From The Social Origins of Educational Systems loc 967:
A basic mediatory mechanism is postulated which carries out this shaping process. It consists in the structural relations of contradiction or complementarity distributing frustrating or rewarding experiences to different situations in which actors find themselves. Where contradiction characterizes relations between elements, strains are experienced as exigencies by groups associated with the impeded operations. In other words, operational obstructions are translated into practical problems which frustrate those upon whose day-to-day situations they impinge.
