 The fourth and final option to consider is to take the derivability of CBF in tense and modal logic at face value, and embrace the conclusion that existence is indeed immutable and necessary. These are the theses that Williamson (2013) calls “permanentism” and “necessitism”. The task for each approach is to explain our initial reluctance to embrace them in the first place. Take the apparent resistance to accept the claim that Socrates will always be something despite the fact that he died in 399 BCE. The permanentist may respond that if we are initially disinclined to accept this claim, it is only because we mistakenly think that because a person, for example, is a concrete object, a past or a future person must be concrete as well. Socrates, which is a past person, was not a person either before 490 BCE or after 399 BCE; indeed, Socrates is now not a person, nor will he be one in the future. Likewise, a merely possible person need not be a person either and neither the Barcan nor the Converse Barcan Formula threaten the temporary and contingent character of concreteness. Since I could have found the time, skill and energy to build a bookcase, some object is possibly a bookcase built by me. But the necessitist will be at pains to add that to be a possible bookcase built by me is not to be a bookcase built by me, much less a bookcase. This outlook is defended by Linsky &amp; Zalta (1994) and Williamson (2013). But there are other points of contact. For example, all versions of necessitism must reject unqualified “essentialist” theses such as the view that a person is necessarily a person; at most, one can perhaps maintain the weaker thesis that a person is necessarily if concrete, a person. Likewise, all versions of necessitism seem committed to the actual existence of many more nonsets than can form a set. Sider (2009), for example, argues that necessitism is committed to the actual existence of at least \(\kappa\) nonsets for each set-theoretic cardinal \(\kappa\). And Hawthorne &amp; Uzquiano (2011) raises other cardinality problems for a combination of necessitism with certain common mereological assumptions.