As we read the letters written to Wormwood, we find Screwtape amazed at how little his nephew knows about tempting. Particularly shocking is an ignorance of the law of undulation and how best to make use of it when attempting to discourage people and encourage them to sin.

The only constant is change. And change is the principle that lies behind the law of undulation.

[people’s] bodies, passions, and imaginations are in continual change, for to be in time means to change. Their nearest approach to constancy, therefore, is undulation – the repeated return to a level from which repeatedly fall back, a series of troughs and peaks.

The word undulation describes a wave-like motion. When this idea is applied to people, as it is by Screwtape, it explains the following phenomenon.

to be in time means to chang

If you had watched your patient carefully you would have seen this undulation in every department of his life – his interest in his work, his affection for his friends, his physical appetites, all go up and down. As long as he lives on earth periods of emotional and bodily richness and liveliness will alternate with periods of numbness and poverty.

Wormwood is reminded that people can be as ignorant of this principle as he is, therefore one of his primary goals is to never let his patient “suspect the law of undulation”.

The challenge for the tempters is, working against this natural flow, to lead a person into thinking that permanence is the normal state of things. Once this is accomplished it works to their advantage in many ways.

When a person , who is riding the peak of the wave, has falsely accepted that this state of emotions will last forever, they are inevitably going to be crushed when it begins to fade. It is the disappointment during this transition that the demons will hope to capitalize on.

Consider marriage:

humans can be made to infer the false belief that the blend of affection, fear, and desire which they call ‘being in love’ is the only thing that makes marriage either happy or holy.

With this false belief, many a marriage can be destroyed when these affections wane and the person thinks they are no longer in love. Equally dangerous can be the spiritual highs that often accompany conversion and retreats, as they can lead to doubts about salvation.

When a person is in the troughs is when the demons really start to work. The same strategy is employed regarding the idea of permanence. The patient must be made to think that there is no escape from his impoverished state, and that they will forever wallow in the emptiness and dullness that they find themselves in. From this trough the demons have a multitude of options to work with. They can persuade a patient to work against the nature flow and to “recover his old feelings by sheer will-power” or perhaps get them to do nothing at all having “become content with [the trough], persuading himself that it is not so low after all”.

While the demons are working to build within people a false expectation regarding  permanence, they are also laboring to create a hatred of permanence, which is called the “horror of the Same Old Thing”. 

The horror of the Same Old Thing is one of the most valuable passions we have produced in the human heart – an endless source of heresies in religion, folly in counsel, infidelity in marriage, and inconstancy in friendship. The humans live in time, and experience reality successively. To experience much of it, therefore, they must experience many different things; in other words, they must experience change. [ie. undulation] And since they need change, the Enemy … has made change pleasurable to them, just as He has made eating pleasurable.

… Now just as we pick out and exaggerate the pleasure of eating to produce gluttony, so we pick out this natural pleasantness of change and twist it into a demand for absolute novelty. …

When the pleasures of change are warped into a craving for novelty it can destroy a person. The more we want change for the sake of change the less content we become with what we have.

This demand [for change] is valuable in many ways. In the first place it diminishes pleasure while increasing desire. The pleasure of the novelty is by its very nature more subject than any other to the law of diminishing returns. …  the more rapacious the desire, the sooner it must eat up all the innocent sources of pleasure and pass on to those the Enemy forbids.

This makes sense. As we let ourselves get taken in by the “horror of the Same Old Thing” we pursue new experiences. As we experience the good things that God has created and as He intended, the less new they become. The less new the become, the less satisfying they  become as well. The demons then use time to their advantage. Eventually the person who does not get this craving under control will move down a path of sin as they push the boundaries in order to get the “pleasure of novelty”.

An ever increasing craving for an ever diminishing pleasure is the formula. It is more certain; and it’s better style.

The demons battle on a tight rope of trying to keep people off balance. They seek to hide the normal seasons of change that occur in our interests, emotions, affections etc, replacing it with the false expectation of permanence, particularly in the highs and lows of life. At they same time they are at work producing this idea of permanence they are flaming the sparks within us to pursue change at all costs.

We must learn that change is normal and become content with this normal flow of life while enjoying the many good things God has given us.