 Thomson-Jones (2010: 284) refers to such a description as a “description of a missing system”. These descriptions are embedded in what he calls the “face value practice” (2010: 285) the practice of talking and thinking about these systems as if they were real. The face-value practice raises a number of questions. What account should be given of these descriptions and what sort of objects, if any, do they describe? Are we putting forward truth-evaluable claims when putting forward descriptions of missing systems?