 J. J. C. Smart (1953) criticized Ryle’s criterion for drawing category distinctions on grounds that it could apparently be used to establish a category difference between any two expressions whatsoever. “Thus ‘the seat of the – is hard’ works if ‘chair’ or ‘bench’ is put into the blank, but not if ‘table’ or ‘bed’ is. And if furniture words do not form a category, we may well ask what do” (1953, 227). Without a test for absurdity apart from a certain kind of intuitive unacceptability to native speakers, we seem to be left without a means of declaring ‘Saturday is in bed’ to be a category violation but ‘The seat of the bed is hard’ not to be. Bernard Harrison attempts to meet this challenge by distinguishing the sorts of inappropriateness that result from violations of category facts (such as the former) from those that result from mere violations of facts of usage (the latter) (1965, 315–16). The use of the term ‘bed’ could conceivably be extended in ways that would make ‘The seat of the bed is hard’ acceptable (e.g., if beds came to be made with seats), whereas ‘Saturday’ could not conceivably be extended in a way that would make ‘Saturday is in bed’ acceptable – any such attempted ‘extension’ would just involve using ‘Saturday’ homonymously (e.g., as the name for a day of the week and for a person) (1965, 316–18). For further discussion of intersubstitutability approaches to drawing category distinctions, see Westerhoff (2005, 40–59 and 2002, 338–339). Westerhoff (2004) develops a method of distinguishing categories based on substitutability in worldly states of affairs rather than language.