Theology is the study of Faith and belief. Although Augustine lived at a time before such specialisation happened in the church, he has been called as the father of theology in the West and one of the greatest teachers of the Church. There can be little doubt that Augustine is one of the greatest writers in the history of the Christian church, but he did not, however, have the final word in Catholic theology.
That task would be left to Thomas Aquinas many centuries later, for whom Augustine served as the source other than the Bible that Aquinas most frequently quoted. Augustine’s achievements were not based on his receiving instruction from great contemporary teachers, as was somewhat the case with Thomas Aquinas. In contrast, Augustine essentially taught himself. He had a curious mind that was broad and insatiable, a deep sense of discerning spiritual matters, and a talent for communicating his thoughts and experiences. To attempt to cover the theology of so prolific a writer as Augustine in a few paragraphs invariably runs the risk of misrepresenting him.
The keynote of the theology of Augustine is his concept of Christ as the Mediator, the God-man through whose humanity we come, in so far as created beings may do so, to the divine nature of Christ. Besides combating the Manichaean heresy, Augustine engaged in two great theological conflicts. The first was with the Donatists, a sect that held the sacraments invalid unless administered by ministers without sin, and the second was with the Pelagians, followers of a contemporary British monk who denied the doctrine of original sin. In the course of this conflict, which was long and bitter, Augustine developed his doctrines of original sin and divine grace, divine sovereignty, and predestination.
In many areas of Christian theology, such as the theology of creation, the problem of evil, ecclesiology, and the virtue of faith, his teaching has been accepted as practically definitive. He attained an insight into the doctrine of the Trinity that none of the Greek Fathers (theologians) had ever equalled, and his theology of grace (in Latin, gratia) still dominates theological investigations. An important factor in the popularity of Augustine as a theologian is the sheer range of his writings. There was hardly any theological problem facing the medieval Latin theologians upon which Augustine had not written. Second only to the Bible, the theological statements of Augustine often became the foundation upon which subsequent theological development was grounded. His works came to be regarded as a kind of theological encyclopedia. Both the Catholic and Protestant protagonists during and after the Protestant Reformation turned to the writings of Augustine in support of their respective stances on numerous theological matters.
His theological and philosophical views significantly influenced great Roman Catholic scholars such as Saint Anselm, Saint Thomas Aquinas, and Blaise Pascal, as well as the Protestant authors Martin Luther, Thomas Cranmer, and John Calvin. If nothing else, this indicates the great range of his theological thinking. The Catholic Church has never adopted the full position of Augustine on a number of theological topics - including a topic as significant as predestination. Augustine remains one of the few Christian scholars of whom persons not Christian are aware, and whose influence on the evolution of the human mind is acknowledged by people, whether Christian or not. Augustine must be reckoned as one of the architects of the unified Christian belief that survived the barbarian invasions of the fifth century and emerged as the religion of medieval Europe.
As part of his legacy, he succeeded in bringing together the philosophic Christian faith of his youth and the popular Christian belief of his people in the church in Hippo. In doing so, he created a theology that has remained basic to Western Christian thought, both Roman Catholic and Protestant, ever since. Even a liberal theologian like Adolf von Harnack (1851-1930) did not hold back his admiration of Augustine: "His name stands written in permanent characters on the leaves of Western history from the days of the great migrations to our own."
Link
The Mark of Augustine on Theology. By Eugene Portalie in the first edition of the Catholic Encyclopedia. Not easy to read. http://www.newadvent.org/cathen/02091a.htm#III
Resource web sites on Augustine of Hippo
Dave Armstrong. Numerous helpful links to web sites about Augustine: his works, his theology, and articles about him, etc. http://web.archive.org/web/20030413170824/http://ic.net/~erasmus/RAZ160.HTM
Ad Limina Apostolorum. Links to the works of Augustine that appear on the internet in English or Latin. And to web sites on Augustine – including Augnet! http://www.ratzingerfanclub.com/adlimina/augustine_resources.html AN2337