Cur Deus Homo was written by Anselm of Canterbury between 1094–1098 A.D. In this work he asks and answers the question of why God became man. Why he wrote Cur Deus Homo is answered in the preface to his work:
I have been often and most earnestly requested by many, both personally and by letter, that I would hand down in writing the proofs of a certain doctrine of our faith, which I am accustomed to give to inquirers; for they say that these proofs gratify them, and are considered sufficient. This they ask, not for the sake of attaining to faith by means of reason, but that they may be gladdened by understanding and meditating on those things which they believe; and that, as far as possible, they may be always ready to convince any one who demands of them a reason of that hope which is in us.
Although he doesn’t provide the reason in this statement, the fact that he has been asked to write about what “gladdens” believers should tell us that it is something quite important–even possibly essential to the Christian life.
And it is.
The doctrine he espouses that brings such joy in understanding is what some call the satisfaction theory of the atonement, which sees the crucifixion of Jesus not merely as a moral example of sacrifice, but as an effectual propitiation for sin. However, as it is true and clearly taught in Scripture, it really ceases to be a theory but can be stated as fact.
This is remarkable. Even in the 11th century, people were craving to hear more and more about the voluntary, substitutionary atonement of Jesus for their sins. As a satisfaction, Jesus’ sacrifice upon a cross fulfilled the just demands of the law.
Because Jesus absorbed the full justice of the law we can absorb the full mercy of the gospel as the recipients of grace and objects of the Father’s eternal, unwavering affection.
Soli Deo gloria!