First, sex is searching for God. I purposely put this thesis up front, as number one. Sex finds its purpose in God in that sexual union is a symbol or a sacrament of union with Christ. Paul writes in Ephesians 5:32 that this is what the mystery of sexual union is about. So you cannot think about sex in its fullest sense without thinking of union with Christ. If sexual union is sacramental in character, you can’t treat it like it’s something dirty or weird, something to avoid. Sexual union does not exist for itself, either. Yes, of course, sex is pleasurable, and bodily satisfaction is part and parcel of the sexual act.

But the pleasure we derive from sex is not its final end. Not even the relationship with one’s spouse, or the kids that may come from sex, are the main point. Sexual union derives its meaning ultimately from union with Christ. That is, our spiritual union with Christ is the great reality in the physical union between husband and wife. When we ignore union with Christ as the final purpose of sex, sexual union loses its truth, goodness, and beauty.

Second, God invents sex. We live in a broken world, but let’s not begin with brokenness. God told Adam and Eve, “Be fruitful and multiply and fill the earth” (Gen. 1:28). The reason God talks about his relationship with us as one of bridegroom and bride is that God invented weddings. God patterned human love on his love for us. Sex, therefore, is God’s idea, not ours. That means that God has a patent on sex. We can’t invent or make up ways of doing sex. We don’t ­create reality; we try to follow reality. That’s a liberating thought. We don’t have the burden of constructing our own realities; we don’t have to invent our own sense of how sex functions; we may simply enter the realities God has already created for us.

Sexual attraction itself, therefore, does not determine what is right and wrong. Just because something feels right does not necessarily make it right. Sexual “inventiveness” is a sign that things have gone awry. Our ­sexual lives are properly ordered when they follow the patent that God has on sex.

Third, sex is not God. Few people will make arguments that identify sex with God, but you and I know that in practice, that’s how we’re tempted to live. Everything around us—and, perhaps just as often, everything inside us—screams that sex is ultimate, and whatever you treat as ultimate is your God. If sexual union is only a sacrament of a greater union, namely, a union with Christ, then we must stop treating sex as though it were our God.

Sex is only one aspect of human life, and not the decisive one. It is union with Christ alone that determines who we are, and sexual union is simply a symbol of our identity in Christ. Put bluntly: You don’t need to have sex to be fully human. To be fully human, what you need is Christ. Sometimes we must say “no,” therefore, to sexual union. Self-denial is an important element of the Christian pilgrimage, for it allows us to focus on what is of ultimate importance in life: union with Christ.

Fourth, God is chastity. Sex may not be God, but the way we treat sex says a great deal about how we think about God. Sex is a good, a sacramental good. It symbolizes our union with Christ. But it’s not just sex that symbolizes union with Christ. It’s also the absence of sex that denotes our union with him. The word chastity simply means purity. (The Latin word castus means “pure.”) God is pure, which is to say, chaste, and he wants us to share in his chastity. When the Apostle John says that in the hereafter we will see God as he is, he adds a word of caution: “Everyone who thus hopes in him purifies himself as he is pure” (1 John 3:3). Why is this? Because only as you reflect the purity of God can you come into his holy temple (Ps. 24:3–4). Only the pure in heart can see the God who is purity itself (Matt. 5:8). To the extent that we regulate our sexual desires with chastity, we share in God’s purity.

Fifth, sex is temporary. Sex is meant for this life only, not for the hereafter. People who are raised from the dead, says Jesus, “neither marry nor are given in marriage” (Luke 20:35). They are, he says, “equal to angels” (20:36). Sex and marriage are for this world only; they’re not for the next. Marriage doesn’t exist for its own sake: Marriage is instrumental. It is a sacrament, and sacraments are means to a greater end. Once you’ve arrived at the greater end, you no longer need them.

The Bible holds up the end before us: “Let him kiss me with the kisses of his mouth!” says the very beginning of the Song of Solomon (1:2). Why is this erotic song in the Bible? Because it speaks of our desire for the spiritual kisses of the mouth of Christ. Once we receive his eternal, spiritual kiss, the erotic attraction of temporal, physical kisses falls away. They have served their purpose.

Sixth, disordered desire makes for disordered sex. Everything I’ve said so far implies that sex is, in principle, a good thing. But we live in a fallen world, and the next two theses are therefore about problems connected to sex. The first thing to observe here is that God made the body in the beginning, that God assumed a body in the Incarnation, and that God will renew the body in the resurrection. That must mean that the body is good. So the problems we experience in terms of sexual desire are not problems that result from the simple fact that we have bodies. Problems related to sex are primarily problems of the mind. It’s our disordered desires that lead us astray. The erotic pictures we conjure up in our imagination result from the mind not functioning properly. Our desires are misdirected. Our will ignores the sacramental character of sexual union; it brackets the reality of union with Christ and focuses on sexual desire for its own sake. The result is disordered sex—sex no longer ordered toward the reality of union with Christ.

Seventh, fallen bodies make for fallen sex. Our bodies, too, are fallen. In Genesis 3 we read that after the Fall, God made for Adam and Eve “garments of skins” (Gen. 3:21). Many in the Christian tradition have taken that comment to mean that the Fall affects our bodies. They have changed. They no longer function exactly as they were meant to, and sometimes reinforce our misdirected desires. We have to wait, therefore, until Christ’s return for our bodies to function properly again. St. Paul comments in 1 Corinthians 15 that the natural body we sow into the ground after death is going to be changed into a spiritual body (1 Cor. 15:42–44). The natural body is like a kernel dropped in the ground; the spiritual body is the wheat that appears in the final harvest (1 Cor. 15:37).

This means that we cannot take our bodily impulses as the final norms, as so often happens today. Some people feel that they are imprisoned in a body of the wrong gender; others are attracted to people of the same sex. What the Christian doctrine of the Fall tells us is this: Your struggles will not last forever. Your fallen natural body is going to be transformed into a resurrected body that is spiritual.

It also means that fallen bodies make for fallen sex; hence, every ­sexual act is ambiguous. Even when sexual union takes place within a loving relationship between husband and wife, the erotic element is not an ­undivided good. The sexual act is an act of self-giving. But this self-giving invariably is accompanied by a passion that seeks to assume command over our souls, resisting orientation toward its proper spiritual end. There’s no such thing as pure self-giving this side of eternity. It’s not just some people but all of us who struggle with defects in the sexual desires of fallen bodies.

Eighth, sex leads to kids. If we follow God’s patent on sex, kids are the outcome. Now, lots of couples grieve that they cannot have kids, and among older people, sex doesn’t lead to kids. What’s more, having children is by no means the one and only purpose of marriage. But the pain of childlessness and the joys that come from children and grandchildren in old age convey the message that sex and having babies belong together. Love bears fruit. Love bears fruit in God himself: God is love, and God in love eternally generates a Son. Our love participates in this fruitfulness: Children are the natural product of sex.

When we deliberately separate sex from having kids, we deny the most basic things about sexual union: that it is sacramental and that God has a patent on it. Throughout the Bible, children are a blessing, not obstacles that stand in our way. The psalmist says it’s a joy to have your quiver full of them (Ps. 127:5) or to have them “like olive shoots around your table” (Ps. 128:3). This is one of the great joys to be found in God’s patent on sex.

Hans Boersma is J. I. Packer Professor of Theology at Regent College.