Screwtape has previously received a letter from Wormwood in which Wormwood expresses his “Great hopes” that the patient is losing his religion. Screwtape angrily tells Wormwood that he must consider the law of “undulation.” Because humans are half spiritual and half physical, they are always bouncing between these two worlds. Thus, the patient is always moving between satisfaction and dissatisfaction with the material world—his friends, his job, etc.—and the same is also true of the spiritual realm. Wormwood shouldn’t take pride in the patient’s dissatisfaction with Christianity, because this dissatisfaction is bound to happen at some point, and it doesn’t necessarily last. Indeed, Screwtape notes that God relies on these periods of dullness and dissatisfaction for converting people to Christianity.
It’s curious that Screwtape is so quick to attack Wormwood for his hope and optimism about corrupting the patient. Perhaps this is supposed to illustrate that to devils, the idea of optimism is utterly foreign. It’s in this section that Screwtape—and the side of evil in general—first shows signs of weakness in the battle with God and Christianity. There’s a sense that even lapses into sin are ultimately useful to God, because they help to give humans the opportunity to repent and embrace God with new devotion. This is the ultimate implication of human freedom itself—it’s only when humans can be evil that they can also truly be good.
Screwtape acknowledges, grudgingly, that God really does love human beings, and wants to fill the universe with them. The goal of devils is to force God to draw all life “into himself.” God, however, wants to fill the universe with beings who are a part of God, and yet distinct from him.
In order to populate the universe with loyal followers, God uses periods of sadness and pain. Instead of simply proving his existence to humanity, as Wormwood might expect him to do, God challenges humans to believe in him even when there are no signs of his existence or his benevolence. Therefore, the prayers people make during periods of sadness please God the most.
Lewis alludes to Job here—a Biblical character whose righteousness and faith God “tested.” Whenever God caused Job pain and sadness, Job praised God’s name. The Book of Job is a complex and intriguing piece of writing, but on one level it declares that suffering and misery can actually bring people closer to God—just as Screwtape affirms here.
Screwtape concludes that the devils’ cause is most threatened when a human being lives through a period of great suffering, and continues to believe in God. Nevertheless, periods of suffering can be useful to devils—Screwtape promises to tell Wormwood how they can be so in his next letter.