 Helmholtz was inspired by the theory of  Hermann Lotze  (1817–1881) in his explanation of these phenomena. For Lotze, Helmholtz observes, “to the sensations from spatially distinct nerve endings correspond various determinate Localzeichen [literally: place signs], whose spatial meaning is learned” (Helmholtz 1968 [1869], 57). My various sensations of my finger are originally unrelated, but I can relate them to each other by means of the concept “my finger,” which serves as a mental Localzeichen that contains the data of all the sensations. The space of perception is a general Localzeichen that relates all possible sensations to each other. The usefulness of Lotze’s theory is that all psychological sensations are mapped directly onto mental concepts, and even space becomes a tool for constructing an interpretation of sense-data, akin to a language. 