Intellectual development is primarily considered a domain specific enterprise. Children develop naïve physics, a folk psychology (theory of mind), a naïve biology, etc. But understanding perspective is a general, overarching phenomenon that cuts across such domains in development and in the brain. This has important theoretical consequences. For instance, our folk psychology cannot consist of a uniform "theory of mind" for explaining behaviour. Parts of the theory that are sensitive to perspective differences have to be separated from those that are not. A central concern is how perspective is represented in the mind. The answer comes from mental files theory. A mental file represents or refers to an object. It presents the object under a particular mode of presentation-perspective. Coreferential files refer to the same object and present the object under different perspectives. Files, thus, give us a concrete way to capture perspectives with the tools for basic object cognition. This book introduces mental files theory in relation to object files and discourse referents and then applies it to the development of perspective taking in early childhood and to brain imaging. The theory goes well beyond perspective; it is the theoretical tool for representing persisting objects, tracking them over time, and storing knowledge about them. From a leading figure in developmental psychology, this book addresses a topic much neglected in the cognitive sciences. The Context and Content series is a forum for outstanding original research at the intersection of philosophy, linguistics, and cognitive science. The general editor is François Recanati (Institut Jean-Nicod, Paris).