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 be