Sensory Qualities, Their Relation to Sensory System and World
Stephen Boydstun*Joseph Levine ponders whether scientifically based theories of conscious mind currently being constructed are such as to plausibly yield a physical-realization theory of conscious mind, provided enough yet-to-be-discovered neurobiological details were added to the theories (2000). I shall be concerned in the present study to make plausible the case for a physical-realization theory of sensory perception. My focus will be on elementary perception, halting prior to perceptual judgment. Making good on a physical-realization theory of the sensory qualities in elementary perception is the gateway, I should say, for a physical-realization theory of conscious mind in general.
Jeffery Poland maintains, rightly I think, that "a realization of an attribute, N, on a particular occasion by a class of physical attributes, P, is a configuration of physical attributes that constitute N on that occasion" (1994, 191). There is, to be sure, "no reason to suppose that there is just one sort of realizing relation that all entities bear to physical entities that realize them. . . . The realization of this world by a purely physical basis may well be the result of many different sorts of modes of constitution" (ibid., 18–19).
In the first section of the present essay, I set out my operating notions of the physical and of sensory qualities in conscious experience. I characterize the divide that looms between them for anyone who would explain the latter wholly in terms of the former. In the second section, I articulate, with some realistic detail, an up-to-date theory of how sensory qualities are plausibly realized entirely by physical elements. In the third section, I indicate the character of the sort of physical realization at work in this theory.
I. Qualities Spurious and FaithfulSensory qualities are the takes of the perceiving animal subject, the ways an item or scene looks, appears, or seems to the animal in a sensory perception. The item or scene as physical is that which is tracked by those qualities in perception. Failure of tracking by a quality is discerned only by discrepancy with other qualities presumed as tracking. A sensory quality that seems not to track in some perception is brushed aside by us (extra smart animals) as spurious, as misleading action, as not true to the physical item or scene in that perception. Some spurious qualities are brushed further, into the animal subject of the perception.
Every sensory quality has a quale, an intensity, and a referral. By referral I do not mean the physical item purported by the sensory quality. I mean, rather, the region of space in which the quale is given as residing (cf. Shepard 1993, 231). Every quale has a presented residence. Coldness of an ice cube in hand is felt, normally, as coldness on parts of the hand. Firmness of the floor under foot is felt as pressure at bottom of the foot. Radiant heat from the fireplace is felt as from the side of the body being warmed by it. Caw of crow in the sky is heard as a certain coarse sound coming from some not-so-certain direction and distance. Tapping at one's chamber door is heard as at the door. Ebony bird seen perched is seen as perched somewhere. Wooziness is felt as within one's head.
Fidelity of sensory qualities to the physical items and scenes of perception admits of assessment in character (quale and intensity) and in referral. Illusory referrals would include the straight oar, with blade in the water, seen as bent; apparent source direction of an echoed sound; apparent distance into a mirror of an image; and apparent depth in a perspective drawing. There is a tradition of construing displaced-referral illusions such as these as having their falseness, to the physical object of perception, within the perception itself (Aristotle 1984, 442b1–10; Leibniz 1989a, 199, 202; 1981, 403–4; Dewey 1925; Dretske 1988, 67–70; 1995, 4, 26–34, 174–75n13; Siewert 1998, 230–34). According to this current of thought, one fully accounts for such falsity by specific comparison and accommodation of the illusory perception with (presumably) veridical ones. One thereby renders the illusory perception true to the full, refined physical scene. Another tradition, also affirming such full, refined trueness in the illusions, construes the falseness as lying not at all in our illusory perception, but in some judgment or inference we make upon that perception (Augustine 1942, 68; Ockham 1990, 26–27; Descartes 1976, Med. IV, Prin. 1.42–43; Kant 1965, B70, B350 A294; Russell 1912, 113–14; 1918, 93).** Falsity and truth are born not in animal perception, but in the rational mind. The latter tradition left fully wide a gap for anyone who would explain the mental entirely by the physical. I cast my lot with the former tradition. Even so, the gap is wide.
The term referral is used in medicine in connection with pains, and that usage is equivalent to what I am in this study calling displaced referral. In medical parlance, one would say that visceral pains are typically not localized to the site of their cause (damaged or threatened tissue), but referred to another site in the body. In our general perspective of perception, we rightly say that these are displaced referrals of pains: illusions in referral.
Our visual perspectives of scenes plainly are functions of our body (head) locations. Rainbows plainly move within a scene in perfect synchrony with changes in the location of one's body. Remove the living animal, Galileo would say (1966, 65–68), and the perspective will remain, but the rainbow will cease to exist. Perspective is in the physical world; colors are in the (literal) eye of the beholder, in the animal subject. A color negative afterimage moves to whatever and wherever one moves one's gaze, preempting the normal colors of things seen there. To persons with jaundice, everything looks yellowish. To normal subjects, grass that looks green at noon looks golden in late afternoon. Remove the animal subject, grass and sunlight will remain, but no colors. Or so conjectured Galileo. Color, sound, and heat (warmth) are as tickling to the motion of a feather. Remove the animal subject. There will be ruffling of the air, but no sound; motions and shapes of minute particles, but no heat; motion of a feather, but no tickling. These qualia—color, sound, heat, tickling—though produced by things outside us, do not themselves exist outside us (ibid.).
In Galileo's picture, illusions of referral show only that referrals can be displaced from true, not that locations, directions, perspectives, nor geometry are per se dependent on the presence of the animal subject. I concur (cf. Dretske 1995, 78–81).
Newton really concurred, but the thought of Newton of moment to us here is his conception of physical body for purposes of rational mechanics. Body is that which fills space, excluding other body because impenetrable. Body in mechanics should be regarded only as extended, impenetrable, and capable of motion. Other properties of bodies, properties not essential to motion, such as the powers bodies have for affecting our senses, are to be disregarded (Newton 1962, 122, 145–48). "The nature of things is more securely and naturally deduced from their operations upon one another than upon our senses" (quoted in Manual 1990, 75, from a college notebook of Newton's).
When we do turn to explaining how sensory qualities arise from the impingements of physical bodies on our sensory systems, referrals look more amenable to physical explanation than qualia. As Leibniz noted, the visual, auditory, and somatosensory systems allow us to know colors, sounds, and tactile qualities, but
they do not allow us to know what these sensible qualities are, nor what they consist in, for example, whether red is the rotation of certain small globes which, it is claimed, make up light, whether heat is a vortex of very fine dust, whether sound is produced in air as circles are in water when a stone is tossed in, as some philosophers claim. We do not see these things, and we cannot even understand why this rotation, these vortices, and these circles, if they are real, should bring about exactly the perceptions we have of red, heat, and noise. Thus it can be said that sensible qualities [qualia] are in fact occult qualities, and there must be others more manifest that can render them more understandable. . . .
I do not deny that many discoveries have been made about the nature of these occult qualities; for example, we know what kind of refraction produces blue and yellow, and that the mixing of these two colors produces green. But for all this we do no yet understand how the perception we have of these three colors results from these causes. (1989b, 186–87)
II. Qualities and Nervous Activity
At present there does remain a gap, in entirely physical explanation (sensory system and world), that is common to the qualia, intensity, and referral of sensory qualities. This is the general gap in explanation of our conscious awareness comprising qualia, their intensities, and their referrals (those three being constituents [always together] of our conscious awareness of items and scenes). This is the gap in our physical understanding of perceptual consciousness as such. Let me relate a recent neurophysiological theory of perceptual consciousness, with its self-acknowledged, general gap. Then I shall descend into the recesses of the gap peculiar to qualia and peculiar to their referrals.
In the theory of consciousness put forward by Antonio Damasio (1999), all conscious perceptual experience requires a sensory deliverance and, (re)emergent within each deliverance, an attendant sense of body self-in-the-act-of-sensory-perception. This is so for what Damasio terms core consciousness as well as for what he terms extended consciousness. Core consciousness is only of and for the immediately present percept (or immediately present image from memory); requiring only low-level automated attention, not focused attention; and not implicating working memory, only a very brief short-term memory (ibid., 15–19, 91, 112–13, 122, 170–72, 184–92, 196–97, 267–72). Extended consciousness is the level of broader perceptual experience and thought, which are dependent, in development and moment by moment, on the presence of core consciousness (ibid., 123–25, 200, 266).
"Core consciousness is the process of achieving a neural and mental pattern which brings together, in about the same instant, the pattern for the object, the pattern for the organism, and the pattern for the relationship between the two" (ibid., 194; also 146–49). The brain structures proposed by Damasio as mediating core consciousness "are of old evolutionary vintage, they are present in numerous nonhuman species, and they mature early in individual human development" (ibid., 106). They are as follows: For the pattern of the organism (human body in particular), we have the somatosensory maps at upper brain stem nuclei and hypothalamus as well as the higher levels of those maps spread over somatosensory cortices (ibid., 153–56, 234–35, 252–55). For the pattern of the perceived object (item or scene), we have the somatosensory cortices (again) and visual and auditory cortices; and we must include subcortical modulating structures for object perception, that is, certain nuclei in basal forebrain, brain stem, and thalamus (ibid., 159–61, 193–94, 235–36, 267–70). For the pattern of the relationship between the animal and the perceived object, we have the cingulate cortices and certain nuclei of the thalamus and superior colliculus (ibid., 177–82, 235, 260–66).
In speaking of "neural and mental patterns," Damasio means to acknowledge that there remains a gap in explanation of how conscious patterns, such as the sensory qualities in conscious experience, arise from neural activity patterns or neural maps. He does not mean to endorse dualism; he expects the gap to be filled by physical phenomena not yet identified. But he does not think it is correct to say, at our present stage of knowledge, that conscious mental patterns simply are the neural patterns or neural maps that he has proposed as bases for core consciousness (ibid., 9, 322–23).10
Contrast this stance with that of Sidney Lehky and Terrence Sejnowski. In reporting their modeling (for the color visual system) of the neural process of decoding (which is a mapping of) neural population-coded inputs, they write:
Damasio, of course, does not posit a homunculus in the brain, but he does think that we must go beyond the neural systems supporting sensory deliverances and bring into our account of the neural bases of perceptual consciousness the neural systems supporting the attendant sense of body self-in-the-act-of-sensory-perception. These latter neural systems do not constitute a homunculus; they do not stand already producing a sense of body self without any deliverances of the senses by the former neural systems (Damasio 1999, 11, 154, 189–91).
One might argue that we have not decoded the population at all, but moved from a population code in one representational space to a population code in another representational space. How do you decode that new population? . . . At some point, one simply has to say that a certain pattern of activity is our percept. . . . The act of decoding implies something "looking at" the population. At the last link in the chain, one cannot decode or interpret [further] without invoking a homunculus. (Lehky and Sejnowski 1999, 1277; emphasis mine)
The somatosensory system is a switch hitter. It contains a spectrum of functions permitting it to support both the core-consciousness sense of body self-in-the-act-of-sensory-perception as well as many sensory deliverances of the body as perceptual object. The somatosensory system contains integrated information on the current internal milieu, chemical and visceral, of the entire body (ibid., 150–52) and on the current positions and movements of muscles and skeleton. The somatosensory system is also the neural system supporting the sensory component of pain, sense of touch in its various submodalities, and the sense of cutaneous warmth or coolness. There can be core consciousness without the visual and auditory systems, but not without the somatosensory system. Moreover, there are no purely visual nor purely auditory perceptions, that is to say, visual and auditory perceptions are always accompanied by signals of adjustments of the body (ibid., 147).
Sensory cortical areas (and reciprocally modulated portions of the pathways to them from earlier sensory processing areas) whose activity levels correlate very well with our conscious perceptions of various items and scenes are being found out by our neuroscience. The qualia of our percepts are not referred to those areas of cortex (and confederate brain areas), and neither we nor any other animal could have come to exist naturally if they were. It might seem then that qualia are not located at the areas of their correlated neural activity.
Straightaway we bring forth, however, the fact that the referrals of qualia are also mediated by neural processing (cf. Ellis and Newton 1998, 422–23, 430). Somatosensory channels (proprio-, noci-, thermo-, and mechanoreception) are all mapped somatotopically in parietal cortex. The dorsal cortical stream of visual processing, projecting from primary visual cortex to posterior parietal cortex (where it joins the subcortical stream from retina to superior colliculus to pulvinar to posterior parietal cortex), performs the transformations that "deliver the instantaneous and egocentric [bodycentric] coordinates of objects and thereby mediates the visual control of skilled actions, such as manual prehension, directed at those objects" (Goodale 1996, 373). Neurons have been located in parietal cortex that evidently "transform information from a retinal coordinate system into a coordinate system that could guide a motor response. These transformations may, for example, enable the reflex-like grasping of moving objects" (Lamme, Supèr, and Spekreijse 1998, 531), such as catching a baseball. There is now evidence also for the existence of a dorsal stream for the processing of auditory spatial information. It is plausible "that parietal cortex contains several space representations, each specialized for the processing of spatial information from different sensory modalities, including audition. In a next step, these unimodal representations may then be integrated into a supramodal representation of space acting on a sensorimotor interface" (Rauschecker 1998, 518).
If the referrals of the qualia in our sensory experience are brought into our awareness by (putting it overly simply) certain sensory and sensorimotor cortical neural activities, yet if no referrals are experienced as at those neural sites, do we all suffer from a systematic illusion of referral? No. I should say with Dewey that veridical referrals are to the locations at which our actions upon and movements about the perceived items and scenes would be effective (1925). Visual referral of the length axis of an oar entirely in air is well tuned to where we should reach. Visual referral of oar axis partly in water partly is not well tuned to where we should reach. If all referrals of qualia in our sensory experience were to nervous tissue in the brain, then we should be under a systematic illusion of referral.
The gap in wholly physical explanation of the referrals of qualia in our conscious perceptions does not seem unsusceptible of being closed, because referrals are simply to places in physical space. Being somewhere in space is something plainly common to world, body, and sensory receptors; and something assuredly susceptible to being mapped into arrays of receptors and subsequent neural networks, which are assuredly then translatable into animal action in space.
Is perceived light the flood of photons (electromagnetic bosons having energies in the optical range) that arrive, after propagation through the lens, at the rods and cones of the retina? Christine Skarda proposes it is so (1999, 83–87). Or is perceived light the changes in membrane potentials that occur in the rods and cones when they absorb photons? I propose this is so. (Surface plausibility of Skarda's account rests on an equivocal use of the term light.) I propose that perceived light consists of the changes in receptor membrane potentials, in the physiological forms into which those changes have been transmuted by the time they reach primary visual cortex (V1) and beyond. Neuronal groups resonant with our conscious visual awareness of patterns in a scene are found plentifully in inferotemporal and parietal cortex, but are found also, more sparsely, "over the entire visual pathway" (Logothetis 1999, 74). I gather, however, that "entire visual pathway" means only back as far as V1 (with LGN implicated, presumably), not all the way back to the retina (Logothetis 1998).
So, I am proposing perceived light to be changes in receptor membrane potentials in the physiological forms they take by the time they reach V1 and beyond. Similarly, perceived sound, I should say, is not the train of stress-strain waves in the basilar membrane and organ of corti, but the changes in the stereocilia of the organ of corti, in the physiological forms these changes take in subsequent neural processing. Similarly, a coolness felt at the hand would not be the flow of heat out of the skin to the environment, but the correlative change of some physiological sort (unknown to me at present) at the end-bulbs of Aδ and C neuronal fibers. Similarly, the pain of pushing back a cuticle would be not the stress of the tissue, but a correlative change of some physiological sort in the end-bulbs of Aδ mechanical nociceptors embedded in the stressed tissue.
My resultant outline of the physical reduction of sensory qualities in our perceptions is, then, as follows: Qualia consist of modifications in physiological activities in our sensory receptors, as articulated by subsequent neuronal processing. Referral of qualia to the locations of their receptors would sometimes be veridical, sometimes not. The latter look especially resistant to wholly physical explanation. That is, qualia whose referrals would be illusions were they referrals to the locale of the receptors for those qualia seem especially resistant to wholly physical explanation.
That the basic quale of vision should consist of changes in membrane potentials of rods and cones as transmuted to V1 and beyond, yet be referred (veridically for the most part) to environmental locations distant from the retina is very counterintuitive. Though less acutely counterintuitive, that the basic quale of audition should consist of physiological changes in the stereocilia in the ear, yet this quale be referred (often veridically) to remote points of the environment, is also counterintuitive. The audition case is not so acutely counterintuitive as the vision case because in audition we are generally more aware that sound (what is becoming heard sound) is being received at the ear, though referred to a distant source location.
Processing of visual spatial information by the dorsal pathway evidently serves to control visually guided action largely unconsciously, in contrast to processing in the ventral pathway which mediates conscious visual perception, including that experienced during action (Goodale 1996, 370–73). Patients who have lost the ability to recognize and expressly represent objects, due to ventrolateral damage, retain their powers of visual reference and of visually guided manipulation of objects. I suggest that in the unconsciousness of dorsal-stream referral for visual perception, we have a root, a neurophysiological root, of why we find it so counterintuitive to think that though a visual quale consists of changes to membranes at the retina (in the form they take at V1 and beyond), their veridical referral is not to the retina, but to some place in the environment.
Visual referral happens instantly and automatically, and, unlike in audition, we have no direct sense (other than pain sometimes) that the proximal stimuli, photons, are in process of arriving at the eye. At the retina, the membrane changes that are (in their form upstream) qualia indicate the arrival of patterns in the flood of photons, but that is not the natural, biological indicating function of those qualia (cf. Dretske 1988, 62–64; 1995, 72, 88–90; Shepard 1993, 223–27). The biologically given indicating function of visual qualia are indication to the animal of the distal stimuli, the items and scenes beyond the animal's eye. Accomplishment of this natural indicating function is in part through the instant, silent referral of visual qualia mediated importantly, as we partly understand now, by the dorsal stream of visual processing and its sensorimotor conjugation in parietal cortex.
III. Qualities RealizedAnimality is realized by the living matter of the animal, the animal acting in the world. I am thinking only of multicellular animals, the ones having muscle and nervous systems. Theirs is the animality I mean. Consciousness is a piece, a very precious piece, of animality. I say that animality is realized in living mater, rather than identical to the living matter composing the animal, because animality requires animal behaviors, to which the living matter is as means.
To say that animality is realized by the living matter of the animal is to say that animality is instantiated in virtue of the instantiation of the living matter. The constituents of the living matter jointly make it the case that animality is instantiated (cf. Poland 1994, 16–19).
Saying that animality is realized comports also with the fact that there are the various species of animals and their behavioral repertoires. In that sense, we could say that animality is multiply realized. But I do not mean to say that animality is multiply realizable in a wider range of creatures, beyond animals: some living though not animals, others not living. Enough for the day is the realm of animals.
Consciousness is realized in living matter in the same sense that animality is realized in living matter. The sensory qualities of conscious perception are realized by their living sensory systems. And I should expect that sensory qualities are not identical with their living sensory systems, because perception requires stimuli and responsive animal behaviors, to which the sensory and sensorimotor systems are as means.
I have proposed that qualia consist of modifications in physiological activities in the sensory receptors, as articulated by subsequent neuronal processing in the animal having conscious perceptions. Is this "consist of" identity or realization? A standard objection to identifying qualia, such as a pain, a sense of coolness, or a color, with physiological activities in the appropriate sensory system is that a given quale might be multiply realizable. I am concerned only with realizabilities by the sensory systems of animals, but the question remains whether a given qualia is realizable in very different sensory systems. I incline to think not, because each of our own different sensory systems gives rise to different qualia. Consistent with that common observation, we expect that sensory systems quite different from any we possess, such as the sonar system of a bat, will not give rise to qualia very like any rising from our systems. So my "consist of" for qualia comes to identity.
The referrals of qualia, however, are multiply realizable. The referrals of different quale can coincide, and they will coincide insofar as they are veridical in their referrals. We then have multiple realizations of the same referral.
The relation of sensory qualities to their sensory systems seems then to be a hybrid: identity with respect qualia (and their intensities), being-realized with respect to the referral of those qualia. In consideration of the natural composite of qualia with their referrals, I should say that the relation of sensory quality to sensory system is a species of being-realized.
The relation of sensory quality to world is one of indication.
* This study was composed in 2000.
** Cf. Aristotle, De An. 427b9−14; D. Kelley 1986, 88, 93, 132-33, 233-35; L. Peikoff 1991, 39-42.
 In the present study, I am omitting the temporal aspects of sensory qualities and, for the most part, the attention profiles of the conscious perceptions in which sensory qualities occur.
 The notion of assessibility for accuracy as applied to sensory qualities is from Siewert 1998, 189–94, 218–22.
 Measurements perfect this process (Plato 1997, Rep. 602c–d; Galileo 1957, 225–26; Leibniz 1989b, 187–88). A superb example is Descartes' explanation of all the particulars, illusory and plain true, of the rainbow (Boyer 1959).
 Radical skeptic Pierre Bayle, of course, pried the gap 360 degrees wide, for he brushed all sensory qualities whatsoever away from "the objects of our senses. They [sensory qualities] are modifications of my soul. I know that bodies are not at all as they appear to me. . . . Still further, sensed objects cannot be the cause of my sensations. I could therefore feel heat and cold, see colors and shapes, extension and motion, even though there were no bodies in the universe. I have therefore no good proof of the existence of bodies" (1966, 342–43).
 Examples are referrals of heart pain to left chest, shoulder, and upper arm; referrals of pain from blood vessels (innervated by trigeminal sensory nerves) in the vicinity of an intracranial lesion to some other region in the head; and referrals of skeletal muscle pains to nearby muscle-related structures (Conn 1995, 159, 246, 442).
 In Newton's picture, mind is located in space also, but mind does not exclude body from those same locations. This idea is alive and productive today (French 1987, 138–39, 146–50, 162–69).
 Aspects of this theory were anticipated by Ellis and Newton 1998 (431–41).
 Core consciousness occurs in a fraction of a second. Working memory, which is crucial to extended consciousness, spans seconds and minutes (Damasio 1999, 197). For a current alternative to Damasio's view on the roles of working and shorter-term buffer memories in the making of elementary consciousness, see John Taylor 1999 (180–82, 220, 260–71, 276–79).
 Damasio conjectures that activities of superior colliculi (which are critical for orienting toward sources of visual or auditory stimuli) may be the neural bases for the simplest form of core consciousness in species with little cortical elaboration. He stresses, however, that functioning of superior colliculi cannot support core consciousness in humans in the absence of functioning thalamic and cingulate structures (Damasio 1999, 265).
 Levine, as is well known, also acknowledges (and stresses) the gap in our explanations of how conscious patterns, such as the sensory qualities in conscious experience, arise from neural activity patterns or neural maps. And Levine, too, does not think dualism can be correct. But Levine maintains, furthermore, that in a fully adequate and fully physical theory of sensory qualities, we should be able to derive an animal's "qualitative state from its physiological state" (Levine 2000, 3.4). Derive for Levine, in this context, seems to include knowing what it is like to have any animal's qualia. He takes the unlikelihood of such eventual knowing by us to mean that our present forms of physical explanation of conscious sensory experience are profoundly inadequate. // Damasio, too, thinks we shall not know what it is like to experience the qualia of a foreign sensory system, even when our neurophysiological theory of consciousness becomes essentially complete. That circumstance will not show that consciousness has not been fully explained physically; the myriad convoluted arguments of philosophers attempting such a showing simply must have gone awry (Damasio 1999, 305–9; see also Churchland 1996).
 The neural decoding of color evidently reaches completion in inferotemporal cortex (Komatsu 1998).
 Evidently, "proprioceptive inputs from all the muscles holding and moving the retina in space, [muscles] from the foot up to the eyes, are used by the brain to process the visual information required to perform spatial localization and reaching tasks" (Roll, Gilhodes, Roll, and Harlay 1996, 291).
 Referrals of head pains due to damage of head tissue, though precise enough for practical purposes, can be suffuse, and we should not always know, without neurology, whether such referrals were to neural tissue itself or to other tissue of the head. Additionally, a headache could be coincident accidentally to neural areas supporting it in consciousness. Are these cases exceptions to my statement in the main text? I shall count them as exceptions, but the only ones. For all other cases, I stand by my statement that the qualia of our percepts are not referred to sensory cortical areas that support them.
 "Whatever is in something is in it according to the mode of that in which it is" (Aquinas 1975, 1.49.3).
 The world, including one's body, is full of natural indicators. Natural indicators are simply the natural traces of things. Natural indicators exist, as they are, independently of whether anyone is cognizant of the indication. The track of a bear is an indication of bear whether or not any animal comes along and becomes cognizant of the indication. Natural indicators cannot indicate incorrectly. They simply indicate the various things they do indicate. // Biological systems having an indicating function exploit natural indicators naturally, in consequence of evolution. In the biological indicating system, the indicator has come to have the function of indicating some of the things it naturally does indicate. Where there is indicating function, there is the possibility of malfunction and misindication. // I acquired this valuable scheme from Fred Dretske, though I here have not reflected his talk of representations in connection with indication functions. Talk of indication functions seems sufficient for elementary perception.
 Forms of realization more commonly contemplated for mind, in contemporary philosophy of mind, are realizations of computer programs by computer hardware and realizations of connectionist computations by neural networks of the brain. The former sort, symbolic-manipulation realization, is surely pertinent to and illuminating of certain reckonings of extended consciousness. However, that sort of realization does not seem pertinent to the manner in which receptor and brain activities realize core consciousness. The connectionist-computation sort of realization seems pertinent to core consciousness (see, e.g., Wray and Edelman 1996), but I must defer assimilation of this into my realization picture of sensory qualities. A third sort of realization, very general, contemplated in philosophy of mind, is realization of function, as when a variety of instruments perform the same function or as when a variety of machines (doing work or computing) perform the same function. The realizations I invoke in the present study are assuredly species of this broad category.
 Cf. Shoemaker 1982, 651–56, and 1993. Also, what qualia would one experience were one given an artificial, nonbiological retina or cochlea? I shall have to look into the details of this technological prospect.
 When Dretske (1995, 82–95), Kathleen Akins (1993, 349–52), and Taylor (1999, 330) contend that we have some sense of the qualia of the electric-field sensing of a dogfish or the sonar sensing of a bat (Simmons and Young 1999, 142–63), I find that they really speak not of qualia but their referrals. Naturally, we have some sense of referrals in all possible sensory modalities. And we can be quite sure that foreign sensory systems of other animals do have some distinctive qualia or other (Loar 1997, 611).
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Edited by Stephen Boydstun, 22 January 2009 - 08:52 AM.