At the moment, I am only going to post some objections to the Augustinian/Thomist view of predestination since I am starting to move away from that view due to the difficulties it poses.
The Augustinian view of predestination suggests that after the fall all of mankind is destined for hell and that God, to show both aspects of his goodness, must either, by justice, condemn the great majority to their natural dwelling place or, by mercy, save a minority. At first, this view seems like a brilliant resolution of the problem of predestination but, later on, we can see that it has some serious difficulties especially as regards God’s love of mankind, free will, and consistency with tradition.
Firstly, this view of predestination ignores God’s universal will to save all of mankind. Surely, mankind deserves condemnation for its great transgression but the Bible and Tradition make it explicitly clear that God, in his great mercy, also desires all to be saved. The Augustinian solution to this problem suggests that God provides all people with an entity called sufficient grace. They say that this entity saves God’s universal desire to save all men because all men possibility of salvation granted them by sufficient grace. However, the Augustinian doctrine tells us that the only way to actualize this sufficient grace is if God converts into efficacious grace and, in so doing, makes it effective for salvation. Whether God does this to any one individual depends on his inscrutable will. Obviously, we have a problem here. How can a grace be sufficient if, by itself, it can produce no effect? It does seem that those who get sufficient grace really get an illusion since sufficient grace cannot at all lead them to salvation. Thus, we find that this doctrine of predestination leads to the conclusion that some individuals are bound, no matter what, to go to hell. There is an even greater consequence. The Augustinians frequently speak about how their doctrine responds to the fall. Nonetheless, why would God allow the fall in the first place if he would purposely ensure that some people will necessarily go to hell? The ultimate conclusion is that God created some people to go heaven and some people to go hell; the passive of reprobation of Augustinianism turns into the double predestination of Calvinism. But such a double predestination is obviously at odds with God’s universal will to save all mankind and so its cause, the “milder” Augustinian doctrine of predestination should be rejected.
Secondly, it is difficult to see how Augustinian predestination preserves free will. If some people will necessarily do this or that then they seem no better than plants or inanimate objects. The essence of free will seems to reside in choosing or not choosing, not in a totally predetermined course of action.
Finally, the Augustinian doctrine of predestination contradicts the entirety of all the Church fathers with exception of Augustine’s own followers. The Eastern Tradition, in particular, has taken a drastically different route.