Augustine (354 to 430, bishop in North Africa), did as much as anyone to shape the theology and ethos of western Christianity. The arguments that rage today in the church are echoes of the fourth-century conflicts in which he was so central, and which were never fully resolved.
Truthfully, Augustine gives us a mixed bag. It was Augustine who interpreted the Adam-and-Eve story as an allegory for original sin, elevating that story for Christians in importance above the Abraham saga that is foundational to Judaism. A piece of our Jewish roots was lost, and not for the better. Augustine rendered sex into the original sin, and you can connect the dots from that to all of the arguments we have today over sexuality. He also explored the idea of predestination and came up with a double-predestination concept that puzzled his contemporaries at least as much as it might puzzle us.
Yet I would give you another picture of Augustine that is worth exploring. He was the first to write a spiritual autobiography, Confessions of a Sinner, and it is still readable today (there are several new translations). He left us hundreds of sermons and major books. Most spectacularly, Augustine explored the meaning of grace, and how grace comes to us free of charge whether we deserve it or not. Augustine was accused of preaching "cheap grace" by those who believed we needed to earn God's favor. Augustine stood firm that grace is a gift of God and not anything we can control. And he preached how we are called to bring heaven to earth -- the city on a hill. Central to Augustine was Christian hope for a better world.
Augustine battled the Donatists, a north African movement that preached that only the pure could be in the church. The Donatists never conceded the point, and they never went away. We see echoes of Donatism today among those who feel the church needs to purge itself of those people who are considered impure or unworthy. Augustine and his arguments remain as relevant today as they were 1,600 years ago.