In volume 2, of his epic work, Shedd has one of the most thorough discussions of the Penal Substitutionary Theory (PST) of the Atonement in any systematic theology (pp. 378-489). He devotes 12 pages (pp. 451-63) to the objection that the innocent cannot justly suffer in place of the guilty.
Respecting the possibility of the substitution of penalty, it is to be observed: 1. In the first place, that the punishment inflicted by justice is aimed, strictly speaking, not at the "person" of the transgressor, but his "sin." The wrath of God falls upon the human soul considered as an "agent," not a "substance." The spiritual essence or nature of man is God's own work, and he is not angry at his own work, and does not hate anything which he has created from nothing. Man's substance is not sin. Sin is the activity of this substance; and this is man's work. God is displeased with this activity, and visits it with retribution. Consequently, justice punishes the sin rather than the sinner, the agency rather than the agent, the act rather than the person. It does not fix its eye upon the transgressor as this particular "entity," and insist that this very entity shall suffer, and prohibit any other entity from suffering for him. Justice, it is true, is not obliged to allow substitution, but neither is it obliged to forbid it. If it were true that the penalty must be inflicted upon the transgressor's very substance and person itself, as well as upon the sin in his person, then there could be no substitution (emphasis mine). . . (p. 451).Shedd maintains that the punishment is not directed at the "person," but at his "sin." He admits that if it must be directed at the person, then substitution is not possible. I think it must be directed at the person. First, how do you punish "sin," except by punishing the person guilty of the sin? Sin is not a separate entity. It is not a substance. It has no existence except as the action of a person. Can one punish crime without punishing a criminal? I don't see how. Second, the Bible itself makes it clear that God's wrath is focused against sinners as persons not against sin in the abstract. For example, when God set out to punish the sin of Sodom, who or what did he punish? He punished the people of Sodom. When Jesus returns, according to 2 Thessalonians 1:7-9, he will punish those who "do not obey the gospel." The cliché that is sometimes used in modern evangelicalism, God hates the sin but loves the sinner, is somewhat misguided. Sin is what a sinner does and it is the sinner who deserves, according to the Bible, punishment for his sin. Third, later in his discussion, Shedd speaks of the theanthropic person of Christ suffering the penalty for man's sin (p. 460). So, it seems to me that, Shedd has unwittingly undercut his whole defense of the PST with his admission that substitution is not possible if punishment must be directed against the person.
Shedd goes on to argue that
the substitution of penalty is implied in the Divine sovereignty in administering government. If God from his very nature could not permit a proper person to take the place of a criminal, but were necessitated in every single instance to inflict the penalty upon the actual transgressor, his government would be just, but not sovereign. He could make no changes in the mode of its administration--which is what is meant by a sovereign government. But God may vary the mode of administering justice, provided the mode adopted really satisfies justice (emphasis mine), and there be no special reason in his own mind why in a particular instance the variation may not be permitted. There were such special reason, apparently, in the case of the fallen angels, but not in the case of fallen men. This exercise of sovereignty in permitting substitution of penalty is by some Calvinistic theologians called a "relaxation" of justice; not in respect to the "penalty" demanded, but to the person enduring it. Justice relaxes its demands to the degree of permitting a vicar to suffer for the actual criminal, but not to the degree of abating the amount of the suffering. The vicar must pay the debt to the uttermost farthing (p. 452).Shedd maintains that God would not be sovereign if he could not allow a substitute to suffer the penalty for sin, with the caveat, provided the mode adopted really satisfies justice. But that is the very point to be demonstrated, namely, that punishing a substitute really satisfies justice. Shedd seems to let his Calvinistic exuberance for the sovereignty of God overshadow the justice of God. Shedd would admit that God's sovereignty is not curtailed by the fact that he cannot do anything which would violate his nature. For example, the fact that "God cannot lie" (Tit. 1:2) does not make God any less sovereign. Nor would the fact that he cannot punish the innocent in place of the guilty.
Shedd holds that if certain conditions are met by a substitute, then it is just for that substitute to take the punishment of the guilty. He writes:
The penalty substituted must be endured by a person who is not himself already indebted to justice, and who is not a subject of the government under which the substitution took place. If he himself be a criminal, he cannot of course be a substitute for a criminal. And if he be an innocent person, yet owes all his own service to the government, he cannot do a work of supererogation such as is implied in vicarious satisfaction. An earthly state could not righteously allow an innocent citizen to die for another, even if he were willing so to die, because there are claims upon the person and life of every citizen which must go undischarged if his life should be taken. These are the claims of family, of society, of the commonwealth, and of God (p. 456).
This is an interesting point and one I have not encountered in any other defense of the PST. Shedd is saying that in human jurisprudence we do not allow a penal substitution because there are claims upon the person and life of every citizen which must go undischarged if his life should be taken. He is saying that to incarcerate or execute a substitute would be wrong because then the substitute would not be able to fulfill his duties to his family, society, state, and God. The non-fulfillment of these duties would constitute an injustice. In the case of Jesus, Shedd believes this not to be a problem, though he never explains why. It would seem that from a human standpoint, that to execute Jesus at his young age would deprive his family, society, and government from the contributions that he would make if he lived a full life. I suppose one could argue that since Jesus was raised a couple of days after his death, then he is still able to fulfill those needs but, if so, he certainly does not fulfill them in the normal way. For example, someone else had to take care of his mother due to his death (see John 19:26-27).
Shedd quotes from two authors who claim that it is not appropriate to use the terms "punishment" or "penalty" with regard to the sufferings of Jesus. William Magee (Discourses and Dissertations on the Scriptural Doctrine of Atonement and Sacrifice , vol. 1, pp. 445-46):
The idea of punishment cannot be abstracted from [personal] guilt. Christ's sufferings are a judicial infliction, and may perhaps be figuratively denominated punishment, if thereby be implied a reference to the actual transgressor, and be understood that suffering which was due to the offender himself; and which if inflicted upon him would then take the name of punishment. In no other sense, can the suffering inflicted on account of the transgressions of another be called a punishment (cited in Shedd, p. 457).Shedd disagrees with these two men quoted above and maintains that it is proper to call what Christ suffered punishment or penalty. He gives three reasons:
Johannes H. A. Ebrard (quoted by J. J. Van Oosterzee, Christian Dogmatics II, p. 603): If I endure the infliction due to another instead of him, this suffering which for him would have had the moral quality of a punishment has not the moral quality of a punishment for me, because I am an innocent person. For the idea of a punishment contains, besides the objective element of suffering inflicted by the judge, also in addition the subjective element of the sense of guilt, or an evil conscience possessed by the guilty (cited in Shedd, pp. 457-58).
(a) There is no other term but this, by which to designate a suffering that is endured for the sole purpose of satisfying justice. It cannot be denominated either calamity or chastisement. (b) When a commercial debt is vicariously paid by a friend of the debtor, it is as truly a "payment" as if paid personally, and the term "payment" is applied to it in the strict sense of the word. But if there is no valid objection to denominating the vicarious satisfaction of a pecuniary claim a "payment," there is none to denominating the vicarious satisfaction of a moral claim a "punishment." (c) At third reason for the use of the term punishment, or penalty, in this connection, is found in the use of the corresponding term "atonement." No objection is made to calling Christ's suffering an "atonement." But atonement and punishment are kindred in meaning. Both alike denote judicial suffering. There is consequently, no more reason for insisting that the term "punishment" be restricted to personal endurance of suffering for personal transgression, than there would be in insisting that the term "atonement" be restricted to personal satisfaction for personal sin. (p. 458).These three points are easily answered. (a) While chastisement or calamity are not proper terms to refer to Jesus' suffering, that does not necessitate calling it punishment. (b)Shedd has already stated that a pecuniary debt and a criminal debt are not the same, so his argument here is misguided. (c)The use of the word "atonement" does not involve the necessity of one's personal guilt as the word "punishment" does. "Atonement" refers to reparation for an offense or injury, i.e., satisfaction; whereas punishment refers to a penalty inflicted on an offender. Anselm marked the distinction hundreds of years prior by applying the word poena (penalty or punishment) to the suffering inflicted upon a sinner for his crime but the word satisfactio for the suffering inflicted upon Jesus(Cur Deus Homo, I, p. 15).
Shedd's final argument for the justice of the PST is that no one can question God and no one's rights have been violated by the substitution. He writes:
The above-mentioned grounds and reasons for the substitution of penalty abundantly demonstrate its harmony with the principles of law and justice; but should they still be disputed, the whole question may be quickly disposed by asking, Who objects? Objections to any method of administering a government can be urged only by some party whose rights and claims have been disregarded, or trampled upon. In the instance of the vicarious atonement of the Son of God, no objection is raised by God the Father, for he officially proposed and planned the method. No objection is raised by God the Son, for he not only consents to be a party in the transaction, but to be the sacrificial victim required by it. And no objection is raised by God the Spirit, for he likewise is a party in the transaction, and co-operates in its execution and application. . . .I think Shedd misses the point here. The question is whether God retains his justice and righteousness in punishing an innocent not whether anyone's rights have been violated. The whole purpose of the atonement was to satisfy God's righteous anger against sin. How that can be satisfied by punishing someone who is not guilty of that sin is the appropriate question. In my opinion, Shedd never answers that question.
And when we pass from the Divine Being to angels and men, and ask for objections from one having real grounds of complaint, there must be of course a dead silence. No angelic or human rights have been interfered with. Objections to the method of vicarious atonement from the world of mankind especially, would be merely unthankful but absurd. That the criminal, who has no claims at all before the law which he has transgressed, and under whose eternal condemnation he lies in utter helplessness; that the criminal in whose behalf Eternal Pity has laid down its own life should object to the method, would deserve not only no reply, but everlasting shame and contempt (p. 463).