Katz recognized the importance of Husserl’s philosophical phenomenology and the application of its method to his research (Spiegelberg, 1972: 43). It is true that he acknowledges that Hering had already argued the need for a phenomenological analysis of color and attributes to Husserl an important role in clarifying the implications of the phenomenological method, rather than in providing particular analyses of color perception (Katz  1999: 18). However, Katz recalled that Husserl’s phenomenology seemed to him to be the “most important connection between philosophy and psychology” (1952: 194). Indeed, the phenomenological method played such an important role in his experimental work that Katz’s research exemplifies how the conceptual and methodological tenets of phenomenology provide a substantial contribution that is internal to the experimental work.
Katz ( 1999: 1, 2) claims that psychological research fields are drawn from the various perceptual aspects of the world that are captured by “a simple description” of the everyday activity of perception. Subjects perceive objects of all sorts, located far or near, with shapes, colors and the structural properties of their material that are visible on the surfaces; but they also perceive the empty space that fills the distance between subjects and objects, assuming no object or property is found in it, the illumination, the movement. Far from being complete, this description represents distinct aspects of the world as it appears in ordinary experience, where the subjects have appearances with an immediate character regardless of whether or not they have names for them. From these appearances the fields of psychological investigation are built: the perception of shape, space, color, structure and movement.
As in Husserl’s “natural world,” the experiences of “colour in their natural unbroken meaningfulness arise out of the need for a practical orientation toward the colour-qualities of the surrounding world” ( 1999: 3). The judgements on colors and their properties are ruled by a “natural” attitude toward the biological value that colors have and their meaning in everyday life. The description of color ordinary experience is the starting point of the psychological research, once the practical orientation is set aside. This description shows that colors are encountered in distinct places. They are perceived in things but also in the grey sky, the green shimmering water, the air full of light beams. This observation is not trivial. In Katz’s view colors are seen as “objective properties” of things and the environment; hence, the psychology of color perception has to treat them as “tangible realities of the world.” This means that psychology has to suspend the natural attitude that uses color properties to refer to things while remaining true to their objective nature in experience to specify their phenomenal content. Indeed, Katz ( 1999: 4) quotes Her- ing in claiming that no theory of colors is possible until they are used only to recognize external things. At the same time he states that “it would be a kind of psychological perversion” if the research neglected the color appearances as “tangible realities,” beginning the scientific investigation with colors that only a specialist is able to produce in the “highly artificial conditions of the laboratory,” like those occurring in the spectroscope, or that are the effect of a momentary malfunctioning of the eyes, such as after-images ( 1999: 3). As it stands, “an unprejudiced description of phenomena” avoids assuming as the object of research a color specimen like the “subjective visual grey,” which subjects are not likely to choose as an example of color experience. Moreover, it prevents the long-established psychophysical attitude of psychology to reduce the account of colors to a physiological explanation in which phenomena are necessarily supplemented with “speculative ideas” (1952: 189).
Katz remarks that the description of color phenomena may consist only in the analysis of the features underlying the colors’ classification in an abstract space like the color circle. “In such cases experimental controls can serve only to render possible a clear presentation of the colour-experiences referred to in other studies” ( 1999: 6). Yet the description also gives the conceptual clarification of the observational basis and of the relevant questions concerning color appearances. In this sense, Katz condenses the connection between phenomenology and psychology of colors in the claim that
neither here nor anywhere else can the psychologist produce new phenomena in the strict sense of the term; what he does is simply to make mental phenomena speak for themselves, and in this way bring them to “official” recognition.
Katz concedes that psychology cannot rest content with the description of color appearances, because the work begins with description to discover the relation between phenomena and the psychophysical, physiological and physical conditions ( 1999: 4). He takes phenomenology as an autonomous method that allows for a correct decomposition of perception and the specification of the features of appearances that could be otherwise neglected or overlooked ( 1999: 2, 5). This is the case of those questions whose successful treatment requires crossing established distinct research fields, like the relations between colors and macro- or microstructures of surfaces as well as space. Indeed, only phenomenological analysis can justify the study of a question in isolation. For instance, illumination can be considered an “independent psychological problem” only if the phenomenological analysis shows it to be an “independent phenomenon.” The observation that space has an influence on color appearances cannot be taken into account if the psychology of space has no interest in color and if color appearances are treated as isolated impressions. In fact, spatial factors are fundamental for the modes of color appearance. Thus an unprejudiced phenomenological description discovers a “borderland” phenomenon despite the customary division of the experimental work into two distinct psychological fields.
Katz maintains that color perception provides knowledge about the world through the “matter” of appearances, that is, being blue, red, white, black, and the modes of appearance. He distinguishes between primary modes, which regard the very color matter, and secondary modes, which regard variations of colors yielded by illumination. He calls the three primary modes of appearance “film-,” “surface-” and “volume-colours.” For instance, the same red may appear as a surface-color or as a film-color. The same red in the two perceptual occurrences is the color matter, while the change in the mode of appearance conveys information about the structure of what is colored.
Surface-colors spread over the surface of a thing to which they belong and inherit the features of the form and the material structure of surfaces; hence they appear opaque, compact and solid so that they oppose a resistance to the sight. Surface-colors are localized in the same visual place of the thing to which they belong; hence, they appear at a definite distance from the per- ceiver. They appear to adhere to things, so they may hold any position in relation to the perceiver with a tilt and slant in accord to the orientation of their surface. Katz remarks that every surface-color is the color of a thing, but the converse is not always true. Some things have colors whose mode of appearance is different, like the red of a glass and the colors that appear in an ice slab or are diffused in liquids. These colors partake of the mode of volume- colors. They appear to fill a piece of three-dimensional space that is not a thing of which the color is part. Volume-colors appear in a spatial substance with sufficient transparency, in the sense that the sight passes through it and reaches other things, for example the colors seen in clouds, steam, vapour and other gases, and a sheet of glass. If the substance is perceived to be roiled or to condense, the volume-color will change into another mode of appearance, namely a film-color.
Film-colors appear to belong neither to a thing nor to the visual place, like the blue of the sky, the grey of smoke and the white of fog. They do not display the same compactness as surface-colors, rather they show a certain thickness with a soft, spongy, fuzzy character so that the sight can penetrate to some extent into it. This does not mean that film-colors are somehow transparent, rather that one who looks at them has indeed the experience of seeing a sort of colored layer, behind which, however, no further thing is visible. This feature accounts for the difference between film-colors and both surface- and volume- colors. Unlike surface-colors, film-colors spread over a two-dimensional plane that is different from a surface. Film-colors appear uniform, homogeneous and do not display visual grain or texture. Unlike volume-colors, film-colors allow the sight to penetrate into them but only to some extent, because they provide the plane on which they appear with a rear boundary. Therefore, both surface- and film-colors delimit the space and occlude what is perceivable behind them, but they do so differently. If surface-colors appear lying on a frontal- parallel plane only as a special case of the many orientations they may have, film-colors are bound to lie on a frontal-parallel plane.
Katz maintains that after-images, spectral colors and the appearances seen through a reduction screen are instances of film-colors. Drawing on observations through the Asher’s spectrometer, he concludes that film-colors always have a perpendicular orientation to the direction of vision, if directly fixated and projected on the fovea, and an “indefinite localization.” This is another difference from surface-colors. If the same color matter is presented in the mode of a surface- and a film-color, for example as a colored paper and a spectral color, it will display either any localization in accord to the place of the paper surface, or a localization that is gauged with uncertainty for any absolute distance at which it appears. Estimated distances from 50 cm to 80 cm may correspond to indefinite localization of spectral colors. Instead, the colored paper can appear definitely at lesser or greater distances and maintain the mode of appearance.
Katz states that the modes of color appearance can be set in correspondence with light conditions. In general, surface-colors correspond to the light reflected diffusely from opaque things with a structure and small heterogeneities, because only solid structured things afford clear-cut surfaces. However, this correspondence does not obey any simple law and transitions are possible between the three modes of appearance ( 1999: 9). The monocular observation, the lack of sharp accommodation, and the reduction screen that excludes the perception of surface and structure are extrinsic conditions in which film-colors replace surface-colors. Film-colors occur with different light conditions, for instance those of the spectrometer or of the uniformly beclouded sky seen through the reduction screen looking upward while lying on the ground. If the intensity of illumination is so reduced that subjects cannot see the structure and orientation of surfaces, notwithstanding the adaptation, the grey colors that stand out solely on the grounds of their different brightness resemble the mode of appearances of film colors. It is worth noticing that the modification of the modes of appearances is not symmetrical. The transition from surface-colors to film-colors is easier than the reverse and the same holds for the transition from film-colors to volume-colors.
Katz’s (1925) work on tactile perception is another example of the contribution of the phenomenological method to the research with regard to general epistemological questions and specific problems, such as the analysis of the form of tactile perception and of the modes of appearance of touch phenomena. Katz (1925: 17) claims that the original sense of the term “sensation” is not consistent with perceptual experiences and quotes Hering (1905: 5) for his objections. Katz claims it does not do justice to color and tactile experience because it implies the reduction of every perception to a sensory trace that is impressed in the sense organs. Instead, phenomena have objective and subjective characteristics that emerge through the comparative analysis of the forms of reference of color and tactile perception. Color appearances refer to the space outside of subjects. They have an “objective” character that is shared even by after-images. This is an inherent feature of all color phenomena, so that a distinction between colors of things or subjective sensations can only be drawn independently if the presence or the lack of an external stimulation is considered as an additional criterion for their classification.
Unlike colors, tactual appearances contain a subjective reference to the body that is, however, always connected to an objective reference to the properties of things. Therefore, Katz calls them “bipolar” phenomena. This bipolarity is a feature of the phenomenal structure of touch. It is always intuitively instanced in any tactual appearance, even if either component may be noticeable to a greater or lesser degree. The slightly tickling contact of a feather with the back of one’s hand is usually not associated with touch, but it is close to what a subjective tactile sensation would look like. Even so, the reference to the external object that acts as the triggering stimulus cannot be suppressed. Conversely, there are tactual appearances that exclusively refer to things, although a change of the ordinary attitude suffices to let the subjective component emerge as a genuine intuitive component of perception. Katz claims that the phenomena of objects’ localization by means of touch are a case in point, since they cannot but imply reference to one’s own body state. Yet even if the subjective component prevails, touch appearances always have an objective character because they also refer to something other than the subject. In comparison, temperature perception is conspicuously more characterized by the subjective character, so that the objective one even disappears when the cold and warm states of various body parts are compared (1925: i63ff.). Katz (1925: 20) suggests that the subjective or objective characterization of tactual appearances may depend on the bodily part where contact or pressure occurs, its usual association with touch and the state of motion or rest.
The unreflective assumption of the construct of sensation has induced the psychology of perception to fail to take the inherent features of phenomena into due account. Katz (1925: 7f.) holds that the reason for this assumption is the development of a sensory psychology that has been substantially tied to sensory physiology. Some psychological constructs were derived from physiology so that the phenomena that seemed to elude an entirely physiological explanation were interpreted as cognitive products of mental or inferential operations. Katz emphasizes that it was the lack of physiological knowledge that forced Weber to provide unbiased insights on touch in relation to ordinary phenomena. The anatomical and histological analysis of perceptual problems might introduce spurious facts as if they were real objects of research; hence, Katz defends Hering’s preliminary distinction between the psychological, namely descriptive or phenomenological, and the physiological issues in perception research. In accord with the atomistic model that ruled sensory physiology, psychology has tried to isolate the sensations that correspond to stimulations of single points of sensory organs, whereas it should have aimed at discovering the “true nature of complex phenomena.” Like for colors, Katz claims that the naturally arising phenomena are the starting point of the research regardless of whether or not they are elementary in the sense of the psychophysiological construct of sensation. Katz (1925: i4ff.) takes the case of pressure, one of the alleged primitive sensations of touch, which is usually accounted for on the basis of the stimulation of individual skin points so that the spatial sense arising from several pressure points of the skin is regarded as an artefact. However, the single isolated sensations must be produced through instrumental devices and artificial procedures in conditions that are different from everyday life and natural perceptual activity. For instance, the reduction of wetness to the mental sum of pressure and temperature sensations on the basis that it may arise also with dry stimuli, is as false an explanation as it is a misleading phenomenological observation. The artificial conditions of study have prejudicing implications because they are “so extraordinarily remote from natural stimulus conditions that even the absurd, multiform accidents of everyday life would hardly ever lead to such situations” ( 1989: 35). Like wetness, such complex phenomena as the visual and tactual integration for perceiving the smoothness and roughness of textured surfaces are not even recognized (see 1925: 97k, 119k, 202f., 218, 222f., for the distinction between pressure and vibration on the basis of the analysis of their phenomena and referents in opposition to the traditional classification and even their physiological localization).
Having settled the questions of the epistemology of tactile perception and of the correct decomposition of perception, Katz analyzes the form and modes of appearances of touch. As regards the form, like colors tactual appearances allow for the distinction between the matter and the mode of appearance. However, the matter of color perception varies through the entire achromatic and chromatic three-dimensional space of colors, whereas there is no respect under which the matter of touch either resembles the distinction between achromatic and chromatic features or is arranged in something like the circle of color qualities. For this reason, Katz claims that the matter of touch has the phenomenal character of “monotony.” Yet the world of touch presents a great variety of shapes in which the matter of touch is concerned. Katz concludes that the form of tactual phenomena is characterized by the monotony of the matter and the “polymorphism” of the tactual world (1925: 24). As regards the modes of appearances, Katz (1925: 21-22) claims it is necessary to adopt the same descriptive method that gives the color modes an order. Then the question to address is “how” touch appears rather than “whence” appearances derive. Touch has to be intended in the broadest sense of naive experience in order to encompass all the appearances that build what the world presents ordinarily to subjects in the form of touch. The description must not be committed to a physiological hypothesis on the cause of touch or pressure phenomena or to any physiological classification of them.
The modes of touch realize the same function as the modes of color: they convey information on the structures at the surface of things. Katz (1925: i7f.) distinguishes the “micro-morphic” from the “macro-morphic” features of structures. He calls macro-morphic the features of the geometric forms discerned in objects, whether they are plane figures or space-filling shapes, like triangular or circular and cubic or cylindrical forms. These features are perceived visually and tactually, and in the latter case they are the objects of “stereognosis.” The micro-morphic features regard properties of the structure of substances, like roughness and graininess, which are specific to touch phenomena. The modes of appearances that provide information on these features are the surface, the space-filling and the volume modes of touch (1925: 26ff.).
The surface mode is experienced when a thing is touched, be it made of metal, wood, glass, cloth and so on (1925: 26). What appears is a connected and unbroken tactual surface lying at the uppermost layer of the thing with curvatures that are shaped in the perception. The tactual surface has a two-dimensional form that encloses a space independently of whether a stiff material like glass or a smooth wool fabric supported by a rigid basis is touched. Like surface-colors, the surface appearances of touch show spatial localization, distance and orientation. They may hold any spatial position, and their distance and orientation in relation to their localization vary within the limits of the perceivers’ body constitution, although they are bound to assume a determinate spatial value under both these respects. Like surface colors, surface touch appearances refer to the properties of things. Nonetheless, there is a difference between color and touch perception in the surface mode with regard to the reference to the qualities of things (1925: 28-29). Surface colors present a barrier to the sight, while surface touch appearances are not inherently associated with a sense of resistance. Katz remarks that if pressure is exerted on a wooden thing, the perception of its resistance is not present in the same way as the perception of the tactile surface is. By increasing the pressure while touching the surface, the perception of resistance begins to emerge and develops to reach a maximum, but this does not induce any essential change in the tactile perception of the surface. Therefore, the resistance is not an inseparable feature of the surface mode of touch appearance, but a feature that can only be associated with it. If the resistance belonged to it as an inseparable part, the perception should be thoroughly altered if the resistance is varied to such an extent. Unlike resistance, impenetrability is an inseparable feature of tactual surface appearances and it founds the perception of the opposition of things to sensory organs. Katz suggests that these features are connected. If the pressure is increased beyond a certain limit, the perception of the impenetrability changes into the perception of resistance.
If the analogy between the color and the touch modes of appearance holds, it might seem that the mode corresponding to film-colors would be coincident with touching a surface that becomes looser and looser. In fact, Katz holds that if a thing made of stiff material, like wood or metal, could be so progressively altered that its uppermost layer appears looser and looser, as if it were made of cloth or wool, the appearance would always present the structural features of the surface. The surface mode is still maintained, however smooth and loose the touched thing might have become. Instead, Katz claims that the characteristics of this second mode of appearance can be derived from the observation of phenomena with a different nature. If a strong air stream is blown against one’s hand, or if a hand is moved with sufficient speed in liquids of various consistencies, tactual appearances arise with a greatly indeterminate form. These appearances are not arranged on the surface of a form to which they could be assigned. This form displays a certain thickness, but it cannot be regarded as really spatial, since it lacks an enclosing rear boundary. Katz calls “space-filling” this mode of tactual appearance. Touch appearances of this kind do not present a stable orientation in space and would rather be designated as space-filling qualia. Though they are not on par with the film-colors with regard to their knowledge function, both phenomena share the fact that they do not stand for the properties of things to which they refer. Space-filling tactual appearances present the characteristics of a material, rather than of things. Through such qualia the subjects are able to ascertain the looseness of the structure of the above-mentioned substances, which yet does not come to appear discontinuous or with gaps. Katz (1925: 30) remarks that the subjective characteristic of touch is more conspicuous in the space-filling appearances, although the consciousness of something objective is clearly present, however instantaneous or transitory it may be. Space-filling appearances are different from surface tactual appearances as regards the perception of resistance. If resistance dropped in a space-filling quale, the whole appearance would disappear. The resistance varies as the force of the stream against one’s hand changes, to disappear as it becomes null. Besides, the resistance in a space-filling appearance is not perceived as rigidity, rather as elasticity.
Katz (1925: 3of.) claims that another mode of touch occurs so that the analogy with the color modes is complete. If a thick piece of wadding is put on a small object, like a lighter box that is laid on a firm ground, and the perceiver means to know what form it has, the overlying stuff provides a spatial-like tactual appearance that presents in a more or less convenient way the form of the underlying object. If the perceiver draws her attention exclusively to the form of the lighter box, the tactual appearance in the surface mode of the wadding actually recedes. It appears instead as a spatial-like intermediate layer that is filled by a soft material. Such appearances have the volume mode of touch that corresponds to volume-colors. Volume-colors are presented as clear-cut only if something else is seen through and beyond them. A trough that is filled with a milk solution does not permit seeing its volume-color if held before the sky with its film-color, but maybe only where things appear to lie behind it. The wadding layer does not provide a clear-cut tactual volume appearance if it lies on a flat ground and no solid three-dimensional thing is touched through it. If a light pressure is exerted, the wadding gives rise to a tactual surface appearance, whereas one’s hand movement with increased pressure gives rise to a tactual volume appearance, even though not in a clear-cut manner. As volume-colors are manifest in the most clear-cut manner inside a medium- thick fog, so volume tactual appearances are presented in a clear-cut way in a medium-thick wadding layer. The soft material of the wadding seems to wrap around the underlying solid thing and its boundaries are located where the surface of the body begins to appear. Just as a volume-color becomes more effective as the thing-like appearance of the object that lies behind becomes more conspicuous, so the volume tactual appearance becomes more evident as the thing-like appearance of the body behind the wadding becomes more determinate. The volume-color of the fog swallows the fine structure of the surfaces of things and is particularly evident before the contours thereof. Likewise, the wadding conceals the fine structure of the underlying thing and its spatial-like character becomes particularly evident only at the contours of the touched thing. If the fog gets thicker, both its spatial-like character and the objects disappear. Likewise, if the wadding becomes so thick that the underlying thing is no longer sensed, the tactual appearances lose their spatial-like character.
Katz claims that the study of important issues like the particular tactual structure of things, the features of touch that enable one to understand the materials of things, needs a phenomenological description (1925: 37). He acknowledges that the description of the modes of appearance of touch is an abstraction (1925: 33). In everyday experience things seldom appear in the pure mode of surface appearances but present a particular tactual structure, just like the visual surfaces that also always present a particular distinguishing structure. Katz maintains that we do not usually perceive surfaces “in general,” rather particular surfaces that are hard or soft, rough or smooth. Indeed, experience presents surfaces with the maximum of smoothness and of roughness, from hard metal to soft tissue, as well as all the intermediate steps in-between. It is straightforward to point out the combinations of the features of the series hard-soft and smooth-rough, whose extremes are glass as an instance of hard smoothness, emery paper as an instance of hard roughness, silk as an instance of soft smoothness and finally a billiard table cloth as an instance of soft roughness.
Katz contends that such features and combinations build the particular distinguishing structures that characterize things’ surfaces and calls them “modifications.” Each modification specifies a particular tactual structure of a surface and corresponds to the members of the series hard-soft and smooth- rough. Such a modification is solely a general characterization of the surface, because it does not provide any reference to the stuff and the material of which the surface is made (1925: 34). Instead characterizations of tactual structures with regard to the stuff or material of surfaces are called “specifications.” The distinguishable specifications depend on the experience of subjects and their number is huge, notwithstanding that natural languages do not provide enough independent words to denote them. Katz suggests that apart from technical languages, very few linguistic expressions are available for denoting their fundamental qualities and the degrees of their increment or decrement. To address this lack of sufficient terms we use compound terms, for example when we denote color qualities for which there are no enough fundamental terms. As we use terms like bluish-purple, emerald green, chocolate-brown, so we use terms in which the suffix “-like” is added to nouns such as “leather, tissue, silk, paper” to denote the specifications of appearances as similar or identical to other experienced tactual structures (1925: 34). A specification is subject to modification in various directions through the series of smooth- rough and hard-soft, and it admits a further form of individualization like when a piece of cloth is recognized as one’s own suit or a piece of wood as one’s own writing desk only by touch. Other specifications are possible. For example, the perception of a piece of wood varies if its being damp, oiled, resined is sensed by touch. Katz holds that these variations affect the tactile perception of things’ surfaces in the same way as the light and dark spots affect the vision of the surface-colors of things.
The phenomenal features that allow one to recognize the material of things is another aspect of tactile perception that is fundamental for the ability to orient oneself in the world. As the variety of colors and illuminations does not prevent the structure of a thing being recognized, so the variety of the flat or curved forms of the surfaces of things does not prevent recognition of the material they are made of (1925: 35-38). The material is perceived through the structure it displays in each set of points of the surface form, whether it is natural or artificial, by means of “form-elements” that occur in vision and touch. As regards visual surfaces, if conditions of optimal distance and illumination are met, the structure of its material appears. For instance, whatever color and form a piece of paper may have, minimal “form-elements” appear in it that have the smallest magnitude possible to still be noticed at minimal values of lightness or colors. Katz claims that these form-elements are so small that a multitude of them can be concentrated in a millimetre. There are manifolds of such elements so that for any two mutually delimiting sets of them, it is impossible to judge them identical. Yet Katz maintains that the irregularity of dissimilar elements is ruled by “the law of the structure of the material” (1925: 36). Form-elements of the same type repeat themselves across the surface so that a thing is perceived as the bearer of the sense “thing of the sort x” where “x” stands for a material with a particular structure. Some materials have form-elements that are unified in arrangements of higher order. An example is the passage from the smallest elements of a panel of a kind wood to the veins they vaguely present and finally to the veins that are manifest to the utmost in the wood section at the levels of the trunk rings.
These observations are true also of tactual surfaces. There are tactual form- elements characteristic of the stuff of a thing which are independent of its outward shape. In order to detect the minimal form-elements, it is sufficient to use the fingertips or the lips. If one touches a piece of stone or wood, one will feel the typical sameness of form-elements that do not, however, imply complete identity. Indeed, a subtle perception may arise of the degree to which form-elements can vary without destroying the unitary character of the perception of that particular material. The tactual form-elements are arranged in ways that are characteristic of a whole of the thing, which make it possible to recognize the material as well as to distinguish, for instance, between stone and wood. For example, if a corrugated pattern is impressed on a piece of wood, one perceives a “ribbed” wood surface, because the form-elements of corrugation are arranged on a larger scale than that of the typical form-elements of the wood material. The perceptual distinction between the corrugation and the wood depends on the fact that the form-elements of the material allow for sensing dissimilar elements, albeit within the limits of the sort of wood structure, while the tactual form of corrugation is founded on the almost identical repetition of the elements.
Source: Calì Carmelo (2017), Phenomenology of Perception: Theories and Experimental Evidence, Brill.