Saturday, December 4, 2010

On Perceptual Reality

The earliest reference I can find to the phrase "perceptual reality" is in English statistician Karl Pearson's "Grammar of Science" (1892):

[The Motion of bodies] is not a reality of perception, but is the conceptual manner in which we represent the mode of perception which consists in the combination of Space with Time, by which mode we describe changes in groups of sense impressions; the perceptual reality is the complexity and variety of sense impressions.
Psychologists studying perception today would consider this rationalistic nonsense, and that it is rather the case that we literally see motion, first and foremost, and it is only the concept that comes afterward, based on the perception.

Perhaps we might try to seek some sort of consensus at this point and see where it takes us. Here is a general proposition:

Reality is achieved within the perceptual world.


  1. Being a realist both about the physical world independently of our perceptions of it, and also about conscious experiences,I can only parially agree with this last statement. Our experiences really occur in perceptual space (which is what I take it you mean by the perceptual world), but I do not think that their physical objects also exist in this world, although they are causally linked to it.

  2. I'm glad you have quickly risen to the occasion in responding, Bob! Can you say what part of the proposition above it is with which you agree? Does the word "achieved" seem valid in it?

    I assumed that we had already all agreed on the terms "phenomenal space," visual space," "visual world," "perceptual world" as each being distinguished from their "physical" counterparts, but perhaps the term "perceptual object" needs to be added to the list. Do you therefore regard perceptual objects as being real, Bob? (Just for reference, the term "perceptual object" seems to appear only in the 1890s.)

    For now, I would prefer if possible to confine discussion to the perceptual world rather than its relationship to the physical world.

  3. "Reality is achieved within the perceptual world." Well, but what reality is achieved? The question is to be confined to the perceptual world, leaving aside its relationship to the physical world. In that case, it is the reality of the perceptual world that is achieved within the perceptual world. Yes, right, of course. But then this conclusion sounds very much like an empty tautology.

  4. Not a tautology I would counter, but an empirical proposition, either confirmed or disconfirmed by the perceptual world itself. Perhaps another question may serve to tease this apart: Is there reality in the perceptual world? Yes or no.

  5. "Is there reality in the perceptual world?" Well, let me see. Is there in fact conscious experience, as opposed to having either radical behaviorism or eliminative materialism be true? Yes. Is the perceptual world like a mere shadow, with the real action going on somewhere else (such as intellectual functioning)? No, but it would be a sizeable project to disprove epiphenomenalism. Beyond that, it is not clear what the question means.

  6. Bob has already alluded to skepticism about the perceptual (phenomenal) world existing, so perhaps we should return to that and ask: Is that world real? If so, how is it real? Or, better still, to what would one compare its reality (or lack thereof)?

  7. There are probably other questions one could pose as well: If the perceptual world does not exist, how did it come to be posited? Conversely, if it is unreal, then what sort of existence does it have for it to have been posited? Surely it is not an abstraction. Is it then fictional?

  8. It probably would help if you reviewed the meaning of 'perceptual world' Bill, in particular if you mean anything else besides events occurring in phenomenal space by it. I certainly am a realist about these events, but, like David, I am unclear about what you mean by "reality is achieved" in this world. If this is meant to imply that this is the sole world that exists, then I disagree, since I am also a physical realist about the physical causes of our experiences, and I think that they have an independent existence apart from our experiences of them.

  9. Perceptual world, like the other terms, just refers to the world perceived, whereas visual space (for example), is (or conceptualizes) just the spatial component of the visual world (the visual part of the perceptual world), as auditory space is the auditory component of perceptual space.

    One could say that the perceptual world is what the average person calls "the world," more precisely, the real world or just "reality." Most people would scoff at the idea that reality is somehow beyond their senses and that they only see a sort of picture of it, because they know nothing about the machinations of philosophy.

    That being so, we need to find a way of recovering the essential meaning of reality from which derivative philosophical/technical senses have come (phenomenology IMO was/is a pretty lame attempt at something like that). People did not just start with an abstract concept of "reality" and then set about deciding what was/wasn't real. That's surely not how the notion of reality came about.

    I see some conceptual/linguistic confusion behind this problem, such that the perceptual world has been robbed of its reality by philosophers, or reality is construed as being a complicated set of abstract interrelationships that can only be understood by set theory (or group theory), whereas I am arguing that the basis of our sense of reality is experiential, not conceptual. This position is approximately that of the psychologist, J. J. Gibson.

    Part of the problem, as I argued early on, is that it is my distinct impression that the *process* of perception has been conceived as something taking place *within* the perceptual world, because in a very *real* sense we do "look" at things in the perceptual world, i.e., both the act of looking and the things looked at are in the perceptual world, and thinkers in the past have tried to base their theories on *that* rather than a relationship between the perceptual world and something beyond it.

  10. "Are rainbows real?" This is a simple question that a child might ask of a parent. But in fact, to answer rightly would require drawing careful distinctions. Most people, just because they are totally innocent of philosophy, would not be able to take the child through even this elementary analysis. Instead, they would very likely find themselves unable to answer, become frustrated, and sweep aside the question impatiently. This way of doing things does not show superior wisdom. It shows the opposite. That being so, why should a philosopher care what most people would or would not say about what it is to be real?

  11. I seriously doubt that anyone would question whether rainbows are real or not.

    Given the insoluble puzzles that philosophers have spawned over the centuries, why should ordinary people care what they think?

  12. In other words, asking for or offering a physical (or scientific) account of rainbows as a physical (or optical) phenomenon is one thing, ascertaining whether rainbows are real or not another. Why should their reality be called into question?

  13. This helps some Bill. Regarding Gibson, I actually prefer his early work, where he talks about the visual field and the visual world more than his later work on ecological optics. One can then take different attitudes towards the space of experience, either an attitude where we just try to describe its own characteristics per se (Gibson's visual field), using perhaps what Husserl calls the epoche, or we can use the naive realist attitude, which is what most people do, and take it as being something physical that has an independent existence apart from experience (I take it that this is at least roughly what Gibson means by the visual world). I at least, am convinced that naive realism is false though, although I do believe that a physical world does exist which both transcends,and is causally linked with the space of our experience. Both are equally real on my account.

  14. I would like to propose that we try as much as possible to deal with what we know, rather than what we believe--at least for now. That way others can more or less say either "yes, I know that, too," or "no, I don't know that."

    IMO, Gibson's fundamental mistake, like other thinkers before him, is that he superimposed physical processes on what is actually a model of the perceptual world, talking in terms of what were really *perceptual objects* and "layouts" of "the environment" (etc.) rather than their physical counterparts, as described by modern physics, which even in Gibson's day were known to have very little similarity to their perceptual counterparts.

    Thus, Gibson's theory exhibits a circularity of reasoning that I see foredooms all models of reality based on the perceptual world, because they inadvertently presuppose that something exists like the perceptual world independently of it, most commonly called the "physical world." Well, as I have noted before, what natural philosophers used to call the "natural world" was just the perceptual world. Natural philosophy is/was basically founded on naive realism.

    Though it is not a matter of belief on my part, I contend that the perceptual world *is* reality, and that there is no corresponding reality of which it is a representation. It is the "real thing." How this is possible (rather than impossible as philosophical criticism and analysis has countered) is quite another matter.

    Bernard Carr (who, just to remind readers is a mathematical astrophysicist at the University of London, and former graduate student of Stephen Hawking's and long time acquaintance of John's and mine) maintains that we *do* directly perceive objects, but since he has not been available here on the blog to make his own points or answer questions, I can only refer readers to a few recent publications of his that expound his theory which, I believe, John has already cited.

  15. A further reply to David's point: Upon what authority has philosophy become the arbiter of what is real or not real, rather than it being a matter of the "evidence" of the senses (i.e. "seeing is believing")?

  16. One could write an essay along the lines of Ray's "Disappearance of Appearance" and call it the "Disappearance of Reality," since there is no doubt that reality holds little weight in the academic humanities today, for one, which seems dominated by an incoherent form of skeptical relativism (e.g., Derrida et al). No one seems to have paid attention to the fact that relativism eventually refutes itself, as does skepticism. To the skeptics I say: How do you know that skepticism is true?

  17. Bob has already stated most succinctly what I hold, philosophically, myself:
    “I at least, am convinced that naive realism is false though, although I do believe that a physical world does exist which both transcends,and is causally linked with the space of our experience. Both are equally real on my account.”.
    So I will take another tack. I have described earlier on this blog, from my own experience in 1951, what derealization, that can be induced by psychedelic drugs, is like. Everything about what one sees is normal (color, shape, size etc.)—except everything is terrifyingly unreal. Things do not merely look unreal (as the stage sets in ”the Cabinet of Dr. Caligari” were designed to do)—they are terrifyingly unreal in their essence: no mere words can really describe it. This contrasts strongly with another effect of these drugs, that I also experienced in 1951, which is a completely hallucinatory perceptual visual field. I went for a walk down Wimpole Street in London. The solid, solemn Georgian houses had all vanished, and were replaced by a great theatrical backdrop of beautiful, and quite different, houses painted with brilliant skill in a shadowy Impressionist style somewhere between Van Gough and Matisse. Curiously enough these looked perfectly real!

  18. I am abiding no sacred cows in the course of this inquiry, and I'd love to know, John, your conception of the physical world, in light of the pictureless picture (if one can use such a phrase to make a point) offered of it by contemporary physics. For example, do you imagine something like Eddington's "second" writing table or something else? Eddington wrote: ""The scientific world is, as I have often repeated, a shadow-world, shadowing a world familiar to our consciousness. Just how much do we expect it to shadow? We do not expect it to shadow all that is in our mind, emotions, memory, etc. In the main we expect to to shadow impressions which can be traced to external sense-organs." But even this "shadow box" picture as he called it is a simplification of something that is more or less impossible to visualize.

    We have already discussed the derealization experienced on or off hallucinogenic drugs. But if not "real" how would you describe the character of what appeared "unreal" while on mescaline, John? But in any case, it suggests that in the perceptual world at least, at a fundamental level not everything we see even "looks" real. Apparently, though, the impression of "unreality" is so strong that it is sufficient to convince a percipient that reality has somehow vanished!

    Why should we assume, therefore, that the physical world is somehow more real than an unreal-looking visual world? This, to me, seems even more naive than naive realism.

  19. Returning to my point of departure, I chose the word "achieved" for a reason, apparently not one that is self evident. My contention is that reality is--in some way--built up through a process of realization in the perceptual world (Lothar may shed some light on this). That's what I mean by "achieved," because I am suggesting an analogy to the expression "achieving an understanding," because it is not a passive process, but an active one on the part of the percipient who uses his senses.

    With all the references to visual agnosia (if only in synopsis) it should be obvious that the process of recognition is separate from seeing, and involves something like a comparison (with a memory image), that it needs visual space, but that visual space is not sufficient for recognition to occur. In cases of amnesia, in some sense one no longer recognizes themselves. With the newly sighted born blind patients, can we really say that the reddish fog they initially perceive after the operation is "reality"?

    The end product of realization is the belief that there is a reality that exists independently of our perception of it, even though no single individual can prove that in the course of his own experience--yet another paradox.

    As Wittgenstein writes of the solipsist, "Now when the solipsist says that only his own experiences are real, it is no use answering him, 'Why do you tell us this if you don't believe that we really hear it?' Or anyhow, if we give him this answer, we musn't believe that we have answered his difficulty." ("The Blue Book," loc. cit., p. 38)

  20. Having read David's well-reasoned arguments re "Quantum Physics and Classical Realism," I would still maintain that the argument for reality of any kind comes entirely from the perceptual world itself, not from an objective world beyond it of which it forms no part (at least that we seem able to know).

    In his "Mystery of the Sensual [Sensory] Qualities" (in "Mind and Matter"), we have quantum theorist Erwin Schroedinger showing how *all* the evidence of physics ultimately depends upon human observation, even the reading of measurements made by measuring devices. Otherwise there is no knowledge of any kind. Wheeler tried to wiggle out of this embarrassing state of affairs, but I find his solution unconvincing, as I have stated before.

    Bernard Carr's symbol for trying to capture Wheeler's observer-participancy is the Uroboros, i.e., the idea that the Universe is observing itself. Whether the head or the tail an argument can be made that it is all of a piece. if the Big Bang is to be believed.

  21. Perhaps much could be gained if John can clarify something about his experience. Traditional realism rests largely on the claim that the impressions one acquires by perceiving through the senses point beyond themselves to something further. This claim is evidently what William is concerned to contest. But now, what about derealization? John, when you were drugged, was it perhaps simply that your sensory impressions did not even seem to point beyond themselves? Or was it perhaps that your experience was somehow "ghostly" as regards its own internal quality? Or both, or neither? Or can you say?

  22. I will be interested in John's answer, but in the meantime it strikes me that the evidence of cognitive psychology in general shows that perceptions tend to point to each other, not beyond themselves, except in the case where they lead to exploration of what lies beyond--that is, what lies beyond *in the perceptual world.*

  23. I am not sure what the question is that Bill is asking us to consider:
    Is it?

    1. “Does anything exist beyond the perceptual (phenomenal Rosar Dec. 4: 10.38 pm) world that we experience? Is what people call “the physical world” (PW) only Eddington’s world—i.e. the largely mathematical description of the PW made by physicists. If so, is there is nothing ‘behind’ the perceptual world?”

    If this is the right version, how does that differ from Berkeley’s theory? If it does differ from Berkeley’s theory, how is it compatible with a denial of naïve realism? Is it possible that naïve realism and the representative theory are both incorrect? Or is it possible that one can hold both of these, normally considered incompatible theories, at one and the same time?
    Moreover, the philosophers of perception H.H. Price and C.D. Broad would not agree that the phenomenal world and the perceptual world are the same. They carefully distinguish between ‘sensing’ our sensations, and ‘perceiving’ external objects. This distinction was made to counter criticisms of the sense-datum theory, namely that it involved us sensing our sensations, and then inferring, from what we found out about them, the nature of the events in the external world that the sensations represented—when no such process of inference actually takes place.

  24. A further clarification of the question would be helpful as we are navigating philosophically very deep waters!

    Further comment:
    When Bill asks “Is A real?’ is that exactly the same as the question ”Does A exist?” If not, what is the difference?

    In response to David’s (8.42) questions.

    “Traditional realism rests largely on the claim that the impressions one acquires by perceiving through the senses point beyond themselves to something further. This claim is evidently what William is concerned to contest.”

    In view of progress in visual and cognitive science I would rephrase this as follows:

  25. “The visual system provides the visual field in consciousness with colored and extended sensations (Lockean ‘impressions’) grouped into ‘phenomenal’ objects along Gestalt principles. This process takes several months to develop. The infant learns that these are related to the things it bumps into while crawling (mediated by the development of the infant’s body-image). This process leads to the development in its mind of the concept of the existence of an external world. Thus the ‘impressions’ do not actually ‘point beyond themselves to something further’. The entire system does this. Moreover, we now know that two different brain systems are involved in this: one mediates the phenomenology (lost in blind sight) and the other mediates the cognition (lost in associative aphasia).”
    Therefore, it seems to me that we should be wary of accepting skeptical arguments to the contrary, however brilliant their reasoning, and however reassuring they may be to our logical instincts.

  26. David’s second question asks if, during mescaline-induced derealization, my sensory impressions “did not even seem to point beyond themselves?” Very difficult to say: but something like that could very well be. Our sensations saturated us with the comfortable feeling of familiarity. We like what we are accustomed to. Anything new is potentially threatening. Mescaline acts by stimulating serotonin 2A receptors in the brain. These receptors have many functions including increasing the salience content of the sensory input. Thus overstimulation might lead to panic buttons being pushed (metaphorically Bill!) all over. This might lead, not only to extreme anxiety, but also to the (preconscious) cognitive reaction “This is so alarming that it cannot be real”. That may not be the case, but, at least, as far as I know, it is the first hypothesis put forward to explain this phenomenon.

    David then asks “Or was it perhaps that your experience was somehow "ghostly" as regards its own internal quality?”
    No, definitely not that. There was no change in the parameters of the visual experience except the unreality.

  27. Reply #1. I must confess, I am confused. John, you seem to be answering questions that I did not ask (see your message of today, 4:14PM). The question you have have in quotation marks are not mind, so your answers are not pursuant to my line of inquiry.

    What I asked for, John, is how you imagine things in the physical world? One example will suffice for now.

    Since I am not advancing Berkeley's theory I shall not comment on it.

    Yes, I am suggesting that both the denial of naive realism (at least a strong denial of it) and that representationalism may both be wrong, and that both may need to be rethought.

    I do not understand the distinction made by Broad and Price, as I am not discussing sense data (as such).

  28. Reply #2. It may be possible to distinguish between things that are real from things that exist, because I don't think those two words are synonyms. A theory of reality is not necessarily a theory of existence, because in the physical world at least, particles are continually coming into and going out of existence.

    The account of the visual system that you provide (to the extent that we understand it) is not a theory of perception, but a theory of the visual system, so this is rather like Berkley's objection to Newton and Descartes, namely, that they substituted a theory of optics for a theory of perception.

  29. The word 'real' is definitely slippery; J. L. Austin has a nice discussion of its different usages in Ch. 7 of Sense and Sensibilia; pointing out that it is often used as a contrast to the various ways something may be unreal, including being fake, artificial, an illusion, or a hallucination. I think often it is used synonymously with being existent, and one needs to be a bit careful about tense here, since with your example of particles going in or out of existence Bill, in at least one sense they would only be real during the time period in which they existed.

  30. Hi, Everyone. Bill Rosar invited me to join the conversation but I must say it is easy to be intimidated by such a formidable group of scholars. It has been a long time since I have been so deep into these topics.

    I studied with James (and Eleanor) Gibson in the 1970's, as a post-doc, at the time when JJG was finishing his final book on Ecological Perception. It was a life-changing couple of years. So much so that I became alienated from mainstream cognitive psychology (in which I had done my dissertation, on "human information processing"), and could no longer even read the journals without scoffing contempt. I taught undergraduates, unhappily, believing I was teaching only lies. I finally left the academic world, out of despair, alienation, and, truth be told, from frustration at being chronically poor. I went into industry as a computer programmer with an interest in A.I., and over two decades became CIO of a national nonprofit corporation. Now I am back in the academy as an adjunct, but I still find myself removed from mainstream thinking in cognitive psychology. This is all to demonstrate that I am by no means an expert in any of the matters discussed here. I have only my humble opinions.

    To address Bill Rosar's post of 12/4 that spawned this thread:

    Gibson often reminded us that it is utterly pointless to speculate on the nature of "reality," that is, on the nature of things presumed to be "behind" phenomenal appearances. He reminded us that Kant himself concluded that whether things-in-themselves even existed could not be determined, simply because it is not possible to perceive that which is beyond perception. This was Gibson's justification for analysis of perception in terms of phenomena, without (much) regard for the nature of "reality."

    At the same time, however, Gibson was heavily influenced by the Gestaltists, especially Ernst Mach and Kurt Koffka. So while he was a phenomenologist, he rejected the elementalism of pure phenomenalism. He wanted to understand the perceptual world as a unity "given" to experience directly, not as a cognitive synthesis of sense-data (e.g., per Locke). He claimed that the distinction between sensation and perception is artificial and meaningless (and I think he was right about that). His 1966 book, The Senses Considered as Perceptual Systems, made this point convincingly. Alva Noe, in Action in Perception (2004) makes the same point, irrefutably, in my opinion(but of course I have believed this since the 60's anyway).

    Thus, as to Bill R.'s suggestion that Gibson erroneously attributed to the perceptual world, attributes of the physical world, I don't know if that's a good reading. Gibson had virtually no concern with or interest in the physical world, because of Kant. His task was analysis of the holistic perceptual world on its own terms. I think he would have no interest in this blog.

  31. This comment has been removed by the author.

  32. Bob is right that we need to take great pains in how we are using the words "real" and "exist" to avoid needless conflation of meanings.

    When I close my eyes, the visual world ceases to exist--at least in one sense of the word. Surely nothing is more disturbing than a power outage, when everything goes dark (even black) and perhaps, just for a moment, we wonder if it has ceased to exist or whether we have suddenly been struck blind . . .

    So following Austin (and Wittgenstein) the first order of business is to specify what one means by "reality" in a theory of reality.

  33. Welcome, Bill! I am very glad to have you on board, especially to help us better understand Gibson who, I believe, offered one of the few coherent and internally consistent theories of perception (at least comparing it with others).

    In the Preface of his "Senses as Considered Perceptual Systems," Gibson writes quite explicitly: "I am attempting to reformulate stimulus-response theory, Gestalt phenomenology, and psychophysics so as to extract new theorems from these old theories."

    I think it is clear from what you say above, Bill, that Gibson's thinking was based on the perceptual world, not the physical one as described by physics, even though he talks of physical processes (like the behavior of light). The "objects" and "edges" to which he often refers are not physical ones, but perceptual ones, so his theory is as I have suspected for a time now is of a process that goes on *within the perceptual world,* not between it and the physical world.

    This serves to highlight that there are really two kinds of perception theories, the kind Gibson articulated, and the kind which relates perception to physical quantities (if one could really build such a theory on the basis of psychophysics alone, as Fechner, Wundt, and Helmholtz attempted to do, before the Gestaltists came along).

    I was surprised to hear that Gibson was influenced by Mach (who he doesn't cite), but it helps make sense of his phenomenalistic approach, which is in a way something like Mach's. Though some contributors have summarily dismissed phenomenalism here already, I'm not sure why, because they have given no reasons.

  34. I also would like to welcome Bill Adams (our second Bill). Perhaps we should add a separate Gibson section to the blog; in particular it would be relevant since he claimed that visual space is three dimensional and possesses a Euclidean metric. I remember that Gibson was very popular at Boston University in the late 1970s and early 1980s when I was there and I believe that two students who I knew, Ed Reed (who has since died) and his wife Rebecca Jones worked with him on his last book The Ecological Approach to Visual Perception. I never read Gibson as being a Kantian, but it would make some sense since Kant also held that the space of outer sense (which he thought was the space described by physics) was three dimensional and Euclidean. As Bill Rosar points out this does raise at least some issues concerning what Gibson says about such things as ambient light,since he at least sounds like a realist about it. I also remember though that some of what Gibson had to say was quite contentious to people working on a cognitive science approach to vision (I once had a conversation with Shimon Ullman on this). In any event I personally was never very sympathetic with any of this, and my own work describing a variable curvature to visual space is in a quite different direction.

  35. Warm welcome, too, to Bill Adams! (Bob named him “our second Bill”—in which case should we call our first Bill “The Duke of Normandy”?).

    Here is a further question for Bill {R}: does your theory differ from Berkeley’s because he suggested that there are objects ‘behind’ our percepts only when we (or God) are perceiving them, whereas you suggest that there are never any objects ‘behind’ our percepts. Or is it something quite different? I am somewhat befogged at the moment on this point.

    A detail I have discussed here before—the visual FIELD does not cease to exist when we are in the dark—it just changes to a black uniformish expanse. Black is a positive color, not a nothing. The visual field only (apparently) ceases to exist in cases of cortical blindness. Of course, you can define, if you like, the visual WORLD as that which we see with our eyes open. But then, if you close your eyes, are you now seeing the back of your eyelids? If so, are the after-images, that you now see, located on the back of your eye-lids? It is not clear to me at the moment how the visual world is supposed to relate to the visual field.

  36. In the cases of NDEs in blind people, reported by Ring and Cooper, the 'seeing' is of an unusual sort. R & C describe it as "...a multifaceted synesthetic perception that seems to involve much more than an analog of physical sight." (One problem is that the subjects find it hard to describe it). This seems to be like a form of perception that occurs sometimes with psychedelic drugs. The subject cannot say if she is seeing or hearing—it seems to be somewhere in between: possibly a very primitive form of perception? This raises the interesting possibility that the specific senses—vision, hearing, etc., evolved from a primitive sensory system (with a specific phenomenology of its own, lacking presumably any ‘spatial’ qualities), which might have been more like smelling—since smell is the most primitive sense we have. The olfactory bulb uniquely projects directly to the olfactory cortex without a relay in the thalamus. (En passant, I have just refereed a paper in which the author makes the good point that the fact of the anatomy of the olfactory system effectively demolishes all theories of ‘consciousness’ (including Crick & Koch’s) that are based on reverberating thalamo-cortical circuits).

  37. A question for Bill (A). If there is no difference between sensation and perception, as Gibson claimed, how does one describe the difference between seeing an after-image and seeing an orange growing on a tree? In after-image experiments the experimenter asks the subject “Describe what you see”: and the subject understands the question perfectly well and describes the after-image. The same applied in my experiments on the stroboscopic patterns (the geometrical patterns that appear in the visual field when you look at a flickering light). I asked the subjects to tell what they saw and they did not ask me what I meant—they unhesitatingly described the geometrical patterns.

  38. As for naïve realism and the representative theory, my opinion is that all current forms of the former are incorrect, and that the current orthodox forms of the latter—in which sensations are identified with certain neuronal events—are equally incorrect. I agree with Bill & Bob that ‘real’ and ’reality’ are slippery terms and, when used, need care. For example, a phenomenologist would call hallucinations ‘real’, whereas ordinary folk would call them ‘unreal’.

  39. Yes, by all means, warm welcome to Bill Adams!

  40. The main difficulty is that I am not convinced that Berkeley did not succumb to a version of naive realism, because the famous illustration of the tree falling in the forest making/not making a sound, presupposes a physical world or world beyond the senses that is like the perceived one (however exactly Berkeley conceived perception, given his descriptions of it).

    But Berkeley could not have taken into account the physical world described by modern physics, which almost "isn't there," let alone making sounds: If it has no appearance, it has no sound (per Ray Tallis).

    So part of the naivete of naive realism is the presumption that there is a physical world like the perceptual one. Nothing in modern physics suggests that this is true. Yet philosophers blithely continue to talk about the "physical world" as if it had some similarity to the perceptual one. Don't they watch the news?

    So, John, please now can you describe your understanding of the physical counterpart of your office desk for us? I'd like to know what you think it "looks like," and at the same time explain how you come to have such faith in its existence separate from your perception of it.

  41. I forgot to sign my last comment:

    Baron de jour Nautonier de Castelfranc (formerly D. Normandy)

  42. Thanks to all for the warm welcomes.
    Reading this blog is like drinking from a fire hose.

    John asked me about the difference between sensation and perception in a Gibsonian context. I misstated if I said they are identical. What Gibson taught was that sensations are meaningless, literally without meaning in the perceptual world. Sensations do not occur in nature, only in laboratories, where their demonstration is “ecologically invalid.” That was the party line. The idea was to allow no quarter for the elementalism of Locke, Wundt, and so many others, nor the associated idea that perception is a cognitive or neurological synthesis of some kind. Gibson was above all a holist.

    Some sensation-like phenomena do occur outside the lab, such as afterimages. I say, in a Gibsonian spirit, that the problem is how these are interpreted. We are quick to apply explanations from neurology and physics to bring the phenomena back into the fold of ecological/intellectual meaning. In an untutored realism, as one might imagine in a pre-industrial society, sensational effects might be either not noted at all (because ecologically meaningless), or be taken as ecologically/culturally meaningful, “messages from the gods,” or some such.

    I remember standing with a fellow student on the shore of Cayuga Lake, in the low sun of a late afternoon, admiring the brilliant white diamonds of specular reflection on the surface. “Are those meaningless sensations?” we asked each other. “What do they afford?” We came up with a range of interesting answers.

  43. Thank you Bill for the clarification! I think what Gibson meant when he said that sensations are meaningless is the same as Edmond Wright meant when he said that sensations are phenomenological, but not epistemic, intermediates in perception. Would you agree?
    After-images might be taken as messengers from the gods by early people, but to me, as to Pylyshyn (Behav.& Brain Sciences, 3, 111-169, 1974), they look like after-glows on a cathode ray oscilloscope.

  44. I did not phrase my last remark about Price & Broad correctly. I did not mean that the non-inferential version of the sensum theory was like Bill's theory. I meant that Bill should look at it more closely and distinguish it from the (false) old inferential sense-datum theory, so as better to understand the difference between sensation and perception.

    I am unable to answer Bill's last question (9.19 pm) because I do not understand what Bill means by the term "perceptual world". I recognise (A) the ordinary world of objects that we bump into as we move around, and that our perceptual apparatus enables us to see and touch. Then (B) the ‘physical world’, which is properly composed of just the mathematical theories of physics. These represent highly specialized and technical humanly devised ways of describing (A). Then there is the phenomenal world (C) that is comprised of all that we experience, including our visual sensations, (that, as Edmond Wright says, are phenomenal, but not epistemic, intermediaries in perception), as well as the body-image. There is abundant evidence from clinical neurology that the visual field, for example, is constructed by a specific mechanism, as described by Schilder, Poppelreuter, Goldstein, Gelb, and others. But I do not know what the 'perceptual world' is except, as a chimera generated by a false theory of perception—naïve realism.

  45. Responding to Bill R’s comment of 12/7 on realism, Berkelean and otherwise:

    1. Whether Berkeley presupposed a physical world hardly matters, I would think, since his is a supernatural, not a naturalistic theory.

    2. I admire Bill R.’s commitment to the reality of the phenomenal world. I am also doubtful that the world of physics must resemble what we perceive (whatever “resemble” means), or even that it is the efficient cause of perception. However, I worry about the slippery slope from skepticism to idealism to solipsism.

    3. One approach to this issue is to entertain a novel definition of “physical.” A physical object is one that is directly explorable by the biological receptors (or, as Gibson would prefer, by the senses considered as a whole-body perceptual system). A nonphysical object (e.g., memory, idea, sense-impression, etc.) is not. Physicality is not, therefore, a metaphysical property of objects but is contingent on what kind of exploration it is susceptible to. For example, a trompe d’oeil window is perceived as physical until one discovers it is not susceptible to visual exploration by typical head movements, and at that point it ceases to be physical and becomes a phenomenal (or at least, pictorial) window, (or an “illusion,” for physical chauvinists). Physicality is thus defined by the animal’s biological exploratory capacity and experience, not by physics or metaphysics.

    4. I don’t mean to speak for John, but if he can explore his desk with his eyes and fingers, it is physical. If he can close his eyes and imagine a desk, he has a phenomenal desk also. Accounting for any correlation between them is a separate problem.

  46. One problem that afflicts us all is habitual ways of thinking about things, and getting into a rut as a result.

    By "perceptual world" is just what most people call "the world." When you open your eyes you see it. When you close your eyes you no longer see it. What you do see with eyes closed has no name, except that we tend to localize it as being "inside" us (inside our heads). Some may call the "perceptual world" the "phenomenal world," but I am unaware of that usage in the context of perception theories.

    Perceptual space is thus a larger *concept* because it abstracts only the spatial component of all that we see, whether with eyes open or closed. Rightly or wrongly, the term is used interchangeably with "phenomenal space."

    "Visual field" is presumably a semantic back formation from "field of view" or "field of vision," and is again an abstraction, fairly close in meaning to visual space.

    "Sensations" are really a hypostasis, and it is not as though we have sensations first and then perceptions. Please correct me if I am wrong, Bill A., but I think that Gibson would say we do not perceive sensations but objects, the environment, and the world--and I would agree with him, but with the caveat that they are *perceptual* objects, not physical ones. This is all something going on in the perceptual world, not between it and the physical world.

    We must bear in mind that the original dichotomy in ordinary usage between "physical" and "mental" did not denote the same things it does now, but a division *within* the perceptual world and world of the imagination (imagery, etc.) This is explained at length in my monograph, "The Localization of the Mind."

    Once again, John, can you provide us a definition/description of your desk as a "physical" object? I am most curious to know how you think of it, and why you call it an "object."

  47. Bill A's definition of "physical" is akin to Jacob von Uexkuell's idea of an animal's "Umwelt," on the grounds that an ant's eye view of the world is very different from ours, not only due to the vast difference is scale, but (presumably) because ants have compound eyes and we don't.

    The perception of scent-oriented mammals are dominated by olfaction rather than vision, seemingly for purposes of recognition, but we don't really know for certain. But theirs is primarily a "smell world," whatever that would be like, not a world defined by sharp boundaries but by olfactory gradients which, in conjunction with vision and exploratory behavior, could nonetheless pinpoint a tennis ball--as my Labs routinely are able to do, finding balls hidden in thickets of tall grass on our late afternoon constitutionals at various nature walks nearby. On the contrary, I would never think of finding a tennis ball in a thicket using my nose! Why? Because my nose is not sensitive to pick up the scent to start such as search.

    So Bill A. is quite right: Their "physicality" or "physical" world (I would counter, "perceptual world") would be rather different from ours.

  48. Yes, I am committed to the reality of the perceptual world and, more importantly, the reality "in" the perceptual world.

    The basic thrust of my train of thought here is that it may not ultimately be possible to "transfer" reality from the perceptual world to the (putative) physical world as science thinks it has done with physical realism. That is because reality may be inextricably bound up with the perceptual world, i.e., it as akin to a "property" of it (alas, any way this is worded comes out in paradoxical statements because we are so accustomed to reifying a physical world separate from the senses.)

    If, as I am proposing, reality is ultimately qualitative in nature, a distinction that is made again within the perceptual world as exemplified by derealization and depersonalization, the hypostacized physical entities of physics cannot be "real" in the same way, unless they, too, are subject to derealization (!)

    I suppose this means that the physical world requires some form of idealism, if in the semi-mental form of Plato's "eidola," or what Jung called the "psychoid" (if any of you are familiar with that concept of his to explain the curious nature of everything from the archetypes and synchronicity to UFOs!). In other words, we habitually tend to think of physical and mental in black and white terms, rather than the possibility of gradations between the two. (Truth to tell, I don't much like the "goofy" way this sounds!)

  49. Returning to John's comment (12/7 @ 5:39) it seems to me that there are conflicting (even contradictory) positions reflected in it that are impossible to reconcile, yet this is not John's fault so much as the state of the field.

    On the one hand, a certain kind of sensation is being equated with the functioning of one sensory system--olfaction, in this instance--yet on another view is considered a generic undifferentiated sense.

    Sensations are also discussed as if they are byproducts of the functioning of those systems, which is the standard view of psychoneural identity theory. These positions are incommensurate. If sensations are an order of existence sui generis, then they cannot also be caused by the functioning of the nervous system.

    Unfortunately the standard causal account of sensory function (stimulus -> sense receptor -> brain -> consciousness) is so well ingrained in our thinking, that it continues to be upheld almost unthinkingly by most of us, and to speak otherwise results in paradoxical statements, or statements that sound "goofy" (as I say).

    I have had a great deal of discussion this past year or so about the concept of synaesthesia, both with members of our group at UCSD, and with a scholar in Germany, regarding the origin(s) of synaesthesia as an idea. My reason for exploring this issue is that one scholar proposed in the 1920s that we all possess in us what he called "primal synaesthesia," sometimes called "the unity of the senses." How is that then different from the more exotic forms we have studied at UCSD?

    More specifically, the first reported case of color-hearing (chromesthesia) does not appear in the literature until the mid-19th century. Why? Did people not have color-hearing before that? There is some indication that is because it was subsumed under the notion of "analogy" between the senses (i.e., a poetic or rhetorical practice, rather than an aspect of perception).

    My (tentative) conclusion is that--somehow--the concept we know today as synaesthesia, like so many diagnostic (nosological) entities, was something invented by medicine or, rather, the mindset of medical pathology. Before that the term was associated with the venerable philosophy of Hippocrates and the theory of the "sympathy of all things." How the term got narrowed down to just mean "double sensations" (as the Germans say with their term "Doppelempfindungen") remains to be ascertained, but prior to that it applied to everything from referred pain to corresponding retinal points!

    In any case, in the 19th century the idea was put forth that in "lower" animals there was a kind of primitive general sense that later differentiated into the special senses. But there is a problem with that proposal, given the compound eyes of insects, which are very ancient, needless to say, developed long before the mammalian olfactory system. Of course, the problem is that we don't know what insects see! Nor do we understand their "chemical communication" that occurs by exchanging substances on the surfaces of their bodies.

  50. Will R, as it rolls around in my mind, I find myself at something of a loss. It seems as if you are looking both to affirm naive realism and also to condemn modern physical science for being tainted with naive realism. I can see how these concerns might be reconciled, but still it is somewhat puzzling. So, what then?

  51. The current orthodoxy is stated thus: "Naive realism is false and scientific realism is true." Need I point out that this may constitute a "false dilemma" and that neither may be wholly true or false?

  52. Since I don't know when I shall get to posting that old paper of mine about topological properties of visual space, I will offer a glimpse of a sort of discovery it contains that I made many years ago, which convinced me at the time that reality (or perceptual reality) may be something like an elaborate hoax. Yes, a hoax! And one perpetrated by an 'intelligence greater than we have even dreamed of,' to paraphrase what H.G. Wells said of the Martians in "War of the Worlds." It also goes to the reason behind my analogy of perceptual reality being something like stagecraft in the theatre:

    I realized that it is impossible to construct a cube out of six faces all of which look square *and* wherein the sides are all connected. It is not just a failing of the limitations of our ability to visualize. As one attempts to visualize such an object, it becomes evident that squareness and cubeness cease to exist in the process--the appearance of this polygon, understood as connected angles, starts to "go away," perhaps as a prelude to Ray's "disappearance of appearance."

    As I have stated previously, what we call "appearance" seems to be something not only of low dimensionality, but *requires* it, e.g., one of the dimensions being projected into the other in the case of perspective projection. If one tries to unfold that projection--voila--appearance disappears: There are no more solid shapes. The same effect would occur if somehow we were able to make everything the same color in visual space--the visual world would cease to be a world anymore.

    If such a Platonic solid as a cube does not really exist as we would like to think it does, just what sort of world are we inhabiting? Where is the back side to visual space? Is this "The Twilight Zone" by any chance? Therein may be the true "nature" of visual space: It is only half real.

  53. Bill R.'s comment of 12/13 on Platonic cubes is "far out," as we used to say. Here are some reactions:

    1. The Platonic forms can be taken as metaphor for the essential absolutes "behind" or within appearances, as Husserl seemed to think in his transcendental phenomenology. Or they may be taken as geometric/mathematical/intellectual abstractions of lived sensory experience, more the Aristotelian view,per, e.g., Merleau-Ponty. I cannot quite discern which attitude Bill R. is talking about. He rejects the Formic cube based on its incompatibility with sensory experience. That seems to point to a flaw in an Aristotelian form: it was a bad/imperfect abstraction. But a pure, timeless, otherworldly Platonic form would be unaffected by such a mental deconstruction. ??

    2. J.J. Gibson's theory of affordances defines physical reality in terms of the interaction between an animal's behavior capacity and its environment. A hole in a tree affords shelter for a bird but not for me. Is the tree really there? If the bird finds shelter, then yes. "Treeness" is our intellectual conceptualization of the situation. The bird has no such perplexity.

  54. Another comment on Bill R.: What is real:

    1. Margolis and Laurence(2007)reviewed numerous studies aimed at determining what is a "natural" object and what is "artificial." Their conclusion was that there is insufficient evidence to suppose that our conceptual categories (including those of science)actually cut nature at its joints. For a quick synopsis, I have a brief review of the book at -- scroll down about 2/3 and click on "full text."

    2. The complementary side of that story is summarized in another recent cognitive psychology offering from Klatzky, MacWhinney, and Behrmann (2008): Embodiment, Ego-Space and Action. The essence of this argument is in the customer who asks the clerk, "How big is the fourteen inch pizza?" It is not a ridiculous question because fundamentally, the world is understood in relation to the body (cf. Lakoff & Johnson). I also reviewed that book, just below the previous one mentioned above, if you would like a brief synopsis.

  55. Well, yes, it is true that ordinarily I cannot see a cube in the same way I see a plane figure. I must walk around it or something. From the series of impressions I have when I do this, I conclude there is a cube. Consequently, there is strictly speaking not the same assurance that the cube is there as there is for the plane figure. If this is all Will R means, then yes, the point must be conceded. But it seems almost as if he is going beyond this to suggest there is some positive reason to suspect the cube is unreal. What about it, William?

  56. Bill A. has hit upon an important point, one which I have alluded to previously, and that is that there can be *spatial* metaphors, or even geometrical metaphors, and that perhaps they should not ultimately be taken literally, but heuristically.

    In the context of my previous comments (made somewhat tongue in cheek), I had just been reading passages in Andre Breton's 1st Manifesto of Surrealism, and it is well to remember how fascinated the Surrealists were by the *idea* of the fourth dimension, as well as the guiding principle that Salvador Dali employed in his paintings, that which he called the "paranoid-critical method." And surely the introduction of "War of the Worlds" is one of the most paranoid pieces of prose ever penned (how's that for alliteration?) with its description likening the Martians observing humanity to a scientist examining the "infusoria" under a microscope.

    But that aside, rather than just taking for granted that cubes exist with six faces and their sides all connected, try the experiment of visualizing such a shape and see what happens. One cannot get all the sides connected, nor all the faces to look square. Even when we look at a (perspective cube) none of the faces truly look square. If represented as a line drawing they simply are not square. To make even one of the faces square one must sacrifice seeing the other faces. What basis do we then have to assume that cubes exist that have these properties?

    I am suggesting that rather than just dismissing this as "perception" that it tells us something about the nature of reality as we understand it, and that there quite simply is no Platonic world of forms at all. That was my point.

  57. "Only those pieces of shapes are actually extant in concrete reality that are presently being observed." Is this what you mean? (The question about some Platonic world of forms gets into a whole other cluster of concerns.)

  58. Thanks also, Bill A., for those references and I will check them out as well as your reviews.

    Yes, how we parse (or don't parse) "the world" is not only relevant to ethology, but to ontology. On the other hand I don't quite buy the idea of "operationalizing" reality, defining it behaviorially, as it were, because it does not explain conditions such as derealization, which as John has attested, can be truly terrifying.

    The moral of the story is that there is no one-size-fits-all definition of reality, as one can see by reading the different meanings of the word in OED.

    Returning to the example of the cube, perhaps a better way of getting at my point is that we need to take a much harder look at our "presumptive world" of perception, and how it gives rise to concepts that presuppose conditions that we not only cannot perceive, but that it is impossible to perceive. Yet we attribute a higher reality status to those very conditions. To me this is a kind of useful delusion, like the "als ob" ("as if"), the "fictional" assumptions we make about the world as developed by philosopher Hans Vaihinger. Here is a brief useful overview of his thinking from Wikipedia:

  59. Yes, the strong ontological claim I am claiming is that there is no such thing as a cube made of six faces all of which look square and whose sides are connected. Whatever "preconditions" make possible "cubeness" are not themselves of the nature of a cube, any more than the swirls on the holographic plate resemble the holographic image when "realized" by a laser beam.

  60. I read Bill A's quite candid review of Margolis and Laurence(2007), and based on it, I will probably skip reading the book itself, which is apparently all research and analysis in search of a missing context. Wittgenstein would probably make short work of it, too, because it appears that the notion of an "artifact" has acquired a new quasi-technical meaning for these writers (or has had one for a while that I don't know of) which has sent them into fits of perplexity. If they had instead analyzed how "artifact" is used in ordinary language, they might have gotten somewhere, let alone shown how the notion of an artifact is somehow at odds with being natural. (Are people somehow not part of Nature?) Redefining ordinary words is almost a guaranteed recipe for trouble, as Wittgenstein was at pains to show at length in his later philosophy.

  61. One further comment in response to David's request for clarification: I would say that this "composite" of "impressions" had by, say, walking around a cube, or looking at one rotating, creates a kind of *equivalence class,* one that all refers back to the perceptual condition I am calling "looking square" (a Gestalt quality).

    This then goes back to my claim that much of what we are attributing to some sort of world beyond our senses (or a state of existence beyond them) upon closer scrutiny can be shown to be recursive, and refers to the world of our senses alone.

  62. So I think that one thing that gets destroyed (or ostensibly so) in spatial agnosia is the very "equivalence class" to which I refer: Patients don't seem to know how the world and the objects in it fit together anymore, because they no longer have the "links" between corresponding spatial impressions.

  63. And this in turn refers to a point Bill A made on his own blog about perspective, namely, that interpreting perspective cues as being equivalent to the depth experienced in stereopsis is a product of perceptual learning, and may indeed have a cultural component to it. But then we come into the world with two eyes, not one.

  64. Do human conceptual categories in fact "cut nature at its joints"? That is in some ways the $64,000 question (or perhaps $128,000 in these days of inflation). To say there "is no Platonic world of forms" may be to say there is no law up in heaven to define what the natural joints are. But why is any such law up in heaven needed? Plato considered that this law is known only through intellectual understanding, which goes beyond the limits of sensory experience. But he considered that knowledge is only as good as the thing known. So, the intellect has superior knowledge by latching onto some superior reality, beyond the things that are seen and touched. These things seen and touched are then known in virtue of embodying this superior reality.

    Along this line, some version or reconstruction of what Plato said would seem to be the alternative to the concerns Will R developed. Visual experience gives rise to puzzles and paradoxes that can only be resolved on a higher level. This is the level of intellectual awareness, on which level one can understand the laws of optical perspective in terms of applied geometry, et cetera. As for the "higher reality status" of those things, well, these things that ground experience are more solid and stable than the experience. Plato would add that they are a superior reality as having to be konwn in a superior way (=intellectually).

    Should one believe all this instead of writing it off as a useful delusion, as William does? That may depend on what should be said about accepting other people's experience as well as one's own. If I had only my own experience to consider, perhpas I might find it reasonable to follow what William said. But if the whole gang is looking at the cube along with me, from different angles, what then? I can combine the several views by saying there is a real cube that exists apart from all of us and by invoking the laws of optical perspective. Perhaps William can also combine all the different views as well, but it would seem to be appreciably more problematic.

  65. It seems that I have anticipated David's rejoinder so will only say that I believe that there is no higher order knowledge of a cube, and that it is an illusion to think that there is one--if, and I stress *if*--I am right in thinking that the equivalence class only refers to itself, not to something outside it, whether several people's combined views of a cube, or my own. Spatial idealism (if I can coin a phrase) seems similar to the illusion that the "grass is always greener on the other side of the hill." What results are not so-called "impossible figures," but figures that are impossible to construct.

  66. Well, but now wait a minute! Which of the two things you said are you proposing? (1) There is in fact some cube, but this cube is only virtually and not genuinely real. (This is what the talk about the holographic projection comes to.) (2) There is only the cluster ("equivalence class") of the experiences themselves, but in fact no cube. Which of these should be said is very important for what is the right ontology.

  67. Point well taken, David. I am saying that a cube is ultimately an "as if" fictitious form, does not exist in any sense (except as a concept, unlike a square, which does exist as seen, s shape that "looks square"). It is therefore not a "virtual" shape, and the hologram analogy should not be taken too literally, because holograms are images of things that we can ordinarily perceive.

    The equivalence class, which is founded on shapes that are deemed equivalent but not congruent with shapes that "look square" is the perceptual basis for the fictional form called a cube.

    The other characteristic of perceptual (visual) solids is that they have no back side to them, because as I have noted, visual space itself has no reverse side. This concerns the topological property of "sidedness," in this case, VS being like a bounded one-sided surface--something that physics would probably dismiss as being impossible. Yet it does exist.

  68. The hologram analogy only works if we assume (1) that (perceptual) reality is the image and (2) the holographic plate is the pre-condition. (This line of reasoning parallels that of David Bohm and Karl Pribram, as should be obvious, with the concepts of "implicate" vs. "explicate" order).

  69. The difficulty with the analogy is that it requires two modes of existence: (1) implicate and (2) explicate, and that these two modes cannot really co-exist. There's the rub!

  70. So, what then? Plane shapes exist, but solid shapes do not. Is that it? Also, if plane shapes exist, are they actually present in concrete reality, or do they exist only as objects of perceptual awareness?

  71. A proverbial "so what" question! I note a shift from talk of perceptual *reality* to perceptual *awareness* and from perceptual reality to *concrete* reality. What sort of awareness is there if not perceptual awareness and what sort of reality is there if not concrete reality?

  72. Well, above perceptual awareness, there is distinctively intellectual awareness. Plato took this point as critical, and so do I. Moreover, I think you need this point in order to make what you said work. You proposed an "equivalence class" of experiences might combine the views of different people. But then this work of combining or coordinating must belong to a neutral or impersonal standpoint, above the separate perspectives of the several people. Now, I think when the implications of this neutral or impersonal standpoint are worked through, the result is truly wondrous. But in any event, this standpoint has to be something distinctively intellectual.

  73. Again, point well taken, and I was using "perceptual" loosely here as shorthand to include *any* content of consciousness. Also, I'm not sure that "intellectual awareness" really means the same thing as "perceptual awareness." Could you possible offer an example of what you mean by "intellectual awareness" relevant to the problem of 3-D shapes?

  74. Along this line, I find I am left with the other question I asked. You seem to be saying plane shapes exist as objects of perceptual awareness, but solid shapes do not have even that much (being merely ideal constructs instead). Is that correct?

  75. I am saying that something that looks square in visual space is a kind of primitive, whereas the notion of a 3-D shape is derivative, derived from and related to looking square. The way we know a cube is by looking at all its sides to see if they look square. Ordinarily we just say that it is not possible to see all a cube's faces at the same time, but what I am saying is something more radical (if you will), and that is to question if such an object is even possible. Again, try my thought experiment and tell me what you conclude.

  76. No, "intellectaul awareness" does NOT mean the same as "perceptual awareness." Plato took the intellectual as *superior* to the perceptual. What does this distinction involve? Well, a mathematician might contemplate intellectually what would be involved in having a solid with 5678 faces, even though he has never seen any example of such a solid and cannot form any picture of it in his mind.

  77. Well, if Plato said that, then it certainly must be true! I suppose one could make a drawing of a polygon with 5679 faces that one could contemplate on a piece of paper. Not quite sure what distinction is relevant here.

  78. Many years ago now, when I was a graduate teaching assistant, there was this one remarkably bright student who was working in mathematics. We got to talking, and he said he was working on negative areas. He explained that some formulas for areas will in some cases give negative values as the result. I asked whether these results had any geometrical interpretation, and he said that was what he was trying to find out. No drawings on paper or images in the mind would help with this inquiry, since the whole question at issue was whether such negative areas could be represented in this way. Quite clearly, therefore, the process of working through the question had to be purely intellectual. In general, mathematicians as well as physicists and chemists are constantly thinking and talking about things that cannot be perceived by the senses, nor pictured in the mind, but only understood intellectually at a very high level of abstraction. There might perhaps be concerns having to do with 3-D shapes that are this way. Anyhow, this is the point of the distinction between perceptual awareness and intellectual awareness.

  79. Yes, that is interesting all right, and mathematicians themselves speak of what they call "mathematical fiction."

    But more relevant to our endeavor are issues associating with the geometrization of the physical world, otherwise known as "physical geometry," a term used by Einstein and his associates, later developed by Wheeler as "geometrodynamics." I have mentioned both of these terms several times already (as well as in my 1986 paper), but there have been no comments as to how they may/may not apply or parallel the geometrizing of visual space, given the "field" effects postulated by the Gestaltists, for one.

    One of the most interesting issues to arise in mathematical astrophysics in recent years grew out of the quest for the unified field theory, and it is one that I have already mentioned, i.e., the question arising as to the *reality* of a number of mathematical dimensions associated with the structure of the physical universe, i.e., whether those dimensions are "real" or not, rather than just being mathematical entities. So the reality status of spatial dimensions is a problem in physics, not just the study of perception.

    Growing out of work in particle physics attempting to reconcile quantum mechanics and general relativity, string theory proposed a manifold of very high dimensionality in which the dimensions higher than the four of space-time were conceived as being rolled up into little balls, and the theoretical question (for a time) was why only four dimensions became macroscopic, whereas the rest did not (and the problem being that the rest of the dimensions were unobservable, "hidden"). That model, was actually anticipated by the thinking of Hans Reichenbach some decades earlier, in which he likened space-time to being something like a surface comprised of a fine layer of sand--an interesting analogy.

    With the multidimensional "quality" spaces developed in the study of color and in the study of smell, it also occurred to me that VS might constitute a projection of a higher dimensional "quality" manifold, but the problem I faced was that it was not clear how to relate the primitives of the quality spaces to the geometry of the visual world.

  80. Bill A., I read your review of Klatzky, MacWhinney, and Behrmann (2008) with much interest, because I am intrigued by the embodied cognition school of thought, even though I find it more than a little muddled for various reasons, among them being an inconsistent notion of reality vs. representation (as you have probably gathered by now, the whole idea of "representation" has become a pet peeve of mine).

    But, yes, "man is the measure of all things," as the ancients maintained and was a popular "topos" in medieval philosophy.

    More and more I am inclined to agree with the contention that the main purpose of the CNS is to control the body, and not to make perceptions.

    One of the silliest phrases I have yet to come across is one you cite in your review: "content-agnostic module." We need a new phrase for that sort of locution--perhaps "cognobabble" will do?