I just came across another article attempting to defend the PST of the atonement. Its entitled: PENAL SUBSTITUTION IN PERSPECTIVE:RE-EVALUATING THE ARTICULATION AND APPLICATION OF THE DOCTRINE by Patrick Franklin (McMaster Journal of Theology and Ministry, vol. 10 (2008–2009), pp. 22–52). Its a very interesting article which actually addresses some of the real problems involved with the PST.
On the matter of the innocent suffering in the place of the guilty, Franklin says this:
One ethical objection commonly raised is that sin and guilt are personal and non-transferable. It is both inappropriate and un-fair for God to satisfy justice by punishing an innocent person (Christ) in place of guilty offenders. Erickson and Grudem respond by emphasizing the fact that Christ’s suffering was voluntarily (sic), that Christ willingly offered his life on behalf of sinners. This response is partially helpful in that it presents Christ as a willing participant, but it does not show how punishing an innocent person serves the cause of justice itself. How is it just to add evil to evil? Does not the death of Christ create a further injustice? Grudem is not very helpful when he responds: "God himself (Father, Son, and Holy Spirit) is the ultimate standard of what is just and fair in the universe, and he decreed that the atonement would take place in this way, and that it did in fact satisfy the demands of his own righteousness and justice.[Wayne Grudem, Systematic Theology, p. 574].
Apparently for Grudem, justice is served because God says so (apparently in good nominalist fashion). God determines what is just and may therefore turn evil into good simply by declaring it to be so. But if this is the case, why cannot God simply declare all sin to be forgiven? (pp. 31-32).
So Franklin recognizes that to say that (1)Christ died voluntarily or that (2)whatever God does must be just are really not satisfactory answers to the question of how can God accept the punishment of the innocent in place of the guilty. I give him credit for seeing the real problem here. Very few evangelicals seem to see it.
So, what is the solution to the problem, according to Franklin? He says:
Perhaps a better response to this charge is that justice is served because Christ is, in some sense, actually guilty. Not that Christ ever committed sin, but in the Incarnation and atonement he united himself to sinful human beings and thus, in a mysterious yet real way, he became “guilty” for us in order to make us righteous. He identified with us, in order to incorporate us into union with himself and thus into deep fellowship with the triune God. As Paul writes, “God made him who had no sin to be sin for us, so that in him we might become the righteousness of God” (2 Cor 5:21). (p. 32).
Okay, this is a much better answer than most theologians give. However, it is not without problems.
1. While the Scriptures teach that Christ did take upon himself a complete human nature; it also teaches that the humanity he took was minus the corruption of the Adamic sin nature. So, while he did share in man's nature, he does not share in man's sin nature. So how can he be found guilty of man's sin?
2. To say that Christ actually became guilty of sin creates another problem. How can the God-man be guilty of sin without destroying the holiness of God?
3. 2 Cor. 5:21 can also be rendered: “God made him who had no sin to be a sin offering for us, so that in him we might become the righteousness of God”.. Thus, the verse does not prove Franklin's point.
I give Franklin credit for recognizing one of the real problems with the PST and for attempting to answer it. As I said earlier, most evangelical theologians never even address this issue. However, I don't find his answer to be satisfying. It creates more problems than it solves in actually compromising the purity and holiness of Christ.