St Anselm of Canterbury, Doctor Magnificus of the Church, wrote a dialogue entitled Cur Deus Homo towards the end of the eleventh century. In it, he explores the question of why God became man and provides the first instance of what is now called the satisfaction theory of atonement. Here, I intend only to summarize his central argument. There is much more that St Anselm discusses which I will not bring up; if the reader is interested there are fine translation available for free online.
Sin and Debt:
We must first begin with what it is to sin. The definition provided by Anselm is simple: “to sin is nothing else than not to render to God his due.” Well, if God is due something from us, then what is this debt we owe to God? “Every wish of a rational creature should be subject to the will of God… his is the debt which man and angel owe to God, and no one who pays this debt commits sin.” To put it in more modern terms, we owe God everything. Christ is not being hyperbolic or metaphorical when He says “be perfect as your heavenly father is perfect.”
So, all men are sinners. For to fail to act perfectly in accordance with God’s will is sin, and all men fail this. What is the result? We have a debt to God.
Can we pay back this debt? Not so, for “the creature cannot restore to God what was taken away.” For to act perfectly for the rest of your life after a sin takes place is to do nothing else than fulfil the obligation you owe God; perfect action is the bare minimum. Anything we could imagine that pays back the debt of sin is something we already owe God anyhow.
We then have a debt of sin that we owe God and cannot pay it back. And it would be against God’s justice to merely forgive this debt; God does not pass over things and leaves them “undischarged.” Anselm says that for God to do so would be not be proper and be against His justice.
Before we move on to the next section, it is worth out time to, as Anselm does, emphasize how great a burden even the slightest sin is. If it is God’s will that you should look straight ahead, but to do so means that the whole universe will pass away (and to do otherwise would save), then it is better that the whole universe will pass away rather than disobeying the will of God. It is better that we let the whole of creation be reduced to nothing than disobey the will of Our Lord in even the slightest of actions.
Satisfaction and Christ:
Man cannot be saved without satisfying God’s justice for the debt of sin. But man is himself unable to provide the satisfaction required. “if in Justice I owe God myself and all my powers, even when I do not sin, I have nothing left to render Him for my sin.”
And satisfaction “requires that you restore something greater than the amount of that obligation.”
Consequently, man cannot be saved unless there be one who can repay to God the sins of man. Naturally, only one who is greater than all that is not God can accomplish this. None but God fit this description; none but God can make the reparation.
But why did God become man to pay the penalty of our sins? Because God’s nature alone will not pay the price of man’s sins to satisfy His justice and man’s nature alone is unable to pay back the debt. To say Christ had a perfect human nature is the same as calling Him sinless. But mere sinless humanity, no matter how admirable and noble, cannot make satisfaction for man’s sins.
For it would be better that the whole universe pass away than for you to damage a hair on Christ’s head, so only Christ can pay the debt of man’s sins for only He is free (in a manner of speaking) from obligation to God. Only He can restore to God what was taken away through man’s sin.
Poetic Cohesion
For this final section I will let Anselm speak for himself. I would do violence to his text, more than I have already, if I attempted to paraphrase this section.
“If unbelievers were thoughtfully to consider how consistently the restoration of humanity was effected, they would not deride our simplicity but would with us praise the wise beneficence of God. For it was needful that as by the disobedience of man death had come upon the human race, so by the obedience of man should life be given back. And that as sin, which was the cause of our condemnation, had its beginning from a woman, so the author of our justification and salvation should be born of woman; and that the devil who had vanquished man by persuading him to taste the fruit of that tree, should in likewise be conquered by man, by that death which He bore on the tree. There are also many other things, which being carefully studied, show the ineffable beauty of the redemption procured in this way for us.”
Bulgakov's Behemoth