Patrolling the Mind's Boundaries

Defenders of the extended mind thesis say that it is possible that some of our mental states may be constituted, in part, by states of the extrabodily environment. Often they also add that such extended mentation is a commonplace phenomenon. I argue that extended mentation, while not impossible, is either nonexistent or far from widespread. Genuine beliefs as they occur in normal biologically embodied systems are informationally integrated with each other, and sensitive to changes in the person's overall system of beliefs. Environmental states, however, fail to satisfy this central feature of the functional role of belief, and hence fail to be genuine mental states.