 Either schema will be adequate to yield the other, given the standard inter-definition of possibility and necessity, provided enough logical machinery is available for reasoning within the scope of the “according to the fiction” operator. As a matter of fact, the above is a simplification, since, according to Rosen (1990, p. 335), what is true according to the fiction of possible worlds may be only a proposition connected with P: the paraphrase of P into the language of possible worlds. In general, for Rosen, this will be the analysis of P in Lewis’s theory of possible worlds. Rosen states the form of the fictionalist biconditionals at its most general as: