 So the constructive empiricist is firm in her construal of the aim of science as truth about the observable. One might worry, though, as James Ladyman (2000) does, that such a view brings with it a commitment to modal realism and belief in whatever entities such a commitment may require. So, for instance, talk of observability might commit the constructive empiricist to belief in the existence of possible worlds, a commitment that an empiricist would prefer not to make.