Just two years after the sack of Rome by Alaric, at the time when Augustine begins work on the City of God, Flavius Marcellinus informs him of a complaint by the pagan proconsul of Africa, Rufius Volusianus, that the non-violence preached by Christ diminishes Christianity's capacity to defend the Roman Empire, and that Christian emperors have in fact harmed it. At the same time, Volusianus writes to Augustine about his objections over the incarnation. How can God be present in Jesus, the proconsul asks, and why, if Christ is God, are his miracles so less impressive than those of other wise and holy miracle-workers in history? Augustine's letters to Marcellinus and Volusianus (Letters 138, 137) reveal how seriously he views these challenges to the political significance of the Christian faith. Both in his letters to public officials and in the City of God he takes as his point of departure what Cicero says in De re publica concerning the statesman and the virtues through which Rome's leading citizens had earlier maintained the justice and security of the res publica. At the heart of Augustine's denial in Books 2 and 19 of the City of God that Rome was ever a true commonwealth is his conviction that it never practised true justice.