“Penal substitution is more than unjust, it is by definition impossible!”
This line of thought represents an important objection leveled against penal substitutionary atonement (PSA) by some philosophers of religion. The key to this objection lies in a widely held definition of punishment. According to a number of philosophers of law, like Joel Feinberg and Mark Murphy, punishment has four necessary conditions:
- Punishment is hard treatment.
- Punishment is imposed by an authority who may legitimately impose hard treatment.
- Punishment is for a failure to conform to some standard.
- Punishment expresses condemnation of the wrongdoer.
These objectors to PSA home in on the fourth condition, arguing that an authority figure cannot truly express condemnation of someone who has done nothing wrong, therefore punishment cannot be transferred. This objection is problematic for believers in PSA because, by definition, PSA is the transferring of our rightly deserved punishment onto Christ who is perfectly righteous. Let’s call this the expressivist objection.
Responding to the Objection
In my opinion, this is the most significant objection to PSA. Thankfully there are a number of ways to respond to the objection. You could, for example, try to show that #4 is false. To do this you could provide examples of clear cases where punishment is in fact transferred onto someone else. One such example is a parking ticket. If I park in a no-parking zone and a parking enforcement officer gives me a ticket, I now have the responsibility to pay that ticket. However, nobody would object if my wife, father-in-law, or even a complete stranger paid the fine on my behalf. Could penal substitution be something like that? (I.e. Christ paying my “parking ticket” on my behalf?) Some legal scholars would be inclined to say no. Here is why: there is a significant difference between consequences for failing to conform to moral standards and failures to conform to conventional standards. Parking tickets, offside penalties, running laps for showing up late to soccer practice don’t address moral issues, they address matters of convention, therefore they are not punishments, and thus substitution is allowed.
Up to this point it seems like legal philosophy is stacking things against PSA; so what is a penal substitution theorist to do? Dig deeper into the philosophy of law.
In a recent book, simply titled Atonement, William Lane Craig shows how the legal concept of vicarious liability can help us to make sense of PSA. The idea behind this legal concept is that there are times when the liability of a subordinate is imputed onto his superior. In ancient law this often involved a master being held liable for his servant’s bad deeds. But this is no ancient concept, vicarious liability has contemporary analogues. There are cases when employers are held liable for acts done by his employees. An employer could, for example, be held responsible if his employees sell illegal items, trade stocks with insider information, or perform illegal acts. One famous example comes from the case of Allen vs. Whitehead (1930). In this case the owner of a café was found guilty because his employees allowed a prostitution ring to be run from the café, even though the owner did not know about the act. Thus, the café owner was held liable to punishment, even though he had not committed any wrong.
Why is the concept of vicarious liability important for the PSA debate? Simply, it shows that #4 is not always true; there are times when we impute punishment to a person who did not perform the wrongful act. This is an important step towards defending the rationality of PSA, however it is just one step.
“Only One (More) Thing Is Necessary”
In order for vicarious liability to apply in legal cases you need to show that the superior stands in a particular relationship to his subordinate, or else imputing a punishment would be unjustified. Legal cases often appeal to the employer-employee relation or the parent-child relation. Theologically we could appeal to the federal headship of Christ to justify applying the concept of vicarious liability to PSA. However, a much stronger case for vicarious liability could be made if we appealed to federal headship in addition to union with Christ. Christ, on such an account, is not only our representative on merely legal grounds; he is our representative because we are united in him. Thus, union with Christ is a truth which not only helps us respond to the expressivist objection, it is a truth which inspires worship because it is the foundation of our atonement. Thanks be to God!
 See Joel Feinberg, Doing and Deserving: Essays in the Theory of Responsibility (Princeton, NJ: Princeton University Press, 1970) and Mark Murphy, “Not Penal Substitution but Vicarious Punishment,” Faith and Philosophy 26 (2009): 253–273.
 William Lane Craig, Atonement. Cambridge: Cambridge University Press, 2018.