C.S. Lewis’s Mere Christianity is a nice and easy introduction to Christianity for people who don’t know much about it. It got a lot of praise back in its day. It takes the reader on a walk from atheism to how we can learn to be like Christ.

C.S. Lewis was an atheist earlier in life, and he addresses a lot of points that atheists supposedly misunderstand, but I found many of them confusing. I’ll write some of them down here, and maybe you can help me. 

I’m not interested in persuading anyone that C.S. Lewis was wrong. I just want to understand a bit more. Every chapter here is my understanding of what C.S. wrote, except for the final paragraphs that add some commentary.

Chapter One — The Law of Human Nature.

The Law of Nature is about gravity, heredity and other scientific laws — laws that can’t be broken. But the Law of Human Nature is more about moral laws that can be broken. C.S. uses various phrases for this idea: Right and Wrong; Moral Law, Moral Behaviour. They all amount to a set of rules that God made for us, and we sometimes fall short and break those (pp.4-5).

C.S says that all people and all civilisations share these same Moral Laws, more or less. They might be a bit different, but are mostly the same. For example, there’s no country where you’ll be admired for running away in battle or for double-crossing people who are kind to you — no more likely than a country where 2+2=5. Men in different countries might differ over whether they can have one wife or four, but they will all agree that you can’t just have any woman you fancy (pp.5-6).

You might sometimes fall short in your attempt to follow the Moral Law — just like you might make mistakes with the multiplication table — but, deep down, you know the Laws, and must try harder next time to do the right thing. Just like when you make a mistake in maths (pp.6-7).

C.S. summarises this with two points: 

1. Everyone all over the world knows they should behave a certain way (they have the same Moral Law).
2. Sometimes they fall short.

I don’t understand these points at all.

C.S. was writing during the Second World War, and there were some pretty bad people in Nazi Germany. Did they not know the rules? Or did they know the rules and fall short? I think it’s more likely the Nazis had a different set of rules altogether; rules that the rest of us — and God — would not approve of. 

C.S. says that there is no sense in saying that what the Nazis did was wrong unless the Nazis themselves knew they were wrong. But even if they didn’t know what was wrong, we’d still fight them, but we would have had no right to blame them (p.5).

I don’t understand this either.

Chapter Two — Some Objections.

Sometimes an instinct will lead you to do the right thing, sometimes not. For example, suppose a man is drowning. You might feel an instinct to save him, or an instinct to be safe and stay away — but those are just instincts. The Moral Law says you should save him whether you want to or not. Even if your instinct to stay away is the stronger one, the Moral Law will tell you to save him all the same. That can’t just be an instinct because it makes no sense for an instinct to override an instinct. It must be a law.

I don’t quite get how I would know whether I am feeling an instinct or a law. In this example, I expect most of us would want to save the drowning man, so it’s hard to distinguish the “Moral Law” from the “good instinct”. In a better example, the good and bad instincts would be harder to choose between, but I still don’t understand how I would tell instincts from laws.

In Pete Singer’s Drowning Child thought experiment, the “good instinct” is much harder to choose. Everyone would rescue the drowning child, even if it ruins our expensive shoes (Moral Law = Good Instinct), but what about a child on the other side of the world who is dying of malaria? The Moral Law would have us save that child, too, but most of us wouldn’t do it (Moral Law = Bad Instinct). It’s hard to know when the Moral Law applies.

Chapter Three — The Reality of the Law.

When you think about a stone falling, the stone doesn’t have a choice whether to follow the Law of Nature. The law just means this is “what stones do”. However, the Law of Human Nature is different. It does not mean “What humans do.” It means “What humans ought to do.” (p.17)

Humans ought to behave decently. But what does it mean to behave decently? It’s not just doing what benefits me — cheating would benefit me, but that’s not behaving decently (p.19). Maybe it means doing what benefits all of society. But why would I care what benefits society, unless it also benefited me? Well, because it’s decent. But now I am back where I started: What does it mean to behave decently (p.20)?

The Moral Law says we should behave decently, but since we don’t have an explanation for why we should behave decently, the Moral Law must come from some other reality. From outside us (p.20).

This leap seems like a big leap to me. We don’t even know what the Moral Law is yet. How would we know where it comes from?

Chapter Four — What Lies Behind the Law?

There are two views of the universe (pp.11-12):

1. The materialist view says that matter and space have always existed, but no one knows why. There is nothing “behind” the matter, and matter just happened to create us by a fluke. 
2. The religious view is that behind the universe, there is something like a mind. The universe partly exists for reasons we don’t know, and partly to make minds like itself.

Science can’t tell us which is the correct view. Science gets us some of the way, but it can’t answer questions like “Why is there anything at all?” or “Is anything behind those things that science can describe?” Even if science helped us understand every single thing in the whole universe, it still wouldn’t be able to answer questions like, “Why is there a universe?” (p.23). We need a better way to know which view is correct.

There is one thing in the universe that knows more than science can tell us, and that thing is Man. We know that men observe a moral law (see Chapter Three); however, we could never observe this moral law from the outside; the only way we know it exists is through a command inside us, telling us how to behave. There is a power outside the universe that tells our minds about the Moral Law (pp.23-24).

We have not explained Christianity yet, but we have shown that there is a Power behind the universe that appears inside of us, telling us how to behave. We have to assume it is like a mind because the only other option is matter, and we can hardly imagine matter giving us instructions (p.25).

The previous leap was difficult to understand, but this is an even bigger leap. If our moral law comes from another reality, it must come from a Power outside of the universe.

My own instinct is that the universe could exist for no reason at all. Perhaps it has always existed. We have no evidence either way. Perhaps it exists for a reason that we just don’t know yet. 

Chapter Five — We Have Cause to be Uneasy

You might feel a little uneasy about what we have learned already, but here are three things that might make you feel a little better.

Firstly, an analogy: you can put a clock back if the clock is wrong. Or, if you have taken the wrong road, you can go back and take a different turning. You can do this when you are doing maths, too. When you make a mistake, you go back and do it a different way. Humanity has made mistakes, and when we make a mistake, we should go back and try a different way (pp.28-29).

Secondly, we have proven that there is Something or Somebody behind the Moral Law (though we haven’t proven that it’s God yet). We have two bits of evidence that Something or Somebody exists. 

1. The universe He has made is one clue. But with the universe alone, we must conclude He is a great artist, but merciless (p.29). 
2. The Moral Law that He has put in our minds (pp.29-30). 

You can learn more about God from the Moral Law than you can from the universe, just as you can learn more about a man from his conversation than from looking at his house. The Being behind the universe — God — must be interested in decent behaviour, although ‘decent’ does not necessarily mean ‘good’ (see chapter two) (pp.29-30). 

And the last point: Christianity makes no sense unless you know these rules. It’s only when you understand that your position is nearly desperate that you will understand what Christians are talking about (p.32). 

Perhaps this is related to his time as an atheist, when he rejected Christianity because he did not understand it. Perhaps discovering these rules helped him find God.

I don’t really understand what the Something is, or how the existence of the universe proves that the Something exists, too. I also don’t understand why the Moral Law and the universe show that God exists.

Thanks for reading Chasing Shadows! I post occasionally on philosophy and culture.

Mere Christianity is one of the most successful books in the twentieth century about Christianity, with millions of readers. It was named the best religious book of the 20th century by Christianity Today (I can’t find the original article, but it is quoted a hundred times on the web). On Goodreads, nearly all the reviews of Mere Christianity are five stars or one star. People love it or hate it. 

The book gets great reviews from Christian websites, too, but apologists and professors are more critical. Some of these apologists say it is dated. Fair enough. But I am still curious what people ever understood it to mean, and why it carried so much power.

I didn’t really understand much of Mere Christianity, and I would love to understand it better. If someone has a more up-to-date book of apologetics for beginners to replace what CS Lewis says, I’d love to read that, too.