Can someone provide a summary of Augustine's soteriological views, and their differences from contemporary views?
I'm particularly interested in a comparison of Augustine's soteriology with the soteriologies of Calvinists, Arminians, and Catholics.
Upon examining the second book of Calvin's Institutes, I found that Calvin and Augustine are pretty much 100% on the same page.
Calvin, Institues, 2.5.2
Thus [Augustine] asks, "What is human merit? He who came to bestow not due recompense but free grace, though himself free from sin, and the giver of freedom, found all men sinners" (Augustine, In Psalmum 31). Again, "If you are to receive your due, you must be punished. What then is done? God has not rendered you due punishment, but bestows upon you unmerited grace. If you wish to be an alien from grace, boast your merits" (In Psalmum 70). Again, "You are nothing in yourself, sin is yours, merit God's. Punishment is your due; and when the reward shall come, God shall crown his own gifts, not yoru merits" (Epist. 52) To the same effect he elsewhere says (De verb. Apost. serm. 15), that grace is not of merit, but merit of grace.
Considering the wealth of quotes, it's pretty obvious Calvin agrees with Augustine on God's grace. Considering the total shunning of any human merit, this at least distinguishes Calvin and Augustine from the Catholics.
Later, in 2.5.8, Calvin quotes Augustine again:
As Augustine says, "What God promises, we ourselves do not through choice or nature, but he himself does by grace."
The mention of the inability of human choice (based, likely, on passages like Romans 9:16) separates Calvin and Augustine again from the Arminians.
The one disagreement I found was in 2.4.3, where Augustine appears to differ on the views of God's "hardening." Calvin believed that God "hardened the hearts" of those whom he did not choose. So here, perhaps, Calvin was even more "frozen-chosen-ish" than Augustine, but otherwise they are in agreement regarding God's grace as the sole means of salvation.
Augustine's Soteriology is hard to nail down because in the particular work we most cite when we think of his soteriology as though it were so fixed, he was reacting to Pelagius who was basically promoting a kind of Deism where God made man able to save himself and had to do nothing to help him. Of course, not everyone would achieve it, only people who were very exceptional. So you must know a bit about Pelagius' supposed teaching when reading Augustine - I somewhat doubt we actually know Augustine's final position on the issue. Those who quote his works to favor a Monergist approach abuse him greatly.