Joy argues that Aquinas' view of the atonement is not the PST as some have alleged but neither is it the same as Anselm's Satisfaction theory. It is actually a middle position between those two views. He explains:
Both Aquinas and the Reformers adopt Anselm’s term, namely “satisfaction”, but the respective meanings which they give to the term vary. This divergence of meaning is located in the relation that satisfaction bears to punishment. For Luther and Calvin only punishment can make satisfaction. Justice is satisfied when sin is punished; therefore, “to satisfy” for sin means nothing other than “to be punished” for sin. Aquinas, on the other hand, takes a slightly different position: although satisfaction always contains something of a penal nature, it is never simply the same as punishment. In his scholastic terminology, satisfactio est poena secundum quid. To compound the problem, neither usage seems to agree entirely with Anselm, who tends to define satisfaction precisely in opposition to punishment: justice demands one or the other, but not both. . . . regarding the relationship between punishment and satisfaction, Thomas walks something of a via media between Anselm’s opposition of the two concepts and the Reformation identification of them (pp. 1-2).
For Anselm, satisfaction and punishment are two distinct things. Joy uses the following example to illustrate the distinction: The man who offends his wife may make up for it by bringing her flowers (satisfaction), or she may make him sleep on the couch (punishment) (p. 22). Either way justice is served. In Anselm's view, the life and death of Jesus is an offering to God which makes satisfaction for man's sin. Those who don't repent and believe will suffer punishment themselves for their own sin. For Calvin, satisfaction and punishment are one and the same. When sin is punished, either vicariously in the death of Jesus or personally in hell in the case of unbelievers, satisfaction is made for sin and justice is served. For Aquinas, satisfaction is a type of punishment but there is also another type of punishment that is distinct from satisfaction. In other words, punishment exists in two forms. Poena simpliciter (basic or simple punishment) and poena secundum quid (punishment as satisfaction). The distinction arises from whether the guilty person suffers against his will or voluntarily. If the person suffers the penalty against his will, then it is the former and if the person suffers the penalty voluntarily (and remorsefully), then it is the latter. Joy explains:
When a judge simply punishes an offender, his act of punishing belongs properly to the virtue of vindictive justice, for he renders to the offender what is due to him, namely punishment. If, on the other hand, the offender wills to make amends by voluntarily compensating the offended one for his injury, his act of satisfying belongs to the virtue of penance, which is a species of justice, for he renders to the offended what is due to him, namely compensation. Justice is done in either case, but the agent and patient of the act differ: in simple punishment, the judge renders what is due to the offender, whereas in satisfaction, the offender renders what is due to the offended (p. 43).
In Aquinas' view, satisfaction (poena secundum quid) can be paid by a substitute whereas basic or simple punishment (poena simpliciter) can only be paid by the offending party. Substitution is possible in the former because technically its an offering of something valuable to make amends for the sin committed; whereas in the latter its basic punishment against the unrepentant sinner. In the former, the sinner is repentant, remorseful, and seeks to make amends with the offended party. In man's case, he has nothing of any real value to offer to God, so Jesus steps in and offers up himself (a life lived perfectly even to the point of martyrdom) as the most valuable gift possible. In the latter, the sinner is unrepentant and must be punished against his will. The former is technically punishment in Aquinas' view but not punishment of Jesus (as in the PST) but punishment of the repentant sinner as he sees how much his sin cost--the very death of the Son of God. Aquinas writes: [T]hus punishment is not lacking to him [i.e., the repentant sinner], as long as he suffers with his suffering friend; and so much the more fully as he himself is the cause of his suffering (Summa Contra Gentiles III, cap. 158, n. 7 cited by Joy, p. 50).
In the next post, I want to examine in more detail Aquinas' version of of substitutionary atonement and see if it is able to evade the problems associated with the PST such as the injustice of punishing an innocent in place of the guilty.