 Fictions are human products: they have authors, and those authors have a good deal of control over what is true according to them (though exactly how much control is controversial). Alternatively, if it is thought that fictions are timeless Platonic abstract entities (sets of propositions, perhaps), we should say that which fictions we consider and express is a matter of human activity: and the ‘authors’ of those eternal Platonic fictions actually expressed have a good deal of control over which of a variety of such fictions they express. However, “theoretical fictions” introduced as an alternative to realist theories, and which are supposed to play a serious role in inquiry, do not seem to be able to be as arbitrary. Not any old story told about possible worlds will serve as the modal fiction, at least if it is to provide the heuristic and other advantages of talk about possible worlds. The suspicion is that in some respects talk of possible worlds cannot be like paradigm fiction, since the ‘choice’ of which story about possible worlds should count as the modal fiction is not as up to us as what to say about Sherlock Holmes was up to Conan  Doyle.[6] 