1. A combination of sensations in which every element is connected with any second element in exactly the same way as with any other, is called an intensive idea. Thus, for example, a compound clang made up of the tones d f a is such an intensive idea. For the immediate apprehension, each of the partial combinations into which this compound clang can be resolved, as df, da, fd, fa, ad, af, are all entirely equivalent, in whatever order they are thought of. This is obvious at once if we compare the compound clang with any succession of the same tones, where df, da, fd, fa, etc., are essentially different ideas. We may define intensive ideas, accordingly, as combinations of sensational elements, in which the order of the elements may be infinitely varied.
It follows from their nature, that intensive ideas do not have, arising from the way in which their elements axe united any characteristics, by means of which they can be resolved into separate parts. Such a resolution is possible only through the differences in the constituent elements themselves. Thus, we discriminate the elements of the compound clang d f a, only because we hear in it the qualitatively different tones d, f, and a. Still, the separate components in such a unitary idea are less clearly distinguishable than in their isolated state. This fact, that the elements are pushed into the 'background by the impression of the whole, is of great im- [p. 94] portance for all forms of ideational combination. We call it the fusion of sensations, and in particular, for intensive ideas, intensive fusion. If the connection of one element with others is so close that it can be perceived as a part of the whole only through unusual concentration of the attention aided by experimental variation of the conditions, we call the fusion complete. If, on the other hand, the elements are immediately recognized in their proper qualities, and merely recede somewhat into the background in comparison with the impression of the whole, we call the fusion incomplete. If certain particular elements are more prominent in their characteristic qualitites thin others, we call them the predominating elements. The concept of fusion as here defined as a psychological concept. It presupposes that the fused elements of the idea are really subjectively distinguishable. It must not be confounded with the entirely different and purely physiological concept of the fusion of external impressions into a single resultant stimulation. For example, when complementary colors unite and give white, the fusion is, of course, not psychological.
In reality, every intensive idea always enters into certain spacial and temporal combinations. Thus, for example, a compound clang is always a process having a certain duration, and is at the same time localized by us in some direction or other, though often only very indefinitely. But since these temporal and spacial attributes can be indefinitely varied, while the intensive character of the ideas remain the same, we may abstract from the former in investigating the intensive attributes.
2. Among ideas of the general sense we have intensive fusions in the form of combinations of sensations of pressure with those of hot or cold, or combinations of pain-sensations with those of temperature or pressure. All these fusions [p. 95] are incomplete, and very often there is no decidedly predominating element. The combination of certain sensations of smell and taste are more intimate.
This is obviously favored on the physiological side by the proximity of the sense-organs, on the physical side by the regular connection between certain stimulations of the two senses. In such cases the more intense sensations are generally the predominating elements, and when these are the sensation of taste, the composite impression is usually regarded as a taste-quality only. Thus, most of the impressions known in ordinary life as "tastes", are in reality combinations of tastes and smells.
The greatest variety of intensive ideas, in all possible gradations of complexity, are presented by the sense of hearing. The relatively most simple of these ideas and those which are most closely related to simple tones, are the single clangs. As more complex forms, we have compound clangs. Complex noises may arise from the latter when they are united with sensations of simple noises, and under certain other circumstances.
3. A single clang is an intensive idea which is made up of a series of tonal sensations regularly graded in quality. These elements, the partial tones of the clang, form a complete fusion, in which the sensation of the lowest partial tone becomes the predominating element. The pitch of the tone is determined by this principal tone. The other elements are higher and are, accordingly, called overtones. The overtones are all grouped together under the name clang-color as a second determinant of the clang, added to the predominating tone. All the partial tones that go to determine the clang color are placed along the tonal line at certain regular intervals from the principal tone.