Helmholtz 2005 [1924] fully accepts the need for local signs in two-dimensional spatial localization, but makes an important modification to Lotze’s theory. In particular, he maintains that local signs are not feelings that originate in the adjustment of the ocular musculature, i.e., a form of afferent, sensory “inflow” from the eyes, but rather feelings of innervation (Innervationsgefühlen) produced by the effort of the will (Willensanstrengung) to move the eyes, i.e., a form of efferent, motor “outflow”. In general, to each perceptible location in the visual field there is an associated readiness or impulse of the will (Willensimpuls) to move eyes in the manner required in order to fixate it. As Ernst Mach later formulates Helmholtz’s view: “The will to perform movements of the eyes, or the innervation to the act, is itself the space sensation” (Mach 1897 [1886]: 59).