  Gilbert’s account differs from Lewis’s in both ontology and ideology. Ontologically, Gilbert isolates a sui generis entity, the plural subject, that Lewis’s “individualistic” approach does not countenance. Gilbert argues that a population could instantiate a Lewisian convention without giving rise to a plural subject. Participants in a Lewisian convention may prefer that other participants conform to it, given that almost everyone does. But they need not regard themselves as responsible for enforcing it or for helping others conform. They would so regard themselves if they viewed themselves as belonging to a plural subject. Thus, a Lewisian convention does not ensure that its adherents constitute a plural subject.