 But Priest’s proposal has difficulties of its  own.[25]  To mention some of them: First, Priest does not give a principled characterization of which properties are existence-entailing and which are not (which looks quite similar to the problem with the nuclear-extranuclear distinction which Priest points out in the above quotation). Second, it remains unclear which properties nonexistent objects have in the actual world (apart from logical properties like being self-identical and intentional properties like being thought of by  Priest).[26]  Furthermore, Priest’s noneism raises difficult questions about cross-world identity and the ontological status of non-actual worlds. The ontological status of non-actual worlds is far from obvious: they may be taken to be concrete objects (structured sets of physical objects) or abstract objects (sets of sentences, propositions, or states of affairs). (For an elaborate survey of various conceptions of non-actual worlds see the entry on  possible worlds, i.e., Menzel  2014.)[27]  Apart from this, it is doubtful whether Priest’s theory provides an adequate account of fictitious objects. Among other things, it does not do justice to the widespread intuition that fictitious objects are created by the authors of the stories to which they  belong.[28]