"If the friend gives the offender a gift sufficient to pay the fine, we have a de facto case of penal substitution. Whoever may sign the cheque, it is the friend who mainly suffers the loss that was meant to be the offender's punishment. . . . If we were single-mindedly against penal substitution, and yet we saw that preventing it in the case of fines was impractical . . . we ought to conclude that fines are an unsatisfactory form of punishment. . . . We might not abandon fines, because the alternatives might have their own drawbacks. But our dissatisfaction ought to show. Yet it does not show. The risk of de facto penal substitution ought to be a frequently mentioned drawback of punishment by fines. It is not. And that is why I maintain that all of us, not just some Christians, are of two minds about penal substitution. . . . [B]oth sides agree that penal substitution sometimes makes sense after all, even if none can say how it makes sense. And if both sides agree to that, that is some evidence that somehow they might both be right." - David K. Lewis, "Do we believe in penal substitution?" in Papers in ethics and social philosophy, Volume 3, (Cambridge: Cambridge University Press, 2000): p. 134-35.
This is hardly a ringing endorsement of the doctrine of penal substitution, which is not surprising given that Lewis is an atheist. Even so, Lewis's argument is flawed.
The chief problem is that he has used an example involving a de facto penal substitution to defend the moral coherence of a de jure penal substitution. But the two are miles apart, morally speaking.
The criminal justice system cannot prevent a friend from, clandestinely, paying an offender's fine on their behalf. But this is very different from the court authorizing such a transaction, treating it as if it were a right and lawful exchange. No judge would ever explicitly sanction, let alone impose de jure penal substitution – even if they are unable to prevent the de facto version.
Yet, the penal substitution of Jesus Christ was pre-planned, authorized, carried out and proclaimed from the hill-tops by God, 'the righteous judge of all'. There is nothing de facto, illicit or behind-the-scenes about 'Christ dying for our sins' at all.
It gets worse.
Theologically, the victim of our sinfulness is none other than God in the person of Christ. So imagine, if you will, a judge turning to the victim of an offence in open court and saying, 'Look, the offender clearly can't pay the fine. So I'd like you to pay it for him. What do you think?'
Even if the victim agreed to this transaction ('Thy will be done'), can you imagine the outcry?
Or again, suppose the fine was so colossal that the victim would be made utterly bankrupt by paying it off: he would lose his house, all his possessions and any savings. Under this scenario, we can well imagine that the victim might be 'sweating blood' over the thought of his impending sacrifice!
But how likely is it that the judge would get away with this bizarre request? Would it not be universally denounced? Politicians, penal theorists, victim groups and journalists would, with one voice, condemn the transaction.
It doesn't change things in the least to suppose that the victim, in this case, is also the judge himself (as is the case in the divine transaction). For a start, this equation would only weaken the analogy even further, since no judge would ever be permitted to serve in a case in which he or she was the victim in question!
But let us suppose that this was legally possible, and that the judge, as the victim, offered to pay off the offender's debt himself. This would still not be morally or legally acceptable. The judge's wish would be interpreted by the public and the entire judiciary as little more than a kind of self-harming exercise, or a misguided martyrdom. His own views and preferences would be over-ruled– as they often are – by the public interest and the rule of law.
If anyone is to be punished, then justice demands that they deserve it; and they can only deserve it if they are personally culpable for the wrongdoing in question.
In short, the concept of de jure penal substitution, in the human context, would violate the fundamental principles of any retributive theory of justice, not to mention the central purpose and rationale of our entire legal system.
It cannot, therefore, be used to lend analogical support to the Christian doctrine of penal substitution.