Demonology 101: Screwtape – Letter 9

The Law of Undulation: Faith in the Peaks and Troughs of Life

Have you ever found yourself on a spiritual high after a powerful retreat, a missions trip, or even just an inspiring Sunday service? In those moments, everything feels vivid, alive, and deeply connected to God. But as the days or weeks go by, that fervor fades, and life settles back into the everyday rhythm. The highs give way to lows, and you may wonder, “Where is God in all of this?”

C.S. Lewis, in The Screwtape Letters, describes this natural cycle of spiritual highs and lows as the law of undulation. Our spiritual lives, much like the rest of life, ebb and flow. There are moments when everything feels vibrant, and moments when things feel cold, dry, or even distant. For new believers, this often happens early in their faith journey—initial enthusiasm cools, leaving them questioning if something has gone wrong. But here’s the truth: these dry spells aren’t signs of failure. In fact, God often uses these trough periods to do some of his deepest, most transformative work in us.


How the Troughs Are Exploited

Lewis warns, however, that these trough periods are prime opportunities for spiritual attack. While God may be shaping us through them, the devil seeks to exploit them. In The Screwtape Letters, the demon Screwtape advises his nephew Wormwood that these times of spiritual dryness are especially fertile for temptations, particularly those of a sensual nature, like lust. This may seem counterintuitive—wouldn’t these temptations be stronger during spiritual peaks when energy and desire are high?

Screwtape points out the opposite: during the high points, resistance is also stronger. It is in the drab, empty, and cold moments of the troughs that the enemy’s attacks can take root. During these times, human desires are easier to twist into unhealthy cravings or even perversions. These desires, which God created to be good and pure, can be corrupted into something far removed from their original purpose.

Take sexual temptation, for example. In the highs, love often accompanies physical intimacy. It is shaped by generosity, creativity, and spiritual connection. In the lows, however, these virtues are absent, making temptation easier to corrupt into selfishness or harm. This principle doesn’t just apply to sexuality. All God-given pleasures—food, drink, entertainment, relationships—can become distorted.


Pleasure as a Battleground

Here’s a profound truth: pleasure was God’s idea, not the enemy’s. Screwtape himself admits that the devil cannot create pleasure—only twist what God has already made. All the joys we experience in life, from the beauty of a sunset to the delight of a well-cooked meal, were designed by God. But the enemy’s goal is to distort these pleasures, tempting us to overindulge, misuse, or seek them in ways God never intended.

Lewis captures this distortion perfectly: “An ever-increasing craving for an ever-diminishing pleasure is the formula.” It’s a destructive cycle that mirrors addiction. We crave more and more, but the satisfaction grows less and less. The devil’s ultimate goal is to leave us enslaved to these cravings while giving us nothing in return.

We see this everywhere today. Pornography and hookup culture twist the beauty of sex. Reality TV degrades storytelling. Even food has been corrupted—processed junk replaces nourishing meals, leaving us addicted to artificial flavors with no real satisfaction. The same goes for social media, which distracts us from genuine connection with shallow scrolling. The enemy works to degrade the pleasures God intended for our good and turn them into hollow imitations.


Misconceptions About Dry Spells

One of the enemy’s most subtle strategies is to keep us unaware of the law of undulation. During a spiritual high, we might assume that our fervor should last forever, and when it fades, we think something has gone wrong. In these moments, the devil whispers lies: “This dryness is permanent. God has abandoned you. Your faith wasn’t real to begin with.” But this couldn’t be further from the truth.

Our spiritual lives are not linear—they’re cyclical. Peaks and troughs are part of the journey, and the troughs are often where the deepest growth happens. The enemy, however, seeks to convince us otherwise. Screwtape outlines several ways this can be done. For those prone to discouragement, the strategy is to isolate us, keep us from mature believers, and tempt us to rely on our own strength to recover the lost feelings. This only leads to frustration and despair.

For others, the temptation lies in complacency. The enemy nudges us to accept the dryness, downplaying its significance. Over time, we might even convince ourselves that our earlier passion was excessive, and moderation becomes the new mantra. A “moderated religion,” as Screwtape notes, is just as dangerous as no religion at all—perhaps even more so because it lulls us into spiritual apathy.


“It Was Just a Phase”

Perhaps the most dangerous tactic, however, is to convince us that our faith was just a phase. The enemy wants us to think of our Christian journey as no different from the fleeting hobbies and interests we’ve outgrown. Personally, I’ve been through several phases—computer building, flight simulators, bowling, and tabletop RPGs. Each one seemed all-consuming at the time, but eventually, they faded into the background. The devil wants us to think of our faith in the same way: just another stage of life we’ve outgrown.

This is why words like “phase” or “adolescent” can be so dangerous. They bypass reason and push us to dismiss our spiritual journey without truly wrestling with its truth. But faith is not a phase. It is a covenantal relationship with the living God, and it is meant to endure through the highs and the lows, the peaks and the troughs.


Waiting on the Lord

If you’re not in a dry spell now, you will be. And if you’re in one, know that it won’t last forever. The law of undulation reminds us that these moments are part of the spiritual life, not signs of failure. The enemy may seek to exploit them, but God is still at work. In these times, our call is to wait upon the Lord, trusting that he is present even when he feels distant. Don’t give in to the enemy’s lies. Don’t try to manufacture feelings or settle for a moderated faith. Instead, lean into the truth that God is faithful in every season, working all things for his glory and your good.

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