Since its inception some fifty years ago cognitive science has seen a number of sea changes. Perhaps the best known is the development of connectionist models of cognition as an alternative to classical symbol-based approaches. A more recent - and increasingly influential - trend is that of dynamical-systems-based ecologically oriented models of the mind. Researchers suggest that a full understanding of the mind will require systematic study of the dynamics of interaction between mind body and world. Some argue that this new orientation calls for a revolutionary new metaphysics of mind according to which mental states and processes and even persons literally extend into the environment. This is a state-of-the-art guide to this new movement in cognitive science. Each chapter tackles either a specific area of empirical research or specific sector of the conceptual foundation underlying this research.