Ran across this and thought of this old thread.
By Anselm of Canterbury, 11th century - theologian"If it be necessary, therefore, as it appears, that the heavenly kingdom be made up of men, and this cannot be effected unless the aforesaid satisfaction be made, which none but God can make and none but man ought to make, it is necessary for the God-man to make it."
"Therefore the God-man, whom we require to be of a nature both human and Divine, cannot be produced by a change from one into the other, nor by an imperfect commingling of both in a third; since these things cannot be, or, if they could be, would avail nothing to our purpose. Moreover, if these two complete natures are said to be joined somehow, in such a way that one may be Divine while the other is human, and yet that which is God not be the same with that which is man, it is impossible for both to do the work necessary to be accomplished. For God will not do it, because he has no debt to pay; and man will not do it, because he cannot. Therefore, in order that the God-man may perform this,
it is necessary that the same being should perfect God and perfect man, in order to make this atonement. For he cannot and ought not to do it, unless he be very God and very man. Since, then, it is necessary that the God-man preserve the completeness of each nature, it is no less necessary that these two natures be united entire in one person, just as a body and a reasonable soul exist together in every human being; for otherwise it is impossible that the same being should be very God and very man."
