The Genius of C.S. Lewis: Mere Christianity (1/2)



Given his prodigious output, it’s very hard to succinctly communicate the full genius of C.S. Lewis. Therefore, to give a broader sampling of his wisdom, in this series I’m going to be looking at some of my favourite books by Lewis and then examining some of the ideas to be found between their covers.


After The Chronicles of Narnia, Lewis’ most well-known book is his seminal work on apologetics, Mere Christianity. The chapters of this book originally began life as radio broadcasts during World War Two, which were later printed in separate books and then finally collected together into a single volume.  Over the course of the book, Lewis defends the Christian worldview.


Matt and I go through this book chapter-by-chapter in Season 1 of our podcast, Pints With Jack, although back then the podcast was named after Lewis’ pub, The Eagle and Child.


So, what makes Mere Christianity so great? Let me count the ways...


1. A common Christianity


You don’t have to go far into this book to uncover treasure. For example, readers shouldn’t skip over the Preface of the book because in it Lewis explains what he is attempting to do, which is to defend what he calls “Mere Christianity”. Jack explains that he’s going to ignore denomination disputes and instead focus on explaining and defending the essentials of Christianity.


Although some people describe themselves as “a Mere Christian”, Lewis doesn’t set up Mere Christianity as its own denomination or as an alternative to the ancient creeds of the Church. He simply says that “Ever since I became a Christian I have thought that the best, perhaps the only, service I could do for my unbelieving neighbours was to explain and defend the belief that has been common to nearly all Christians at all times”. He felt compelled to do this because he thought that few others were defending this.


Lewis argues that this “Mere Christianity” is not a watered-down, vague, unsubstantial lowest-common denominator Christianity. Instead, he casts it as the highest-common factor Christianity, held across denominations and something which is both substantial and challenging. This is a sentiment which can be found in John-Paul II’s 1995 encyclical, Ut Unum Sint, where he quotes Pope John XXIII who said that “What unites us is much greater than what divides us.”


2. Choosing a denomination


Although Lewis purposefully avoids all denominational disputes in Mere Christianity, I think he gives really good advice about denominations.

He asks us to imagine a house. He describes the hallway as Mere Christianity and the rooms as denominations. He says that his goal in his book is to move people from outside the house into the hallway. However, he makes it clear that the hallway is not a place to remain indefinitely. He urges his readers to find their way into one of the rooms where “there are fires and chairs and meals”. 


He cautions us though in the selection of a room. He says “…above all you must be asking which door is the true one; not which pleases you best by its paint and paneling. In plain language, the question should never be: ‘Do I like that kind of service?’ but ‘Are these doctrines true: Is holiness here? Does my conscience move me towards this? Is my reluctance to knock at this door due to my pride, or my mere taste, or my personal dislike of this particular door-keeper?’”


3. The Moral Law


After the Preface, Lewis spends the first portion of the book arguing for the existence of God and he does this by appealing to our common human experience. 


Jack asks us to think about when we’ve heard people quarrelling. He points out that those who are quarrelling do not merely say that the other person’s behaviour displeases him. He says that “He is appealing to some kind of standard of behaviour which he expects the other man to know about… trying to show that the other man is in the wrong. And there would be no sense in trying to do that unless you and he had some sort of agreement as to what Right and Wrong are; just as there would be no sense in saying that a footballer had committed a foul unless there was some agreement about the rules of football”.


So from this, it appears that there is a Moral Law which exists. Over subsequent chapters Lewis looks at the possible origin for this Moral Law. Is it simply a matter of personal taste? Is it simply cultural convention? Is it simply instinct or taught to us in education? Lewis concludes that none of these are sufficient and starts building a cumulative case that this Moral Law is grounded in Moral Law Giver, God.


4. The Argument From Desire


This isn’t the only argument Jack gives for the existence of God. Although not presented as a formal syllogism in rigorous philosophical terms, he argues that our innate desires point to a world beyond this one. 


He first observes that this world cannot fully satisfy us. Inevitably, it will let us down. “How will we respond when this happens?”, he asks. The hedonist will simply try and consume more – a new wife, a new job, a new car… The stoic will simply try and grin and bear it. Lewis says that the Christian, however, draws a different lesson:

The Christian says, “Creatures are not born with desires unless satisfaction for those desires exists. A baby feels hunger well, there is such a thing as food. A duckling wants to swim: well, there is such a thing as water. Men feel sexual desire: well, there is such a thing as sex. If I find in myself a desire which no experience in this world can satisfy, the most probable explanation is that I was made for another world.

Although perhaps not the most rigorous of proofs for God, Dr. Peter Kreeft, I personally find that this argument resonates most deeply with my own personal experience.


5. The Use of analogies


One cannot read Mere Christianity without noticing how often Lewis uses imaginative analogies to bolster his arguments and make different philosophical ideas easier to understand.


For example, in one chapter, Jack breaks down morality into three distinct parts. However, he does so by asking us to imagine a fleet of ships travelling across the ocean. For the fleet to make it safely home, three important factors must be present….


First of all, the ships must remain in formation and not crash into each other. Secondly, the ships themselves must be in good working order so that they can be steered correctly. Lastly, the ships must travel in the right direction in order to make it to their destination. 

Lewis then draws parallels to morality. We must act rightly in relation to each other – we can’t be crashing into each other. We must be rightly-ordered internally – if we can’t control ourselves, it won’t be long before a collision is inevitable. Lastly, we must consider our teleology, our ultimate purpose, which is informed by the Creator who made us.


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