Critics are quick to dismiss the doctrine of penal substitutionary atonement as unjust. In fact, many dismiss it with a single sentence that God would be unjust to punish an innocent person (Jesus) for the sins of others (mankind). But as philosopher William Lane Craig argues in his recent book The Atonement, this critique is far too simplistic.
Essentially, penal substitution is the “the doctrine that God inflicted upon Christ the suffering that we deserved as the punishment for our sins, as a result of which we no longer deserve punishment.”
There is precedent for substitutionary atonement in both the Old Testament (Isaiah 53:4-6; Exodus 32:30-34) and in the New Testament (1 Corinthians 15:3; 1 Peter 2:24). While there are a variety of models to understand atonement, as Craig notes, any adequate biblical theory of the atonement must incorporate penal substitution.
But Is It Unjust?
Defining substitutionary atonement brings to the surface the aforementioned objection, namely, how God can be just in punishing an innocent person for others’ sins.
The classic Christian response is that God exempts sinners from punishment by transferring it to Jesus. In other words, God imputes the righteousness of Christ to us so that we are no longer held guilty for our sins (2 Corinthians 5:21). Christ endures the suffering we would have received had it been inflicted upon us. And as a result, through faith in Christ, we can be declared innocent.
In The Atonement, Craig asks whether fruitful parallels of such transfer can be found in our legal system. And there are many! For instance, sometimes an employer can be held liable for actions committed by an employee, even though the employer did not do these acts himself. The legal charge against the employer is not complicity or negligence, but rather “the liability incurred by his employee for certain acts is imputed to him in virtue of his relationship with the employee, even though he did not himself do the acts in question” (p. 65). In many cases, the superior can choose to bear the full weight of the punishment and relieve the subordinate of liability (p. 79). This is a remarkable legal parallel to substitutionary atonement.
Legal Fictions and the Law
In my favorite part of the book, Craig explains how the law often utilizes “legal fictions.” Essentially, a legal fiction is something a court knows is false, but nevertheless adopts as if it were true for a particular case.
For instance, in Mostyn v. Fabrigas (1774), Mr. Fabrigas sued the governor of the Mediterranean island of Minorca, which was under British control, for trespass and false imprisonment. But since the governor himself had to approve such suits, Mr. Fabrigas brought the case to London. The problem was that the London court only had jurisdiction in cases brought by London residents. As a non-resident, Mr. Fabrigas was seemingly stuck! Nevertheless, to ensure a just hearing, the court invented the idea that Minorca was part of London (p. 62-63). It was a legal fiction that ensured justice.
The point is not that Christ’ death or substitution is a fiction. Far from it! Christ truly bore the punishment we would have received. Rather, God adopts the “legal fiction” that Christ did commit sin, so he could justly act as our substitute.
On the Judeo-Christian worldview God is the Legislator, Judge, and Ruler of the moral universe. Why can’t God adopt such a posture in order to be both merciful and just?
Of course, this does raise many other objections. There are further nuances that need to be considered. I am not attempting to defend the entirety of penal substitution in one post.
Nevertheless, as Craig observes, it is simply false to claim there are no legal analogies of someone’s responsibility or guilt being imputed to another innocent party. Whether skeptic or Christian, if you have been tempted to dismiss penal substitution as either unbiblical or immoral, you owe it to yourself to consider the arguments in The Atonement. It won’t disappoint.
 William Lane Craig, The Atonement (UK, Cambridge: 2018), 53.