Note 5 — Chapter IX

This empirical law of the relation between body and soul consists in the fact that consciousness everywhere ceases, if the bodily activity upon which it depends sinks below a certain degree of strength, which is called the threshold. Now in proportion as it extends itself more widely, can it the more easily, on account of the accompanying weakness, fall below this level. As the total consciousness has its threshold, which makes the dividing line between sleeping and waking in the whole man, so, too, is it with the details of consciousness, whence it comes that during waking now this, now that idea presents itself or sinks out of sight, according as the particular activity upon which it depends rises above or sinks below the special threshold. (Compare “Elem. der Psychophysik,” Kap. X, XXXVIII, XXXIX, and XLII.)