On p.95 he says:
Chastity is the most unpopular of the Christian virtues. There is no getting away from it; the Christian rule is, 'Either marriage, with complete faithfulness to your partner, or else total abstinence.' Now this is so difficult and so contrary to our instincts, that obviously either Christianity is wrong or our sexual instinct, as it now is, has gone wrong. One or the other. Of course, being a Christian, I think it is the instinct which has gone wrong.
He then compares and contrasts our appetites for sex and for food. Generally we become most warped through an over-indulgence. But I thought it interesting what he had to say about those who believe they are unable to resist. On 101 he says...
We may, indeed, be sure that perfect chastity - like perfect charity - will not be attained by any merely human efforts. You must ask for God's help. Even when you have done so, it may seem to you for a long time that no help, or less help than you need, is being given. Never mind. After each failure, ask forgiveness, pick yourself up, and try again. Very often what God first helps us towards is not the virtue itself but just this power of always trying again. For however important chastity (or courage, or truthfulness, or any other virtue) may be, this process trains us in habits of the soul which are more important still. It cures our illusions about ourselves and teaches us to depend on God. We learn, on the one hand, that we cannot trust ourselves even in our best moments, and, on the other, that we need not despair even in our worst, for our failures are forgiven. The only fatal thing is to sit down content with anything less than perfection.
Ooh, baby. Process...
A great one-liner on p. 102: "Virtue - even attempted virtue - brings light; indulgence brings fog." Yep, too often we seem to think we gain better understanding by giving in to indulgences. That usually just lends itself to a cloudier vision until we're completely unable to see our wrong. Yesterday I read on p. 93, "When a man is getting worse he understands his own badness less and less. A moderately bad man knows he is not very good: a thoroughly bad man thinks he is all right."
And he saves perhaps the best for last with this gem on pp. 102-103:
Finally, though, I have had to speak at some length about sex, I want to make it as clear as I possibly can that the centre of Christian morality is not here. If anyone thinks that Christians regard unchastity as the supreme vice, he is quite wrong. The sins of the flesh are bad, but they are the least bad of all sins. All the worst pleasures are purely spiritual: the pleasure of putting other people in the wrong, of bossing and patronizing and spoiling sport, and back-biting, the pleasures of power, of hatred. For there are two things inside me, competing with the human self which I must try to become. They are the Animal self, and the Diabolical self. The Diabolical self is the worse of the two. That is why a cold, self-righteous prig who goes regularly to church may be far nearer to hell than a prostitute. But, of course, it is better to be neither.