Moreover, it is also unclear whether the nominalization program advanced by the mathematical fictionalist can be extended to other scientific theories, such as quantum mechanics (Malament 1992). Mark Balaguer responded to this challenge by trying to nominalize quantum mechanics along mathematical fictionalist lines (Balaguer 1998). However, as argued by Bueno (Bueno 2003), Balaguer's strategy is incompatible with a number of interpretations of quantum mechanics, in particular with Bas van Fraassen's version of the modal interpretation (van Fraassen 1991). And given that Balaguer's strategy invokes physically real propensities, it is unclear whether it is even compatible with nominalism. As a result, the nominalization of quantum mechanics still remains a major problem for the mathematical fictionalist.