The truth is humans are pretty clearly divided on (the matter of indecent or bawdy humour) into two classes. There are some to whom "no passion is as serious as lust' and for whom an indecent story ceases to produce lasciviousness precisely in so far as it becomes funny: there are others in whom laughter and lust are excited at the same moment and by the same things. The first sort joke about sex because it gives rise to many incongruities: the second cultivate incongruities because they afford a pretext for talking about sex. If your man is of the first type, bawdy humour will not help you — I shall never forget the hours which I wasted (hours to me of unbearable tedium) with one with one of my early patients in bars and smoking-rooms before I learned this rule.A thousand bawdy, or even blasphemous, jokes do not help towards a man's damnation so much as his discovery that almost anything he wants to do can be done, not only without the disapproval but with the admiration of his fellows, if only it can get itself treated as a Joke.
CS Lewis
Screwtape Letters
