Here's a recap of a debate I had with Theojunkie and Turretinfan on Calvinism and determinism. The debate cover all kinds of topics, like determinism and Molinism but one aspect that we kept coming back to was Christ's death and determinism. Here's some key quotes and links to the posts:
Opening Argument: Calvinism is Determinism - A brief review of TULIP in light of Determinism Christ's death was sufficient for all meaning if He had died for the reprobate, He could have been able to save them. The "possibility" of salvation is based on a different past then the actual past - a hallmark of determinism.
Theojunkie Response 1 If Christ had died for the reprobate, then 1) they would with certainty be saved, and 2) they would not be reprobate. Salvation is not "possible" for anybody-- it is certain. No where does the bible speak of the "possibility of being saved". No where does anyone in the bible present the Gospel as a "possibility" for a person. Therefore, nothing here is based on a false history.
My Response How could Christ’s not dying for someone be the basis of His death’s being sufficient for them? Further, you deny that salvation is possible for anyone, but rather that it is certain (presumably for the elect and them alone). This implies that Christ is unable to save the non-elect. If Christ is unable to save them, how then is His death sufficient for them?One way to explain it would be that given the hypothetical that they were elected, Christ wouldn’t have had to suffer any more? (i.e. an alternative past to correspond to the alternative future). There’s a power or possibility in Christ’s death that’s accessed with an alternative past.
Theojunkie Response 2 "Christ not dying for someone" is not the "basis for his death being sufficient for all." The basis for saying that Christ's death is sufficient for all, is simply this: He is the spotless lamb of God.
Turretinfan Response 1 GIMJ claims that Calvinism teaches, "The "possibility" of salvation [based on the sufficiency of Christ's death] is based on a different past then the actual past ... ." This is not true, either, because the sufficiency of Christ's death is a matter of intrinsic value. Christ's death is in actuality sufficient for all the sins of each and every person.
Response to TF 1 Yes, but I suspect that your very concept of “actual sufficiency” with respect to a counterfactual future (i.e. the salvation of the non-elect) entails a counterfactual past. When determinists claim we are able to do otherwise, if we had chosen to, or we are able to choose otherwise, if we had wanted to; they are defining “ability” in terms of a counterfactual past. For more please see here. Can Christ save the reprobate? Under Calvinism, in one sense He can and in another sense He cannot. The sense He cannot is obvious. Given the Father didn’t elect them, Christ would almost have to “freak out” and run contrary to the Father to do so. Obviously that can’t happen. But the sense in which He can relies on a counterfactual past in which they were not reprobate.
Turretinfan Response 2 As I already said, "actual sufficiency" has to do with intrinsic value. To build on the Scriptural analogy of redemption with a price, the price of Christ's death was enough to save an infinite number of people. The question of people's choice is really irrelevant to the issue of Christ's sufficiency. If only Paul had been elected, Christ's death would have been exactly as sufficient as it is in reality.
Response to TF 2 This explanation wouldn’t be an issue if Calvinists only said the value of Christ’s death was sufficient for all. But they say Christ’s death was sufficient for all [meaning the value of Christ’s death was sufficient for all], while in the background, other aspects of Christ’s death move against Christ’s death being sufficient for all. Granted, these other aspects don’t “block” the value of Christ’s death from saving, but perhaps they make use of the value of Christ’s death in such a way that the reprobate remain unsavable. If the reprobate are unsavable, clearly Christ’s death was insufficient for them. Something more than the value of Christ’s death is required. This article suggest that the “something more” is intention, and that intention is implied in the phrase sufficient for all. (link) But whatever the “something else” is, if something more is required from X for Y, X is insufficient for Y. This is why I suspect you are speaking in a divided sense.
Turretinfan Response 3 GIMJ's argument glosses over the difference between sufficiency and savability. The price is sufficient to save, but is not used to that end. To go back to the ransom analogy, if the cost to ransom any and all captives is $1 Million, then a payment of $1 Million is sufficient for all, even if it is not intended or used to free all the captives.... Intention is not something "added" to Christ's death to make it sufficient - it is not even, itself, the thing that makes the death of Christ efficient. It is the "joy that was set before him," as Scripture teaches. The act of offering is what makes the sacrifice efficient, and the Holy Spirit actually executes the effect in the life of the elect.
Response to TF 3 Owens says God lays the sins of the elect on Christ first, then Christ carries them to the cross and pays the price, actually satisfying justice through His death. The intention, sin transfer, offering, and acceptance are all required. Without them, Christ’s death would not, and could not save anyone. As it stands, you seem to hold to the contradiction that the value of Christ’s death is both sufficient and it requires something else.