The doctrine of the unconditional election of a part, necessarily implies the unconditional reprobation of the rest. I know some who hold to the former, seem to deny the latter; for they represent God as reprobating sinners, in view of their sins. When all were sinners, they say God passed by some, and elected others. Hence, they say the decree of damnation against the reprobates is just, because it is against sinners. But this explanation is virtually giving up the system, inasmuch as it gives up all the principal arguments by which it is supported. In the first place, it makes predestination dependent on foreknowledge; for God first foresees that they will be sinners, and then predestinates them to punishment. Here is one case then, in which the argument for Calvinian predestination is destroyed by its own supporters. But again if God must fix by his decree all parts of his plan, in order to prevent disappointment, then he must fix the destiny of the reprobates, and the means that lead to it. But if he did not do this, then the Calvinistic argument in favour of predestination, drawn from the Divine plan, falls to the ground. Once more: this explanation of the decree of reprobation destroys all the strongest Scripture arguments which the Calvinists urge in favour of unconditional election.” (Calvinistic Controversy: Embracing A Sermon On Predestination And Election, And Several Numbers, Formally Published In The Christian Advocate And Journal, By Rev. Wilbur Fisk, D. D.)
The Calvinist who wants to claim that the condemnation of the reprobate is conditioned on their sinfulness while the salvation of the elect is conditioned on nothing at all run into serious problems regarding the typical Calvinist accounting of foreknowledge and the exhaustive pre-determinations of a divine secret eternal decree. If the decree is the basis for foreknowledge (as traditional Calvinism asserts), and therefore the means by which God foreknows anything, then it must be admitted that God irresistibly decreed the sinfulness of the reprobate from eternity, just as He decreed all else, and it is only because of God’s eternal decree that He is able to foreknow the state of the reprobate as sinful (because He previously decreed that it must be that way).
So the reprobate finds himself in a sinful state for no other reason than because God irresistibly decreed it from eternity. If that is the case it is nonsense to say that God’s decree for the reprobate is based on them being considered as rebellious and deserving of condemnation already. And as Fisk points out, it cuts against the typical Calvinist argument concerning the nature of foreknowledge, that it is based on the eternal decree. And in doing so, it affirms the Arminian view that God has foreknowledge of true contingencies that are not based on the necessity of an irresistible eternal decree.
This is the same problem that Calvinists encounter who want to claim that Adam had libertarian free will (LFW) when he fell in the garden after the pattern of what Augustine taught (which is often quoted or paraphrased by Calvinists),
God holds us accountable because we were included in Adam so far as God is concerned. Adam was our source, our representative, our “head.” When he rebelled and fell into death and condemnation, we all fell with him. Before he fell, Adam had the power not to sin; after he fell, he lost that power. We are born in the condition of Adam after the fall: unable not to sin. (God in Dispute: “Conversations” Among Great Christian Thinkers, by Roger E. Olson, pg. 93)
Or as R.C. Sproul puts it in Chosen by God,
The Reformed view follows the thinking of Augustine. Augustine spells out the state of Adam before the fall and the state of mankind after the fall. Before the fall Adam was endowed with two possibilities: He had the ability to sin and the ability to not sin…stated another way, it means that after the fall man was morally incapable of living without sin. The ability to live without sin was lost in the fall. This moral inability is the essence of what we call original sin. (pg. 65)
Clearly, the claim is that Adam had the “ability” and “power” to avoid temptation in the garden and “not sin.” That is an apt description of libertarian free will: the power of contrary choice. But if Adam did not have to sin in the garden, then how did God foreknow that He would indeed sin?
This is no problem for the Arminian who claims that God has the ability to foreknow libertarian free will choices. But this is precisely what traditional Calvinists deny. Instead, they say that God can only foreknow what He first decrees. If that is the case, then Adam had no power to not sin since God irresistibly decreed from eternity that he would sin. Clearly, Adam could not have the power to act contrary to the irresistible eternal decree of God (by definition you cannot resist the irresistible). This leads to major theological problems for the Calvinist who claims that Adam had libertarian free will prior to the fall, but this power was lost by all after the fall (following Augustine). He would need to affirm that:
1) God could not foreknow Adam’s sin (if it were truly free), or
2) Admit that God can indeed have foreknowledge of libertarian free will choices and that not all of what God foreknows is based on a prior decree
#1 puts the Calvinist in the arms of Open Theism
#2 puts the Calvinist in the arms of Arminianism
On this score, the Calvinist simply cannot have his cake and eat it too
So if foreknowledge of libertarian free will choices be denied, the oft repeated argument that God’s decision to reprobate was justly in view of mankind’s sin and rebellion must fall (as Fisk notes above).
And if foreknowledge of libertarian free will choices be affirmed (as it must be to claim that Adam did not have to sin in the garden), then the arguments against Arminianism based on the incompatibility of free will and foreknowledge must fall (as well as arguments that try to paint LFW as logically absurd).
The only way to avoid the horns here is to accept the view that Adam’s fall was irresistibly predetermined by God and Adam’s posterity are therefore sinful and rebellious by divine necessity so that God’s decision of reprobation cannot be based on a sinful state that God simply found them in (of their own accord), and justly left them in as a result. Instead, it is a state that God Himself necessitated by way of an irresistible eternal decree. The reprobate has no power over his depraved state or over his actions, and never did. So reprobation can only be based on raw decree, which includes the fall of Adam and the sinful state and actions of all his posterity.