Augustine of Hippo (A.D. 354–430) presented a classic teleological perspective in his work "City of God". He describes the "city of man" and essentially posits that God's plan is to replace the city of man with the city of God (at some as-yet-unknown point in the future). Whether this is to happen gradually or suddenly is not made clear in Augustine's work. He did not, however, make a formal argument for the existence of God; rather, God's existence is already presumed and Augustine is giving a proposed view of God's teleology. Augustine's perspective follows from and is built upon the "neo-Platonic" views of his era, which in turn have their original roots in Plato's cosmogony.