Why did the Son of God take our human nature? Thomas points out that everything acts according to what it is so that humans act in a reasonable way. How would we describe God’s nature? Thomas thinks the description of God by the Syrian theologian, Dionysius, quickly gets to the heart of what God’s nature is. Thomas explains: “The very nature of God is goodness, as is clear from Dionysius. Hence what belongs to the essence of goodness befits God” (3a. 1, 1).
Since everything acts as it is and God’s nature is goodness, then God acts in good ways. Thomas draws upon another principle of Dionysius, “It belongs to the essence of goodness to communicate itself to others…” (3a. 1, 1).
We know that good people are generous but God’s goodness and generosity exceed whatever we experience in our human encounters. Thomas explains: “It belongs to the essence of the highest good to communicate itself in the highest manner to the creature” (3a. 1, 1). God’s generosity flows from His goodness. God’s generosity and His goodness are the ultimate explanation for the Incarnation.
Why was the Incarnation good? From the perspective of the divinity of the Son of God, which surpasses our humanity, there doesn’t seem to be any reason why it would be appropriate or fitting for the Son of God to take our nature to Himself. The one way that it seems appropriate is for our sakes, as Thomas explains that “God by reason of His infinite goodness should unite human nature to Himself for our salvation” (3a. 1, 1, ad 2).
Was the Incarnation the only way we could have been saved? Thomas recalls John’s Gospel: “God so loved the world that He gave His only-begotten Son so that those who believe in Him may not perish but may have eternal life” (Jn 3:16). Thomas thinks that the Incarnation was not the only way that we could be saved but it is a way that achieves its goal “better and more conveniently” (3a. 1, 2). Thomas offers the example of a horse as a better, although not necessary, way to travel. We might think of a car or a plane as a better way.
Why is the Incarnation a better way to bring about our salvation? According to Thomas the Incarnation is most effective in achieving God’s purpose “for the restoration of human nature.” The Incarnation strengthens our faith because we are more likely to believe God than to believe each other. When Jesus speaks to us, “God Himself speaks.”
The Incarnation strengthens our hope. Thomas recalls Augustine’s words: “Nothing was so necessary for raising our hope as to show us how deeply God loved us. And what could afford us a stronger proof of this than that the Son of God should become a partner with us of human nature?”
Our love for God, “is most greatly enkindled by the Incarnation” because we see how much God loves us. Thomas refers to Augustine’s words “What greater cause is there of the Lord’s coming than to show God’s love for us? … If we have been slow to love, at least let us hasten to love in return.”
The Incarnate Son of God teaches us the right way to live by His example. Thomas alludes to Augustine’s words: “Humans whom we can see are not to be followed but God who cannot be followed is not seen. God was made man that He might be seen by us and that we might see the one we should follow.”
Thomas states that “full participation of the Divinity is our true happiness and the goal of human life.” This sharing in divinity “is bestowed upon us by Christ’s humanity.” Thomas remembers Augustine’s affirmation, “God was made man that man might be made God.”
Thomas adds that the Incarnation delivers us from evil. This liberation begins by instructing us not to be overwhelmed by the devil. He recalls Augustine’s words that since “human nature is joined to God as to become one with Him in person,” there is no cause to be affected by evil spirits since “they are without flesh” and the Son of God has come closer to us by taking our flesh.
We are also taught “how great is the dignity of human nature,” which should make us reluctant to sin. Thomas evokes Augustine: “God showed us the exalted place that human nature holds in creation by appearing to men as a true man.” In a similar way, St. Leo instructs us: “O Christian, acknowledge your dignity; having been made a sharer in the divine nature, refuse to fall back into your previous worthlessness by your conduct.”
Again, Thomas says that one of the effects of the Incarnation is “to do away with human presumption. He refers to Augustine, “The grace of God, with no preceding merits on our part, is shown to us in the man Christ.” Thomas affirms that Jesus’ humility can heal our pride, as Augustine says, “Man’s pride, which is the greatest stumbling-block to our clinging to God, can be convinced and cured by humility so great.”
The Incarnation rescues us from slavery. He returns to Augustine, this “should be done in such a way that the devil is overcome by the justice of a man, Jesus Christ.” Thomas adds that this is accomplished by “Christ making satisfaction for us.” Since a human person could not make satisfaction for the whole human race, Thomas explains, “It is fitting, then, for Jesus Christ to be both God and human” (3a. 1, 2). He calls upon the words of Leo: “Weakness is received by power, humility by majesty, that one and the same mediator between God and man might die from the one and rise from the other, and so were we fitly restored. Unless He were truly God, he could not provide a cure; unless He were man, He could not offer an example.”
Thomas recognizes that ultimately the reasons for the Incarnation are God’s reasons but theology applies reason to the mysteries revealed in faith, although always recognizing the limitations of our human thinking when applied to divine mysteries. He notes: “There were many other advantages resulting, which are beyond our present earth-bound comprehension.”
Denis Vincent Wiseman, O.P.
 Dionysius is the author of De Divinis Nominibus, part of four theological and liturgical works. He wrote about the year 500. Because he wrote under the name of Dionysius who was converted by Paul at the Aereopagus in Athens, he is often called Pseudo-Dionysius or Dionysius the Aereopagite. Thomas finds his answers to God’s nature in the first part of the De Divinis Nominibus.
 References are to the Summa Theologica, trans. English Dominicans (New York: Benziger Brothers, Inc, 1947), pp. 2025-2027. The citations give the part of the Summa, the question and the article. In this case, it is the third part, the first question and the first article in that question.
 The preposition “ad” indicates that this is Thomas’ reply to one of the objections that he used to introduce the question.
 Augustine, De Trinitate (“On the Trinity”), XIII, 10.
 Augustine, Liber de catechizandis rudibus (“The Instruction of the Unlearned,” 4.
 Augustine, Sermo CCCLXXI, 2: PL 39, 1660.
 Augustine, Sermo CXXVIII PL 39, 1997.
 Augustine, De Trinitate XIII, 17, PL 42, 1031.
 Augustine, De Vera Religione 16. PL 34, 134-5.
 Leo, Sermo CCI. PL 54, 192.
 Augustine, De Trinitate, XIII, 17.
 Augustine, De Trinitate, XIII, 17.
 Augustine, De Trinitate, XIII, 14. An earlier source along this line is Irenaeus, Adversus haereses IV, 28.
 Leo, Sermo XXI, PL 54, 192.
 3a. 1, 2.