1. It would seem most fitting that by visible things the invisible things of God should be known; for to this end was he world made, as is clear from the word of the Apostle, “Ever since the creation of the world his eternal power and divine nature, invisible though they are” (Romans 1:20). But, as Damascene says, by the mystery of the Incarnation are made known as once – “the goodness, the wisdom, the justice, the power, or the might of God – the goodness, for He did not despise the weakness of his own handiwork; the justice, since on man’s defeat, He caused the tyrant to be overcome by none other than man and yet He did not snatch men forcibly from death; the wisdom, for He found a most suitable discharge for a most heavy debt; the power, or infinite might, for there is nothing greater than for God to become Incarnate.
2. To each thing is befitting that which belongs to it because of its nature; thus, to thank befits man, since this belongs to him for he has a rational nature. But the very nature of God is goodness. Hence, what belongs to the essence of goodness befits God. But it belongs to the essence of goodness to communicate itself to others. Therefore it belongs to the essence of the highest good to communicate itself in the highest manner to the creature and this is done chiefly by His so uniting created nature to Himself that one Person is made of these three – the Word, a soul, and flesh, as Augustine says. Hence it is manifest that it was fitting that God should become Incarnate.

To be united to God in unity of person was not fitting to human flesh, according to its natural endowments, since it was above its dignity; nevertheless it was fitting that God by reason of His infinite goodness, should unite it to Himself for man’s salvation.

Augustine says: “God is great not in mass, but in power. Hence the greatness of His might feels not straits in narrow surroundings. If the passing word of a man is heard at once by many, and wholly by each, it is incredible then that the abiding Word of God should be everywhere at once?” Hence nothing unfitting arises from God becoming Incarnate. (3a, q. 1 a. 1.)