Midway between these two groups are the imaginers in whom the internal life predominates in the form of combinations of images, which fact distinguishes them clearly from the abstractors. The former alone interest us, and we shall try to trace this imaginative type in its development from the normal or average stage to the moment when ever-growing exuberance leads us into pathology. The explanation of the various phases of this development is reducible to a well-known psychologic law--the natural antagonism between sensation and image, between phenomena of peripheral origin and phenomena of central origin; or, in a more general form, between the outer and inner life. I shall not dwell long on this point, which Taine has so admirably treated.[149] He has shown in detail how the image is a spontaneously arising sensation, one that is, however, aborted by the opposing shock of real sensation, which is its reducer, producing on it an arresting action and maintaining it in the condition of an internal, subjective fact. Thus, during the waking hours, the frequency and intensity of impressions from without press the images back to the second level; but during sleep, when the external world is as it were suppressed, their hallucinatory tendency is no longer kept in check, and the world of dreams is momentarily the reality. The psychology of the imaginer reduces itself to a progressively increasing interchange of roles. Images become stronger and stronger states; perceptions, more and more feeble. In this movement opposite to nature I note four steps, each of which corresponds to particular conditions: (1) The quantity of images; (2) quantity and intensity; (3) quantity, intensity and duration; (4) complete systematization.