Wormwood reports, hopefully, that the patient’s religious enthusiasm seems to be fading — and Screwtape responds with real exasperation at his nephew’s inexperience. Doesn’t anyone teach the basics anymore? He’s talking about what he calls the Law of Undulation, and it’s one of the most important ideas in the whole book.
Humans, Screwtape explains, are amphibians — half spirit, half animal. Their spirit belongs to eternity, but their bodies and moods live in time, and to live in time is to constantly change. So the nearest thing to stability a person ever gets isn’t a flat line — it’s a wave. Peaks and troughs, over and over, in every part of life: work, friendship, even appetite. The dry, flat, uninspired stretch the patient is currently in isn’t Wormwood’s doing at all. It’s just ordinary human rhythm — and whether it helps hell or not depends entirely on what Wormwood does with it.
Here’s where the letter turns genuinely surprising. Screwtape admits that God relies on the troughs more than the peaks to actually form a soul — some of His closest followers have gone through the longest, driest stretches of all. The reason gets at the whole difference between what hell wants and what Heaven wants. Hell wants cattle — souls absorbed, consumed, made into food. Heaven wants sons — free wills that choose to conform, not wills that get overridden. And a will can’t really choose anything while it’s being flooded with obvious, undeniable spiritual comfort. So God, according to Screwtape, deliberately withdraws the emotional sweetness after an initial season of it — not because He’s absent, but because a person only really grows into who they’re becoming when they keep obeying with no felt reward at all. Screwtape says it plainly: hell is never in more danger than when a person, no longer even feeling like they want to obey, still intends to, and still does — while staring at a universe that seems to have gone silent.
The trough itself isn’t the temptation. It’s ordinary. What matters is what a person does inside it — whether the flat, uninspired season becomes the reason to quit, or the actual proving ground nobody warned them about.
Where This Shows Up Now
It’s the dry, uninspired stretch in prayer or church attendance that so easily gets mistaken for losing your faith, rather than recognized as a completely normal season. It’s the quiet, unglamorous choice to keep showing up — to a marriage, a discipline, a practice — with no emotional payoff at all, simply because it’s still the right thing to do. It’s the difference between a faith that runs on feeling good and a faith that can survive not feeling anything.
For Discussion
- Have you experienced a genuine spiritual “trough” — a flat, dry season with no obvious payoff? How did you interpret it at the time?
- Screwtape says God is pleased even by stumbling obedience during dry seasons, as long as the will to keep walking is really there. Does that change how you think about your own dry seasons?
- What helps you keep showing up to something — faith, a relationship, a discipline — when the emotional reward isn’t there?
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