This book develops a theory of how the imagination functions, and how it evolved. The imagination is characterized as an embodied cognitive system. The system draws upon sensory-motor, visual, and linguistic capacities, but it is a flexible, developmental ability, typified by creative improvisation. The imagination is a voluntary simulation system that draws on perceptual, emotional, and conceptual elements, for the purpose of creating works that adaptively investigate external (environmental) and internal (psychological) resources. Beyond the adaptive useful values of this system, imagination also possesses significant intrinsic value (e.g., in the joy of play, and states of wonder). The book argues that imagination is not a late arrival in the evolution of mind, but one of the earliest human abilities