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Rh that slowly changes the place of its summit. If we call this the under-wave, then the movements of shorter period, on which the more special conscious states depend, can be symbolized by wavelets superposed upon the under-wave, and we can call these over-waves. They will cause all sorts of modifications of the under-wave's surface, and the total wave will be the resultant of both sets of waves.

"The greater, now, the strength of the movements of short period, the amplitude of the oscillations of the psycho-physical activity, the higher will the crests of the wavelets that represent them rise above, and the lower will their valleys sink below the surface of the under-wave that bears them. And these heights and depressions must exceed a certain limit of quantity which we may call the upper threshold, before the special mental state which is correlated with them can appear in consciousness" [pp. 454-456].

"So far now as we symbolize any system of psycho-physical activity, to which a generally unified or principal consciousness corresponds, by the image of a total wave rising with its crest above a certain 'threshold,' we have a means of schematizing in a single diagram the physical solidarity of all these psycho-physical systems throughout Nature, together with their pyscho-physicalpsycho-physical [sic] discontinuity.