From Talcott Parsons and Neil J

"A social system [...] is any system generated by the interaction of two or more behaving units. The basic criterion for establishing the existence of such a system is the existence of meaningful interdependence between the actions of the units (interaction). Thus[,] the consequences of actions by any one unit can be traced through the system; ultimately[,] these consequences 'feed back' to the units initiating the change. All this is implied by the notion of interdependence. In this more general sense we propose to treat the economy as a social system.