Below is an decent illustration between the various views (by an Arminian-not a Calvinist). I normally don't like illustrations as they are difficult to evaluate as they lack scripture (I'm a sola scriptura type of guy). But I think it's fair and relatively unslanted.
All the people are on the boat with the God. At this point, in their natural condition, they dont need to be saved as they are not in danger. However, most (if not all) people will eventually jump in the water (sin) and find themselves in need of Gods grace. The reason why they jump in the water is because they are following numerous example of those who jumped before them. This example goes all the way back to the first two who jumped into the water, setting the first bad example. God them offers them a life preserver when they call on him for help. If they respond they will be saved (synergism).
Semi-Pelagianism
All people are in the water drowning. They are born drowning. This is the natural habitation of all humanity since the first man and woman jumped into the water. Their legs are cramping and they cannot swim to safety on their own. However, they may desire salvation on their own. Though they cannot attain it, they can call, with a wave of their arm, to God who is eagerly waiting on the edge of the boat. At the first sign of their initiative, God will then throw out the life preserver (grace). If they respond, they will be saved (synergism).
Roman Catholicism and Eastern Orthodoxy
All people are in the water drowning. They are born drowning. This is the natural habitation of all humanity since the first man and woman jumped into the water. Their legs are cramping and they cannot swim to safety on their own. God, standing on the edge of the boat, makes the first initiative by throwing a life preserver to them (prevenient grace). Upon seeing this act, they make a decision to grab a hold (faith) or to swim away. If they grab a hold, God will slowly pull the rope connected to the life preserver. But they must do their part by swimming along with Gods pull (grace plus works; synergism). If at any time they let go or quit swimming, they will not be saved.
Arminianism
All people are floating in the water dead in their natural condition (total depravity). They are born dead because that has been the condition of humanity since the first man and woman jumped into the water and died (original sin). Death begets death. There must be intervention if they are to be saved. God uses his power to bring every one of them back to life (prevenient grace), but they are still in the water and in danger of drowning. With the regenerated ability to respond to God, now God throws the life preserver to them and calls on them all to grab hold of it. They then make the free-will decision on their own to grab a hold of the life preserver (faith) or to swim away. If they grab a hold, they must continue to hold as God pulls them in (synergism). They dont need to do anything but hold on. Any effort to swim and aid God is superfluous (sola fide). They can let go of the preserver at any time and, as a consequence, lose their salvation.
Calvinism
All people are floating in the water dead in their natural condition (total depravity). They are born dead because that has been the condition of humanity since the first man and woman jumped into the water and died (original sin). Death begets death. There must be radical intervention if they are to be saved. While God calls out to all of them (general call), due to his mysterious choice, he brings back to life (regeneration) only certain people (election) while passing by the rest (reprobation). He does not use a life preserver, but grabs a hold of the elect individually and immediately pulls them onto the boat (monergism). They naturally grab a hold of God as a consequence of their regeneration (irresistible grace; sola fide). They forever stay on the boat due to their perpetual ability to recognize Gods beauty (perseverance of the saints).
In the first four cases man must do something. Try as they might, there is not much difference from the Roman Catholic position and the Arminian position. I would argue that the condition of man is meaningless (whether he's alive but unable to respond or dead). It is the method by which God saves that is most important. In the first four man must do something (although the author takes pains as to say this isn't so). Calvin's interpretation is that man is totally dead and absolutely unable to respond to God. God must reach out and yank him into the boat.
I bring this up because this is the conclusion Augustine came to late in his life and he credits the early church father Cyprian as helping him come to this understanding. As Augustine stated:
HarleyD:
Nobody is rejecting that it is God’s Grace that saves. That is not the issue. Nowhere does St. Augustine reject Free will and if you are pitting works against Grace, then Grace wins because Grace is the cause of both faith and works of charity.
I agree the Catholic and Orthodox position is accurately stated and is synergism, i.e. man cooperates with Gods Grace and Gods Grace empowers and enlights inner mans will and actions to live out the theological virtures of faith, hope and love.
I agree the Calvinist position is monogersim and thus is different than the Catholic and Orthodox Position and it is also different from the Arminianism position found in other Protestant Doctrines [Methodist and Wesly, most Baptist would be here and Most Anglicans and even some Lutherans].
So the only issue I take with your post is the notion that St. Augustine was a monergist. I think the corpus of his work indicates he was a synergist and strongly believed in the Sacraments as the means of God’s Grace that inabled man to live out the Christian virtures of Faith, Hope and Love.
What St. Augustine was investigating is How God’s Election, Grace and Free will are all reconciled. I think ultimately that is one of those mysteries that God did not reveal definitively to the Church thus on this side of the heaven will never be fully understood so it as never been Dogmatized by the Catholic Church nor the Eastern Orthodox Church and was never Defined in a Council when Rome and the Eastern Orthodox were in full communion before the split in 1054 between Rome and Constantionopile.