As promised, Screwtape elaborates on the sin of lust. Christians are required to practice abstinence outside of marriage, and Screwtape encourages Wormwood to take advantage of the inherent challenges this poses for humans. In particular, he urges Wormwood to capitalize on the fact that humans have come to regard “being in love”—a necessarily transient state—as a prerequisite for entering or remaining in a marriage. God intends sex to function not so much as an expression of love as a way of producing it—literally, when a child results who depends on the parents’ care. By obscuring this, Wormwood can encourage the patient either to engage in sex outside of marriage or to marry someone unsuitable on a whim.

Screwtape reflects on his prior letter’s claim that love—in its most disinterested form—is an “impossibility” because all beings are necessarily in conflict with one another. This is an axiom of Hell, and he is worried he has slipped into “heresy” by previously claiming that God “really loves” humans. He wonders what God’s motives for claiming to love humanity truly are and admits that the question of love has been a point of contention since the fall of “Our Father” (i.