1. The normal state of consciousness upon which the discussion of the foregoing paragraphs has been based may undergo such a variety of changes that general psychology must give up the attempt to discuss them in detail. Then, too, the more important of these changes, namely, those which are observed in the various forms of nervous diseases, brain diseases, and insanity, belong to special branches of pathology which border upon psychology and are more or less dependent upon it. All that psychology can do is to indicate the main psychical conditions for such abnormal states of consciousness. We may distinguish in general, in accordance with what has been said about the attributes of psychical processes and their interconnection in consciousness three kinds of such conditions.
They may consist 1) in the abnormal character of the psychical elements, 2) in the way psychical compounds are constituted, and 3) in the way psychical compounds are combined in consciousness. As a result of the intimate interconnection of these different factors it scarcely ever happens that one of these three conditions, each of which may appear in the most various concrete forms, is operative alone; but they usually unite. The abnormal character of the elements results in the abnormity of the compounds, and this in turn brings about changes in the general interconnection of conscious processes.
2.The psychical elements, sensations, and simple feelings, show only such changes as result from some disturbance in the normal relation between them. and their psycho-physical conditions.
For sensations such changes may be reduced to [p. 268] an increase or decrease of the sensitivity for stimuli (by hyper-aesthesia, and anaesthesia) resulting especially from the of certain physiological influences in the sensory centres. The most important psychological symptom in this case is the increased excitability which is one of the most common components of complex psychical disturbances. In similar fashion,. changes in the simple feelings betray themselves in states of depression or exaltation as a decrease or increase in the affective excitability.
These different states may be recognized from the way in which the emotions and volitional process occur. Thus, changes in the psychical elements can be demonstrated only by the influence that they exercise on the character of the various psychical compounds.
3. The defects in ideational compounds arising from peripheral or central anaesthesia are generally of limited importance. They have no far-reaching effect on the interconnection of psychical processes. It is essentially different with the relative increase in the intensity of sensations resulting from central hyperaesthesia. Its effect is especially important because under such circumstances reproduced sensational elements may become as intense as external sense-impressions.
The result may be that a pure memory-image is objectified as a sense-perception.
This is an hallucination. Or, when elements axe united which are partly from direct external: stimulation, partly from reproduction, the sense-impression may be essentially modified through the intensity of the reproduced elements. The result is then an illusion of fancy. [ 1 ] [p. 269]
The two are not always distinguishable.
In many cases, to be sure, particular ideas can be shown to be illusions of fancy, but the presence of pure hallucinations is almost always doubtful because it is so easy to overlook some direct sensational elements. In fact, it is by no means improbable that the great majority of so-called hallucinations are illusions. These illusions are in their psychological character nothing but assimilations (p. 228 sq.). They may be defined as assimilations in which the reproduced elements predominate. Just as normal assimilations are closely connected with successive associations, so for the same reason the illusions of fancy are closely related to the changes in the associative ideational processes to be discussed later (5).
4. In the case of complex affective and volitional processes the abnormal states of depression and exaltation are clearly distinguishable from the normal condition. The state of depression is due to the predominance of inhibitory, asthenic emotions, that of exaltation to a predominance of exciting, asthenic emotions, while at the same time we observe, in the first case a retardation or complete checking of resolution, in the second an exceedingly rapid, impulsive activity of the motive. In this sphere it is generally more difficult to draw the line between normal and abnormal conditions than in that of ideational compounds, because even in normal mental life the affective states are continually changing. In pathological cases the change between states of depression and exaltation, which are often very striking, appear merely as an intensified oscillation of the feelings and emotions about an indifference-condition (pp. 34, 80). States of depression and exaltation are especially characteristic symptoms of general psychical disturbances; their detailed discussion must therefore be left to psychical pathology. General psychical disturbances are always symptoms of diseases of the brain, so [p. 270] that these abnormities in affective and volitional processes are doubtless accompanied, like those of the sensations and ideas, by physiological changes. The nature of these changes is, however, still unknown. We can only surmise, in accordance with the more complex character of affective processes, either. that they are more extensive than the changes in central, excitability accompanying hallucinations and illusions, or that they effect the central cortical regions directly concerned in apperceptive processes.