The chapter examines a realization-based interpretation of the extended mind thesis, which holds that cognitive states belong to an organismically bounded system but can have physical implementations that extend beyond the organism's boundary. Functionalism and the concept of physical realization in philosophy of mind are explained in detail. The author argues that this extension-friendly approach to realization is untenable: it either undermines the examples that motivate the extended view or becomes too liberal to be useful in cognitive science. The difficulty arises because standard examples of extended cognitive processing involve interactions with the environment, yet during these interactions, the realizers of the cognitive states are distinct from the things the system interacts with.
The philosophical hypothesis of extended cognition holds that human cognitive processes literally include elements beyond the body, such as tools or the environment. This book argues against that view, defending a systems-based approach that places the boundary of cognitive systems at the human organism. It contends that this systems-based view explains the successes of cognitive psychology better than extended conceptions do, and that once adopted, it reveals flaws in arguments for extended cognition. The book also examines embedded and embodied views, concluding that they do not radically depart from orthodox computational cognitive science, and that the embodied view offers no fundamentally new role for the nonneural body.