Do you want to know some differences between Augusine and Pelagius and the implications thereof? Do you care? Well, I wrote a paper about it:
The point of departure between Augustine and Pelagius was in one's ability to fulfill the commands of God. Pelagius believed that if God commanded something, then certainly humans would have the ability to fulfill said commands. After all, why would God demand something impossible, thereby setting God's creatures up for immediate failure?
Augustine disagreed. He describes Pelagius' position by writing, "For that grace and help of God, by which we are assisted in avoiding sin, he [Pelagius] places either in nature and free will." For him, humans did not have the capacity to do any good whatsoever, apart from God's grace. God draws humans towards God with grace, and not by the good working of a person. Once a person accepts this grace, they then have the capacity to do good, which Augustine defines as loving God as God loves God and loving others as God loves others. Augustine claims that due to the fall, the Bible and human nature, there is no way that a human could follow God of his or her own volition.
The trick is that Augustine highlights the word 'love' to justify his position, as opposed to words like 'sin,' 'inability,' 'idiocy,' or 'ignorance.' Some of these words are present, but Augustine instead focuses his readers' attention on grace and love in order to highlight God's generosity. However, grace comes off seeming a lot like coercion, privilege, and power. But, projecting those loaded words on the Divine sounds better than having one obtain such esteem on one's own. "God so teaches, that whatever people learn, they not only see with their perception, but also desire with their choice, and accomplish in action. By this mode, therefore, of divine instruction, volition itself, and performance itself, are assisted, and not merely the natural "capacity" of willing and performing."
The Pelagian view esteems both God and humanity: "Humans are therefore to be praised for their willing and doing a good work," he [Pelagius] added, as if by way of correcting himself, these words: "Or rather, this praise belongs to the human and to God." In contrast, the Augustinian view leaves glory to God only. Augustine heavily relies on Scripture to back his position, particularly the notion of the utter incapability of humans to seek God or do good.
Although they did not know it then, the Pelagian view would allow for an appreciation for all humans (valuing the good present within each individual, Christian or not), while the Augustinian position debases humanity almost to the point of incompetence: "What is the bad person except one with a bad will." Both ideas have their slippery slopes and absolutes (secular humanism and Calvinist fundamentalism), but neither were notions while the debate raged.
However, Augustine would argue that his system rightly prioritizes God in the process of salvation. Because God is the highest good and Supreme Being, only God deserves such glory and prioritization. Believing that any human could navigate these waters is not only to elevate humanity, but to also dethrone God.
However, immediate implications for their time, ecclesiology, and sotierology mainly centered on infant baptism. Previously, converts were baptized after training and acceptance into the community. However, to assure that a child would go to heaven (if they were part of the elect), that child would need to be baptized due the utter moral filth with which they were born.
Augustine's trump card for his position is Scripture. His treatise relies heavily on Biblical texts and he uses verses time and again to refute Pelagius. Therefore, not only does he claim that his view of original sin and the inability of humans honors God, but it also stays true to God's word: "Now even Pelagius should frankly confess that this grace is plainly set forth in the inspired scriptures." By doing do, he hopes to persuade Christians across the empire to reject Pelagius and accept his view of grace.