Presents a theoretical analysis of the representational mechanism underlying a child’s ability to pretend. This mechanism extends the power of the infant’s existing capacity for (primary) representation, creating a capacity for ‘metarepresentation.’ It is this, developing toward the end of infancy, that underlies the child’s new abilities to pretend and to understand pretense in others. There is a striking isomorphism between the 3 fundamental forms of pretend play and 3 crucial logical properties of mental state expressions in language. This isomorphism points to a common underlying form of internal representation that is here called metarepresentation. A performance model, the ‘decoupler,’ is outlined embodying ideas about how an infant might compute the complex function postulated to underlie pretend play. This model also reveals pretense as an early manifestation of the ability to understand mental states. Aspects of later preschool development, both normal and abnormal, are discussed in the light of the new model.