Plutarch wrote in his Life of Numa `If a boundary is respected it is a restraint on the use of force; and if it is not respected then it is proof of an abuse of power'. Whittaker's study examines both the ideological significance and practical meaning - in terms of military, economic and social function - of the Roman imperial frontiers; he argues that the success of these frontiers as permeable border zones both encouraged their later destruction and permitted a level of imperial reinvigoration by the barbarian migrations.Plutarch wrote in his Life of Numa `If a boundary is respected it is a restraint on the use of force; and if it is not respected then it is proof of an abuse of power'.