Three Things I’ve Learned from Reading C. S. Lewis

I’ve been reading and rereading the writings of C. S. Lewis over the last 45 years. In fact, the very first Christian book I ever read was Lewis’s modern classic Mere Christianity. I’ve also read a lot about Lewis’s life and thought from the various writings of leading Lewis scholars and researchers.

I often say that Lewis is part of my “big three.” That is, outside of Scripture my three favorite Christian thinkers and writers are St. Augustine, Blaise Pascal, and Lewis. I write about all three of them and others in my book Classic Christian Thinkers: An Introduction (see chapters 3, 8, and 9, respectively).

We’ve done many programs about Lewis on Reasons to Believe’s podcast Straight Thinking (now titled Clear Thinking), including a series where I listed 25 things I’ve learned from his writings. In this brief article I’ll mention just three. But these three mean a lot to me as a Christian thinker and apologist. I hope they resonate with you as well.

1. The Need to Cojoin Substance with Accessibility
A master communicator in both speech and writing, Lewis wrote:

“I have come to the conviction that if you cannot translate your thoughts into uneducated language, then your thoughts were confused. Power to translate is the test of having really understood one’s own meaning.”1

During World War II, Lewis gave inspirational presentations on the BBC and talks to members of Britain’s Royal Air Force, whose mortality rates during the war were extremely high. He soon learned that he couldn’t use his regular “Oxford speak” when communicating to laypeople. Thus, he developed the insight that the truly cogent speaker or writer should be able to translate his or her thoughts in a way that the layperson can understand.

It is definitely a challenge to successfully cojoin substance with accessibility in such fields as science, philosophy, and literature. But when it is done well, everyone benefits. This insight is something I have tried to incorporate into my speaking and writing.

2. The Power of Explanatory Reasoning
This famous Lewis quote reflects the power he saw in Christianity’s explanatory reasoning:

“I believe in Christianity as I believe that the sun has risen, not only because I see it, but because by it I see everything else.”2

Lewis often used an abductive type of reasoning (inference to the best explanation) and a cumulative case approach to affirm the truth of Christianity. Much of his apologetics reasoning attempted to show that Christianity makes the best sense of the world and life compared to competing worldview systems.

While there are various approaches to doing Christian apologetics, I’ve found that presenting the faith in abductive terms makes sense to a broad audience. Abductive reasoning has been described as the natural way human beings reason.

3. The Idea of Mere Christianity
The book Mere Christianity also contains the idea of mere Christianity. In looking broadly at Christianity, Lewis writes:

“When all is said (and truly said) about the divisions of Christendom, there remains, by God’s mercy, an enormous common ground.”3

In the preface of Mere Christianity, Lewis introduces the engaging idea that there are essential doctrinal truths (such as the Trinity, incarnation, atonement) that all branches of Christendom, including all theologically conservative denominations within Protestantism, accept. This “agreed, or common, or central”4 Christianity doesn’t encompass everything that Christ’s followers need to believe and affirm to live out their faith, but it does constitute a large doctrinal slice of historic Christianity.

Yet, while the idea of “mere Christianity” doesn’t address all of Christendom’s important theologically debated issues, the substantial theological common ground shared by the churches gives them an important connection and a place to carry on further dialogue. It can serve as an important bridge between the Orthodox, Catholics, and various Protestants.

As a person who grew up Catholic then became an evangelical in college and is now a conservative Anglican, the idea of mere Christianity helps me to focus upon truth, unity, and charity in my interactions with other Christians.

While I don’t agree with all of Lewis’s views, he’s a profound and influential thinker and I’m deeply grateful for the many insights he offers in his books.

Reflections: Your Turn If you’ve read Lewis, what are some of the more significant things you’ve learned from him?



1. C. S. Lewis, “Christian Apologetics,” in God in the Dock

(Grand Rapids, MI: Eerdmans, 1970/2014), 96.

2. C. S. Lewis, “Is Theology Poetry?” in The Weight of Glory (New York: HarperCollins, 1949/2001), 140.

3. C. S. Lewis, Christian Reflections (Grand Rapids, MI: Eerdmans, 1967), vii.4. C. S. Lewis, Mere Christianity (New York: Simon & Schuster, 1996), XI.