 Alternatively, one might choose to insist that if anything at any possible world is Vulcan, it has to possess at that world the properties relevant to the introduction of the name ‘Vulcan’, such as being the heavenly body with such-and-such mass and orbit and other astrophysical characteristics and being between Sun and Mercury in a Newtonian universe. This is supported by descriptionism concerning the semantics of proper names, according to which ‘Vulcan’ is a proper name which is semantically equivalent to a definite description (‘the heavenly body with such-and-such mass and ...’). But forceful criticisms of descriptionism for proper names were launched in the early 1970s (Donnellan 1972, Kripke 1972). Kripke’s criticism has been especially influential. The kernel of Kripke’s criticism rests on the intuitive idea that a sentence containing a referring proper name expresses a singular proposition about the referent independently of any qualitative characterization of the referent but that a corresponding sentence containing a description does not so express a singular proposition. If Kripke’s criticism applies to ‘Vulcan’, it is difficult to defend descriptionism for ‘Vulcan’. But ‘Vulcan’ and other apparent proper names of non-actual possible objects may not be as readily amenable to the Kripkean considerations as proper names of actual objects are. The so-called “problem of empty names” is the problem of providing a semantic theory for “empty names” like ‘Vulcan’ as non-descriptional designators. For some recent contributions to the project of solving this problem, see Braun 1993, 2005, Everett &amp; Hofweber 2000, Brock 2004, Piccinini &amp; Scott 2010, Cullison &amp; Caplan 2011, Kripke 2013.