For Augustine, only saints were predestined, but the word often means God’s supposed pre-determination of both the blessed and the damned. Anyone denying the Scriptural basis of the pre-determination of the damned will be scandalized in a few places: 1.) Paul’s “vessels of wrath” and “vessels of mercy” (Romans 9:23) (2.) The claim in 1 Peter 2:8 that both the saints and the disobedient are stones that have been prepared by God, and (3.) Proverbs 16:4 “The LORD works out everything to its proper end– even the wicked for a day of disaster.”
But none of these argue for reprobation, in fact each objection falls apart as soon as one tries to formulate them. Paul’s “vessels of wrath” statement is a counterfactual; and I Peter and Proverbs make no reference to the predestination. Done.
The Scriptural case against reprobation is not best made by trading gotcha-quotes but by seeing it as contrary to the whole narrative of the text. One would predict an entirely different Scriptural narrative if both the saints and the damned arose from God foresight and planning. God divides the light from the darkness, but he never makes the darkness nor says anything about it (it is the only feature of creation that God does not call good). God makes one first couple in blessedness, not a blessed and a cursed couple. God makes covenants with Abraham, but he does nothing to build or cause the construction of the city of Cain, Sodom, the Moabites, etc. In all of Christ’s parables of the kingdom, sin arises either by an accident outside the intention of God himself (the sower) or from the free action of creatures (the wheat and the tares, the wedding feast, the foolish virgins, the talents etc.) Christ speaks all the time of those who don’t make it into the kingdom, but he never describes them with metaphors that suggest a divine foresight that withholds things from certain persons.
Scripture paints a clear picture of a God that always frustrates evil by ordering it to a good, given it exists, but it never paints the picture of evil arising out of a previously established plan. We get a vision of God who always deals with evils post factum, not a God who cleverly green-lights evils whose execution he outsources to the reprobate. To say the least, the narrative arc of Scripture does not suggest a God who has planned to hold things back from creatures.
Just what sort of metaphysics we would have to develop in order to explain this is not clear. My suspicion is that we have missed important asymmetries between good and evil. Created goods require foresight and planning and have a real genesis that involves the transfer of actuality from agent to patient that ultimately traces back to the divine action; but evil has no such logos. We can give a narrative of it and find someone responsible for it, but, compared to good things, evil simply happens. We don’t need a divine permissive will to green-light the process or to cause it per accidens by the withholding of grace. All these assume that evil must have the same ontologically-satisfying reduction that goods have. But they don’t. Modern thought is certainly right that, without God, all things trace back to brute facts about which we can say no more than that they happen. And that’s what evil is.