This work examines the central position of Augustine of Hippo in the evolution of Christian political thought. Born less than fifty years after the Edict of Milan and dying less than fifty years before the collapse of the Western Roman Empire, Augustine’s stature in life and in history and the survival of most of his works make him an important thinker in western political philosophy. Augustine's thought allows Christianity to assume political power while retaining its otherworldly orientation and forms a transition from traditional Christian acceptance of power to its use. That Augustine and his contemporaries in the Church would have participated in the administration of the Western Empire, as he did in the last years of the Empire, would have been unthinkable at the time of his birth. The dissertation ascribes the development of Augustinian political thought to the confluence of his reading of Neo-Platonic and Pauline sources and the growing political and social darkness he finds around him. In particular, the dissertation holds that Augustine found that a believer has obligations in two different worlds, i.e., the political and social world of earthly existence and the spiritual obligations of the world to come. The work describes his thoughtful analysis of the believer's duties in the family, the Church, and the world, based mainly on Pauline injunctions. Finally, it analyzes the application of the use of the civil power in combating the Donatist schism, a position which may have been based on an historical accident, for Augustine previously shunned the use of force. Once the command to use force is given, however, he supports it fully. For Augustine, it is obedience to duly constituted authority that is required and the internal disposition of love that governs such obedience. Subjection of the will of man to man is necessary to effect a complete subjection to the will of God to attain salvation