Is it then possible, in the field of our sensations, to reduce to elemental categories or units the manifold[1] of concrete sense experience? In the case of visual sensations almost everybody knows that there are certain so-called “primary” colors, from which can be produced the whole range of color experiences known to man. Blue and yellow, red and green, these are the primary colors, and if to these, in their varying intensities, be added gray, with its range of brightnesses, we have the elementary components of all our visual experience. Such a distinctive color as that of fire clay, for example, may thus be said to contain, in specified degree and proportion, red, yellow, and gray, while the familiar color of a wild flower may contain, in specified relations, red, blue, and gray. Footnote 1: By a “manifold” is meant a great variety of objects or experiences organized into one system or constituting one field. In a strict psychological sense, it remains true that each color experience is relatively unique and distinct. But it can readily be shown that these psychological fusions and compounds are elaborations of more unitary experiences which have as their basis distinct mechanisms in the nervous system and sense organs. For example, the sensation of “heat” is a readily recognizable and identifiable experience, yet the physiologist tells us that there is no separate sensory apparatus for this impression. Cold and warmth, we are told, depend on the stimulation of specific nerve endings. When these two types of endings, in the same general region of the skin, are simultaneously stimulated, as the result of the application of a stimulus with very high temperature, there arises that new experience of “hot,” which is in this sense a combination of warmth and cold. Is it similarly possible to reduce to elementary units the rich manifold of taste and flavor? If this can be done, in what way must such an analysis proceed? What principles of classification are revealed, and what and how numerous are the elementary taste qualities? The various attempts that have been made to analyze the taste manifold are as interesting as their results are instructive. _The Classification of Tastes_