VII. Inner Processes in the Human Organism. Sense-Perception, Breathing, Sleeping, Waking, Memory

At this point we must think of how man is subject to the alternating states of waking and sleeping life. Sense-perception too is subject to alternation. Perceptions would not have the right effect upon our consciousness if we were not able continually to interrupt the process involved. You know from purely external experiences that prolonged surrender to a sense-perception impairs consciousness of it. We must again and again withdraw from a given sense-impression, that is to say, we must alternate between the impression and a condition when we have no impression. For our consciousness to be normal as regards sense-impressions depends upon our being able also to withdraw the senses from the impression that is being made upon them; sense-perception must always be subject to these brief alternating conditions. These alternations also occur in longer periods of our life, for we alternate once in every twenty-four hours between waking and sleeping.