Commenting on the "double payment" objection to universal atonement (within a Penal Substitoinary model), Oliver Crisp wrote:
However, for the objection to have teeth it needs to be able to make good on the claim that (a) Christ’s atonement effectually pays for the sin of all fallen humanity, and (b) those who die without faith and are damned also effectually pay for their sin in their everlasting punishment in hell. In other words, there must be a kind of symmetry between the efficacy of the payment for sin Christ’s atonement and in the punishment of the damned. Both must generate an actual and effectual payment for sin that is atoning. In the case of Christ, this is actual and effectual, and competed in his sacrificial work on the cross. In the case of the damned, it is actual and effectual, and ongoing in their everlasting suffering in hell.
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On this iteration, the concern is that Christ’s atonement pays for all human sin in ordained sufficiency, except for the sin of unbelief. Then, it appears that the hypothetical universalist is committed to the rather implausible theological claim that those who are damned are suffering only for the sin of unbelief, not for other sins because other sins have been atoned for by the work of Christ. But, it would be argued, the damned cannot be held responsible for failing to believe the great things of the gospel because faith is a divine gift. So the hypothetical universalist ends up holding a view according to which the damned suffer only because they lack saving faith, though they cannot be responsible for this lack of faith because faith is a divine gift. It would be like refusing medication to someone who lacks the ability to walk to a pharmacy to pick it up. Such a person can hardly be responsible for not being able to pick up their medicine!
This is a stronger version of the objection. In response to the question of whether it is merely unbelief that damns a person, it is clear that all Christians would agree that such a condition is normally a reason to think a person is outside the bounds of salvation, other things being equal (i.e., excepting limited cases such as those discussed earlier). So that cannot be the problem. Rather, the concern is that it is of this alone that damns a person because the rest of her sin has been atoned for in Christ. This the hypothetical universalist need not concede. As we have already seen, the idea of an ordained sufficiency to the atonement is like the idea of a bank of vaccination ready to be mobilized. It has a potency to deal with the disease affecting the populace. But it needs to be applied to them. This is what is meant by the ordained sufficiency of Christ’s work. It has a merit sufficient in the fact to atone for the sin of each and every human sinner. But it is only made efficacious upon being delivered to those to whom the gift of faith is given. So the real problem boils down to the question of the gift of faith. Now, all Reformed theologians agree that faith is a divine gift. So this cannot be the point in dispute. Rather, the concern is that the hypothetical universalist is withholding salvation from those who lack the gift of faith, for which they cannot be held responsible. For the gift is not something that they can attain; its bestowal is an act of unmerited grace. But once again, this is a problem common to all Reformed (and more broadly Augustinian) accounts of salvation. Now, a tu quoque response is not a decisive way of addressing the problem, and this is a tu quoque response. That said, it is a way of pointing out that those who defend a limited atonement doctrine have exactly the same problem to address since on the limited atonement doctrine only those given the gift of faith are able to receive the benefits of Christ’s atonement, and faith is an unmerited divine gift. So this is not a difficulty peculiar to the hypothetical universalist, but a problem common to the sort of Reformed, and more broadly, Augustinian scheme of salvation. (Oliver D. Crisp, “Anglican Hypothetical Universalism,” in Unlimited Atonement: Amyraldism and Reformed Theology, ed. Michael F. Bird and Scott Harrower [Grand Rapids, Mich.: Kregel Academic, 2023], 35, 37-38)