Thomas Aquinas’s second greatest work, Summa Contra Gentiles (SCG), is a monument in the history of Catholic apologetics. Studying it pays great dividends not only in defending the Faith but also in deepening and encouraging our own faith and our love for God.
Aquinas thinks the good apologist is like a doctor—a doctor of souls—who longs for spiritual health in those he treats. As we continue to bask in the glow of the Christmas season, I’d like to offer a small dose of Aquinas’s medicine for the soul based on his defense of the reasonableness of the Incarnation found in the SCG, book 4, chapter 54.
St. Thomas has an elegant understanding of the relationship between human reason and the truths of Christian faith. There are some things we can convincingly show by using reason or philosophy; there are other things that we can’t know by reason alone.
Consider your very self. Others may know, merely by looking across a room, that you exist. They can know your approximate height, weight, and hair color. They can see the defining features of your face. The deep and profound things about you, however, can only be known if you reveal them. If you share with someone deeper truths (for example, your core beliefs, the ideas and the people that have most influenced you), they can choose to believe what you say. Those truths are not immediately apparent to them, so revealing our inner life implies a request for a trusting, loving response by others.
They may choose to reject our self-revelation, however. And so it is with God. We can know some things about God just by looking at him (as it were), whereas there are other things that God must reveal if we are to know them at all. Like others must to our own personal revelations, we must choose how to respond.
What can we know of God through reason? Well, we can know that there is a first cause of all dependent, changeable things. We can know also that human beings aren’t ultimately happy with anything in this world. We spend our restless lives searching for a final and complete happiness that this world is powerless to give us. Our seemingly insatiable desire for enduring happiness and fulfillment is radically disproportionate to anything we encounter in this finite, material world.
Thomas Aquinas saw this problem keenly. He knew it was a dead end to think that finite things can satisfy the human desire for happiness. This, he thought, should nudge us to the conclusion that our happiness can only be found in something that is greater than any finite thing. And that is God.
But he also saw that it is hard for typical human beings to live consistently with this conclusion. Our animal bodies are such a powerful diversion from our more noble desires. We need something to bend our will toward something higher and greater than our animal or bodily fulfillment.
What is that something? “Nothing,” Aquinas writes, “so induces us to love one as the experience of another’s love for us.” Love inspires love. Those who love us the most sincerely and consistently are those who we are most drawn to love in return.
He continues that “it is proper to love to unite the lover with the beloved so far as possible.” To the degree that you love someone, you want to be joined together with him. The old Greek myth about original human beings having four legs and four arms, tragically divided in two and separated from each other (resulting in humans with two legs and two arms), vividly sets forth the regular human experience of incompleteness as well as longing for fulfillment in loving union with others. The notion of “soul mates” makes the point, too.
So, here is the situation. First, we want eternal, unending happiness, and nothing in this world can give it to us. Second, the greatest motivation for us is love, especially the love of those who care so much for us that they want to unite their lives to our own as much as possible.
Based on these considerations, Aquinas reasons that there is “no more effective way” that God could show his love than by willing “to be united to humans in person.”
A lover wants to be united with his beloved. We love happiness, goodness, truth, and beauty; but the world, at best, teases us with finite and fading flashes of these things. The Christian faith tells us that to find this happiness we crave we must look to Jesus, who not only is in himself perfect goodness, truth, and beauty, and the source of all happiness, but in the Incarnation has forever united himself with the human family.
There was no higher way to show us his love. There was no higher way to show that our desires mean something, after all. God’s personally seizing and drawing to himself a human nature was the most wonderful indicator that he loves us, wants to be near us, and that final and enduring happiness is achievable. Our songs, plays, poems, movies, and art regularly set before us the paradox of human desires and the futility of our efforts to solve the riddle of our own selves. The Incarnation is God’s definitive answer.
Looking across the “room” of the universe, we can get a glimpse of God’s existence and even some attributes that must belong to him. That God intensely loves us can be known, however, only by looking in loving trust to Jesus. He is God’s love taking hold of our nature and, by doing so, telling us: I love you.
Aquinas has not, by these considerations, compelled us to believe in the Incarnation. He has, however, given us a powerful reason for entrusting ourselves to this loving revelation of who God is.
Check out Mark's conversion story from Oneness Pentecostalism and defense of the Holy Trinity, All in the Name, from Catholic Answers Press.