From the theme on which it was published I have called it Cur Deus Homo, and have divided it into two short books. The first contains objections of the infidels…and also the reply of the believers…[and] proves, by absolute reasons, the impossibility that any man should be saved without [Christ].
Cur Deus Homo: Why God Became Man, St. Anselm (also available online)
Anselm begins by stating that his purpose is not to satisfy believers of their faith through reason, but to offer to believers reasons for their faith such that they may stand against anyone who demands these. It is necessary to accept the deep things by faith, but then helpful, even necessary (in defense), to delve into these through reason.
The issue being addressed here:
… for what cause or necessity, in sooth, God became man, and by his own death, as we believe and affirm, restored life to the world; when he might have done this, by means of some other being, angelic or human, or merely by his will.
All the while, Anslem recognizes that what ought to be sufficient on this topic has already been said by the fathers (as I have previously offered the words of St. Atanasius as one such example).
Boso cautiously plays the role of the infidel, asking questions and raising objections. For example, that we dishonor God by claiming that he descended into the womb of a virgin and grew on the nourishment of men. Anselm offers that it is no injustice, but cause to give to God the highest honor and thanks. God offered to us the greatest love possible.
Why our salvation had to come through a man (as opposed to through an angel or simply a decree from God) is considered: as death came through the human race, life had to also come through the human race; as the first sin was through a woman, restoration of life had to come through a woman; and as sin came through the eating of the tree, life had to come through a man suffering on a tree.
But it is not sufficient to consider that man alone could do this work:
Do you not perceive that, if any other being should rescue man from eternal death, man would rightly be adjudged as the servant of that being?
We were created to be servants of God, not servants of man or servants of angels. In sum, there is necessary reason that Christ was man and necessary reason that Christ was God. But as I am only on page ten (at this point of the argument) of eighty-four pages, there is clearly much more to be said on this topic: Boso doesn’t let it go at this, therefore neither does Anselm.
Boso: For if he could not save sinners in any other way than by condemning the just, where is his omnipotence? If, however, he could, but did not wish to, how shall we sustain his wisdom and justice?
We will find, through this study, that, once again, God can do anything except the nonsensical.
Anselm: For the Father did not compel him to suffer death, or even allow him to be slain, against his will, but of his own accord he endured death for the salvation of men.
To which Boso again objects: there are many passages which seem to indicate obedience as opposed to Christ’s free will.
It was obedience that demanded of Christ that he maintain truth and justice, and it was for this that the Jews persecuted him unto death. It seems clearly inconceivable that God might be capable of violating the perfect law that God created. Hence, Christ had to be obedient to this law of truth and justice, because He created it perfectly.