 Since most philosophers who invoke the distinction want to reject “thing”, “object” and “entity” as non-sortals, Griffin’s suggestion is inadequate, or at least is a shift to a different concept with the same label. The question “How many things/objects/entity are in the space S?”, where S is an empty space has the determinate answer “zero”, so all of these terms pass the Griffin standard. One could attempt to amend the criterion by requiring that there can be cases which satisfy the above criteria and where there is at least one A. However, this fails to delineate the right cases, because there are sortals such as “unicorn” and “square circle” which have no instances. These points, and the observation that some of the various notions of sortal diverge, were first made in Feldman 1973 but have not been widely noted (see the entry on relative identity). We will revisit some of these issues in  Section 7.1  on sortals and infant cognition.