My senior year of college I lived on a floor with gender-neutral bathrooms. One evening I came in with my toothbrush to find a friend from down the hall standing in front of the mirror. She had come from a conservative evangelical family and was now a feminist majoring in sociology. But that night she stood there in hurt astonishment, repeating to herself, “How did I become so cheap?”

American young people have come of age in a time when the ideals of the sexual revolution are unquestioned gospel truths. On the one hand, the sexual revolution taught us that the physical and emotional pleasures of sex are the highest goods in life. On the other hand, it taught us that sex is not sacred, but simply a natural urge, like our desires for water and food. People in my generation are beginning to see the cost of these precepts, especially for women.

Young people like my friend need to know how to love and be loved in a way that acknowledges their great value, and Christians are called to show them a more excellent way. This can be done by example, of course, but we also have the aid of thinkers who help us to articulate the dignity of each person and the sanctity of sex.

Some of the most successful articulations of Christian sexual ethics in the twentieth century have come from personalist philo­sophy. Instead of emphasizing rationally derived rules, personalism focuses on the realities that we perceive through our experience of being human. One of the first personalists was Dietrich von Hildebrand, who fled Germany after opposing Hitler and spent the rest of his years writing and teaching in New York. Von Hildebrand’s work – especially his writing on love and the spiritual life – had a great impact on subsequent authors, including Dorothy Day, Pope John Paul II, and Pope Benedict XVI.

In the 1920s, von Hildebrand published In Defense of Purity, which has recently been re-released. The book is a meditation on the depth and mystery of sex. In contrast to his contemporaries, who emphasized the dangers of impurity and sin, von Hildebrand’s account is grounded in the beauties of purity and virtue.

It begins by preemptively countering one thesis of the sexual revolution: unlike hunger and thirst, sex is “essentially deep” and “involves the soul deeply in its passion” (all italics are original). This is because sex is our most intimate act of self-disclosure, “the secret of the individual, which he instinctively hides from others.” Therefore, “to disclose and surrender it is in a unique sense to surrender oneself.” We often talk about finding ourselves. For von Hildebrand, we find ourselves only by giving ourselves away. Only by losing our lives for the sake of love of God and neighbor will we find them. We can find ourselves through sex, therefore, not by the strength of our passion or pleasure, but by the depth with which we offer ourselves to another, body and soul.

The danger of such a gift lies precisely in this power. Because sex is a real and final self-gift, it requires entering into a lasting external union, “a permanent objective community of life.” Without such a union, there is a lack of harmony between the objective character of the act – what one is doing – and the intention with which it is performed – why and how one does it. In order to be true to the reality it expresses, sex must take place within the bond and love of marriage.

Together, purity and reverence cultivate tenderness.

When it comes to our sexuality, von Hilde­brand concludes, we are faced with a mystery on either side: “Either the mysterious union of two human beings takes place in the sight of God … or man flings himself away, surrenders his secret, delivers himself over to the flesh, desecrates and violates the secret of another, severs himself in a mysterious fashion from God.”

For Christians, marriage is ultimately an expression of the bond between Christ and the Church, as Paul teaches in Ephesians 5. Surrender to a spouse must be formed by surrender to God. Marriage is also a sign of the union between the persons of the Trinity, a union that overflows into the new life of creation. As such, von Hildebrand argues, procreation is a vital part of marriage: “The marriage act can only be transformed qualitatively and ennobled from within when the immensely powerful thought of the inception of a new human soul influences the physical act of sex through the medium of wedded love.” This is not to say that infertile couples do not have real marriages. Rather, Christians should cultivate an openness to receiving children as gifts from God. They are not an optional accessory to marriage, like a dog or a cat.

Having laid out his understanding of human sexuality, von Hildebrand turns to the definition of purity. Contemporary Christians tend to think of purity as a matter of guarding one’s heart and body so as to give them to a future spouse unstained. For von Hildebrand, however, purity is a matter of union with and conformity to Christ. “It is the surrender to this splendor [of God] which formally constitutes purity,” he writes. The soul of a pure person is marked by radiance and clarity, full of love and humble sincerity, living in the world illuminated by the light of God’s truth.

“Reverence is a fundamental component of purity,” von Hildebrand continues. Purity is not prudery or insensibility. Rather, the pure person clearly sees the powerful mysteries of God and loves them rightly. To borrow a metaphor from art history, the pure person’s solution to the danger of lust is not to put fig leaves on statues, but to look at nudes that faithfully depict the beauty of the human form.

Together, purity and reverence cultivate tenderness. Of all the traits von Hildebrand discusses, tenderness is most conspicuous in its absence from the fruits of the sexual revolution, as the New Yorker story “Cat Person” and contemporary TV shows and films attest. Tenderness requires truly willing the good of the other, reverence for the other, and vulnerability – the kind of things that casual sex destroys. Hence, von Hildebrand writes, “It is now clear what sex is as exercised by the pure: an unconstrained, tenderly affectionate surrender of love grounded in a humble, reverent, serene, and radiant attitude. No sultry heats are here, nor grossness of triumphant flesh.”

This is true, in a sense, but also shows the drawbacks of In Defense of Purity. Von Hilde­brand’s writing can seem maudlin to a modern reader – the prose equivalent of a German drawing room from the 1920s. In exalting the spiritual nature of marital love, he sometimes misses its earthiness and humanity. Sex may elevate raw physical desires, but it does not escape them. It is hard to see how von Hildebrand accounts for the comedy of marital love, the fact that one can burst out laughing in the middle of it. Yet that humor, physicality, and humanity are precisely what make Christian marriage participate in the mystery of the Incarnation, when Christ took on our human nature in all its curious aspects.

Tenderness requires truly willing the good of the other, reverence for the other, and vulnerability.

Furthermore, in the century since In Defense of Purity was written, other philosophers have given accounts of Christian sexual ethics, chief among them John Paul II’s Love and Responsibility and “Theology of the Body.” Contemporary authors such as J. Budziszewski and Alexander Pruss offer arguments for the intrinsic meaning of sex that go beyond von Hildebrand, largely because today we require those arguments in a way his audience did not.

Finally, von Hildebrand turns to the question of consecrated virginity. He argues that the person who does not find a spouse is not necessarily purer than the one who does. What the church values is not celibacy, per se, but consecrated virginity, which is freely chosen and sealed with vows like a marriage. Consecrated virginity is a spiritual marriage with Christ. The church considers it the highest vocation, not because sex is dirty, but “because as a state of life it is the expression freely chosen as such of what is essentially the final and supreme vocation of every man.”

I reflected on this when a friend of mine made her final profession as a Dominican nun this fall. My own marriage reflects the reality of Christ’s espousal of the church, but Sister Diana Marie’s consecrated life reflects the reality that our souls ultimately belong to Christ alone, now and forever.

When I was in Buffalo for her final profession, I told the hotel’s shuttle driver the reason for my visit. He couldn’t fathom the life she had chosen: “Having just one woman for the rest of your life – that’s a good thing, right?” Yes, I replied, and held up my wedding ring, I’m doing that myself. But Sister Diana Marie has chosen a different kind of marriage. (No watching football games either, he was stunned to hear, though I assured him that nuns relax in other ways.) “So it would be kind of like going to church on Sunday, and giving God part of your time, but then staying in church with the same people, all the time?” Yes, a bit like that. It is a total consecration to God, all the time, a heightened way to live the baptism all Christians have and a foretaste of what we hope to enjoy forever. For the vision of God is the end goal of all Christian lives, and the greatest fruit of purity.

Image from Bridgeman Images, New York copyright © 2018 / Artists Rights Society (ARS), New York