The social system is made up of the actions of individuals. The actions which constitute the social system are also the same actions which make up the personality systems of the individual actors. The two systems are, however, analytically discrete entitites, despite this identity of their basic components. The "individual" actor as a concrete system of action is not usually the most important unit of a social system. For most purposes the conceptual unit of the social system is the role. A social system having the three properties of collective goals, shared goals, and of being a single system of interaction with boundaries defined by incumbency in the roles constituting the system, will be called a collectivity. A social system, then, is a system of interaction of a plurality of actors, in which the action is oriented by rules which are complexes of complementary expectations concerning roles and sanctions.