Anselm on the Atonement

Anselm (1033-1109); from Cur deus homo?

Book I
xi. The problem is, how can God forgive man's sin? To clear our thoughts let us first consider what sin is, and what satisfaction for sin is. ...To sin is to fail to God His due. What is due to God? Righteousness, or rectitude of will. He who fails to render this honour to God, robs God of that which belongs to Him, and dishonours God. This is sin. ...And what is satisfaction? It is not enough simply to restore what has been taken away; but, in consideration of the insult offered, more than what was taken away must be rendered back.
xii. Let us consider whether God could properly remit sin by mercy alone without satisfaction. So to remit sin would be simply to abstain from punishing it. And since the only possible way of correcting sin, for which no satisfaction has been made, is to punish it; not to punish it, is to remit is uncorrected. But God cannot properly leave anything uncorrected in His kingdom. Moreover, so to remit sin unpunished, would be treating the sinful and the sinless alike, which would be incongruous to God's nature. And incongruity is injustice.
xiii. It is necessary, therefore, that either the honour taken away should be repaid, or punishment shouyld be inflicted. Otherwise onenof two things follows--either God is not just to Himself, or He is powerless to do what He ought to do. A blasphemous supposition.
xx. The satisfaction ought to be in proportion to the sin...
xxi. And thou has not yet duly estimated the gravity of sin. Suppose that thou wast standing in God's presence, and some one said to thee--'Look yonder.' And God said, 'I am altogether unwilling that thou shouldest look.' Ask thyself whether there be aught in the whole universe for the sake of which thoug oughtest to indulge that one look against the will of God. Not to preserve the whole creation from perishing oughtest thou to act against the will of God. And shouldest thou so act, what canst thou pay for this sin? Thou canst not make satisfaction for it, unless thou payest something greater than the whole creation. All that is created, that is, all that is not God, cannot compensate the sin.

Book II
iv. It is necessary that God should fulfill His purpose respecting human nature. And this cannot be except there be a complete satisfaction made for sin; and this no sinner can make.
vi. Satisfaction cannot be made unless there be some One able to pay to God for man's sin something greater than all that is beside God. ...Now nothing is greater than all that is not God, except God Himself. None therefore can make this satisfaction except God. And none ought to make it except man. ...If, then, it be necessary that the kingdom of heaven be completed by man's admission, and if man cannot be admitted unless the aforesaid satisfaction for sin be first made, and if God only can, and man only ought to make this satisfaction, then necessarily One must make it who is both God and man.
xi. He must have something to offer greater than all that is beow God, and something that He can give to God voluntarily, and not as in duty bound. Mere obedience would not be a gift of this kind; for every rational creature owes this obedience as a duty to God. But death Christ was in no way bound to suffer, having never sinned. SO death was an offering that He could make as of free will, and not of debt. ...
xix.Now One who could freely offer so great a gift to God, clearly ough not to be without reward. ...But what reward could be given to One who needed nothing--One who craved neither gift nor pardon? ...If the Son chose to make over the claim He had on God to man, could the Father justly forbid Him doing so, or refuse to man what the Son willed to give him?
xx.What greater mercy can be conceived than that God the Father should say to the sinner--condemned to eternal torment, and unable to redeem himself--'Receive my only Son, and offer Him for thyself,' while the Son Himself said--'Take me, and redeem thyself'?
And what greater justice than that One who receives a payment for exceeding the amuont due, should, if it be paid with a right intention, remit all that is due?