ABSTRACT
But even if sensations are not literally extended, it is still an open question whether there is something in the coexisting order of sensations that corresponds or is analogous to the spatial order of qualities that occasion them. According to Reid, there is indeed a covariance between the qualities in the external objects affecting the sense organs and the sensations they occasion. This covariance does not imply that sensations and qualities are literally similar to each other. For example, the sensation caused by hardness is different from the sensation caused by color, and both are different from the sensation caused by sound, and so on for different sensations and their causes. Moreover, as a quality varies in degree the sensation that ensues also varies in degree without the two ever being literally similar to each other.9 It is then legitimate to ask whether there is something in each sensation that corresponds or stands in a one-to-one relation to the location in space of the quality (or perhaps only to the location in space of the part of the sense organ affected either directly or indirectly by the quality). In early nineteenth-century German psychology this aspect of an unextended sensation correspondent to the particular point of stimulation of our sense organs was called a ‘local sign.’10 A local sign does not make the sensation itself actually located in space or extended, but stands in a one-to-one sign-signifier relation to a particular location in our body. If we reject the existence of local signs, or, in Reid’s terms, the existence of sensations appropriated to specific locations, we are then espousing a more radical reading of the thesis that sensations do not resemble the qualities of material objects. Without local signs it would not even be possible to construct an abstract topology of sensations that could be interpreted according to the model given by the space we ultimately end up perceiving.
