 An objection more specifically directed toward efforts at extending rigidity to expressions for just kinds and properties, is that such efforts would also have to extend the status of rigidity to terms for artificial kinds or properties (see, e.g., Glüer and Pagin 2011; Haukioja 2012; Nimtz 2019; Schwartz 2002; 2018; 2020; whether this vast application of rigidity should be thought problematic might be questioned:  see e.g., Salmon 2005). The singular terms ‘soda pop’, ‘bachelorhood’, ‘livestock’ and so on, would also seem to designate an abstract object rigidly (soda pop, bachelorhood, livestock, respectively), if terms for natural kinds and natural properties do so. So the foregoing proposal for the rigidity of kind and property terms might be thought to be too indiscriminate in what it allows to be rigid—maybe even so indiscriminate that it mistakes sameness of meaning across possible worlds, which every meaningful expression enjoys, for sameness of designation, which only rigid designators are supposed to have (Schwartz 2002, p. 272; 2020, p. 263n.). 