basis for the Catholic concept of the treasury of merit. Aquinas also articulated the ideas of salvation that are now standard within the Catholic Church: that justifying grace is provided through the sacraments; that the condign merit of our actions is matched by Christ's merit from the treasury of merit; and that sins can be classified as mortal or venial. This sounds like penal substitution, but Aquinas is careful to say that he does not mean this to be taken in legal terms: What he means by "satisfactory punishment," as opposed to punishment that is "penal," is essentially the Catholic idea of penance. Aquinas refers to the practice saying, "A satisfactory punishment is imposed upon penitents" and defines this idea of "Satisfactory Punishment" (penance) as a compensation of self-inflicted pain in equal measure to the pleasure derived from the sin. "Punishment may equal the pleasure contained in a sin committed." Aquinas sees penance as having two functions. First to pay a debt, and second "to serve as a remedy for the avoidance of sin". In this later case he says that "as a remedy against future sin, the satisfaction of one does not profit another, for the flesh of one man is not tamed by another's fast" and again "one man is not freed from guilt by another's contrition." According to Aquinas "Christ bore a satisfactory punishment, not for His, but for our sins." The penance Christ did has its effect in paying the "debt of punishment" incurred by our sin. This is a concept similar to Anselm's that humans owe a debt of honor to God, with a critical difference: While Anselm said we could never pay this because any good we could do was owed to God anyway, Aquinas says that in addition to our due of obedience we can make up for our debt through acts of penance "man owes God all that he is able to give him...over and above which he can offer something by way of satisfaction". Unlike Anselm, Aquinas claims that we can make satisfaction for our own sin, and that our problem is not our personal sin, but original sin. "Original sin...is an infection of human nature itself, so that, unlike actual sin, it could not be expiated by the satisfaction of a mere man." Thus Christ, as the "second Adam," does penance in our place – paying the debt of our