 The interaction between pure quantificational logic and tense and modality suggests the domain of ontology is immutable and necessary. But we can only draw these conclusions by making use of some auxiliary assumptions, some of which are far from obvious. The highly counterintuitive character of the conclusions has consequently led many philosophers to place some of the auxiliary assumptions under close scrutiny. Other philosophers have followed argument where it leads, and they have sought to reconcile the eternal and necessary character of the domain of ontology with the apparent temporary and contingent character of existence. In fact, Williamson 2013 set out to provide a separate battery of arguments for the necessity and immutability of ontology.