1. All the contents of psychical experience are of a composite character. It follows, therefore, that psychical elements, or the absolutely simple and irreducible components of psychical phenomena, can not be found by analysis alone, but only with the aid of abstraction. This abstraction is rendered possible by the fact that the elements are in reality united in different ways. If the element a is connected in one case with the elements b, c, d . . ., in another with b', c', d' . . ., it is possible to abstract it from all the other elements. because [sic] none of them is always united with it. If, for example, we hear a simple tone of a certain pitch and intensity, it may be located now in this direction, now in that, and may be heard, alternately with various other tones. But since the direction is not constant, or the accompanying tone the same, it is possible to abstract from these variable elements, and we have the single tone as a psychical element.

2. As products of psychical analysis, we have psychical elements of two kinds, corresponding to the two factors contained in immediate experience ( 1, 2), the objective contents and the experiencing subject. The elements of the objective contents we call sensational elements, or simply sensations: such are a tone, or a particular sensation of hot, cold, or light, when we neglect for the moment all the connections [p. 29] of these sensations with others, and all their spacial and temporal relations. The subjective elements, on the other hand, are designated as affective elements, or simple feelings. We may mention as examples the feelings accompanying sensations of lightt, sound, taste, smell, hot, cold, or pain, the feelings aroused by the sight of an agreeable or disagreeable object, and the feelings arising in a state of attention or at the moment of a volitional act. Such simple feelings are in a double sense products of abstraction: each is connected with an ideational element, and is furthermore a component of a psychical process which occurs in time, and during which the feeling itself is continually changing.

3. The actual contents of psychical experience always consist of various combinations of sensational and affective elements, so that the specific character of the simple psychical processes depends for the most part not on the nature of these elements so much as on their union into composite psychical compounds. Thus, the idea of an extended body or of a temporal series of sensations, an emotion, and a volition, are all specific forms of psychical experience. But their character as such is as little present in their sensational and affective elements as the chemical properties of a compound body can be defined by recounting the properties of its chemical elements. Specific character and elementary nature of psychical processes are, accordingly, two entirely different concepts. Every psychical element is a specific content of experience, but not every specific content of immediate experience is at the same time a psychical element. Thus, especially spacial and temporal ideas, emotions, and volitional acts, are specific but not elementary processes. Many elements are present only in psychical compounds of a particular kind, but since these compounds regularly contain other elements as well, their special characteristics are [p. 30] to be attributed to the mode of union, rather than to the abstract attributes, of their elements. Thus, we always refer a momentary sound-sensation to a definite point in time. This localization in time, however, is possible only by relating the given sensation to others preceding and following it, so that the special character of the time-idea can not arise from the single sound-sensation thought of as isolated, but only from its union with others. Again, an emotion of anger or a volition contains certain simple feelings that are never present in other psychical compounds, still each of these processes is composite, for it has duration, in the course of which particular feelings follow one another with a certain regularity, and the process itself is not complete without the whole train of these feelings.

4. Sensations and simple feelings exhibit certain common attributes and also certain characteristic differences. They have in common two determinants, which we call quality and intensity. Every simple sensation and every simple feeling has a definite qualitative character that marks it off from all other sensations and feelings; and this quality must always have some degree of intensity. Accordingly, we distinguish the different psychical elements from one another by their qualities, but regard the intensity as the quantitative value which in any concrete case belongs to the given element. Our designations of psychical elements are based entirely upon their qualities; thus, we distinguish such sensations as blue, grey, yellow, hot, and cold, or such feelings as grave, cheerful, sad, gloomy, and sorrowful. On the other hand, we always express the differences in the intensity of psychical elements by the same quantitative designations, as weak, strong, medium strong, and very strong. These expressions are in both cases class-concepts which serve for a first superficial arrangement of the elements, and each embraces [p. 31] an unlimitedly large number of concrete elements. Language has developed a relatively complete stock of names for the qualities of simple sensations, especially for colors and tones. Names for the qualities of feelings and for degrees of intensity are far behind. Clearness and obscurity, as also distinctness and indistinctness, are sometimes classed with quality and intensity. But since these attributes, as will appear later (§ 15, 4), always arise from the interconnection of psychical compounds, they can not be regarded as determinants of psychical elements.

5. Made up, at it is, of two determinants, quality and intensity, every psychical element must have a certain degree of intensity from which it is possible to pass, by continual gradations, to every other degree of intensity in the same quality. Such gradations can be made in only two directions: one we call increase in intensity, the other decrease. The degrees of intensity of every qualitative element, form in this way a single dimension, in which, from a given point, we may move in two opposite directions, just as from any point in a straight line. This may be expressed in the general statement: The various intensities of every psychical element form a continuity of one dimension. The extremities of this continuity we call the minimal and maximal sensation or feeling, as the case may be.

In contrast with this uniformity in intensifies, the qualities have more variable attributes. Every quality may, indeed, be so arranged in a definite continuity that it is possible to pass uninterruptedly from a given point to any other points in the same quality. But the various continuities of different qualities, which we may call systems of quality, exhibit differences both in the variety of possible gradations, and in the number of directions of gradation. In these two respects, we may distinguish, on the one hand, homogeneous and complex, on [p. 32] the other one-dimensional, two-dimensional, and many-dimensional systems of quality. Within a homogeneous system, only such small differences are possible that generally there has never arisen any practical need of distinguishing them by different names. Thus, we distinguish only low quality of pressure, hot, cold, or pain, only one feeling of attention or of activity, although, in intensity, each of these qualities may have many different grades. It is not to be inferred from this fact that in each of these systems there is really only one quality. The truth is that in these cases the number of different qualities is merely very limited; if we were to represent it geometrically, it would probably never reduce entirely to a single point. Thus, for example, sensations of pressure from different regions of the skin show, beyond question, small qualitative differences which are great enough to let us distinguish clearly any point of the skin from another at some distance from it. Such differences, however, as arise from contact with a sharp or dull, a rough or smooth body, are not to be reckoned as different qualities. They always depend on a large number of simultaneous sensations, and without the various combinations of these sensations into composite psychical compounds, the impressions mentioned would be impossible.

Complex systems of quality differ from those we have been discussing, in that they embrace a large number of clearly distinguishable elements between which all possible intermediate forms exist. In this class we must include the tonal system and color-system, the systems of smells and tastes, and among the affective systems those which form the subjective complements of these sensational systems, such as the systems of tonal feelings, color-feelings, etc. It is probable also that many systems of feelings belong here, which are objectively connected with composite impressions, but as [p. 33] feelings are simple in character, such are the various feelings of harmony or discord that correspond to the different combinations of tones.

The differences in the number of dimensions have been determined with certainty only in the case of certain sensational systems. Thus, the tonal system is one-dimensional. The ordinary color-system, which includes the colors and their transitional qualities to white, is two-dimensional; while the complete system of light-sensations, which includes also the dark color-tones and the transitional qualities to black, is three-dimensional.

6. In the relations discussed thus far, sensational and affective elements in general agree. They differ, on the other hand, in certain essential attributes which are connected with the immediate relations of sensations to objects and of feelings to the subject.

1) When varied in a single dimension, sensational elements exhibit pure qualitative differences, which are always in the same direction until they reach the possible limits of variation, where they become maximal differences. Thus, in the color-system, red and green, blue and yellow, or in the tonal system, the lowest and highest audible tones, are the maximal, and at the ,same time purely qualitative, differences. Every affective element, on the contrary, when continuously varied in the suitable direction of quality, passes gradually into a feeling of opposite quality. This is most obvious in the case of the affective elements regularly connected with certain sensational elements, as, for example, tonal feelings or color-feelings. As sensations a high and low-tone are differences that approach more or less the maximal differences of tonal sensation; the corresponding tonal feelings are opposites. In general, then, sensational qualities are limited by maximal differences, affective qualities by maximal opposites. Between these opposites [p. 34] is a middle zone, where the feeling is not noticeable it all. It is, however, frequently impossible to demonstrate this indifference-zone, because, while certain simple feelings disappear, other affective qualities remain, or new ones even may arise. The latter case appears especially when the transition of the feeling into the indifference-zone depends on a change in sensations. Thus, in the middle of the musical scale, those feelings disappear which correspond to the high and low tones, but the middle tones have still other, independent affective qualities which do not disappear with these opposites. This is to be explained by the fact that a feeling which corresponds to a certain sensational quality is, as a rule, a component of a complex affective system, in which it belongs at the same time to various dimensions. Thus, the affective quality of a tone of given pitch belongs not only to the dimension of pitch-feelings, but also to that of feelings of intensity and finally to the different dimensions in the clang-qualities of tones may be arraigned. A tone of middle pitch and intensity may, lie in the indifference-zone so far as feelings of pitch and intensity are concerned, and yet have a very marked clang-feeling. The passage of affective elements through the indifference-zone can be directly observed only when care is taken to abstract from other accompanying affective elements. The cases most favorable for this observation are those in which the accompanying elements disappear entirely or almost entirely. Wherever such an indifference-zone appears without complication with other affective elements, we speak of the state as free from feelings, and of the sensations and ideas present in such a state, as indifferent.

2) Feelings of specific, and at the same time simple and irreducible, quality appear not only as the subjective complements of simple sensations, but also as the characteristic attendants of composite ideas or even complex ideational [p. 35] processes. Thus, there is a simple tonal feeling which varies with the pitch and intensity of tones, and also a feeling of harmony which, regarded as a feeling, is just as irreducible, but varies with the character of compound clangs. Still other feelings, which may in turn be of the most various kinds, arise from melodious series of clangs. Here, again, each single feeling taken by itself at a given moment, appears as an irreducible unit. Simple feelings are, then, much more various and numerous than simple sensations.

3) The various pure sensations may be arranged in a number of separate system is, between whose elements there is no qualitative relation whatever. Sensations belonging to different systems are called disparate. Thus, a tone and a color, a sensation of hot and one of pressure, or, in general, any two sensations between which there are no intermediate qualities, are disparate. According to this criterion, each of the four special senses (smell, taste, hearing, and sight) has a closed, complex sensational system, disparate from the other senses; while the general sense (touch) contains four homogeneous sensational systems (sensations of pressure, hot, cold, and pain). All simple feelings, on the contrary, form a single interconnected manifold, for there is no feeling from which it is not possible to pass to any other through intermediate forms or through indifference-zones. But here too we may distinguish certain systems whose elements are more closely related, as, for example, feelings from colors, tones, harmonies, and rhythms. Still, they are not absolutely closed systems, but there are everywhere relations either of likeness or of opposition to other systems. Thus, such feelings as those from sensations of moderate warmth, from tonal harmony, and from satisfied expectation, however great their qualitative differences may be, are all related in that they belong to the general class of "pleasurable feelings". Still closer relations [p. 36] exist between certain single affective systems, as, for example, between tonal feelings and color-feelings, where deep tones seem to be related to dark colors, and bright colors to high tones. When in such cases a certain relationship is ascribed to the sensations themselves, it is probably due entirely to a confusion of the accompanying feelings with the sensations.

This third distinguishing characteristic shows conclusively that the origin of the feelings is more unitary than that of the sensations, which depend on a number of different and in part distinguishable conditions. It is the same distinction that we find in the characterization of the subject, which stands in immediate relation to the feelings, as a unit, in contrast with the plurality of the objects, to which the sensations are related.

6a. It is only in modern psychology that the terms "sensation" and "feeling" have gained the meanings assigned to them in the definitions above given. In older psychological literature they were sometimes used indiscriminatingly, sometimes interchanged. Even yet sensations of touch and those from the internal organs are called feelings by physiologists, and the sense of touch itself is known as the "sense of feeling". This corresponds, it is true, to the original significance of the word, where feeling is the same as touching, still, after the very useful differentiation has once been made, a confusion of the two terms should be avoided. Then again, the word "sensation" is used even by psychologists to mean not only simple, but also composite qualities, such as compound clangs and spacial and temporal ideas. But since we have the entirely adequate word "idea" for such compounds, it is more advantageous to limit the word sensation to psychologically simple sense-qualities. Finally, the term "sensation" has sometimes been restricted so as to mean only those stimulations which come directly from external sense-stimuli. For the psychological attributes of a sensation, however, this circumstance is entirely irrelevant, and therefore such a definition of the term is unjustifiable. [p. 37] The discrimination between sensational and affective elements in any concrete case is very much facilitated by the existence of indifference-zones in the feelings. Then again, from the fact that feelings range between opposites rather than mere differences, it follows that they are much the more variable elements of our immediate experience. This changeable character, which renders it almost impossible to hold an affective state constant in quality and intensity, is the cause of the great difficulties that stand in the way of the exact investigation of feelings.

Sensations are present in all immediate experiences, but feelings may disappear in certain special cases, because of their oscillation through an indifference-zone. Obviously, then, we call, in the case of sensations, abstract from the accompanying feelings, but never vice versa. In this way two false views may easily arise, either that sensations are the causes of feelings, or that feelings are a particular species of sensations. The first of these opinions is false because affective elements can never be derived from sensations as such, but only from the attitude of the subject, so that under different subjective conditions the same sensation may be accompanied by different feelings. The second is untenable because the two classes of elements are distinguished, on the one hand by the immediate relation of sensations to objects and of feelings to the subject, and on the other by the fact that the former range between maximal differences, the latter between maximal opposites. Because of the objective and subjective factors belonging to all psychical experience, sensations and feelings are to be looked upon as real and equally essential, though everywhere interrelated, elements of psychical phenomena. In this interrelation the sensational elements appear as the more constant; they alone can be isolated through abstraction, by referring them to external objects. It follows, therefore, of necessity that in investigating the attributes of both, we must start with the sensations. Simple sensations, in the consideration of which we abstract from the accompanying affective elements, are called pure sensations. Obviously, we can never speak of "pure feelings" in a similar sense, since simple feelings can never be thought of apart from the accompanying sensations and combinations of sensations. This fact is directly connected with the second distinguishing characteristic mentioned above (p. 34 sq).