Excerpted from Swear to God: The Promise and Power of the Sacraments with permission of Doubleday.
If married love is a sacramental sign of God's love for His people-as both testaments of the Bible testify-then the act itself must accurately reflect that love. It must be faithful, monogamous, indissoluble, and fruitful. This is the foundation of all traditional Christian sexual morality, though it will surely come as a surprise to many Christians today. I know this, because it took me completely by surprise, some twenty years ago.
Return with me, for a moment, to the early 1980s, when Kimberly and I were newlyweds. Ardent Presbyterians, we both were studying theology at a conservative evangelical seminary.The curriculum was demanding; money was tight; and we, like all our married friends, were using contraceptives. Children would have to wait till we were ready, financially and otherwise. In the meantime, artificial birth control allowed us the pleasure of what we considered "normal" marital relations. We thought of it as an extended honeymoon.During our second year at seminary, however, Kimberly discovered the lie that was at the root of our married life. In research for an ethics course, she found that, until 1930, Christian churches-without exception-condemned contraception in the strongest terms. The Protestant reformers, whom we revered, went so far as to call it "murder." Kimberly also found out that the anticontraception laws-which were on the books in many states until the 1960s-were largely the work of evangelical Protestant legislators.Yet Christian history's overwhelming verdict on contraception arrived as news to us, as did the powerful arguments for this teaching from Scripture and moral reasoning. Confronted with the evidence, Kimberly and I felt compelled to change our lives. So we threw the contraceptives away, and soon afterward our change of theology produced a change in Kimberly's anatomy. Our first child, Michael, was on the way.
Until then, we had lived a lie. It was not until years later, however, when I became a Catholic, that I could understand the true nature of our sin. Pope John Paul II has rightly called contraception "a lie in the language of love:" Sex, according to Catholic faith, should be an oath in action, a complete gift of self, an embrace in which a man and a woman hold nothing back from one another. It is a gift of an entire life, and so it belongs only in a lifelong, exclusive marriage. It is a covenant exchange, an exchange of persons: "I am yours, and you are mine." Marriage is what makes sex sacramental and covenantal.The total gift of self rules out the possibility of divorce, adultery, premarital sex-and contraception. For contracepting couples do hold something back, and it's perhaps the single greatest power two human beings can possess: their fertility, the ability to co-create with God a new life, body and soul, destined for eternity.The sexual act says in its ecstasy: "I give you everything." But contraception renders that communication untrue.For sex is a sign, a sacramental sign. Sex is, in the traditional lingo, "the marital act," the act that consummates the sacrament of marriage. And a sacrament is a channel of divine grace, which is the very life of God. So when we mess with the "sign" of sex, we're not just changing the way we talk about love; we're ceasing to love. What the novelist Flannery O'Connor said about the Eucharist could well be applied to all the sacraments: If it's just a symbol, then to hell with it.
In sacraments, we incarnate the truth. The word becomes flesh. Thus, for Catholics, sex is a mystery, but it is not something that eludes moral certainty or verifiable reality.It helps for us to know that the root of the word "sacrament" is the Latin word for "oath." When we make love, we place ourselves under solemn oath-to tell the truth, the whole truth, and nothing but the truth. (So help me, God.) Sexual union is now, as it was in ancient Israel, an oath in action.And what is the truth we tell under the oath sign of marriage? We say that God is one, and God is a Trinity. The two become one flesh, and soon they are joined by a third; yet they remain one family. Pope John Paul II wrote: "God in His deepest mystery is not a solitude, but a family, since He has in Himself fatherhood, sonship, and the essence of the family, which is love." And the Catechism adds: "The communion of the Holy Trinity is the source and criterion of truth in every relationship" (n. 2845).By God's design, marriage is the only relationship that reveals the life-giving power of love. Human love, with its fruitfulness, vividly manifests God's own being and inner life. Marriage is a sacramental sign of the Trinitarian life we hope to share forever in heaven: "In the joys of their love and family life [God] gives them here on earth a foretaste of the wedding feast of the Lamb" (CCC, n. 1642; see also Rev 19:9).
All that is the truth we tell with our bodies.