Another characteristic of those sense materials which enter into art products,—especially vision and hearing,—is the fact that the various experiences constituting the sense manifold exhibit structural and systematic relationships. We do not here refer to the possibility of spatial arrangement and form. This we have already discussed and dismissed as an inadequate criterion. We mean, rather, those facts represented, in the case of vision, by the color pyramid and similar schemes for representing the qualitative relations of visual sensations; and, in the case of sound, by the tonal scale and such graded intensity scales as may be devised. Definite and formulable relations with respect to such facts as fusion, harmony, tonality, and melody; saturation, contrast, complementariness, mixture, etc., may be made out in the cases of vision and hearing. Æsthetic manipulation takes the form of playing upon these relationships. The visual and auditory qualities constitute not merely a manifold, but yield systematic structures. But the sense of taste and the other lower sensation modes tend to constitute a mere unorganized manifold. Now, it may be at once suggested that we here have the adequate criterion of the æsthetic for which we are searching, and that this is at bottom the reason why it is the visual and auditory experiences that are “described, discussed, repeated, and measured (and) creatively reëmbodied in works of art.” But even this account is, as a matter of fact, very one-sided and in part, at least, fallacious. We do not know what structural systems would be exhibited by the lower sense experiences if we had only discussed them, measured them, and creatively embodied them to the degree to which we have gone in the case of the higher senses. We cannot be sure, in the present state of our knowledge, to what degree the appearance of superior organization on the part of the higher senses is due to the amount of effort and inquiry we have bestowed upon their examination. All that we really know is that innumerable studies have been made of sight and sound, and that we are able to represent their results in the form of schemes and systems; whereas, comparatively few studies of the intensive type have been made of the various “lower senses,” and we are proportionately unable to construct the corresponding schemes and structures. Which is cause and which is effect? Do the lower senses fail to provide the raw materials of æsthetic construction because of their lack of elaborate and systematic organization, or do they owe this very deficiency to the relative neglect they have suffered at the hands of the artist? _The Motive of Æsthetic Products_