The Satisfaction (or Commercial) theory of the atonement was formulated by the medieval theologian Anselm of Canterbury (1033-1109) in his book, Cur Deus Homo (lit. ‘Why the God Man’). In his view, God’s offended honor and dignity could only be satisfied by the sacrifice of the God-man, Jesus Christ.
Anslem believed that humans could not render to God more than what was due to him. The satisfaction due to God was greater than what all created beings are capable of doing, since they can only do what is already required of them. Therefore, God had to make satisfaction for himself. Yet if this satisfaction was going to avail for humans, it had to be made by a human. Therefore only a being that was both God and man could satisfy God and give him the honor that is due him.
The classic Anselmian formulation of the Satisfaction View needs to be distinguished from Penal Substitution. Penal Substitution states that Christ bore the penalty for sin, in place of those sinners united to him by faith. Anselm, by contrast, regarded human sin as defrauding God of the honour he is due. Christ's death, the ultimate act of obedience, gives God great honour. As it was beyond the call of duty for Christ, it is more honour than he was obliged to give. Christ's surplus can therefore repay our deficit. Hence Christ's death is substitutionary in this sense: he pays the honour instead of us. But that substitution is not penal; his death pays our honour not our penalty.
The Protestant reformers shifted the focus of this satisfaction theory to concentrate not merely on divine offense but on divine justice. God's righteousness demands punishment for human sin. God in his grace both exacts punishment and supplies the one to bear it.
This is an important difference. For Anselm, Christ obeyed where we should have obeyed; for John Calvin, he was punished where we should have been punished.
Anselm was made Archbishop of Canterbury following the Norman conquest. His theory of the atonement relied heavily on the feudal system of his day, in which serfs worked on an estate for an overlord. The overlord - a knight - protected the estate from attack. The knight in turn had to honor the King. The serfs owed the knight a debt of honor for their protection and livelihood. Anselm pictured God as the overlord of the world to whom is owed a debt of honor. Failure to honor God is therefore a sin. God cannot overlook such an offence and demands satisfaction. While it is man who owes such a debt to God, the only person capable of paying the debt is God himself. God therefore became man so that he himself could satisfy God's offended character. Christ's death accrued a superabundance of merit (also known as supererogation), which is now available for distribution to those who believe.
Anselm's theory takes seriously the gravity of sin and the holiness of God. Unfortunately it goes beyond what the Bible teaches and reads in too much of a culture foreign to the Scriptures. The satisfaction of God's character that is described is totally external to the individual believer. There is no personal response involved or any change worked on the individual.
Sin is viewed as the withholding of honor due to God. In his death, since he was under no obligation to die, being sinless, Christ brought infinite glory to God. This brought a reward to Christ that he did not need so he passes it on to sinners if they live according to the gospel (supererogation). Thus, the basis for receiving the benefit of Christ's death is works. While Anselm's interpretation permitted man to offer Christ to God, the Protestant Faith insists that it is God, not man, who reconciles fallen humanity by sacrificing His son. Thomas Aquinas (1225-1274) developed Anselm’s theory more fully, including the “treasury of merit” concept, which became the general understanding of the atonement in Roman Catholicism.
In addition to basing the necessity of the atonement on the honor of God rather than the justice of God (consistent with the later Reformers), Anselm’s theory rules out Christ's bearing the penalty of sin and dying in the sinner’s stead.