 the estimation of the intensity of sensation (Empfindungsintensität) is a complicated process, upon which—in addition to the central sensory excitation—the effectiveness of the center of apperception will exert considerable influence. We can obviously say nothing immediate about how the central sense-excitations would be sensed independently of the latter; thus Weber’s Law, too, concerns only apperceived sensations, and therefore can just as well have its basis in the processes of the apperceptive comparison of sensation as in the original constitution of the central sensory excitations. (PP I: 391–2)