We develop a new theory of the cognitive changes around 4 years of age by trying to explain why understanding of false belief and of alternative naming emerge at this age (Doherty & Perner, 1998). We make use of the notion of discourse referents (DR: Karttunen, 1976) as it is used in File Change Semantics (Heim, 2002), one of the early forms of the more widely known Discourse Representation Theory (Kamp & Reyle, 1993). The assumed cognitive change exists in how children can link DRs in their mind to external referents. The younger children check whether the conditions for a DR match the conditions of an external entity (an implicit/procedural understanding of reference). The older children, in addition, have an explicit understanding of reference in virtue of making explicit identity assertions. This involves the metarepresentational ability of representing that different DRs represent the same external referent, which — we argue — is required for alternative naming and for the false belief task.