Turretin attempts to define and explain the Penal Substitutionary Theory (PST) of the atonement which had been merely proclaimed but not explained by Luther and Calvin. He builds his theory of the atonement upon the foundation already laid by Anselm in the 11th century, the need for the Divine Judge to receive satisfaction for sin. Turretin writes:
The satisfaction which is here discussed is not regarded in a broad sense . . . but strictly as the payment of a debt, by which that is paid which another owes and by which satisfaction is made to the creditor claiming a debt or the judge claiming punishment (Institutes of Elenctic Theology, vol. II, question X, cited in A Short History of the Doctrine of the Atonement, by L. W. Grensted, p. 241).Turretin sees a threefold character to sin: 1) a debt; 2) a hostile act against God; and 3) a crime. A proper theory of the atonement must deal with all three elements, according to Turretin:
[In the PST] can be perceived the nature of the satisfaction which ought to be offered for sin, viz. that in which these three characteristics concur, in that it is the payment of the debt, the placating of the Divine wrath, through our reconciliation with Him, and the expiation of guilt through the complete suffering of the penalty (Ibid., quoted in Grensted, p. 242).Turretin next turns to the question of how a substitute can pay the penalty owed by the wrongdoer.
But here again the actual punishment, which the judge demands, must be distinguished accurately from the mode and circumstances of punishment, for these two things are not upon the same footing. . . . For though a sinful person fully deserves punishment and may justly be punished, yet it is not so necessary and indispensable but that for certain definite and weighty causes a transference of punishment to a substitute may be made. And in this sense it is said by theologians that impersonally punishment must of necessity be inflicted upon all sin, but not immediately personally upon every sinner; since by His singular grace God can exempt some from it, a surety being substituted in their stead. But that it may be conceived that God can accomplish this, He must be viewed, not as an inferior and subordinate judge, set up under the law, who would be unable to dispense from the rigour of the law by transferring the punishment to another, but as a judge supreme and free from liability, who, even as He wills to satisfy His own justice by the punishment of sin, so in accordance with His supreme wisdom and pity, was able to relax the strict justice of the law by exempting sinners from the punishment due, and by transferring it to a sponsor (Ibid., quoted in Grensted, pp. 242-43).Punishment is required but the "mode and circumstances" of the punishment is up to the judge, according to Turretin. In the case of the divine judge, he believes that he had the right and freedom to transfer the punishment to a substitute. He seems to be saying that while God's justice demands that sin be punished, it does not demand that the sinner himself be the object of that punishment. That assumes that sin somehow can be separated from the person who commits it and transferred to another. He makes no attempt to explain how this is possible. He also does not explain on what grounds he believes it to be an act of justice to punish an innocent person. He simply states that it is the prerogative of the supreme judge. What Turretin needs to do is show how the punishment of an innocent substitute can be a just act itself.
Turretin maintains the justice of the penal substitution depends upon two factors:
Again as the satisfaction which is demanded by God's justice it makes two special demands, (1) that it should be paid by the same nature which had sinned, and (2) that it should be of value and even of infinite price to take away sin's infinite demerit : In Christ were the two natures necessary to the payment of satisfaction, the human to suffer, the Divine to add value and infinite price to the sufferings (Ibid., quoted in Grensted, p. 243).He argues that Jesus must share in the nature of humanity in order to function as a legitimate substitute and that he must share in the divine nature in order for the substitution to have infinite value. It seems that he has left out one important requirement--Jesus must be guilty of the sins of all of mankind in order to be legitimately punished for them. He is implying that by sharing the human nature that all men possess that somehow that is an adequate connection. However, he believes as do virtually all evangelicals, that the human nature that Jesus possessed was without the corruption of sin. It was the human nature as it existed prior to the Fall. Thus, in his human nature he did not share the guilt that all humanity since Adam shares--a human nature that is corrupted by sin. This pre-fallen human nature did not deserve punishment.
He maintains that in Christ the necessary requirements for a just penal substitute are found.
But that that substitution may be wrought lawfully and without any mark of injustice, various conditions are required in the sponsor, all of which meet perfectly in Christ, (i) Communion of nature, that sin may be punished in that nature which was guilty, Heb. 2 14. (2) Consent of will, that -he may take that burden upon himself freely and voluntarily, compelled by none, Heb. 10 9. ... (3) Power and lordship over his own members, that in his own right he may be one who can determine concerning himself, John 10 18. . . . (4) Ability to bear all the penalties due to us, and of bearing them away both from himself and from us ; otherwise, if he could be held by death, he would be able to free no one therefrom. That this ability was in Christ, the God- man, none can doubt. (5) Sanctity and purity unspotted, that being stained by no sin, he might have no need to offer for himself, but only for us, Heb. 7 25, 26, 27 (Ibid., quoted in Grensted, p. 244).As stated above, Turretin is forgetting the fact that Jesus took upon himself a human nature that was free from the corruption of sin. It was a pre-fallen human nature, thus it was not "that nature which was guilty." He says as much in point #5. Again in order to make the punishment a just act, somehow the sins of mankind must legitimately belong to Jesus, but as Turretin acknowledges, if they do belong to Jesus, then he can only suffer for himself and not anyone else. Thus, the PST has an unsolvable problem. He continues:
Under these conditions it was not unjust that Christ the righteous should be substituted for us the unrighteous. For here no injury is done to any. Not to Christ Himself, both because He willingly took this penalty upon Himself, and because He had power to determine concerning Himself, and ability to raise Himself from the dead. Not to God the Judge, because He willed and commanded this, or to His natural right (emphasis added) which is safeguarded by the punishment of the sponsor. Not to the republic of the world through the death of the innocent by which it was deprived of its best citizen ; for Christ having been freed from death, lives for ever; nor by the life of the guilty, surviving to the hurt of the republic, for they are converted through Christ,and are made new creatures. Not to the Divine law, which is guarded beforehand in its most perfect fulfillment accomplished by Christ, and by our twofold union with Christ, natural and forensic or mystical , through which, even as He was made one with us and we with Him, so He was able to take our sin and evil things upon Himself, and to pour out upon us His righteousness and good things (Ibid., quoted in Grensted, pp. 244-45).
Turretin in the above quotation, basically says that there are two things that ultimately make the punishment of a substitute a just act. 1) God as the supreme judge has a natural right to punish a substitute. This is the argument based on the sovereignty of God. The problem here is that while God may be sovereign there are certain things he cannot do, for example, he cannot lie (Tit. 1:2; Heb. 6:18). The Bible teaches that God cannot act contrary to his nature, a nature which is holy and just. Thus, if the punishment of an innocent is unjust (which I have argued it is), then he does not have a natural right to punish the innocent anymore than he has a natural right to lie. 2) The believer's union with Christ makes it possible for him to share the sinner's sin and for the sinner to share his righteousness. The problems with this explanation have been dealt with in prior post but suffice it to say that the union which the NT describes is a union which is brought about by his death and resurrection. There is no union prior to his death, thus, there is no way for him to share in man's sin at the cross. In addition, if the imputation of Christ's righteousness to the believer and the imputation of the sinner's sin to Christ are both due to the mystical union of Christ and believers, then there is a problem. When Christ's righteousness is imputed to believers, he does not cease to be righteous; so, when the sinner's sin is imputed to Christ, the sinner does not cease to be a sinner. Thus, the transfer, even if it were true, does not accomplish what the defender of the PST needs it to accomplish.
In many ways, Turretin was the first to attempt to offer an explanation of how the PST works. Luther and Calvin had proclaimed the doctrine of the PST but had never tried to explain its mechanics. While a gallant effort, I agree with the conclusion of L. W. Grensted below that the effort ultimately fails.
Grensted remarks:
This passage is noteworthy, not merely as an excellent example of the scholastic method of the age, but also as showing the uneasy self-consciousness of the later Penal theory. It is no longer a joyful assertion of that wondrous substitution whereby man no longer trembles before avenging justice. The theory is already upon the defensive, not only against the criticism of its opponents, but against the human instincts of its own supporters. The attempt to describe the Atonement in terms of retributive justice seemed after all only to reveal a radical injustice within God's very being And Turretin's defence, wise and true as it is, does not really meet the attack. It is a lawyer's defence to the end, based upon a legal substitution described in legal language, and the language fails to touch reality. When all is said the " just judge " remains alternately overcruel and over-lenient, demanding penalty where it is not due, and remitting penalty where it should be enforced (emphasis added, pp. 245-46).

