 Apart from any objections that might be leveled at strong modal fictionalism, the advocate of this variety of modal fictionalism faces the challenge of stating the contents of the modal fiction without relying on modal notions in a way that would make the explanation of those modal notions circular. Since the fiction explains the truth of modal claims, explaining the content of the modal fiction by reference to modal claims would be circular (e.g., by stipulating that all of the propositions which are necessary hold in all worlds, or that objects have in all worlds in which they exist the properties which they in fact have essentially). Stating, in non-modal terms, general principles about possible worlds that would enable one to determine, when presented with a proposition, whether it holds at all worlds, at some but not others, or none, is a difficult and controversial matter. Plausibly, a strong modal fictionalist will owe us such a non-modal specification of the contents of the modal fiction, if our understanding of the contents of the modal fiction is to allow us a useful method of assessing the truth of modal claims. Furthermore the strong modal fictionalist seems committed to there being a fact of the matter about the content of the modal fiction which is not itself to be explained or analysed in terms of further modal facts of the matter. 