I came to Mere Christianity with mixed feelings.
Growing up, I had no idea C. S. Lewis was this major Christian apologist. To me he was just the author of The Lion, the Witch and the Wardrobe. And if I’m being honest, I preferred The Hobbit.
Since finding faith, I kept coming across him. Quoted in sermons, referenced in talks… the kind of writer you’re told you probably should read.
I had far too many years being an argumentative atheist. Taking on Jehovah’s Witnesses and street pastors. Debating on early bulletin boards. Badly quoting Richard Dawkins.
If I’m honest, I wasn’t searching. I was trying to feel clever, like I’d worked something out that centuries of Christian thought had somehow missed. Which is probably why I know exactly what kind of Christian I risk becoming… someone who has traded one set of arguments for another and confused the swap with a transformation.
There’s something I’ve noticed working with young people. They always know when something’s wrong. A kid who’s crossed a line carries it before you’ve said anything. They might push it down or close ranks around their group, but it doesn’t disappear.
Lewis calls that the Moral Law, and it’s where the book begins. His opening argument names that experience. People behave as though some things are genuinely wrong, not just inconvenient. They appeal to a standard they expect others to recognise.
He doesn’t present it as a proof. More a clue. But it’s enough to start asking questions that pure materialism struggles to answer. Physics can describe what is. It doesn’t really account for what ought to be.
The book started as radio talks during the war. Lewis was speaking to people who had never really been given a serious reason to take Christianity seriously. He was making a case.
And the book is still worth the time. Not because it wins arguments. It doesn’t really try to. But it takes them seriously without pretending they are enough.
Lewis builds that case carefully. Morality, human nature, the claims of Christ… step by step. It feels almost mathematical at times, and you can see why it has lasted. It respects the mind.
But what stayed with me wasn’t just the clarity of the arguments. It was their limits. Lewis is trying to point beyond reason even as he uses it. The logic opens a door, but it doesn’t make you walk through it.
I can still feel that instinct now, especially with atheist friends. They’re often genuinely curious about what changed, and I can feel myself reaching for arguments… trying to explain, defend, make the case. When the truth is, what actually changed isn’t something I argued my way into.
The arguments can clear the ground. They don’t seem to be the thing that actually grows anything.
One of Lewis’s most helpful pictures is the idea of an invasion. Not the world as a tidy place needing improvement, but something more contested than that… something that needs rescuing rather than refining. That framing comes up a lot in youth work.
Self-improvement isn’t wrong. But it doesn’t really hold on its own. Not without direction, not without something underneath it.
The trilemma… liar, lunatic, or Lord… sits in that same space. I’ve found it useful, not as a way to win, but as a way to focus a conversation. To directly forgive sins as though he were the offended party, to speak with the authority he consistently displayed… this isn’t the behaviour of someone who thought he was just one voice among many.
If we accept that Jesus existed and he isn’t Lord, something else has to explain what he said. It narrows things down. But it’s rarely where conversations start, and it’s not what seems to carry the weight. What seems to matter more is something lived… trust, timing, relationship.
Lewis describes what he calls mere Christianity as the hallway of a house. Not somewhere to stay, but somewhere to begin.
I’m in a room now… evangelical, broadly charismatic, community-oriented. What that room has given me is something the hallway never could: people, relationships, a rhythm that keeps faith lived rather than just thought about.
There’s a cost. The emphasis is outward-facing, and depth for those already in can run lighter than it should. But Lewis’s point still stands. The hallway is a beginning, not a place to live.
This is where the book shifts. From making a case to describing what the case is pointing toward.
The distinction between Bios and Zoe has stayed with me more than almost anything else. Bios is the life we already have, the natural, everyday kind. Zoe is something different… life from God himself, shared with us.
Not improvement. Something new at the source.
That resonates with me, although not in a neat way. When we moved to Pembroke it didn’t feel like improvement. It felt like loss. The usual support network wasn’t there, and a quick drink with a mate was now two hours away. At the time it didn’t feel like something better starting, just something stopping.
It’s only with distance that it has begun to feel different… less like being an outsider, more like something new taking root. Not one life gradually becoming another, but something new arriving.
I need to be careful what I mean when I say the Spirit is a source of novelty. I’m wired to fix things, to find better ways, to work problems through until they make sense. That instinct shows up everywhere.
If someone I care about is struggling, my instinct is to reach for a solution… something practical, something that moves things forward. But more recently I’ve noticed something else. A quieter nudge to stay, to sit with them, to offer reassurance instead of an answer.
That feels different. Not like a better version of my usual thinking, but something from a different place.
There’s a poem that belongs alongside this book. Lewis’s Apologist’s Evening Prayer. A warning to himself. From all my proofs of Thy divinity… deliver me.
He’s asking not to lose the relationship in the argument. I recognise that. I used to argue, and there’s a real risk of becoming an argumentative theist instead. Am I loving someone, or trying to win? The posture needs to shift… from proving to walking with.
The pressure Lewis wrote under was visible and immediate. Ours feels different. Less visible, more constant. Questions of identity and belonging don’t come and go… they sit underneath everything, shaped by social media, by expectation, by the need to present a version of yourself that holds together.
For teenagers, I’m not sure the main pressure is opposition. It’s the fear of becoming less yourself, of being labelled, of standing out in ways that cost you. I see that in my son… the pull to fit in, to not be different, and how easily that pushes against anything that looks like a distinct Christian identity.
In that sense, the threat isn’t always opposition. It’s dilution.
Lewis’s answer is that the Christian life is not becoming nicer but becoming more real. He describes us as lamps carrying his light. The lamp doesn’t disappear. It becomes what it was made for.
The framework is useful. It helps keep conversations from drifting. But I’m not sure that’s what carries the weight.
What actually seems to move things is something closer to personal testimony. Not argument, but relationship. Not explanation, but something lived.
I think I’ve spent too long trying to explain the light, and not enough time just letting it be seen.
