Law of Undulation

The Law of Undulation is Screwtape’s account of the recurring fluctuations in human bodily and emotional life, including religious feeling. Its decisive significance is that a spiritual low is not, by itself, a loss of faith: when a person continues to choose obedience without feeling its former sweetness, the trough can become a deeper form of spiritual growth than the peak. Screwtape presents the same condition as both a natural rhythm and a contested opportunity, one the demons must interpret and manipulate rather than simply cause.

Definition and Human Nature

Screwtape rebukes Wormwood for assuming that the patient’s religious phase is dying away, and invokes the law of Undulation as a basic fact Wormwood should have recognized. Humans are amphibious, in Screwtape’s account: spiritual beings directed toward eternity, but also animals whose bodies, passions, and imaginations inhabit time. Because temporal existence means change, their nearest approach to constancy is not an unchanging state but a repeated movement between troughs and peaks.

That movement reaches beyond religion. The patient’s interest in work, affection for friends, physical appetites, and emotional liveliness all rise and fall. Periods of richness and energy alternate with numbness and poverty. The current dryness and dullness, Screwtape insists, are therefore a natural phenomenon, not a condition Wormwood has manufactured. They will benefit the demonic cause only if Wormwood learns to exploit them.

The Trough and Spiritual Growth

The law reverses a simple measure of religious progress. The Enemy, as Screwtape calls God, may initially offer a person a sense of divine presence, emotional sweetness, and apparent ease in resisting temptation. But this state does not last indefinitely. The feeling of support may withdraw, at least from conscious experience, leaving the person to perform duties that have lost their emotional appeal.

For Screwtape, that withdrawal serves a purpose: obedience becomes a choice of will rather than a response to felt reward. God wants creatures who remain distinct while freely conforming their wills to his, not beings whose wills have been absorbed or overridden. Accordingly, Screwtape argues, the trough may contribute more to that growth than the peak. Prayers made in spiritual dryness please God especially because they persist without the relish that once accompanied them.

The contrast clarifies the opposing aims behind the law. The demons treat humans as food and seek to absorb their wills into their own; God seeks servants who may become sons, united to him but still distinct. In Screwtape’s formulation, the demonic aim is to take in, while the divine aim is to give out. The fluctuations of human feeling matter because they expose the difference between coerced or appetite-driven conduct and freely maintained obedience.

Divine Withdrawal and the Test of Will

Screwtape explains why God does not remain sensibly present whenever a person wants reassurance. A presence strong enough to override human choice would defeat the purpose of a relationship that depends on freely given consent. God may begin with communications that feel powerful to the human recipient, but does not allow the resulting ease and sweetness to continue without limit. The person must eventually stand on their own legs, carrying out duties whose emotional attractions have faded.

The trough is consequently a test without an easy emotional confirmation. A person may look across a universe in which every trace of God seems absent, wonder why he has been forsaken, and still intend to do God’s will. Screwtape calls this the point at which the demonic cause is in its greatest danger. The crucial fact is not that the person feels confident, joyful, or spiritually alive, but that intention and obedience survive when those feelings no longer sustain them.

This account also distinguishes the ordinary experience of dryness from its spiritual use. The low period itself is natural; its consequences depend on what the person does and what the demons encourage the person to believe about it. Wormwood’s mistake would be to treat the trough as an automatic victory. Screwtape instead frames it as an exposed interval in which emotional support has receded but the will remains capable of choosing.

Demonic Exploitation and Misinterpretation

Screwtape’s follow-up letter makes clear that the trough does not automatically surrender the patient’s soul; it must be properly exploited. He first describes sensual temptation, especially sexual temptation, as more promising when the person is dull, weary, and inwardly cold than when energy and resistance are both high. A low mood can also make drink attractive as an anodyne. More broadly, demons try to detach pleasure from its healthy, satisfying form, pushing a person toward forbidden uses and diminishing returns.

Another tactic is to prevent the patient from recognizing the law itself. If the patient assumes that the early ardours of conversion ought to have lasted forever, the present dryness may seem like permanent failure. Alternatively, the patient may decide that the low temperature is acceptable and that the earlier intensity was excessive. Screwtape identifies moderation as a useful rationale for making religious commitment retreat to a harmless limit. These interpretations convert a passing trough into either despair or complacency.

The strategy exploits a confusion between feeling and truth. Losing interest in a belief does not logically prove that the belief is false, but Screwtape expects the patient to be vulnerable to that inference when the trough is mistaken for a permanent condition. He also recommends keeping the patient away from experienced Christians, whose understanding might correct the misconception. The law thus names not only a rhythm of changing human experience but a point of vulnerability: the experience is temporary, while an interpretation imposed upon it can redirect conduct and belief.