Talk about Talk about Surfaces
by Avrum STROLL and Robert FOELBER
Summary This paper contains a detailed investigation of the way ordinary persons talk
about surfaces. Among the results achieved are: 1) No theory of perception can be correct which holds that it is a necessary condition for seeing an object that we must also see its surface; 2) Not all cases of visual perception can be analyzed in terms of seeing part (or even all) of some surface as a necessary condition for seeing the object which has that surface; 3) Not every physical object has a surface, and 4) sur- faces are sometimes identified with a particular medium, such as macadam, and some- times are considered as a kind of logical entity - not visible, without depth, having no mass, a mere outer aspect.
RCsumC Cet article contient une investigation dCtaillCe de la manikre dont on parle habi-
tuellement de u surface a. Parmi les rksultats obtenus, on note: 1) Aucune thCorie de la perception ne peut valablement affirmer quune condition nicessaire pour voir un objet, est quon voie aussi sa surface; 2) On ne peut pas anlayser tous les cas de per- ception visuelle en prktendant que voir une partie ou la totalit6 de sa surface est une condition nCcessaire pour quun objet soit vu; 3) I1 nest pas vrai que tout Iobjet phy- sique ait une surface et 4) Les surfaces sont quelquefois identifiCes avec une substance particulitre, comme le macadam, alors que dautres fois elles sont considkrCes comme une sorte dentitk logique, non visible, sans profondeur, privie de masse, un simple .x aspect extkrieur B.
Zusammenfassung Diese Arbeit enthalt detaillierte Untersuchungen iiber die Art und Weise, wie
in der Alltagssprache iiber Oberflachen gesprochen wird. Die wichtigsten Ergebnisse lauten: 1) Keine Wahrnehmungstheorie, die behauptet, dass das Sehen der Oberflache eines Gegenstandes eine notwendige Bedingung fur das Sehen des Gegenstandes selbst sei, kann richtig sein; 2) Nicht alle Falle von Gesichtswahrnehmungen konnen dadurch analysiert werden, dass man von der Wahrnehmung eines Teiles oder der ganzen Oberflache des Objektes spricht, das wahrgenommen wird; 3) Nicht jedes physikalische Objekt hat eine Oberflache; 4) Oberflachen werden gelegentlich mit einem besonderen Medium identifiziert, wie z. B. einem Teerbelag; manchmal werden sie aber als eine Art von logischer Entitat betrachtet, die unsichtbar ist, keine Tiefe oder Masse hat und bloss einen eausseren Aspekta darstellt.
How do we talk about surfaces? The question arises if we wish to become clear about the nature of surfaces - what they are, what sorts of objects have them. The answers we give will depend upon the sorts of objects about which we are speaking. It will also depend on what we have
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done, can do, or wish to do, to such objects; and thus how we talk about surfaces will also depend upon the specific features which differentiate particular objects of the same sort from one another. In what follows we shall describe a gamut of increasingly complex cases in order to indicate how variegated our talk about surfaces is. We shall then point out some of the implications which these findings have for philosophy
Talk about marbles
We start with marbles (i. e., the sorts of small, round balls used in the childrens game) because they represent the simplest kind of case. To begin with, it should be noted that a marble is par excellence the sort of object that has a surface. It is also a paradigm of the sort of thing philosophers have called a physical object. Despite what many philosophers have asserted or at least implied, not everything which is a physical object, in the sense in which they use that term, has a surface; but we shall defer consider- ation of these sorts of cases until later. We shall also wholly ignore in the paper the difficult question of what ijs, or might be, meant by physical object. We merely wish to state here that marbles are good examples of things which are normally said to have surfaces. The surfaces of marbles can be described as rough, smooth, slippery, chipped, sticky, blemished, pitted or damaged; we can speak about sanding, polishing, painting, or waxing the surface of a marble; and of light being reflected from its surface. There is also a gamut of prepositional phrases which can be used in such talk. We can speak about imperfections in, below, at, near, on, or towards the surface. Sometimes such prepositional phrases have a spatial sense and
1 The subject of surfaces has not been dealt with directly in the philosophical literature. Interest has been limited primarily to the role surfaces play in a theory of perception. (See, e. g., G. E. Moore, A Defence of Common Sense, in Con- temporary British Philosophy [ed. by J. H. Muirhead; London, 19251, and his Visual Sense-Data, in British Philosophy in the Mid-Century [ed. by C.A. Mace; London, 19571; C. D. Broad, Mind and Its Place in Nature London, 19231, pp. 148-151; H. H. Price, Perception [London, 19321, pp. 106-111, 142-144; J. L. Austin, Sense and Sensibi- lia [Oxford, 19621, p. 100; Thompson Clarke, Seeing Surfaces and Physical Objects, in Philosophy in America [ed. by Max Black; Ithaca, 19651.) The psychological litera- ture is more extensive, in particular the work of J. J. Gibson (The Senses Considered as Perceptual Systems [Boston, 19661 and An Ecological Approach to Visual Perception [forthcoming], but its concerns are less directed toward clarifying the nature of the concept of a surface than toward resolving issues in the psychology of perception, as properly they should be. Brian OShaughnessy (in his Material Objects and Per- ceptual Standpoint, Aristotelian Society Proceedings, 65, [1964-651, pp. 77-98) does say a few things about surfaces but his main interest is in how to characterize the nature of a material object. We hope in this paper to make a start toward exploring the logic of surface and to illustrate the fertility and importance of this concept for epistemo- logy and for a theory of persons.
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sometimes not; to say that there are flaws in the surface may, on some occasions, be to say that the surface itself is imperfect, on other occasions to say that there is, say, a speck in an otherwise homogenous surface.
Before going on to show how our talk about surfaces will vary depending upon the different sorts of objects we are speaking about, let us now indicate how complex such talk may be even with respect to particular objects of the same sort. Suppose, for example, we bave a group of marbles manufac- tured in an identical way, so that to the naked eye they are indistinguishable from one another. They are the same size, the same color (say blue), made of glass, solid (i. e., not hollow, or built up in layers, or containing steel inserts or cores), and they come to us pristine from the manufacturer; that is, they are not painted, polished, waxed or in any other way altered by human artifice.
Then of those marbles we can say that their surfaces are smooth or rough, shiny or dull, blemished or unblemished. But we cannot say that they are thick or thin, transparent or opaque, heavy or light, hard or soft (or mushy, pulpy, spongy). If, however, we were to paint a marble from this set, then depending on the nature of the covering material we used, whether it was a heavy enamel or light stain, viscid or smooth, clear or opaque, we might be able to say some of these things.
The operations we perform upon these objects will thus have important implications for how we talk about them. Once a marble has been painted, we can speak about its new surface, and about the properties that surface has; and speak also about exposing or looating the original surface, for example, by chipping away or sanding away the paint. Certain kinds of contrasts now become applicable that were not applicable to the original marble. Of a solid glass marble, of the sort described above, we cannot speak of exposing its original surface by sanding or chipping the surface it has. Even though those marbles, as they come to us from the manufacturer are blue, there may be some hesitation in speaking of their surfaces as blue.
Furthermore, of such marbles we cannot say that any of them has an inner or an outer or an upper or a lower surface; and because that is so, certain other important kinds of contrasts will not be possible.
We cannot, for example, speak of painting or sanding or polishing the inner surface of such a marble. In this respect, solid glass marbles will differ from hollow marbles; these latter can be cut open and their inner surfaces painted a different color from their outer surfaces. With hollow marbles the inner-outer contrast becomes applicable in a way it does not with solid marbles. Even, if we cut a solid glass marble in half with a fine diamond saw,
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we would not normally speak of the newly-exposed surfaces of the marble as its inner surfaces. With an imperfection (a bubble) that exists in a trans- parent hollow glass marble, we can say that the bubble lies on its inner surface or that it lies just below the outer surface. But we cannot say of a solid glass marble that a bubble-like imperfection lies on its inner surface or just below its outer surface. The inner-outer contrast makes no sense in this case. We could, of course, say that the imperfection lies below its surface or perhaps even just below its surface, depending on how deep within the marble it lies.
Suppose our solid glass marbles were transparent, like a thick optical glass, rather than opaque, and not colored rather than blue. Being solid they cannot be described as having transparent surfaces, just as being blue they could not be described as having blue surfaces. Even if they are hollow and transparent, one could not say, in general, that their surfaces are trans- parent. But if they are hollow, and if their inner surfaces were painted while their outer surfaces were not, then one might say that their outer surfaces - or in some contexts that their surfaces - were transparent. The inner-outer distinction is not in general applicable with respect to such a feature as transparency; it becomes applicable depending upon how the objects we are speaking about are made.
Assume now that one of our original marbles comes from the manufac- turer with a large chip in it. Where is the chip? One might say it is in the marble, or that the marble has a chip in it. One might say that the surface of the marble has a chip in it. We can also say that the chip itself has a surface; its surface may be rough or smooth, for example. Though the chip has a surface, and though the chip may be in the surface of the marble, with respect to some operations - such as feeling, examining, or touching the chip - it would be peculiar to say that we are carrying out those operations with respect to the surface of the marble. Compare this example with that of a giant quarry gouged out of the surface of the earth. Does the quarry have a surface? If so, in looking at it, are we looking at the surface of the earth? It is questionable that we can say so without a special story. If we are examining a deep well with a flashlight can we say that we see the sur- face of the well when we see its bottom; and can we say that the well is in the surface of the earth?
Talk about the surfaces of solid marbles is complex in other ways. As we have seen, we do not speak of the inner or outer surfaces of such marbles. But in addition we do not speak of other surfaces such marbles have or might have. Rather, one is inclined to say that the surface of a solid marble
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is homogenous, or continuous, or uninterrupted, or perhaps even unbroken - though, no doubt, each of these idioms may have special employments that can be misleading with respect to the point in question. Perhaps this point can best be brought out by saying that such a marble has one and only one surface, and accordingly that talk about the surflace or its sur- face is talk about one and only one surface.
Such talk will therefore be unambiguous in a way in which talk about the surface of a table or a hollow pipe may not be. Suppose we ask some- one to sand and then paint the surface of a solid glass marble. Generally speaking, we would expect him to carry out these operations with respect to all of its surface. But in general, asking someone to perform an operation 0 on the surface of such a marble is not necessarily asking him to do 0 to all of its surface. Thus asking someone to try to scratch the surface of a glass marble with a diamond stylus is not necessarily to ask h i d o scratch all (i. e., every portion) of its surface. What the request that he scratch the surface, and the request that he sand the surface, have in common is that each of these operations will be performed upon one and the same thing; or, to put it somewhat differently, in making either request we are implicitly excluding the possibility that the object has other surfaces upon which these operations can be performed.
But not every request, with respect to some operation, will be unambigu- ous in the sense that there is one and only one surface upon which it can be be carried out. Suppose for instance that we ask someone to paint the surface of a solid, wooden table. Normally, we would not expect him to paint all of the surface of the table; that is, we would not expect him to paint the sides, legs, or underside of the table. What we would expect him to do is to paint the sur-face, or upper face, or top, of the table. Now sup- pose that he is asked to try to scratch the surface of the table; would it be peculiar if he tried to scratch one of its legs, or can he carry out the oper- ation correctly only if he tries to scratch its upper surface? With respect to this example it is less clear what we would say.
The burden of these remarks is to establish that it will depend on the operation to be performed, as well as on the particular constitution or dis- position of the object upon which it is to be performed, as to what one will mean by the phrase the surface in the requests that person makes. In asking someone to paint the surface of a marble, we intend that he shall paint all of its surface; but in asking him to paint the surface of a table we do not normally intend that he paint all of its surface. In particular, we are not asking that he paint the undersurface of the table. Thus, in speaking
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about tables we may presuppose that a table has more than one surface. Yet we also sometimes speak in such a way as to presuppose that a table has only one surface. Which presupposition we make will depend upon the operation we have in mind. With respect to the operation of calculating the surface area of a table, we presuppose that the table...