The use of contraceptives did not really take off until the advent of the pill in the early '60s. At the time, the pill was heralded as a great boon to married couples because it would remove from sex the fear of pregnancy. The divorce rate in America was 25 percent. It proceeded to double quite rapidly. While there were a number of reasons for this general breakdown of marriage, the pill certainly contributed. One obvious reason is that it makes infidelity easier by taking babies out of the picture. It also turns premarital sex into a recreation like tennis or bungee jumping, so that many enter marriage with a consumerist attitude toward sex that is easily bored and dissatisfied.
But there are more profound reasons why the pill is so disruptive to marital happiness. It has to do with the nature of sexuality itself. Sex, we tell our audience, is a mystery that can never be reduced to mere biology. It has a meaning far beyond the physical act of love. In The Graduate when Mr. Robinson confronts young Benjamin Braddock about his adultery with Mrs. Robinson, Benjamin defends himself by saying that it was no big deal: "Mrs. Robinson and I might just as well have been shaking hands." Mr. Robinson gets even more upset, and rightly so; because behind Benjamin's statement is a gnostic separation of spirit and flesh, of heart and body, which even the dimmest of cuckolds can sense is utterly wrong.
Our culture has been able to turn sex into a casual activity because it has separated personhood from the human body. Most people have the idea that their real self is somewhere inside the proverbial ghost in the machine and that what they do with their bodies doesn't make much difference. But this has never been the view of the Church, which teaches that the body is not a mere appendage, but is as much a part of us as our soul. After all, we don't say in the Nicene Creed that we believe in the immortality of the soul, but in the resurrection of the body. In a very significant way, we are what we do with our bodies.
The Old Testament uses a very interesting verb for sex: to "know." One of the things we surrender in the act of love is knowledge about ourselves that only our spouse should have. Nobody has written about these aspects of sex more profoundly than John Paul II in Love and Responsibility (1959). In that book, the future philosopher-pope argues further that each person is an irreducible subject "a person, not a thing," who ought never to be used as an object. As we know, sex is an appetite which has a tendency to do just that: to treat persons as objects. A couple can easily slip into treating one another as objects, as things to be used in bed, rather than as persons giving and receiving the spousal gift of love. And this may be why so many couples are bored by modern sex: You can tire of an object, while you can never tire of a person.
There is also the matter of babies. God's first command to humanity was to be fruitful and multiply. For those made uncomfortable by divine injunctions, the most elementary biology textbook will explain that sex is for making babies. And since sex is such a deep part our identity, it may be that when you sterilize the baby-making potential of sex, you are doing damage to yourself.
Artificial contraception is wrong because it violates the gift of self that ought to be at the center of every act of physical love. When you take the pill or use a foam, diaphragm, condom, or whatever, you are, in effect, saying to your spouse, "In this, the most intimate act of our marriage, I am going to give myself to you, but only up to a point." Or, conversely, you are saying, "I want you in this act to make a total gift to me of yourself, except that part of you which so deeply defines you as a sexual being, your fertility."
The body has its own deep language, and when we add chemicals or latex to the act of love, when we deliberately destroy its potential for making new life, we falsify the nuptial meaning of its actions. We hold back the full gift of self which during the wife's fertile period must include an openness to new life.
A couple who use artificial birth control are not only falsifying the meaning of sex, they are also behaving immaturely: trying to extract gratification from an act while getting rid of its natural consequences. It is not unlike certain eating disorders.
Chesterton put it well when he said that birth control "is a name given to a succession of different expedients by which it is possible to filch the pleasure belonging to a natural process while violently and unnaturally thwarting the process itself."