation for present experience's being the way it is depends on a prior acceptance of the world being pretty much as we think it is, with people who give you information, etc. At that level (the level of reliable knowledge) we're not asking about the possibility of objects outside perception in general, but of this or that object that's outside present perception, given that objects exist outside perception in general.

However, that idea (the general idea) isn't something that you could logically derive from present perception without any additional ideas, truths, or auxiliary hypotheses that you've already accepted that you're taking in from a world outside present perception. Even calling present experience "perception" already takes too much for granted if you're strictly going on present experience. Really, the most you can get is the non-dual mystical position, which is somewhat similar to the radical empiricist position of Mach - e.g. consider Mach's "self-portrait." https://binged.it/2nBJUOZ (Obviously we're meant to include the whole panoply of things you can find in present experience in this - ghostly "thoughts" and images, vague bodily sensations, etc.)

Here you have something like "experience" as a thing-in-itself with which we have direct, immediate contact, floating in a palpable void (as it were). There's depth to the thing (it's not 2-d) but the depth is only within the experience itself, there's no necessary connection between that perceived 3-dimensionality and "a world outside the experience." Also, there's no subject "perceiving" this thing - that too is a hypothesis that has no justification - this experience-thing just sheerly exists in its own palapable void (by which I mean the absence-of-it that surrounds and envelops it).

think this fundamentally confuses how we come to know about the world with the way the world is itself. Just because we can't get outside ourselves to imagine exactly how the world is without us observing it does not entail that the world cannot exist without us perceiving it. — Marchesk

No, the point I made is that the way that the world is, is completely dependent on one's temporal perspective. Without a subject, an observer, there is no temporal perspective. Without a temporal perspective there is no such thing as the way that the world is. That's why it's a senseless question to ask about the way that the world would be without an observer. Without an observer there is no such thing as the way that the world is.

If the paper in your drawer no longer exists unperceived, then the piano falling toward you no longer exists when you look away.

So you should be fine as long as you don't look back. Same with crossing a street. Long as you can keep yourself distracted with headphones and only looking straight ahead, there shouldn't be any issue. — Marchesk

Your argument is that if Idealism were true and I saw a car coming towards me, I could stop myself getting hit just by looking away, since the car only exists when perceived. Idealism need not have that consequence.

It could be that it is just a brute fact that usually the experience of a car hurtling towards you is followed by the experience of a car striking you in the back if you look away. The Idealist can posit the two items experienced - the car that you see and the car that hits you- and say that usually seeing one is followed by feeling the other. He need not posit the existence of a car that exists in between these two states, nor need he say that all three are "the same" car.

The same with the piano. The Idealist says that there is the piano that you see falling towards you, and there is the piano that strikes you in the head, but he need not postulate another piano which exists when you aren't perceiving it, nor that all three are "the same" piano. Moreover, he will say, there is no reliable means at all, to tell that there is a car or piano which existed when unperceived.

Thought experiments are used in philosophy. — Marchesk

I know that they are, and for the most part I think they shouldn't be.

And this one can be performed in the real world. But you can change it a situation where there was a fire but nobody was aware of it, because they were asleep or it was in another part of the building, and they suffocated.

Similar to leaving the car running in the garage with you in it. — Marchesk

These examples can be explained as above.

Someone slips an odorless, tasteless poison into your drink when nobody else is looking. They leave the room.

Now the poison should ceased to exist just like the paper, right? You drink from the chalice and next thing you know you're vomiting blood and being rushed to the emergency room where the doctor figures out what poison was used and counters it to save your life.

So somehow that unperceived poison came back into existence. — Marchesk

I can perceive the drink. Am I perceiving the poison when I perceive the drink? The poison is part of the liquid isn't it? So surely I am. So why would the poison cease to exist according to Idealism? It wouldn't. I'm not perceiving the poisonous chemical constitution of the drink, but I can infer that chemical constitution from the effects that the drink has on me. I still don't see the issue. I am not saying that you can only know about things that you can see. I am saying that you can only know what you have a reliable ground to believe. I allow that you could know something by inference.

No, the idea that the existence of some unperceived object is a reasonable explanation for present experience's being the way it is depends on a prior acceptance of the world being pretty much as we think it is, with people who give you information, etc. — gurugeorge

Why can't I argue like does above, pointing out that if the car didn't exist when unperceived, I could save myself by simply looking away? Since I can't, we might conclude that the car must exist unperceived. As I pointed out to him/her, the Idealist can modify his view to accommodate these consequences. But could Marchesk not criticize the Idealist view then for being ad hoc, less explanatory and (in some sense which would need explication) less parsimonious? A number of people have hinted at this argument. I am trying to get someone to state it more fully. In what sense is Idealism less explanatory? In what sense less ad hoc? In what sense less parsimonious? I think these questions will prove difficult to answer, but if they could be answered, I don't see why doing so would assume anything like "the world being pretty much as we think". It depends what exactly I would have to assume, and why it is that I can't assume it. But you haven't said on either front.

Best,
PA

The Idealist can posit the two items experienced - the car that you see and the car that hits you- and say that usually seeing one is followed by feeling the other. He need not posit the existence of a car that exists in between these two states, nor need he say that all three are "the same" car.

The same with the piano. The Idealist says that there is the piano that you see falling towards you, and there is the piano that strikes you in the head, but he need not postulate another piano which exists when you aren't perceiving it, nor that all three are "the same" piano. — PossibleAaran

The idealist can make this move, but there is also the possibility that experience just ceases. Other people will infer that the falling piano or oncoming car killed you. The examiner might say poor sap didn't even feel it.

So the idealist has to include the possibility that not looking will result in no longer experiencing, for no reason at all, since there is no unperceived death event.

There is something to be said against views which we can't disprove but are absurd. Let's say that instead not existing, the piano turns into a pink elephant that squashes you, but then turns back into a piano when people find your body. Can you disprove that possibility? No, but it's silly and absurd on the face of it.

The idealist can make this move, but there is also the possibility that experience just ceases. Other people will infer that the falling piano or oncoming car killed you. The examiner might say poor sap didn't even feel it.

So the idealist has to include the possibility that not looking will result in no longer experiencing, for no reason at all, since there is no unperceived death event. — Marchesk

The possibility of 'not experiencing' doesn't make any sense to the subjective idealist. For the subjective idealist semantically reduces the meaning of what is meant by a cause to the collection of observations that are said to verify it. Hence the idealist cannot make sense of the postulation of a cause that he cannot consciously verify.

In conclusion the subjective idealist is a solipsist who cannot make sense of the statement "I am mortal". Yet why should this be absurd by your criteria? After all, the solipsist is not only against holding views that he cannot disprove, he is even against attributing meaning to such views.

The possibility of 'not experiencing' doesn't make any sense to the subjective idealist

...

In conclusion the subjective idealist is a solipsist who cannot make sense of the statement "I am mortal". — sime

I don't know how you've come to that conclusion. One doesn't need to believe that one's experiences are eternal to believe that one's experiences are all that exist, just as one doesn't need to believe that matter is eternal to believe that matter is all that exists.

In conclusion the subjective idealist is a solipsist who cannot make sense of the statement "I am mortal". Yet why should this be absurd by your criteria? After all, the solipsist is not only against holding views that he cannot disprove, he is even against attributing meaning to such views. — sime

The solipsist thinks they are eternal and their experience will never end? How is that not completely unfounded?

I don't know how you've come to that conclusion. One doesn't need to believe that one's experiences are eternal to believe that one's experiences are all that exist, just as one doesn't need to believe that matter is eternal to believe that material things are all that exist. — Michael

All i mean to say is that if subjective idealists are understood to be verificationists in the strongest possible sense, then it makes no sense for them to speak of an absence of experience when it comes to their own experience.

All i mean to say is that if subjective idealists are understood to be verificationists in the strongest possible sense, then it makes no sense for them to speak of an absence of experience when it comes to their own experience. — sime

Would such verificationism also commit one to not being able to speak of past experiences except as memories now, or future experiences except as anticipation now?

IOW, all that could be known to exist is the solipsist's perception right now.

The solipsist thinks they are eternal and there experience will never end? How is that not completely unfounded? — Marchesk

Would such verificationism also commit one to not being able to speak of past experiences except as memories now. — Marchesk

Verificationism and presentism go hand in hand. For according to the verificationist, to speak of the past or the future is to refer to their criteria of verification, a verification that consists of temporal signification within the present.

But even if you reject verificationism, say because you are metaphysical realist concerning the past, suppose that a living brain which from your perspective is most definitely mortal, says of itself "I am mortal". What is the brain asserting of itself here? Does it make sense to think that a brain can represent to itself the criteria of its own existence?

Does it make sense to think that a brain can represent to itself the criteria of its own existence? — sime

Sure, why not? The brain recognizes that it has a limited lifespan. It sees that it's made of the same biological stuff that everything else is, which means it will die.

So the idealist has to include the possibility that not looking will result in no longer experiencing, for no reason at all, since there is no unperceived death event. — Marchesk

We already agreed that the Idealist can posit (a) a car hurtling towards him when he sees it, and (b) a car hitting him in the back when he feels it. He need not postulate a car which exists in the interim, when he is not seeing or feeling a car at all, nor need he postulate that these three are 'the same' car. But, if he holds that (a) is usually followed by (b) - even if you look away - then why can't he hold (c) being hit in the back by a car will probably kill me? Would he be holding (c) for no reason at all? Surely not, unless for some reason the Idealist isn't allowed to think that bodily damage can kill him.

Best
PA

@PossibleAaran -- I suppose I'd first ask, what is it about perceiving the paper that makes you believe you know, in the same sense that you're asking about knowing how the unperceived paper exists, that the perceived paper exists?

Clearly if you believe that then there's some kind of method you're already accepting as a path to knowledge of what exists. What constitutes that method?

But this feeling that the diver has is one which he has as a result of falling. — PossibleAaran

That is the common belief, but it is a misconception. It is actually the feeling of the absence of gravity. The diver's accelerated motion - in the reference frame of the diving board - exactly cancels out the impact of gravity. What a diver feels the instant after leaving the platform is exactly what is felt by a person in what is considered a 'gravity-free' environment such as a space station, or even just a 'motionless' space ship in deep space.

The point is that we feel gravity all the time, in our innards as well as on the soles of our feet. We are so used to it that it feels normal, and it feels weird and scary when gravity disappears.

The more general point is that there are many things that we continuously perceive without realising it, by which I mean that we would notice and pay attention if they were to suddenly cease. Other examples are a faint drone of an electric motor, which we only notice when it suddenly stops. Or one of the many instruments in a thick 'wall of sound' musical arrangement of a song, which one doesn't notice until the instrument stops, and thereby subtly alters the texture of the music.

The idealist can make this move, but there is also the possibility that experience just ceases. Other people will infer that the falling piano or oncoming car killed you. The examiner might say poor sap didn't even feel it. — Marchesk

This really weird thought occurs to me often, and seems completely divorced from any philosophical discussion of materialism vs idealism.

When I was first told about the forgetting drug Midazolam, which is used in uncomfortable but not super-painful procedures like endoscopies, I tied my brain in knots trying to 'understand' it. Apparently you are conscious, though drowsy, during the procedure, but have absolutely no memory of it, so after the event it's absolutely indistinguishable from it never having happened - you feel the same as if you'd had a general anaesthetic (but without the nausea). I still can't quite get the idea of it straight in my head.

Sometimes when I'm in a dangerous situation that could kill me, I think: If I were to be killed, there would be no more consciousness, so any brain activity shortly before the death will be as if it never happened (we could say that for all my brain activity ever, but leave that aside for now - I'm just describing my train of thought). But here I am alert and conscious of what's happening, so it seems as though that means that I won't end up dead in the next minute or so.

I'm just saying that one doesn't need philosophy and theories like idealism and materialism to get tied up in absurd-seeming but inescapable knots, over the notion of consciousness.

Without a temporal perspective there is no such thing as the way that the world is. That's why it's a senseless questi, on to ask about the way that the world would be without an observer. Without an observer there is no such thing as the way that the world is. — Metaphysician Undercover

And I explained how I disagree with that, given that we can depict the world mathematically without a perspective, and given that our lack of a ability to picture a perspectiveless world does not necessitate the world can't be that way.

We already agreed that the Idealist can posit (a) a car hurtling towards him when he sees it, and (b) a car hitting him in the back when he feels it. He need not postulate a car which exists in the interim, when he is not seeing or feeling a car at all, nor need he postulate that these three are 'the same' car. — PossibleAaran

But he might not feel anything as well. Experience just ends.

And I explained how I disagree with that, given that we can depict the world mathematically without a perspective, and given that our lack of a ability to picture a perspectiveless world does not necessitate the world can't be that way. — Marchesk

That's not true though. We cannot produce a mathematical model of the universe which is independent from perspective. This is one of the key things that special relativity demonstrates to us. And, my explanation demonstrates that to speak of things existing in a perspectiveless world is completely nonsensical.

e cannot produce a mathematical model of the universe which is independent from perspective. This is one of the key things that special relativity demonstrates to us. — Metaphysician Undercover

Pretty sure you're wrong about this.

No.

The boiling soup is in front of you. You close your eyes, and it vanishes. Has it ceased to exist? You still hear it boiling. Does it still exist? Maybe something else is making that noise. But you can smell it? Maybe something else is producing that smell?

You're deaf and blind. You have no sense of smell. Does the soup still exist? You reach out and touch the boiling soup. Ouch. What if you have no sense of touch? Or if you can't reach the soup? Does it exist?

Well, at this point you're nothing but consciousness. Do you exist? Descartes says you do because you are conscious of yourself. But what is it that you are conscious of? Only your own consciousness.

Your consciousness is axiomatic. You can't contemplate your own consciousness without reference to it. So you know that for sure. It's the only sure thing.

But that ain't too satisfying, is it?

Does existence exist? Well, that's axiomatic, too. How can you contemplate existence without existing?

If you exist--and you do--do you exist alone? Perhaps.

That's all very cute, and very obvious. But what about that boiling soup? You regain your senses and the soup reappears in all its smelly, noisy glory. You perceive it again. But what does that mean? Maybe your view of the soup is totally subjective and it doesn't exist for the other perceiving consciousness sitting at the table opposite you. Maybe you're imagining the soup. You go to serve it to the other but they can't receive it since for them it doesn't exist. Is it getting a little nutty?

At some point, everything is axiomatic since you can't interact with it unless you reference it in the interaction. And others can't interact with it unless they too perceive it in about the same way you do. You could say that objectivity--that entities exist independent of your consciousness--is the degree to which subjectivity doesn't obtain; the degree to which axiomatic-ness is common.

You're living in the Matrix. And that matrix is called reality. Yes, the boiling soup exists.

This reminds me of the line that there are no postmodernists on an airplane in flight. The lesson we should learn from the knowledge that perception is a dynamic co-construction between object and subject is not that underlying machinery can't exist(or any other lawful, stable empirical descriptions), but that the stability and usefulness of our scientific accounts of p0erception or any other aspect of the world is made possible by the abstractive nature of those descriptions.They are designed to make room for a certain degree of inter and itra-personal interpretive flexibility even when most of us think that the meanings of our scientific-mathematical descriptions are being understood by each other self-identically.

For sure there is an obvious distinction between the identity of what is being understood and the difference between individual acts of understanding.

RIght. It comes down to the question of how we make things work based on our designs, how the plane stays up in the air, if those designs are understood slightly differently every time anyone who is making use of them turns their attention back to them after a break, or shares those designs with another who in turn is contributing a slightly different interpretation relative to the first. The answer is paradoxical. The technological vocabulary of the design easily accomodates these discrepancies and shfits of meaning, even as we are accustomed to thinking of such a vocabulary as the essence of precision. There is good and there is awful postmodern thinking.The good gets a bad rap because writers like Derrida are actually saying something like the above when they talk about otherness and incommensurability in relation to science.