Screwtape has learned from Wormwood that the patient has befriended the married couple’s other friends. In his last letter, Wormwood mentioned that these new friends are “great laughers.” Screwtape explains the role of humor and laughter in the devils’ cause.
The structure of the novel is loose and free-wheeling—one gets the sense that Lewis throws new challenges in the patient’s way simply so that Lewis has a chance to talk about them. This gives Lewis the freedom to follow his own stream of thought about Christianity, making the work a personal, thoughtful look at God.
Screwtape divides the causes of laughter into four groups: happiness, amusement, jokes, and flippancy. Happiness is beyond devils’ understanding, much like music, and the experience of being in Heaven. These sensations cannot be explained or analyzed—they just “are.” As such, they’re useless to devils.
There’s a limit to how much Screwtape can say about humanity, in spite of his experience with temptation. His knowledge of basic human emotions (like happiness) is essentially zero—because anything pure and true originally comes from God.
Fun is sometimes useful to devils, because it can distract them from God, but it also promotes courage, peace, and generosity, meaning that it’s usually bad for devils. Jokes are more complicated. There are many kinds of jokes, and they all have different purposes. One use of humor is to render sin acceptable. Thus, meanness and cruelty in their naked forms are for the most part socially unacceptable, but if they are disguised with humor then they become social acceptable. In this sense, jokes can be useful to devils.
In a way, Lewis is using his book to “reclaim” thoughts and emotions that are typically understood as being un-Christian and immoral. Thus, he shows that fun, sex, pride, etc., can actually be virtuous, not sinful. This is a bold and brave attempt to keep Christianity from being boxed out of the modern world. Lewis wants to show that Christianity is directly relevant to humans’ everyday emotions and experiences—not an outdated and joyless institution.
Flippancy is the best form of laughter for devils. When people speak flippantly about serious things, they belittle them and imply that they’re not important. Thus, when people talk flippantly about Christianity, they are more likely to move away from God’s majesty.
Lewis is remarkably insightful about “flippancy,” which we can understand as sarcasm or excessive irony. In a way, he’s predicting the rise of the “irony generation” of the present, when nothing is taken too seriously and nothing is “sacred”—this does immediate harm to religion.