The coming of the Savior was necessary, for three reasons: first, because the world was imperfect in many was; second, because man was cast down from his rightful honor in a foul way; and third, because God was offended by man in a wondrous way. Therefore, he came in order to grant to the whole world the highest grade of dignity, in order to lead man back to his proper human state, and in order to take away the offense of man against God ...
When Christ came into this world, he accomplished a new union, he took on a new generation, and he brought along a new perfection. So in the world one grade of union was lacking, the one more wonderful than the others. For in our world there are four kinds of union: the first is the union of something corruptible with something corruptible, as in natural things. The second is the union of something corruptible with something incorruptible, as in human beings. The third is the union of something incorruptible with something incorruptible, as in spiritual things: a union of essentia and potentia. The fourth, however, was lacking: the union of something temporal with something eternal. Well, this union was made when "the Word became flesh and dwelt among us," as it says in John 1:14; "when he emptied himself (and took on the form of a slave; made in the likeness of human beings he was, through his way of life, found a man)," as Phillipians 2:7 reads; that is "when the king of Israel disguised himself," as it is said in 1 Kings 22:30; and Is 43:19 reads: "Behold, I make all things new."
Also, the one way of generation was lacking that more wonderful than the others. For there are four kinds of generation in the broad sense of the word: the first is from the Father without a mother, the generation that occurs eternally. The second is without a father and without a mother, in the beginning, as with the first parents. The third is from a father and a mother, the generation that occurs all around us. The fourth did not exist before, namely, the generation from a mother without a father in time. Well, this generation was made when the Virgin conceived, when, as we read in Isaiah 10, "the stone is hewn from the mountain without hands."
- St. Thomas Aquinas, Doctor of the Church, was a Dominican priest from Italy - December's Magnificat