 Structuralism about physics is sometimes formulated in terms of the distinction between extrinsic and intrinsic properties (Chalmers 1996: 153–55; see the entry  intrinsic vs. extrinsic properties).  But those formulations have been challenged on similar grounds: a ball’s sphericality is usually counted among its intrinsic properties, as are other properties in terms of which physical theory characterizes its basic entities (Ney 2015; Stoljar 2015). (We will henceforth use ‘extrinsic’ and ‘relational’ interchangeably, and likewise for ‘intrinsic’ and ‘non-relational’.) It might therefore be preferable to explicate the structural/non-structural distinction in a different way.