  By ascribing the causes of sensible qualities to relational properties of atoms, Democritus forfeits the prima facie plausibility of claiming that things seem P because they are P.  Much of Theophrastus' report seems to focus on the need to make it plausible that a composite can produce an appearance of properties it does not have.  Democritus is flying in the face of at least one strand of commonsense when he claims that textures produce the appearance of hot or cold, impacts cause colour sensations.  The lists of examples offered, drawing on commonsense associations or anecdotal experience, are attempts to make such claims persuasive.  Heat is said to be caused by spherical atoms, because these move freely: the commonsense association of quick movement with heating is employed.  The jagged atoms associated with bitter taste are also said to be heat-producing: there, the association of heat with friction is invoked.  It is not so much the specific intrinsic qualities—smooth or jagged shape—as the motion of those shapes that provides the explanation. 