The key concept bridging the gap between statics and dynamics in functional theory is that of strain, tension, contradictions, or discrepancy between the component elements of social and cultural structure.  Such strains may be dysfunctional for the social system in its then existing form; they may also be instrumental in leading to changes in that system.  In any case, they exert pressure for change.  When social mechanisms for controlling them are operating effectively, these strains are kept within such bounds as to limit change of the social structure (1968, p. 176).