 Hyman’s theory has been criticised on various grounds. First, and most generally, Michael Podro argues that it expresses a bias in favour of realistic or literal representation (Podro 2010: 457). However, Hyman replies that the optical principles he defines “do not dictate or limit the forms artists create, the models they follow, or the values they embody in their work”, any more than English grammar limits the imagination of English poets (Hyman 2012: 145). Second, it has been alleged that Hyman’s theory cannot explain “the depiction of nonexistent objects” (Abell 2009: 195). However, this objection depends on the questionable assumption that resemblance is invariably a relation between existing particulars (see above  §1.1).  Third, it has been argued that indeterminacies in the occlusion shapes of objects represented in a picture may not match the indeterminacies in the shapes of the parts of the picture that depict them (Kulvicki 2014: 61–62). Finally, it has been argued more generally that the exact correspondences in shape and colour between the surface of a picture and its content, which Hyman’s theory predicts, sometimes break down; and that the correspondences which do exist depend on contingent features of the human visual system (Newall 2006; Hyman 2007; Newall 2011).