The object of this chapter is to elucidate the meaning of this diagram in Parsons' social action programme. In terms of the PVs and FDs, he discusses the patterning or structure of a social system. These variables are ways of describing certain .features of the consensus which is inherent in his core case. They are, as fits with this core case, categories of meaning. In ·terms of the relationships among the PVs and FDs, Parsons establishes certain limitations on the possible patterning of ~he meanings involved in action.