When I was a youngster, all the progressive people were saying, “Why all this prudery? Let us treat sex just as we treat all our other impulses.” I was simple-minded enough to believe they meant what they said. I have since discovered that they meant exactly the opposite. They meant that sex was to be treated as no other impulse in our nature has ever been treated by civilized people. All the others, we admit, have to be bridled. Absolute obedience to your instinct for self-preservation is what we call cowardice; to your acquisitive impulse, avarice. Even sleep must be resisted if you’re a sentry. But every unkindness and breach of faith seems to be condoned provided that the object aimed at is “four bare legs in a bed.”It is like having a morality in which stealing fruit is considered wrong—unless you steal nectarines.And if you protest against this view you are usually met with chatter about the legitimacy and beauty and sanctity of “sex” and accused of harboring some Puritan prejudice against it as something disreputable or shameful. I deny the charge. Foam-born Venus … golden Aphrodite … Our Lady of Cyprus… I never breathed a word against you. If I object to boys who steal my nectarines, must I be supposed to disapprove of nectarines in general? Or even of boys in general? It might, you know, be stealing that I disapproved of.
C.S. Lewis, God in the Dock: Essays on Theology and Ethics
commentary, cs-lewis, morality