Is the External World Invisible? Mark Johnston Philosophical Issues, Vol. 7, Perception. (1996), pp. 185-198. Stable URL: http://links.jstor.org/sici?sici=1533-6077%281996%297%3C185%3AITEWI%3E2.0.CO%3B2-5 Philosophical Issues is currently published by Ridgeview Publishing Company.
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PHILOSOPHICAL ISSUES, 7 Perception, 1995
Is the External World Invisible? Mark Johnston
Why is it such a good thing to see, to hear, to smell, taste and touch? What if anything makes perception intrinsically valuable, as opposed t o just a useful means for getting around our environment? An important part of what seems to make perception intrinsically valuable is that as well as providing us with propositional knowledge about just which properties objects have, perception also acquaints us with the nature of the properties had by those objects. It reveals or purports to reveal what those properties are like. As well as providing a map of our environment which helps us steer our way through the world, perception also seems to do something that no ordinary map could do, acquaint us with or reveal the natures of the perceptible properties of the things mapped. Explaining as I go what I mean by acquaintance with or revelation of the nature of a property, I shall suggest that acquaintance with perceptible properties is something we non-derivatively want from perception, and show that perception seems to provide just such acquaintance. Unfortunately, upon examination, perception's promise to acquaint us with properties of external things seems to be utterly fraudulent.
Just to fix ideas, let us take some examples. I am acquainted with a certain property of digitally reproduced sound (the sound of CDs), I know or a m acquainted with this characteristic property of digitally reproduced sound thanks to having listened to enough of the stuff. Knowing or being acquainted with this property, sometimes called "digital brightness", enables me to recognize digital sound and come out with comparative statements about analog and digital sound, e.g. Don't throw away your LPs, analog is much more pleasing than digital. But what I came to know when I came to know or be acquainted with the brightness of digital sound is not exhausted by my recognitional capacity nor by my capacity to come out with various statements about digital sound. I could have both those capacities without knowing the brightness of digital sound. I could instead be recognizing and comparing on the basis of knowing another characteristic property of digital sound, a certain sucked-out quality in the reproduction of the sound of stringed instruments. By listening, I know what these sound qualities are like. There is a certain way, perhaps impossible to fully characterize linguistically, that hearing represents these sound qualities as being. I not only hear that the Deutsche Grammaphon CD of Herbert Von Karajan conducting the St. Matthew's Passion has these sound qualities. I hear what they are like and so a m acquainted with them. Equivalently, the natures of these two sound qualities are revealed to me. Or so it seems. For another example, take what one knows when one knows what it is like to feel pain. One of the things one knows or is acquainted with is a property or feature of a sensation -what some call the painfulness of pain- the feature that makes pain awful. I claim that perception in general and vision in particular purports to acquaint us with some properties of external objects in the way that sensation acquaints us with features of sensations. But perception cannot carry through on this promise. To locate the notion of acquaintance among more familiar epistemic concerns, consider two familiar philosophical cartoons by which the traditional skeptical problem of the external world is typically presented, the case of the eternal movie buff and the case of the brain in the vat. The eternal movie buff has spent all his life in a dark room watching images on a screen. Never having left his video room he has no idea whether the images correspond to anything outside his room. The brain in the vat is fed a full sensorium by fiendishly clever form of neural stimulation. A computer coordinates the pattern of stimulation so that the brain has a complete and consistent sensory illusion, say as of living an ordinary life in Boise, Idaho.
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These bizarre predicaments are typically employed to highlight a skeptical worry about our own predicament. The eternal movie buff cannot be justified in holding any visually generated beliefs about the external world, restricted as he is t o mere images which he cannot check against external reality. He can only check experience against experience. But this, so it is said, is also our predicament. We too can only check our experiences against other experiences. It is no more possible for us to attempt to match our experience against external reality as it is in itself, as it is independently of how it is experienced by us. The case of the brain in the vat is supposed to deflate the natural response that we have an epistemic advantage over the eternal movie buff by having a number of potential windows on the world which we can use to triangulate to an external reality as it is in itself. The triangulations of the envatted brain lead it to false beliefs about a life lived in Boise, Idaho. Now there is no sign in our experience which differentiates our condition from the condition of the brain in the vat. So we possess nothing to rule out the alternative hypothesis that we are brains in a vat. So we are not justified in believing that we are not brains in vats and hence are not justified in believing the things we standardly do believe about the external world. Or so the argument goes. Whatever the force of these cartoons in presenting the traditional problem of the justifiability of our beliefs about the external world, and even if their force is undermined by noting that a spontaneous and utterly natural belief is justified or a t least does not need justification in the absence of a good case against it, the cartoons also serve to illustrate a deeper epistemic anxiety about our own condition, one overlooked by fixating on the problem of justification. This other problem of the external world is the problem of acquaintance, the problem of how, given the nature of information transmission, we could be acquainted with the nature of any of the properties of external things represented by our experience. The nature of any signal received is partly a product of the thing sending the signal and partly a product of the signal receiver. It seems that we cannot separate out the contribution to our experience of our own sensibility from the contribution to our experience of the objects sensed. The case of the brain in the vat shows that our experience does not discriminate between many different kinds of external features so long as their effects on our sensibility are isomorphic in certain ways. Therefore, despite the seductive offer that perception makes, we cannot take our perceptual experiences t o reveal the natures of external things. For no perceptual experience could at the same time reveal two things so intrinsically unalike as
life in Boise and the inner workings of the vat computer. Conclusion: perceptual experience does not reveal the nature of its causes. In other words, it does not acquaint us with the external features causally responsible for our experience but only with their effects in us. We can of course refer to the external features as the features that are standardly causally responsible for our experiences, thereby making them objects of thought and reference -but a t best we know these features by description- we know them as the features that are standardly causally responsible for our experiences, whatever those features might be like in themselves. We could put the conclusion this way: relative to the problem of acquaintance, even if we are not brains in vats, things are as bad as they would be if we were brains in vats.l Both the cartoon of the eternal movie buff and the cartoon of the brain in a vat highlight the problem of acquaintance by inviting us to think of perceptual experience as simply an effect of external causes whose natures are in no way revealed by the experiences they cause. Perceptual experience in no way acquaints the brain or the buff with the nature of the external causes of that experience. In this respect, perceptual experience is unsatisfyingly like morse code reception; both involve interpretable effects at the end of an information-bearing process or signal. But the intrinsic natures of the originators of the signal are not manifest in the signal. This is a depressing comparison. Perception represents itself as (or is at least spontaneously taken by its possessors as) a mode of access to the perceptible natures of things; a mode of acquaintance with their perceptible properties. When I see the sun setting against the magenta expanse of the sky, I seem to have something about the nature of the sky and the sun revealed to me. I seem not to be merely under their causal influence in a way that leaves completely open what their natures might be like. Just as I take myself as knowing the painfulness of pain as it is in itself, and digital brightness as it is in itself, perception encourages the thought that I know sky blue as it is in itself. Russell expresses just this thought in The 'In Reason, Truth and I f i s t o q (Cambridge, 1983), Ch. 2, Hilary Putnarn claims t h a t if we were brains in vats then we couldn't mean t h e standard thing by "WE A R E BRAINS I N VATS" so t h a t we could not formulate t o ourselves t h e traditional problem of t h e external world. Notice t h a t even if this were so, it would not in any way deal with t h e deeper epistemic anxiety associated with t h e problem of acquaintance. Indeed, Putnam's modelktheoretic picture of t h e determination of meaning just capitulates on t h e problem of acquaintance. I see little interest in a proposed solution t o t h e traditional problem if t h e proposal implies t h a t t h e problem of acquaintance cannot be solved.
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Problems of Philosophy: "the particular shade of colour that I am seeing.. . may have many things to be said about it.. . But such statements, though they make me know truths about the colour, do not make me know the colour itself better than I did before: so far as concerns knowledge of the colour itself, as opposed to knowledge of truths about it, I know the colour perfectly and completely when I see it and no further knowledge of it itself is even theoretically possible" .2 The acquaintance with external features which vision seems to provide is something we have reason to value. I think that it is because vision seems to acquaint us with visible properties of external things and thereby acquaint us with the natures of visible things that we take a certain kind of epistemic pleasure in seeing. My pleasure in seeing color is not simply the pleasure of undergoing certain sensory experiences, it is also the pleasure of having access by sight to the natures of the colors and hence access to part of the nature of colored things. The deeper problem of the external world, as it applies to visibilia, is that this characteristic pleasure of seeing seems inevitably to be a pleasure founded in a false belief, a pleasure which philosophical reflection would have me see through. Once my eyes were covered with bandages for five days. Part of what I longed for in longing to see again was not simply more information by which to negotiate my environment, nor simply more visual sensations. I longed for the cognitive contact with external features which vision seems to provide. It is depressing to conclude that what I longed for -acquaintance with visible properties- can never be had, even with the bandages off. I suspect that such longing for cognitive contact is an important aspect of the longing to know. Consider the metaphors of knowledge: apart from the metaphors of light and sight, they are metaphors of touch and digestion; we grasp things, digest facts, absorb points, assimilate information. (Digestion is of course just touch gone to extremes.) The phenomenology of touch is the phenomenology of getting at the shape and texture of the thing touched and not at all the phenomenology as of having a tactile experience produced at the end of a (very short) causal chain which began with the thing touched. Touch represents itself as providing acquaintance with tactile qualities. For whatever psychological reasons, we place an important value on acquaintance, i.e. not just on knowing that external things have certain properties but also on knowing those properties. Indeed it 'See The Problems of Philosophy (London, 1912), p. 47.
is hard to make sense of having genuine acquaintance with things without being acquainted to some extent with their natures and so with some of their properties. An important part of what seems so bad about the predicament of the brain in the vat, and an important part of what seems eerie about the condition of the inhabitants of IVozick's experience machine, is that there is no acquaintance with sensible properties of external objects. Though the subject's experiences are internally coherent they are not revelations of the nature of the computer processes responsible for those experiences. That is why I believe that if we cannot solve the problem of acquaintance, then the thing to say is that even if we are not brains in vats, we are nonetheless as badly off as brains in vats are. If that is right, knowledge or justified propositional belief about the external world may remain valuable instrumentally, as input for strategies for getting by, but the core of what made knowledge seem valuable in itself has been rotted out. Knowledge of the external world is left schematic and bloodless, if it includes no acquaintance with properties and hence no acquaintance with the natures of things and hence no real acquaintance with things. Well, just why is it that a veridical perception cannot fully reveal the nature of perceptible features of external things? To run through the specific version of the argument in the case of vision, begin with the obvious causal condition on seeing a feature or property of a thing. If a property of a thing is literally seen then the thing's having that property must be part of the causal explanation of the visual experience which counts as seeing that the thing has that property. If I see the greyness of my dog's coat, as opposed to having a (perhaps accidentally veridical) hallucination of the greyness of the coat, then it will be the case that the visual experience which represents my dog's coat as grey is partly caused by my dog's coat being grey. But if my visual experience is to be a revelation of the nature of the greyness of my dog's coat, then that visual experience must correctly represent how that greyness is. Now the way my visual experience represents greyness as being is fixed by the internal states that I a m in at the time of the experience.3 By the causal condition on seeing, those internal states are to be 3 ~ h best e motivation for this local supervenience claim is given by Ned Block's Inverted Earth example. The example simply mobilizes intuitions. The argument for local supervenience of the higher-order "depictions" of the natures of the colors is t h a t the alternative, namely that the content of these depictive representations of the colors of external objects are fixed by the natures of those colors themselves, makes color misperception much harder than it is.
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causally explained by my dog's being grey. This means that there is a causal process connecting the state of my dog's coat and my internal states. Barring a pre-established harmony no such causal process will preserve and transmit information so as to secure a naturerevealing match between how some feature of the cause, say the greyness of my dog's coat, is and the way I am caused to represent that feature as being. To see involves having the natures of visible properties revealed by a causal process, but this is just what no causal process actually does. The originally unbelievable conclusion now follows: we cannot see color, because our visual experiences as of the colors of things do not reveal to us what the colors of the external causes of our experience are like. But if we do not see color, we do not see color difference, and if we do not see color difference, we see neither edges nor colored areas, and if we see neither edges nor colored areas, we do not see surfaces, and if we do not see surfaces, we do not see anything in the material world.4 Our visual experience is then just a "false imaginary glare", simply an arbitrary medium in which the material world is mapped for the purposes of intentional action. The characteristic pleasure of seeing, the pleasure of having the nature of visible properties and visible things revealed to us, is a false pleasure. The promise of vision now appears totally fraudulent. What is driving the general argument about perception and the specific argument about color seems to be a certain standard of acquaintance with or revelation of the natures of perceptible properties, in effect the standard Russell arrived at by taking visual perception on its own terms. The obvious response is to suggest that the standard of acquaintance naively derived from the case of seeing color, the standard that Russell described, is impossibly high. It is the standard of complete knowledge of a property as it is in itself, a standard not satisfiable even in the case of the colors. Perhaps we can be acquainted with properties by a less demanding but nonetheless significant standard? 41n arguing this I a m not assuming t h a t we see edges or areas or surfaces by seeing color difference. I assume only t h a t certain necessary conditions on seeing these things hold. If we could see color and hence color difference and hence shape, then it might be right t o count as seeing making out shapes with nightvision goggles which misrepresent all t h e colors in t h e scene before t h e eyes. B u t if we never see colors, then this does not count as seeing either. All t h a t is going on is t h e systematic representation in a n arbitrary medium of information in t h e scene before t h e eyes. This is as good as what we call seeing, but neither is seeing in t h e sense of visual acquaintance with t h e scene before t h e eyes.
The notion of acquaintance with a property or better with a family of properties -the shapes, the colors, the textures, etc.- is obscure because acquaintance with properties is not equivalent to knowledge of a statable set of linguistic descriptions of those properties. However, although acquaintance is not exhausted by such linguistic descriptions it does not directly issue in such propositional knowledge. Let us say thak Fl through Fn constitutes a family of properties when there are essential similarities and differences among Fl through F,, similarities and differences that hold in any possible situation. Then if you know or are acquainted with the nature of properties Fl . . . Fn by means of the operation of some faculty K, then (i) you can recognize other instances of Fl . . . Fn just by relying on K, and (ii) you can know a family of similarity and difference relations ("unity principles") holding among Fl through Fn and know these just by relying upon the operation of K . So it seems that I am acquainted with the ordinary Euclidean shape properties on the basis of perception. Having seen pyramids, cubes, spheres, cones, etc. (i) I can recognize other instances of the same shapes, and (ii) I know a family of shape similarities and differences -cubes are not conical- cones, pyramids, and cubes are alike and together unlike spheres in having apexes. Crucial to this operational characterization of acquaintance with properties is that such acquaintance issues in knowledge of comparative similarities among families of properties, e.g. that the property Fl is more similar to the property F2 than either is to the property F3. Again, the similarities knowledge of which is generated by acquaintance are "essential" similarities. They are the similarities which follow from the natures of the properties in the family and so hold among the properties in every possible situation, i.e. no matter how the contingent relations among properties are varied and no matter how the facts about which things have properties are ~ a r i e d . ~ Obviously, on this criterion, acquaintance turns out to be a matter of degree, depending on the range and detail of the knowledge of property similarities it grounds. It may now seem to follow that we are indeed acquainted with the colors, as well as the shapes and the textures. Take the colors. It is often said that just on the basis of visual experience (and maybe a bit of visual memory) we know a host of propositions about the similarity and difference relations among the colors. For example, we know 5 ~ similarities o and differences in how properties look or perceptually seem to a class of perceivers under this or that condition will not count as essential similarities.
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that canary yellow is not a shade of blue. And that is to know that the blue shades are more similar (in hue) among themselves than any are to canary yellow. Indeed, for each of the phenomenally evident relations among the shades and the hues which we express by means of the predicate "x is not a shade of y" we know a proposition about comparative essential similarity, a proposition of the form "The y's are more similar in hue among themselves than any is to x". Since the phenomenally evident relations among shades are available in visual perception, visual perception acquaints us with the colors. Or does it? The reason for hesitating is that it is difficult to find a conception of the colors as features of external objects on which the similarities we know to hold just by seeing are indeed similarities among properties of external objects, rather than just similarities in respect of how those properties st,rike us as being. Once we take colors to be categorical properties of external things all we may really be able to know about canary yellow and the shades of blue may be that the blues happen to look more similar among themselves than any of them look to canary yellow. This is not an essential similarity among shades but only a similarity among how the shades happen to appear to us. If that is all we can know by perceiving the colors, then even by more reasonable standards of acquaintance we turn out not to be acquainted with colors. To see how the conception of colors as categorical features is at odds with acquaintance, consider the Primary Quality Account of the colors, the view that the colors are the non4ispositional properties of external objects standardly responsible for the appearances as of the respective colors of external object^.^ So the shade canary yellow is the non-dispositional property which standardly explains the appearances as of canary yellow things. Mutatis mutandis for the various shades of blue. Suppose that color science ends up discovering this: the property which standardly explains the canary yellow appearances and the various properties which standardly explain the various appearances as of the shades of blue are not, when taken together, as similar among themselves as the properties which standardly explain the various appearances of the shades of blue are similar among themselves. (Remember, it is "essential similarity" which is at issue.) On the Primary Quality Account so far adumbrated this would be the discovery that canary yellow is not a shade of blue, i.e., not to be counted a blue. 'This is the view of the colors we find in Saul Kripke's Naming and Necessity (Harvard, 1980), fn. 66.
But is it really a matter of scientific discovery that canary yellow is not a shade of blue? No. Such similarity and difference principles surely have a different status. We take ourselves to know those principles just on the basis of relevant visual experience and ordinary grasp of color language. No one had to wait until the end of the second millennium A.D. to find out whether or not canary yellow is a shade of blue. Any account which implies this along with corresponding things about the other similarity and difference principles concerning the colors thereby implies that perception does not acquaint us with the colors even by our less demanding criterion of acquaintance. That, of course, is just a first move against the Primary Quality Account. The friend of that account should be allowed to answer that indeed it is not a matter of scientific discovery that canary yellow is not a shade of blue. Rather, he might say, such a principle along with other unity principles must be held true as a condition on any family of properties deserving the color names. So the principle that canary yellow is not a shade of blue turns out to be relatively a priori after all. More exactly, what is a priori is a conditional: if any property is to deserve the name of canary yellowness, then it cannot be a property which is as similar to the blues as they are among themselves. On the revised account, some property turns out to count as canary yellow only if a complex condition on that property along with a host of other properties is discovered to hold. The candidate properties to be the blues have to show a natural or genuine similarity among themselves, a similarity which they do not share with the candidate to be canary yellow. Suppose color science discovers this condition holds along with the other unity conditions which the Primary Quality theorist regards as central. Then some (complex, disjunctive) physical properties turn out to be canary yellowness, teal, turquoise, sky blue, and so on. But then what gives one the right to say that there is a property canary yellow and it is not a shade of blue is not simply visual perception but also and crucially recherche facts from color science. That is to say that on the Primary Quality Account perception still does not acquaint one with canary yellow, nor with the other shades, even by our less demanding criterion of acquaintance. Color here is just an example; the same result will follow for any quality conceived of as a primary, i.e. as the microphysical causal basis of a class of perceptual experiences. Physics may tell us that the microphysical causal basis of appearances of Euclidean shape do not themselves have a Euclidean shape and may be features whose adequate description
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involves characterizing things extended in nine or ten dimensions. There is no guarantee derivable from vision that there will be essential similarities and differences among nine dimensional properties which mimic the essential similarities and differences that Euclidean shapes present to vision. Weakening the criterion of acquaintance far enough so that it could turn out that vision acquaints us with the colors as the Primary Quality Account represents them would necessarily involve allowing that one could be acquainted with a property even if the property does not exist, so long as one knows that if the property exists and certain other properties exist, then they are similar and different in certain ways. But to suppose that I am acquainted with a property even when it might turn out that there is no such property breaks the intuitive link between acquaintance and the cognitive contact which makes knowledge non-instrumentally worthwhile. I a m not here following Russell, as he is usually interpreted, in suggesting that there is something about the subjective side of acquaintance which guarantees that acquaintance has an object; I a m only saying that something7 that could occur whether or not there was a property F does not deserve the name of acquaintance with the property F. What then of the account that has it that the colors are dispositions to appear colored, the so-called Secondary Quality Account? Again, colors are here standing in for any secondary quality, so the considerations that follow are in fact perfectly general. The colors conceived of as dispositions are genuine, albeit relational, features of external objects. Their manifestations are the various experiences in various subjects as of the various colors. These sensory manifestations are not simply the effects of the dispositions they manifest. They are or can be manifestations in a more interesting sense -they can be revelations of the nature of the dispositions in question. For about any disposition of objects to produce a given experience, it is plausible to hold that if one has an experience of the kind in question and takes that experience to be a manifestation of the experience i n question, one thereby knows the nature of the disposition in question. Of course one does not thereby know the facts concerning how in general the disposition is specifically secured or realized. But these are 'AS emerges in my response to Alan Gibbard, it would be better t o say "knowledge" rather than "something" here. T h e vaguer term allows a reading t o t h e effect that a n ezpen'ence which could occur whether or not there was a p r o p erty F could not constitute acquaintance with F. Of course, that is the very Russellian claim about acquaintance which I a m concerned to rule out.
facts concerning the disposition's contingent relations to other properties. They do not concern the nature of the dispositional property. So I take myself as having come to understand the complete nature of the property of being nauseating on the high seas one afternoon thirty years ago when I tasted a juicy apricot on a ferry crossing from Melbourne to Hobart. I had the experience of nausea and thought of it as a manifestation of a power of juicy apricots to produce nausea on the high seas. But I did not then know anything about the physical basis of juicy apricots being nauseating. Similarly, if I conceive of the blue of the sky as a disposition to produce a certain visual response in subjects like me, and I now discover myself t o be responding just so, I can be in possession of all there is to know about the essential nature of the dispositional property that is sky blue. I do not thereby know the contingent details of how sky blue might be physically realized here before my eyes or anywhere else. But that is ignorance of the contingent relations between the disposition and the other properties which happen to realize the disposition. I do seem to know everything essential about the disposition that is sky blue. Mutatis mutandis for the other colors. On the basis of visual experience as of canary yellow, teal, turquoise, etc., and conceiving of such experience as the manifestation of the dispositions that are canary yellow, teal, turquoise, etc., I can satisfy the condition for acquaintance with the colors. Just on the basis of visual experience, I can know that the manifestations of the dispositions that are teal, turquoise, sky blue, etc., are more similar than any are to the manifestation of the disposition that is canary yellow. But this means that I can know that the first family of dispositions are more similar in nature, more similar essentially than any are to the disposition canary yellow. Hence I am on the way to satisfying the condition for being visually acquainted with the colors conceived of as dispositions. Suppose for a moment that this works.8 Vision is then a faculty by which we could become acquainted with the properties which are the visual response-dispositions. It is not a faculty by which we could become acquainted with the bases of visual response-dispositions, i.e. it is not a mode of acquaintance with the properties which the Primary Quality Theorist identifies as the colors. Since it is a commonplace in the philosophy of color that we are inevitably in the business of revising our naive color concepts, we should make the revision which allows us to secure a n important cognitive value -the
or
more on this aspect of the dispositional account, see my "How To Speak of The Colors", Philosophical Studies 68, 1992, pp. 221-263.
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value of acquaintance with those salient, striking and ubiquitous features that are the colors. We should think of colors as dispositions if we are to get what we really want from seeing color. That is the hope: acquaintance with the colors is at last secured by conceiving of the colors as dispositions to produce visual responses. (We can engage in a kind of second-order seeing. We can take our visual representations as manifestations of the dispositions of external things to produce those visual representations.) I believe that the hope is severely threatened by the consequences of the following observation: response-dispositions come in pairs. That is, whenever there is disposition of some external object or objects to produce a sensory, emotional or cognitive response in a class of subjects under certain conditions, there is also the correlative or dual disposition of the subjects in question to issue the response in question upon being presented with the objects under the conditions in question. So as well as the apple's disposition to look red to me, there is my disposition to have a n experience as of the apple looking red when the apple is presented. T h e same perceptual experience is as much a manifestation of my disposition to see the apple as red as it is a manifestation of the apple's disposition to look red to me. So the same response is potentially as much a revelation of a dispositional property of mine as it is a revelation of a dispositional property of the apple. These dispositional properties may not be really distinct but may represent just two ways of characterizing, as it were from different ends, one relational complex comprising features of the apple and features of my sensibility. This odd thing, the relational complex, may be more evenhandedly described as a disposition of a certain subject, me, and of a certain object, the apple, taken together, namely a disposition to interact to produce certain experiences. This, if you like, scattered capacity partly in the object of perception and partly in the perceiving subject, though odd enough not to have any familiar name, is the characteristic kind of property with which vision in particular and perception in general can acquaint us. But perception will only acquaint us with such scattered capacities if we conceive of our perceptual experience as manifestations of such scattered capacities. That requires that we take our perceptual experiences as revealing features which are as m u c h features of ourselves as they are features of external objects. That is none too easy a thing to do. And it is entirely against the phenomenological grain of perception, against what we might call the outerdirectedness of perception as opposed to bodily sensation. To give up on this phenomenological outerdirectedness is t o leave the topic of vision entirely.
So it is still far from clear how acquaintance is possible even with dispositional features of external things and even by reasonable standards of acquaintance. If that remains unclear, the conclusion that threatens is that perceptual knowledge is not what it is cracked up to be. Without being founded in acquaintance with properties, our knowledge of the external world, though vast and probably entirely unthreatened by standard skeptical worries, is nonetheless bloodless and schematic, devoid of the very substance which seemed to make it intrinsically appealing -acquaintance with properties.
