 (See Thomson 1983, Simons 1987: §5.2, Masolo 2009, Giaretta and Spolaore 2011; see also Kazmi 1990 and Hovda 2013 for tensed versions of this strategy.) The need to relativize parthood to time, and perhaps to other parameters such as space, possible worlds, etc., has recently been motivated also on independent grounds, from the so-called “problem of the many” (Hudson 2001) to material constitution (Bittner and Donnelly 2007), modal realism (McDaniel 2004), vagueness (Donnelly 2009), relativistic spacetime (Balashov 2008), or the general theory of location (Gilmore 2009, Donnelly 2010). One way or the other, then, such revisions may be regarded as an indicator of the limited ontological neutrality of extensional mereology. But their independent motivation also bears witness to the fact that controversies about (28) stem from genuine and fundamental philosophical conundrums and cannot be assessed by appealing to our intuitions about the meaning of ‘part’.