  Aristotle sometimes criticizes Democritus for claiming that visible, audible, olfactory and gustatory sensations are all caused by touch (DK 68A119).  Quite how this affects the account of perception is not clear, as the sources tells us little about how touch is thought to work.  Democritus does not, however, seem to distinguish between touch and contact, and may take it to be unproblematic that bodies communicate their size, shape and surface texture by physical impact. 