not excited by sensory stimuli... but it is not the lack of sensory stimuli that conditions sleep, but rather a lack of interest for the same; some sensory impressions are even necessary in so far as they serve to calm the mind; thus the miller can fall asleep only when he hears the rattling of his mill, and he who finds it necessary to burn a light at night, as a matter of precaution, cannot fall asleep in the dark" (p. 457).
"The psyche isolates itself during sleep from the outer world, and withdraws from the periphery.... Nevertheless, the connection is not entirely interrupted; if one did not hear and feel even during sleep, but only after awakening, he would certainly never awake. The continuance of sensation is even more plainly shown by the fact that we are not always awakened by the mere sensory force of the impression, but by the psychic relation of the same; an indifferent word does not arouse the sleeper, but if called by name he awakens...: hence the psyche differentiates sensations during sleep.... It is for this reason that we may be awakened by the lack of a sensory stimulus if it relates to the presentation of an important thing; thus one awakens when the light is extinguished, and the miller when the mill comes to a standstill; that is, the awakening is due to the cessation of a sensory activity, which presupposes that it has been perceived, and that it has not disturbed the mind, being indifferent or rather gratifying" (p. 460, &c.).
If we are willing to disregard these objections, which are not to be taken lightly, we still must admit that the qualities of the dream life thus far considered, which originate by withdrawing from the outer world, cannot fully explain the strangeness of the dream. For otherwise it would be possible to change back the hallucinations of the dream into presentations and the situations of the dream into thoughts, and thus to perform the task of dream interpretation. Now this is what we do when we reproduce the dream from memory after awakening, and whether we are fully or only partially successful in this back translation the dream still retains its mysteriousness undiminished.
Furthermore all the authors assume unhesitatingly that still other more far-reaching alterations take place in the presentation material of waking life. One of them, Strümpell,66
