This is the fourth paper in a series proposing a psychoanalytic concept of community. The third paper of the series centered on the unconscious psychological tasks involved in creating and sustaining a community and in it achieving its reason for existence; tasks such as the formation of bonds, identity and boundary. In this fourth paper we propose that the effectiveness with which a community can carry out these tasks determines how well that community is able to function. The successful performance of the tasks is dependent on: (1) a community's capacity for psychic function, that is, its capacity to process internal tension and conflict, and both everyday and adverse experiences; (2) the effectiveness of its social defense against anxiety; and (3) its adaptability to changes and challenges in its environment.