Augustine of Hippo was one of the most important men of his era, and is still one of the most influential men in ours. The body of thought that he established both in the realm of philosophy and Western Christianity is second to none in his era, and his thoughts and conclusions are still read, discussed, and debated today. Perhaps his most famous single quote is the prayer of his that he recalls in his Confessions, "Give me chastity and continence, but do not give it yet," which establishes him as something of a wit in the popular imagination, but this does not begin to plumb the depth and intensity of his thinking.

One of Augustine's major contributions to Christian doctrine was his condemnation of Pelagianism, the belief that original sin did not taint every subsequent human soul. Augustine denounced this as a heresy, claiming that only through the grace of God could anyone be saved, and not by their own works. This is and was a belief held by many Christians, including the Puritans who settled in America, and was arguably the cause of their emigration. Augustine's works had powerful reverberations in his own time, too; his writing condemning the Pelagians led it to be officially adopted in many early synods of Church fathers, when the shape of Christianity was still very much n flux.

Augustine was far from an austere man of the Church, however. His thinking betrays a kind, loving, and even lustful heart. The aspects of his thinking that led more towards individual expression and aesthetic enjoyment found and continue to find resonance with later philosophers. Augustine believed that love should be the central motive to all human actions, even war, and there is another line from one of his sermons that is often quoted: "To sing once is to pray twice." The joy Augustine took in God and life, as well as the serious consideration he gave to theological issues, show how much he cared about his religion and his fellow man. This caring, and the amazing intellect behind it, influenced both his own era and every period of human thought since, making it clear that Augustine of Hippo is the most influential man of his time.

Source

Internet Encyclopedia of Philosophy. http://www.iep.utm.edu/a/augustin.htm#H5