The Law of Undulation: a Concept by C.S. Lewis

In 1942, C. S. Lewis published The Screwtape Letters. The story is written as a series of letters from a senior demon, Uncle Screwtape, to a junior demon (his nephew), Wormwood. Each letter is advice on securing a man’s soul and covers many different aspects of life. Because it is written in from a demon’s perspective, Christians have to get used to the unique dialogue and characters, such as “the patient” (a man), “our father below” (the devil), and “the Enemy” (God). While the whole book is well worth reading, here I will focus on one particular concept in chapters 8 and 9, the Law of Undulation.

The Law of Undulation is explained as the peaks and troughs humanity experiences in every area of our lives, such as our work, friends and, most importantly, our relationship with God. Peak times are characterized by feelings of richness and liveliness, where everything is new and exciting. Troughs are full of numbness and poverty. Humans are by nature unstable and, according to Lewis, this roller coaster of feelings is the “nearest approach to constancy” that we will ever have.

Specifically, Lewis talks about the difference between our initial Christian experience vs. our ongoing spiritual lives. Uncle Screwtape states that God initially sets us “off with communications of His presence which, though faint, seem great to them, with emotional sweetness, and easy conquest over temptation.” Later, however, our spiritual life changes as we begin experience difficulties. Screwtape says that God “withdraws, if not in fact, at least from their conscious experience, all those supports and incentives. He leaves the creature to stand up on its own legs—to carry out from the will alone duties which have lost all relish.”

In short, we begin our Christian life in the “honeymoon phase.” Our first love for God is all-encompassing and seems that it will carry us through to eternity. Later, however, it seems that God is nowhere to be found and we must keep being Christian regardless of our feelings. It is during these emotional troughs that Satan frequently attacks. He attacks our body, usually with lust and sexual temptation, where we take the pleasures “which God has produced, at times, or in ways, or in degrees, which He has forbidden.” And he attacks our mind, “making us doubt whether the first days of Christianity were not, perhaps, a little excessive.”

I think it is safe to say that every Christian experiences this undulation. In my early walk with Christ, I remember praying for God to prove his existence by getting me a Toyota hippie van (no comments please). A few weeks later, I found one for $100 (true story). I remember feeling God’s presence in every area of my life, as if completely surrounded by his love at all times. Many of my friends were using terms like “Ned Flanders” or “Bible thumper” to explain me, I was proud of it. I was even honored to be cleaning church toilets — for Jesus!

Now, it is fifteen years later. I have made many decisions of faith that have steered my life this way and that, and I have reaped the benefits of many of those good decisions. Yet no matter how much God has done for me, I still doubt Him on occasion. Sometimes, I can’t even remember why I am doing basic things like writing testimonies or doing daily devotionals. It is at these times when acts which used to bring me joy lose their fervor, and I am left wanting, sad, and alone.

My adventure through getting a doctorate has been especially trying at times. Last semester, I was studying for the last, and most difficult, exam of my last semester. For the first time since I became a Christian, I doubted God’s presence. Sure, I often feel as though God is gone, but I still know He is there. But this time I actually thought He was not with me anymore. I began to think my WHOLE grad school experience was me walking out on a limb without His holy presence protecting me. This was the most frightened I have been since I became a Christian.

So what are we supposed to do about this? How can we manage this fundamental tension? We are human, so we have extreme highs and lows. And we are Christian, so we must serve God regardless of how we are thinking or feeling at the time. In The Screwtape Letters, Lewis offers a few hints that I find helpful about how to endure the troughs.

First of all, we need to know WHY God is letting this happen to us. Screwtape tells his nephew, “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.” This means that God is training us to be more like Christ at these times. He allows us to understand something of what it felt like when He was alone on the cross, so that we can grow up in our spiritual lives. Our fear and feelings are not unvarnished reality. And God has a plan behind all of it. This reminds me of Joseph, who didn’t understand why he was a slave or prisoner. And Job, whose whole life was taken away. And the Apostle Paul, who was beaten, jailed, and shipwrecked. Each one of these men were trained through these hard times and made much greater than they would have been.

Second, we need to seek help from those who understand our condition. Screwtape recommends his nephew to keep his patient out of the way of experienced Christians who will offer up passages that will help him in his hour of need. Verses like Matthew 11:28-29 or Exodus 14:13-14 give us hope when we are most vulnerable. Christians who are not accustomed to troughs need to find someone they can talk to and seek help from.

Knowing that we will surely experience this Law of Undulation, we can use our peak times to prepare for the troughs. We all need to come together as the Body of Christ and reach out for help or offer help to those in need.

What about you? Have you experienced this Law? Is there a particular Bible verse or passage that has helped you in times of fear or doubt? Have you been helped out of a trough by a brother or sister in Christ?


  1. Great post, Tuf. Thanks.

    St. John of the Cross perhaps calls this Undulation “The Dark Night of the Soul.”

    A favorite verse of mine during Undulation might be Genesis 50:20. Check out this post:

  2. Tunde Adebola

    Hi Tuf,
    Thank you for answering some of the questions I’ve had in this article.
    I often wondered why God allows his people experience this law of undulation? Can’t we be christians without the highs and lows of our lives of faith? Sometimes fiathfulness does not spare us of the consequences of living in a fallen world. But regardless of these problems, we must keep being faithful as your rightly said.
    Do I want a problem free life? By all means! But that life is reserved for me in heaven (Thank God!)
    As life swing from one extreme to the other (like a pendulum bulb), in the end I’m convinced it will be well and that one day we will go from analog to digital.
    In the meantime, I’ve found that the time of greatest needs have often brought me into the place of prayer and a deeper connection with God through each of my difficult experinces…Maybe that’s why God permits difficulties in my life – to show how much I need Him, and to draw me closer. Thanks again.

  3. Tuf Francis

    Ben – nice post. Joseph was an amazing man of God who represents undulation more than anyone in the Bible. Thank God we have examples like him, who went through more than we could ever understand. Yet, remained faithful and Christlike to the end.

    Tunde – I agree. Things would be better without the pendulum. But God is good, and grows us into His servants through all things. I like your analog to digital reference, things will definitely be clearer then. Thanks for the post.

  4. Ben Westerhoff

    I’ve certainly experienced the Law of Undulation and the troughs against my will! What has often helped me is daily Bible reading, discussing Christian issues with Christian friends with whom I can be open and honest, and partaking in the Lord’s Supper. The last one may be a little unusual for Evangelicals. The Lord uses the Lord’s Supper to put everything into perspective. Thanks for this article, Tuf. This kind of writing will help people come out of the trough to the peak.

  5. Tuf Francis

    Ben W –

    Can you explain what you mean by partaking in the Lord’s supper? Is it only an Easter thing? Where did you do it? Sounds very interesting.

    • Ben Westerhoff


      Thankfully the Lord has provided his Supper in the right time for me. We don’t do it much in Chicago, though I wish we did. When we do have communion I realize how much I need it and how restorative it is. How often to you have communion in your neck of the woods?

  6. Dr. Bill

    This post reminds me of something I heard many years ago when discussing this up-and-down kind of experience with an elder brother in Christ… his response was memorable, and I will not forget it – he said, in effect “The Christian life of faith is like going through peaks and valleys. When you first come to Christ and are born again, it is like being on the peak of a mountain. Then, you go down into a valley. Then, a new understanding of some aspect of the Truth comes, and again you are up on a mountain peak, but this time not quite so high. Then comes another valley – a little lower than the first one. This cycle repeats throughout our Christian life of faith until finally we find ourselves in the deepest, darkest valley of our lives.” Then this older brother in Christ paused, and I asked him “What happens next?” and he said, unforgettably, “That is the high point of our walk of faith where we see nothing but the morning star, Jesus Christ.”

  7. Thank you for this post, Tuf. I love the Screwtape quotes that you chose. I’d like to comment on your second point: that we need to seek help from someone who has experienced a similar trough. I recently have begun to emerge from a long trough that began around the time I turned 40 (I am now 48). I felt like I had suddenly lost footing and spiritually and physically fell down a slippery slope. Honestly, during this walk in a shadowy valley, there was only one woman in UBF that seemed to be going through something similar, who I felt comfortable confiding in. Reading books helped. And most recently, God’s word from Isaiah 40:21-31 spoke to me in a way that has helped me to come out of spiritual and physical exhaustion. Our Almighty God neither slumbers nor sleeps. He has eternal power to give strength to the weak, and bring us out of our troughs and valleys. I am beginning to rely on his strength in a new way. Respectfully, is it just me, or could it be that Korean women tend to either keep weaknesses to themselves or among themselves and don’t like to expose their vulnerability? I think that women going through troughs should feel comfortable seeking advice and prayer from those who have gone through something similar. I know I have felt quite lonely these last 8 years. I hope that women in UBF in particular, can feel comfortable seeking help from those who understand them.

  8. Brian Karcher
    Brian Karcher

    Welcome, Kathy, and thanks for sharing your experience. I would say “it’s not just you…”. In my observation the past 20-some years, one of the greatest areas for improvement in UBF ministry is in the area of helping women, both young and more-advanded-in-years, to find God’s joy, God’s life and God’s purpose.

  9. Tuf Francis

    Kathy – I take your point. There is something about “silent suffering” that carries some weight, I am not sure why. Though part of it may be cultural, I think there is something more than this also. In a ministry so geared toward leadership, some feel they cannot hurt and be vulnerable. Everyone trying to look as mature and together as possible to avoid losing face. This is, I think, most intense with women as their husbands are often on the front lines of ministry. I know my wife often feels like she has to bottle up her suffering so that she doesn’t burden me, as she feels my outside stresses are too much to bear. I agree with Brian, this is something that woman need to stand up and demand help with. I also find a particularly difficult pocket to reside in this ministry is the 30-somethings – mainly those with little kids. You can’t do what you used to in your 20s, you look like you have slipped spiritually, and you always feel like people are looking down on you. It is a horrible time. I think as these problem areas are revealed, our ministry needs to address them and find ways of serving people of all ages equally.

    I am glad you found some help and comfort in God’s word.

  10. Jennifer

    Hi Tuf, I am one of those 30-something year old women you speak of with children who find this phase of life challenging and lonely at times. There is this expectation to serve as we have done before- and for me, this pressure came from my bible teachers, leaders and myself. When i confided my struggle to balance serving God and raising my family to older women missionaries, the response i usually heard was to entrust my family to God and serve Him first. I really do want to love God as my priority of life, but i cannot simply make the sacrifices that others seem to suggest. In my situation, i have no family close by and depend solely on a babysitter for help with my children. I don’t mean this as a complaint, but i have found limited comfort or reassurance from those who “have been there”- it’s as if they forgot what is was like to take care of young children. As you mentioned Tuf, I think it would be great if our ministry can provide more support for young mothers who desire to support God’s mission in their new phase of life.

  11. Dr. Bill

    Hi Jennifer. To be honest I’m not sure which Jennifer you are, but the point you make is very, very important. A simple example: Wes Stafford, who is now president of Compassion International, is an MK (missionary kid). As a child he, along with many other MKs, was farmed off to a ‘private’ school for MKs far away from the mission field. The ‘believers’ running the school abused the children in many ways – physical, emotional, spiritual, and destroyed the faith of many. Wes came through it by God’s grace and now leads one of the largest Christian outreaches to children worldwide – Compassion International ( It is a holistic ministry that addresses the needs of impoverished children worldwide, including spiritual, physical, emotional, etc. (We support two children, one in Indonesia and one in South America.) My takeaway from Wes’ story is that missionaries must be *more* diligent to take proper care of their children lest they lose them to the world. I do not believe we will be excused simply because we held the title ‘missionary.’ We need Christians, especially in America, who will raise Godly men and women that excel in their studies and careers and by so doing lead this nation in Godly paths. May the Lord grant us wisdom to do so.

    • Jennifer

      Bill, i really appreciate your comment. As a parent, i definitely go through many undulations that it made me feel like a failure, both in human terms and spiritually. God is training me more through my children than the other way around. I regard my children as precious as any sheep in the world and i hope that i can fulfill my role as a mother with a degree of awesome respect towards the Lord for entrusting this task to me. I realize that ultimately the decision will be up to my children whether they want to know the Lord or not. But i do hope that my own life and the home we create will give them something good to turn to, like the prodigal son when he came to his senses.

  12. Tuf Francis

    Jennifer, my wife and I have had to come to terms with this struggle on many levels. My son – 3 years old – and daughter – almost 1 – are my first (not chronologically, obviously) and most important Bible students. God has given them to me to take care of and raise in His word, and I will do the best I can do. I really don’t care what others think and sometimes have to tell them that. To me, this doesn’t mean skip meetings, miss Bible studies and Sunday worship, and so on. But it does mean that in all ways they are as important as any college student or person in our ministry, and I divide my time accordingly. I refuse to live with a deep regret when my children become older because of the errors I made when they were little. I refuse to allow my family to implode out of a sense of fear, guilt, or duty – as this will ultimately ruin my whole spiritual life later. As a rule, I try to spend 3 hours of undivided time with them everyday – more on weekends sometimes. I try to take them somewhere at least once per week (zoo, park, etc.), every week. For the most part, they are in bed everyday by 7:30 and then I can begin ministry work and continue with endless homework. I don’t know if people think this is too much time, not enough, or just right (and like I said earlier…), but this is the way I have found to balance my ministry, doctoral studies, and family life. When I keep this balance, I have NO GUILT OR SHAME (note, guilt or shame can be either perceived or real, and the balance I speak of helps both).

    Much like our finances – if we don’t have a time budget we are in danger of feeling out of control and chaotic and horrible all the time. My thinking is you need to come up with a budget, or a division of your time and effort, that you truly believe is serving all areas of your life in a healthy and God-fearing way. When you reach that balance, and you believe God has helped you reach it, you will have peace and can go on without fear, guilt, or duty. You will reach a new level of freedom.

    Anyone else have any wisdom on this one?

  13. Samantha Siy

    I really appreciate all of the articles and follow up comments on this website!! I haven’t known when and where to begin to share…but this topic caught my heart!

    I want to briefly share my experience. Five years after leaving HQ and beginning a ministry which includes only our family, God has revealed many things to me. I think the main thing I have learned has been the importance of my personal relationship with my God – which in reality has nothing to do with my outward ‘spiritual’ activities. (This may seem like a cliche –or really obvious to some.) But, when I found myself without even one other person to talk and share with, I didn’t know what to do and I entered a very dark and difficult time spiritually.

    But, God used this darkness to reveal how little I knew Him. I knew about Him plenty. But not Him. At that time, all that was before me was my family. So, I committed myself to being a full time mom. And I must say it has been a time to treasure. I struggled with guilt because I felt as though I was living a ‘family-centered’ life (a UBFism). But it has been an amazing experience and I am so thankful that God gave me this time to spend with my kids–watching them grow –and can I just say how amazing it is how FAST they grow?

    Throughout this time, God has helped me begin a new journey to know Him –not through many activities – but by just studying His word and spending time with Him. [I am not advocating stopping outward activities–just sharing my experience.] One turning point was participating in a local Bible study where many of the women in my small group were older – mostly grandmothers. They shared their love for God with me. They shared the pain they experience because some of their kids don’t know the Lord. They encouraged me when I struggled with my own spiritual life as well as raising our kids. It was clearly Titus 2:3-5 playing out in my life. I am so thankful for God’s intervention in my life.

    Not sure if this will be helpful to anyone. But, I wanted to share the way that God has been working in and around me!! Much love and blessing to all!!

  14. Jennifer Espinola

    I’m really thankful to God for this forum. To be able to share this struggle with other Christians in our ministry who understand where i’m coming from is a blessing. :) I realize God wants me, and not my activities. He wants me to live as a genuine Christian before Him and man. Thank you all for your encouragement. Being a parent has opened up a new dimension in my relationship with God that i never appreciated much before having children- that God is my Perfect Heavenly Father. Yesterday I read something from Psalm 16 that really encouraged me: “Lord, you have assigned me my portion and my cup; You have made my lot secure.” It made me think of my life as custom- designed by God and something i don’t need to compare with another. I need to fix my eyes on Jesus and not let distractions pull me down. Thank you all again for sharing your testimonies. We truly serve a mighty God. :)

  15. James Kim

    Hi Samantha. I am a late comer to the blog. Thank God for many people who made this blog site possible. It can be a good medium to connect people around the world in a good and constructive way. Someone said when we go to heaven, most of our job is to praise God. For how long? For eternity without tiredness! That means we have to practice diligently to praise God and thank God while we live on this earth for a short time. Otherwise when we get to heaven it would be very awkward place. This talks about perspective. How important it is to have right perspective! Praising God daily and giving thanks in all circumstances with right perspective would solve a lot of problems and heartaches. I have four grown up children. Problem with children never stops even after they married! I pray with my wife daily for my children and the ministry only trusting in God, believing that God is sovereign and we are only stewards of them. These days my wife gradually learned the importance of praising God. I thank God for that.