The Law of Undulation

The news is filled with updates on the Coronavirus and its impact on our economy, our health, and our lives.  For most Americans, indeed, for most of the world, we find ourselves in a period of fear.  But fear not. We may be quarantined in the valley of darkness today, but things will get better. 

Consider the Law of Undulation as defined by C.S. Lewis.

When I heard that the Fellowship of Performing Arts would be showcasing a play about one of my favorite C.S. Lewis books, The Screwtape Letters, I knew that Patrice and I needed to make every effort to attend the live adaptation of this amusing and witty commentary between two demons.

It was a thought-provoking, entertaining, and provocative performance.  The stage became a sizzling venue to display the wiles and schemes of Uncle Screwtape, a senior tempter in Hell, as he counsels his nephew Wormwood, through a series of letters, on how best to wage spiritual warfare against unsuspecting souls.  Wormwood, an apprentice demon, has much to learn from his wise as a serpent Uncle Screwtape. 

I found the play to be an accurate adaptation of the book…and its description of the Law of Undulation. It was in chapter 8 of Lewis’ book, The Screwtape Letters, where Uncle Screwtape admonishes Wormwood about his apparent ignorance of the Law of Undulation.  Humans, according to Uncle Screwtape, go through peaks and valleys and are most susceptible to temptation when in the valley. 


…Has no one ever told you about the law of Undulation?…(Humans) nearest approach to constancy, therefore, is undulation—the repeated return to a level from which they repeatedly fall back, a series of troughs and peaks. 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. The dryness and dulness through which your patient is now going are not, as you fondly suppose, your workmanship; they are merely a natural phenomenon which will do us no good unless you make a good use of it.” (1)

But he explains to Wormwood that the Enemy (God) actually relies on the troughs of life even more than the peaks to win the soul.

“Now it may surprise you to learn that in His efforts to get permanent possession of a soul, He relies on the troughs even more than on the peaks; some of His special favourites have gone through longer and deeper troughs than anyone else.” (2)

Screwtape goes on to warn his incompetent nephew that the Enemy’s (God’s) plan serves a purpose.

“It is during such trough periods, much more than during the peak periods, that it (the human) is growing into the sort of creature He wants it to be. Hence the prayers offered in the state of dryness are those which please Him best. We can drag our patients along by continual tempting, because we design them only for the table, and the more their will is interfered with the better. He cannot “tempt” to virtue as we do to vice. He wants them to learn to walk and must therefore take away His hand; and if only the will to walk is really there He is pleased even with their stumbles. Do not be deceived, Wormwood. Our cause is never more in danger, than when a human, no longer desiring, but intending, to do our Enemy’s will, looks round upon a universe from which every trace of Him seems to have vanished, and asks why he has been forsaken, and still obeys……..

Your affectionate uncle,   Screwtape” (3)

Most of us would agree that living through a pandemic is one of the deepest troughs of our lives. But let us not forget the lessons learned from the peaks, or, more importantly, the lessons we learned from our last trough. Don’t panic, don’t allow this time of despair, desperation, and discouragement to defeat us.  This too shall pass.  Rather,

Look to the LORD and His strength; seek His face always.  I Chronicles 16:11

The Law of Undulation reminds us that life in a fallen world has its ups and downs.  And what better time to seek God’s grace and to follow Him then during “trough” times. 




  1. C.S. Lewis, The Screwtape Letters, Simon & Schuster, 1996, pg 40
  2. C.S. Lewis, The Screwtape Letters, Simon & Schuster, 1996, pg 41
  3. C.S. Lewis, The Screwtape Letters, Simon & Schuster, 1996, pg 42

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