 Hirsch’s doctrine of quantifier variance QV dominates current metaontological debate. Some have questioned whether interpreters on one side of an ontological dispute can admit that the language of those on the other side is possible. For to do so each interpreter must be able to provide a Tarskian semantics for the other’s language. But an Endurantist won’t be able to do this for the Perdurantist’s sentence such as ‘Alicet is a temporal part of Alice’ since the predicate ‘is a temporal part of’ has an empty extension in the Endurantist’s language [Hawthorne 2006; Eklund 2009]. Others suspect QV is an internally unstable position: how can an Endurantist speaking her language E allow that a sentence like ‘Alicet is a temporal part of Alice’ is a true sentence of the Perdurantist’s language P without admitting that there are temporal parts [e.g. Hale and Wright 2009; Dorr 2014]? Warren 2015 provides a convincing QV response to this ‘Collapse’ argument. An important resource, containing papers by some of the authors cited, is the collection of essays anthologised in Chalmers et al 2009 [For background on mereology see the entry  mereology  and for discussion of whether there are composite objects, see the entry  material constitution  and the entry  ordinary objects].  