On the Reasons of the Holy Spirit, Book II

and justice [is in vain] unless there is a just compensation for injustice. Now, it appears that he who is bound to an infinite punishment by finite power must nonetheless be led to eternity according to the preordination and providence of God. Therefore, a new subject is necessarily required in which both the rigor of justice is preserved and the favor of mercy is set aside. Infinite mercy is required to wash away the crime of an infinite offense. A subject compacted of human flesh is required in which as many punishments as can be devised are taken for the crime committed by human nature, and in a way so excellent, so exquisite, and so alien to any law of equity, as nature can endure. And because human nature, being finite, could not endure the infinite, it was necessary to contend with infinite will and power for satisfaction, so that through a vow it might be done in one what otherwise had to be done in all. It was necessary that the innocent one, being free and alien from all crime and obligation of punishment, be the one to whom such a great sum was to be paid. For if he had already owed something on his own account, he could not have paid the infinite for another. It was necessary, therefore, that the preordained salvation be restored to human nature, that one person of the Godhead be made man, and that in one subject of infinite divinity and finite humanity, He should pay such a great punishment with such exquisite torments, that He Himself would satisfy God and pay on behalf of man. Therefore, it was necessary for God to satisfy God, with God repairing, and God accepting the reparation through God.

O divinity of mysteries. O abyss. O depth of the knowledge and wisdom of God, how profound have Thy thoughts become?
The Son and wisdom of God took upon Himself both the flesh in which there was sin, and