Peter Kreeft’s new book Practical Theology promises “358 pieces of wisdom from Saint Thomas’s masterpiece the Summa, which are literally more valuable than all the kingdoms of this world because they will help you to attain ‘the one thing needful,’ the summum bonum or ‘the greatest good,’ the ultimate end and purpose and meaning of life.” Kreeft, a professor of philosophy at Boston College and the author of many books, presents “Spiritual Direction from Saint Thomas Aquinas” — in “an easily digestible sample” of Aquinas’s “distinctly religious wisdom.” He responds to questions here about it. — KJL

Kathryn Jean Lopez: Is your Practical Theology a self-help version of Saint Thomas Aquinas’s Summa? An executive summary for beginners? Is it just for beginners?

Peter Kreeft: Practical Theology is as far from self-help nonsense, i.e. pop psychology, as you can get. It’s theology, and it’s Aquinas, and it’s the Summa, for goodness’ sake. I have no idea what “an executive summary” is, but I’m quite sure this isn’t it. And it’s for everybody, therefore it’s for beginners. When it comes to God we’re all beginners, especially the ones who think they are experts. Only fools think they’re sages; sages know they’re fools. (P.S. Aquinas wrote the 4,000-page Summa “for beginners.” That was not satire. It’s really a very simple book.)

Lopez: Is theology ever practical, really?

Kreeft: Theology is always practical because nothing is more practical than living in reality, living in the real world, and God is the origin, center, end, and meaning of reality. If that’s not true, let’s be pagans, atheists, or TV executives.

Lopez: You say that “if our love is right, everything else will be right.” How does the Angelic Doctor propose that we get love right? Is he the love doctor, too?

Kreeft: Augustine wrote, “Amor meus, pondus meum” — “my love is my weight,” my gravity, my destiny. How to get love right? Ask its inventor, origin, and standard, the God who is love. He told us in many ways: conscience, saints, Scripture, Church, above all Christ. Yes, he is the love doctor. And he’d tell a culture like ours that identifies that title with Ruth Westheimer that it is as right about this as it would be in identifying expertise on Einstein with Archie Bunker.

Lopez: What is an angelic doctor, anyway?

Kreeft: He’s called “the” (not “an”) angelic doctor because (a) he got the angels right, and, most especially, because (b) like an angel, he was remarkably free from lust, greed, and other foolish human passions.

Lopez: Why is Saint Thomas Aquinas such a big deal? And one of the best spiritual directors?

Kreeft: He’s big because he was very large, like G. K. Chesterton. His mind is big because he gives us “big pictures” all the time, not little crabbed clever pieces of “scholarship.” And he’s a great spiritual director because he has the personal virtues that takes: personal sanctity (love of God and His creation, especially human beings), brilliant insight into good and evil, humility and open-mindedness, absolute honesty, and the habit of saying everything as simply, clearly, and directly as possible.

Lopez: Unless you’re discerning a religious vocation, or deeply invested in Catholic apostolic work, the phrase “spiritual direction” may be foreign to a lot of Catholics, as a practical matter in their lives. Should it be an element of every Catholic’s life?

Kreeft: A Catholic is one who believes what the Catholic Church teaches. The Catholic Church teaches that the meaning of life is holiness, happiness, and heaven. Spiritual direction means help in that journey. If that’s practical only for priests or apostles, we laypeople can say, of the supreme wisdom, “The hell with it; it’s not for me.” It’s the other way round: The clergy are for the people, not vice versa. The pope is “the servant of the servants of God.”

Lopez: What does the Summa have to do with human happiness?

Kreeft: The Summa is a map of reality and human life. Are we happy when we can get Home, or when we are lost?

Lopez: Last month at the Vigil for Life before the March for Life, Sean Cardinal O’Malley talked up chastity. What does chastity have to do with a culture of life and a renewal of the family? What does Thomas Aquinas have to offer here from his own experience and writing?

Kreeft: Chastity means moral virtue, moral goodness, in matters of sex. No culture in history has ever more radically or selectively repudiated its sanity than ours has in that area. Human life begins in sex. Families begin in sex. Sex is part of the image of God, according to Genesis 1:27 and Saint John Paul II’s “theology of the body.” The family has always been the primary building block and clearest indicator of a happy society. Aquinas puts everything in its place, including chastity. He’s neither a puritan nor a libertine. He’s not a new, creative, original theologian but a synthesis of the Church’s perennial teaching on pretty much everything, including chastity. He’s also good at talking about it because he was good at living it.

Lopez: How does Thomas Aquinas say the Eucharist keeps one from sin? And how is he so sure sin is the worst thing in the world?

Kreeft: The Eucharist keeps us from sin because the Eucharist is literally Christ, whose given name, “Jesus,” means “savior” — from sin. And that means not just salvation from sin’s punishment (hell) but from sin itself, i.e., He sanctifies us as well as justifying us, makes us heavenly here as well as taking us to heaven there.

He is sure that sin is the worst thing in the world, even worse than pain (which very much surprises and discombobulates nearly everyone in our culture) for the very simple reason that sin means separation from God, and God is the supreme good, joy, happiness, and fulfillment. Sin is much worse than just disobeying laws; sin is the dying of the soul, the personality, the Who, the I, the self. God is the source of all life and joy; sin cuts that umbilical cord. We’re all sinaholics. And quite insane, by the way; for we know, by experience, not just by faith, that sin and selfishness (“my will be done”) always bring us misery, in the end, and that unselfish love and faith (trusting God: “Thy will be done”) always bring us joy and peace, in the end. So the next time you’re tempted to sin, think this way: God, in giving you free will, is asking you: “Which hand will you pick? In my right hand is the key to joy, in my left hand is the key to misery. You know that every time you picked my right hand you got joy. What about this time?” And we say: “Hey, God, let’s try the left hand; maybe it will work this time.” We are quite insane.

Lopez: How do you envision regular, non-scholar Catholics making use of this book? Would a non-Catholic scholar have any use for it?

Kreeft: Pretty much the only person who might have no use for this book would be the kind of non-Catholic scholar who scorns simple reason, hugs non-Catholicism to himself as part of his very identity, and is proud of being a “scholar” rather than a lover of wisdom. For everybody else, here’s some food you can really eat.

Lopez: You take a frequently-asked-questions approach to the book, with practical questions. Which are some of your favorite questions and answers?

Kreeft: My favorites are (a) the most obvious but forgotten “big ideas,” such as the idea that the only three reasons anyone ever should do anything are that it’s practically necessary, morally virtuous, or pleasant. That wonderfully simplifies your life. And: (b) unexpected little pieces of wisdom such as “cure for sadness: a good glass of wine, a hot bath, and a good night’s sleep,” and calling Socrates the greatest of all philosophers because, like Christ, he wrote nothing (the “secondary” kind of teaching), but simply lived his philosophy wholly (the “primary” kind).

Lopez: What is your prayer that people walk away from Practical Theology knowing about Thomas Aquinas?

Kreeft: I did not write the book so that readers could know Aquinas. I wrote the book so that readers could know themselves. That is why I used Aquinas. He tells you nothing about himself, but a lot about you.

— Kathryn Jean Lopez is senior fellow at the National Review Institute, editor-at-large of National Review Online, and founding director of Catholic Voices USA.