It is the traditional view of psychology that the attributes of sensation show a one-to-one correspondence to the dimensions of the stimulus. Some such view is also implicit in the naïve epistemology of the physicist. He often thinks of pitch as if it were the perception of the frequency of a tone, but that view soon runs into difficulties. Within psychology it was Wundt who originally equipped sensation with two attributes, quality and intensity, thus making sensations mirror the more obvious (...) aspects of stimuli which differ as to kind and in degree. Later it became clear to Külpe that extension must be an attribute of visual and tactual sensations because the retina and the skin are areal organs and because extent enters into perception quite as ‘immediately’ as does intensity. A loud sound is not a congeries of faint sounds, nor is a perceived line a row of sensations. In a similar reaction against Wundtian atomism Külpe also added duration to the list, for a tone that lasts 0.8 sec. yields a different perception from one that lasts 0.6 sec. and yet there is no sense to saying that the first represents a greater number of seried sensations than the second. Thus the four classical attributes of sensation are quality, intensity, extensity and protensity. The conventional view has been that they are respectively correlated with four aspects of the stimulus, and this paper is written with the intention of refuting this view. (shrink)