When Hering outlined his view of the nature and science of perception, he made alternative claims to von Helmholtz’s theory on the epistemology of perceptual reference, the theoretical decomposition of perception and the associated methodological issues. For example, Hering considers it an unquestionably observable fact that naive subjects ascribe colors to things as independent properties.
To be sure, color terms are variously used (1905: 2). For naive subjects they denote properties of the common-sense things. For physicists they denote properties of light radiations. Were the physical characteristics of the reflected light different from everyday daylight, the same objects would appear differently colored. The meaning of color terms would designate a different phenomenal world. For physiologists, color terms denote properties of nervous system cells. It can be ascertained that color appearances are affected by the eccentricity of the retinal points stimulated by light. Furthermore, the same blue-red afterimage occurs upon looking at a green paper by either fixating a white surface or closing one’s eyes, although in the first case the white surface reflects the same radiation as when it is seen white, whereas in the second case no light stimulates the peripheral sense organ. Finally, for psychologists color terms denote conscious phenomenal contents that could not share properties with common-sense, physical and physiological referents, although the latter may be taken as their correlates.
This variety notwithstanding, colors as properties of things or after-images maintain a phenomenal face value for natural scientists and psychologists to the extent that they perceive things, rather than treating them as the constructs of their disciplines. The science of perception has to account for colors as they occur in perception, taking them at their face value in naive experience. It is well known that Hering looks for an explanation of color perception that includes a physiological basis, but unlike von Helmholtz he believes that the naive phenomenal value of colors is a probe for physiological research. The phenomenal features of colors have to be specified to avoid mistaking them for the properties of the hypothetical constructs. Hering (1905: 2-3) draws a distinction between “visual things” and external things in order to extract the features of appearances and prevent the knowledge derived from other sciences from being prejudicial to the collection and observation of the phenomenal data. This is a phenomenological rather than a conceptual distinction. It is not concerned with the question of which objects, among those that are perceived as independent of subjects, physically exist. Colors are considered the phenomenal “stuff” that fills the surfaces of both external things and afterimages up to their boundaries. As such they are the phenomenal building blocks of the world.
This is a momentous epistemological disagreement between Hering and von Helmholtz. Hering claims that the theory of the perceptual reference to the world needs the distinction among physical and visual things, physical and visual space. The phenomenal features of this reference can be studied only if the referents are not identified with physical objects, namely with the cause of physical stimulation, but with visual, that is perceivable, things. Accordingly it is not appropriate to treat color as a “sensation.” Colors are properties through which things perceived as external pieces of the world are segregated from and stand out against one another. The term “sensation” refers to something felt in the body, while colors appear outside the perceiver’s body. The physiological process triggered by an object standing before the perceiver, for example a cherry, is located in the body, but it does not have any property of the perceived cherry appearing red or round. To construe colors as sensations, and to denote colors and physiological processes with this term, is to risk misinterpretations and obscurities (1905: 5). For example, colors always appear extended and located outside subjects in the visual field. Since by definition sensations lack spatial properties, the integration of psychological factors is required to explain an observable fact with a mechanism of projection. Moreover, if the spatial properties of color are neglected, their essential role as constituents of things cannot be explained. Therefore, Hering concludes that either the term sensation is barred from denoting appearances, or the sensations must be located outside one’s own body. Likewise, vision does not consist in seeing light radiations. The eyes are not required to provide information on the intensity and quality of the light coming from things, but rather on the outside things by means of light. In a theory of perception, the color terms do not denote light radiations (1905: 13-14). If colors are classified according to their simple or composite nature that yet is determined by the radiation, as in von Helmholtz ( 1925, ii), undecidable questions arise from the equivocal use of terms and concepts. On the basis of this principle, ultramarine and chrome yellow could count as simple colors and green as their composite color in opposition to von Helmholtz results. Hering (1905: 4) emphasizes that while this principle of classification is reliable in textbooks on physics and color techniques, it cannot be admitted as a guideline for research into perception (1878: 56-57).
Hering (1878: 1) rebukes von Helmholtz’s Physiological Optics for having reduced phenomena to the known physiological processes and explained them away with mental constructs if the physiological account seems insufficient.
Once the phenomenal component of perception is restricted to sensations, von Helmholtz believes that appearances need the integration of “psychological,” that is, non-phenomenal factors. If appearances consisted solely of sensory effects, they could not be effective representations of external things. Then von Helmholtz assumes that psychological factors bestow on appearances the role of being a useful seeming of physical objects. Hering also rejects the research methodology deriving from this decomposition of perception that itemizes perception on the basis of available physiological knowledge. Anything that is not justified by the current knowledge can become a psychological factor, hence unproven mental posits explain away the phenomenal features of appearances that are not even recognized as proper objects of experimental research.
Source: Calì Carmelo (2017), Phenomenology of Perception: Theories and Experimental Evidence, Brill.