X.
Reference has already been made to the different character of the groups of elements that we have designated by A B C … and α β γ. As a matter of reality, when we see a green tree before us, or remember a green tree, that is conceive a green tree to ourselves, we know right well how to distinguish these two cases. The imaged tree has a much less determinate, a much more changeable form; its green is much paler and more evanescent; and, what is of especial note, it distinctly appears in a different sphere. A movement that we propose to execute is always only a conceived movement, and appears in a different field or sphere from that of the executed movement, which moreover always takes place where the image becomes vivid enough. The statement that the elements A or α appear in a different sphere, means, if we go to the bottom of it, nothing more than that they are united with divers other elements. To this extent, accordingly, the basal component parts in A B C …, α β γ … would be the same (colors, sounds, spaces, times, motory sensations, innervations …), and only the character of their union different.
Pain and pleasure are ordinarily regarded as different from sensory sensations. Yet not only tactile sensations, but also all other kinds of sensations, can gradually pass into pleasure and pain. Pleasure and pain can also justly be called sensations. Only they are not so well analysed and so familiar as sensory sensations. Sensations of pleasure and pain, however faint the mode of their appearance, make up indeed the real content of all so-called feelings. Thus perceptions, as well as ideas, volition, and feelings, in short the entire inner and outer world, are composed of a small number of homologous elements united in relations now more evanescent and now more lasting. These elements are commonly called sensations. But since vestiges of a one-sided theory now inhere in this term, we prefer to speak simply of elements, as we have already done. All research aims at the resolution of the union of these elements.[21]
[21] Compare the remarks appended to my treatise: Die Geschichte und die Wurzel des Satzes der Erhaltung der Arbeit. Prague. Calve. 1872.