In this chapter Lewis will discuss sex and the Christian virtue of chastity. Chastity is the most unpopular of all virtues, he says. It would seem that either our innate sexual instincts are wrong, or Christianity itself is wrong. Lewis, of course, claims that our instincts are wrong. To begin with, he says, let’s agree that the biological purpose of sex is to produce offspring. If healthy young people were to follow their sexual instincts without any caution, they’d produce enough children to populate a village. So for practical purposes alone, there needs to be some kind of prohibition on sexuality.
This is one of the most controversial chapters in Mere Christianity. In it, Lewis argues that humans should refrain from having sex before marriage, even if their biological instincts urge them to do so. Clearly, there is some practical reason for humans to refrain from sex—if everybody had sex constantly, the world’s population would explode and people would starve to death.
Imagine a hypothetical society in which audiences would pay to see a “strip-tease” except with food instead of a naked performer (so the audience would salivate as someone slowly lifted up a tray of bacon or chocolate). Clearly, Lewis argues, something would be deeply wrong with this society.
For many years, Lewis claims, he’s been hearing nothing but lies about sex. He’s been told that the sex instinct is just a natural, healthy instinct, no different from hunger or thirst. The problem with such an idea, however, is that when we permit sex and normalize it, nothing gets better. For twenty years at least, Lewis argues, sex has not been “hushed up,” and yet sex is still “a mess.” Lewis is also tired of hearing that Christianity condemns sex and the human body. On the contrary, Christianity glorifies the human body and encourages people to “be fruitful and multiply.”
In retrospect, Lewis’s argument that normalizing sex just makes sex more of “a mess,” based on English society in the 1940s, could be considered short-sighted—since, by 21st century standards, Lewis’s society was still very repressed and ignorant of sexuality. Nor does Lewis acknowledge the anxiety and self-hatred that the Christian prohibitions against having sex out of wedlock have caused.
Even if sex itself isn’t inherently evil, the state of human sexuality in modern society is shameful. (Similarly, there’s nothing wrong with eating food, but “if half the world made food the main interest of their lives,” there would be a problem.) People are obsessed with sex, to the point where they can’t think about anything else. Movies, books, and plays tell us that having a lot of sex is glorious, fun, and happy. This is a lie—there’s nothing automatically joyful about sex or having sex frequently. If humans gave into their instincts at all times, the world would fall apart—the sexual instinct is no different.
This passage could be considered an example of the “false dichotomy” logical fallacy. Lewis seems to believe that society must choose between two extremes: 1) constant sex and sexual perversion, and 2) Christian chastity. The possibility of a compromise between 1) and 2) does not come up here.
Few people try to practice Christian chastity. There are several reasons why: 1) the modern media makes sex seem completely normal; 2) people don’t think that Christian chastity is possible, so they’re convinced that they’d never be able to sustain it; 3) people believe that chastity leads to “repression” and neurosis. Such a belief is based on a misinterpretation of modern psychology, Lewis claims. There is nothing inherently unhealthy about refusing to give in to an urge; indeed, it is perfectly possible to deny oneself sex without becoming neurotic.
Lewis argues that the modern media glamorize sex and sexuality to the point where most people believe that it’s “normal” to have sex all the time. (You can’t help but wonder what Lewis would have to say about 21st century American society.) Lewis also insists that one can refrain from sex without becoming a neurotic—but he doesn’t really address how such repression often does lead to real psychological harm.
One final note—although the denial of sex has been one of the most notorious features of Christianity, it’s not a particularly important part of the religion. True Christians don't really believe that sex is one of the worst sins; indeed, it’s possible for a priggish virgin to be more sinful than a prostitute.
Lewis seems eager to end his discussion of sex as soon as possible. Even if his ideas about sexuality seem dated by today’s standards (even among many 21st century Christians), he ends with a characteristic display of moderation—sexual sins might get more attention than most, but they’re far from the worst of sins.