  Armstrong's rejection of possible worlds is not exactly a nominalistic stance about them since his opposition to them is not based on their alleged abstract character. In believing that possible worlds do not exist, Armstrong is rather a kind of fictionalist about possible worlds, and so he calls himself (1989, 49). But if one believes that possible worlds do not exist, and so one is a fictionalist about possible worlds in this sense, one can also be a fictionalist about possible worlds in a different sense, namely the sense of so-called modal fictionalism. According to modal fictionalism sentences with an apparent quantification over possible worlds must be understood as quantification within the scope of a story prefix (Rosen 1990, 332). Let PW be a theory that postulates possible worlds. ‘According to PW’ is then a story prefix.[30] Thus the modal fictionalist says that when he utters ‘There is a possible world where there are blue swans’ what he is really saying is that according to PW there is a world where there are blue swans (Rosen 1990, 332). But since quantification within a story prefix is not existentially committing, the modal fictionalist can utter things like ‘Since there might have been blue swans, there is a possible world where there are blue swans’ without committing himself to possible  worlds.[31] 