# The Foundations of Normal and Abnormal Psychology/Part 1/XXIII

Contrary to the view maintained by many psychologists we have laid special stress on the fundamental qualitative difference between image and sensation. We shall not venture far from our facts, if we arrange images and sensations in two qualitatively different psychic series. Sensations can be ranged in a graduated series of intensities, while images or representations can be ranged in a graduated series of clearness and distinctness, or of vividness, as it is sometimes described by some psychologists. I use the term vividness in the sense of clearness and distinctness and not in the sense of intensity as it is often used; even those psychologists who do not use intensity and vividness indiscriminately ascribe both of them equally to sensation and image.
Vividness and intensity are understood by me to be two fundamentally qualitatively different aspects, or attributes. Sensations have intensity, but no vividness; images or representations have vividness, but no intensity. Sensory elements may vary from minimum to maximum intensity. This variation in intensity holds true both of primary and secondary sensory elements. Similarly, images or representations may pass through all degrees of vividness from minimum to maximum. The image represents the sensation. In this respect we may somewhat modify the well-known dictum of the sensationalists into: ‘Nihil est in imagine quod non antefuerit in sensu.’ The sensory element is represented by its respective representative element.
The representative elements may refer with different degrees of vividness to the same sensory elements. An image with one degree of vividness can be substituted for another with a different degree of vividness and still refer to the same sensory elements. The degree of vividness does not change the qualitative character of the representation. Not so is it with the qualitative attribute of the sensation. The slightest change in the intensity of the sensation changes its qualitative character. A sensation with one degree of intensity cannot be substituted for another. A sound or a color of a definite intensity cannot be substituted for a sound or color of a different intensity. The two are different sensations and no sensation can substitute another. Sensations falling in the same series of intensity are really independent of one another, but each sensation of the intensive series can be represented by a whole series of representations of different vividness,from minimum to maximum. Different series of representative elements may also be regarded as independent, since they refer to independent sensations.
If we symbolize a series of sensory elements by the letters: A$_1$, A$_2$, A$_3$, A$_4$, A$_5$, . . . A$_n$; and if we symbolize the corresponding series of representative elements by a$_1$, a$_2$, a$_3$, a$_4$, . . . a$_n$, then the series of both sensory and representative elements may be symbolized by the following formula:
A$_1$ A$_2$ A$_3$ A$_4$ A$_5$ . . . A$_n$ a$_1$ a$_2$ a$_3$ a$_4$ a$_5$ a$_n$ a$_1$$^1$ a$_2$$^1$ a$_3$$^1$ . . . a$_1$$^2$ a$_2$$^2$ a$_3$$^2$ . . . a$_1$$^3$ a$_2$$^3$ a$_3$$^3$ . . . a$_1$$^4$ a$_2$$^4$ a$_3$$^4$ . . . a$_1$$^5$ a$_2$$^5$ a$_3$$^5$ . . . . . . . . . . . . . . . . . . . . . a$_1$$^n$ a$_2$$^n$ a$_3$$^n$ a$_4$$^n$ a$_5$$^n$ a$_n$$^n$
The characteristic of the image, or of the representative element is just its extraordinary plasticity and possibility of substitution. This function of substitution was described by Taine with all the power of his lucid style. The great modifiability of representation plays an important role in psychic life―adaptability to various conditions of life increases, reactions cease to be rigid and uniform, but change easily in response to a changing environment. Variations of sense-organs with their physiological processes are rather slow and tardy, often requiring generations for an effective change, while the representative element can be modified and adapted within the life-existence of the individual and often in a very short time. In brief, the function of substitution possessed by the representative element in the processes of mental selection is the substitute for natural selection in the highest representatives of animal life.
Now under ordinary conditions of life the graduated series of representative vividness runs parallel to the gradated series of sensory intensities. Usually a more intense sensation is represented with greater vividness. The increase or decrease of intensity of the sensory series has a corresponding change in the vividness of the elements of the representative series. Intensity and vividness vary directly. Such direct variation, however, is not always the rule. There are cases, when the two part company. In states of distraction, in subwaking states, in states of dissociation, and generally in the conditions of functional psychosis, intensity and vividness do not vary directly. Strong stimulations may give rise to sensations of great intensity, but the vividness of the representative elements may fall so low as almost to reach the minimum. When the vividness is so low as to reach the minimum, the representative elements cannot be used as substitutes and, since reproduction belongs to representative elements which symbolically reproduce the sensations by the process of substitution, reproduction or memory of the original experience is absent and there is a break, a gap in mental continuity, dissociation results. The depths and extent of dissociation of mental systems may be regarded as variables of vividness. Dissociation varies inversely as vividness. When vividness is at its minimum, dissociation is at its maximum. The phenomena of functional psychosis having their origin in states of dissociation may thus be regarded psychologically as functions of vividness, the most characteristic attribute of representative elements. Functional psychosis with all its protean manifestations, the great variety of dissociated and subconscious states may thus be reduced to variations of one fundamental attribute―vividness.