 Structuralism’s stand on the Demarcation Problem is by and large an open question. Unlike similarity, which has been widely discussed across different domains, structural mappings are tied closely to the formal framework of set theory, and have been discussed only sparingly outside the context of the mathematized sciences. An exception is French (2003), who discusses isomorphism accounts in the context of pictorial representation. He considers in detail Budd’s (1993) account of pictorial representation and points out that it is based on the notion of a structural isomorphism between the structure of the surface of the painting and the structure of the relevant visual field. Therefore representation is the perceived isomorphism of structure (French 2003: 1475–1476) (this point is reaffirmed by Bueno and French (2011: 864–865); see Downes (2009: 423–425) and Isaac (2019) for critical discussions).