What happens in Letter XVIII – Eros and Sexuality of The Screwtape Letters?
In Letter XVIII, Screwtape focuses on human sexuality and romantic love, advising Wormwood on how to manipulate these emotions for Hell's agenda. The patient has fallen in love, and Screwtape is worried—not about love itself, but about the spiritual threats it poses to their demonic plans. He analyzes the experience of "being in love," cautioning Wormwood that the Enemy (God) uses Eros to promote unselfishness, which is exactly what Hell seeks to undermine. Screwtape suggests that the demons' most effective strategy is to make the patient confuse the fleeting emotion of being in love with the lifelong commitment of Christian marriage. This way, when the initial passion fades—as it inevitably will—he'll feel deceived and disillusioned. Screwtape also distinguishes physical desire from romantic love, explaining that Hell can manipulate both, but in different ways. He is particularly derisive of the modern idea that "falling in love" excuses any behavior, a misunderstanding that Hell has deliberately fostered. The letter concludes with Screwtape reminding Wormwood that the objective is to prevent the patient from realizing that love is a choice and a discipline, not just an emotion.
Analysis
Lewis sharpens Screwtape's cold, analytical intelligence to its fullest in Letter XVIII, where he uses the demon's clinical breakdown of Eros to highlight what he saw as a key modern misunderstanding: the idolization of romantic feelings. The clever technique here is inversion—by portraying Hell's spokesperson as afraid of true love, Lewis suggests love's transformative and sanctifying power without explicitly stating it. Screwtape's disdain for selflessness inadvertently turns into an endorsement of it.
The letter works on two tonal levels at once. On the surface, it's dryly humorous—a bureaucrat complaining about bothersome human virtues. However, underneath that, Lewis presents a serious philosophical discussion about the conflict between commitment and emotion. The demon's voice, precise and managerial, embodies the very dehumanization it promotes.
Lewis also introduces a crucial structural motif of the entire collection here: Hell's strategy is not to create new vices but to corrupt genuine goods. Eros isn't directly attacked; instead, it is redirected, exaggerated, and ultimately emptied of its essence. This reflects Lewis's broader theological argument in The Four Loves—that disordered love turns into a demon of its own. The letter's most enduring craft achievement is making readers feel the tragedy of love diminished to mere appetite through the very enthusiasm with which Screwtape describes this reduction. The irony is essential throughout.
Key quotes from Letter XVIII – Eros and Sexuality
“Humans are always putting up some kind of resistance to Hell, but the resistance of a man in love is particularly annoying.”
Screwtape opens his complaint about the patient's new romantic attachment, framing genuine love as an obstacle to demonic progress.
“The Enemy described a married couple as 'one flesh.' He did not say 'a happily married couple' or 'a couple who happened to be in love.'”
Screwtape cites scripture to illustrate that God's design for marriage is covenantal and unconditional — a fact Hell must obscure at all costs.
“We have done this through the poets and novelists by persuading the humans that a curious, and usually shortlived, experience which they call 'being in love' is the only respectable ground for marriage.”
Screwtape reveals Hell's long cultural campaign to replace the theology of marriage with the romanticism of feeling, identifying literature itself as a weapon.