Mere Christianity is a revision of a series of radio lectures that C.S. Lewis gave during World War II. It is a qualitative argument justifying the reasonableness, correctness, and implications of Christianity, beginning with observations of the world that have nothing to do with Christianity. It is an argument for Christianity from the ground up, as it were. Although quite different in style and in the arguments used, Mere Christianity is reminiscent of a modern version of the book of Romans.

Lewis begins by observing that there seems to be a universal morality among all people. Although different cultures have varying ideas of what specific things are moral and immoral (for example, one wife or four, but never any woman you want), they all agree that things like selfishness are bad. We also see this standard when someone breaks their promise to us: we may not feel that it is wrong to break our promises, but we feel hurt when someone does it to us. This morality that we unconsciously expect is what Lewis calls the Moral Law.

Many argue that this Moral Law is really instincts, social convention, or just a statement that we should do things for the benefit of society. The Moral Law cannot be an instinct, because often the Moral Law tells us to do something (e.g. help someone) that we’d prefer not to do. Instincts always act for our benefit. It cannot be a social convention, because we feel that societies that violate the Moral Law (like Nazi Germany) are less Moral; we cannot judge another society unless there is a standard outside of the society. And the Moral Law cannot be a different way of saying that we should do something to benefit society, because that just raises a different moral standard. Why be good if it does not benefit me? Because it benefits society; in other words, because you ought to do it.

Now suppose that there were a supernatural being who wanted to reveal itself. Since it is not directly observable, it can only reveal itself indirectly. So it would try to get inside the creation in order to direct it. This is, in fact, what we see. We know that we have this moral law inside of us, which would be unobservable from outside us, since we don’t actually obey it. Clearly, though, this being expects us to obey this law, and clearly we do not.

So now that we can suspect that there is a supernatural being, Lewis needs to discuss religion, or the nature of this being. Although a lot of people think that religion is something we have gotten over, the truth is that men in all ages have held that either there is a supernatural being (or beings) and that there are none. None of this is new to our age. He then argues that the atheistic view is too simple. “If the whole universe has no meaning, we should never have found out that it has no meaning: just as, if there were no light in the universe and therefore no creatures with eyes, we should never know it was dark. Dark would be a word without meaning.” The pantheistic view, that both the good and the bad are part of God is self-contradictory, since if God is good, he cannot be not good. (“Bad” in fact, would not be bad)

At this point we know that there must be a God who is completely good. However, there is clearly bad in the world, which leads to only two explanations. One explanation is that there is another being with equal power that is bad.  But since the two powers are equal, you can only determine which one is good by introducing a third thing, which turns out to be the real power. The other option is that the bad power is subordinate to the good power. This is exactly what Christianity says, that the Devil got his power from God, but turned it to bad uses.

How could the Devil rebel against an omnipotent being? God chose to create beings with free will, so that there would be real consequences to their actions—good actions would really be good, and bad actions would cause real harm. This is no toy Universe. Free will gives the opportunity to rebel, and the Devil took it, and taught it to us. So now we have a problem: we have rebelled against God. Unfortunately, God cannot overlook our sin, or He would not be Just, so He needs to forgive us. There was, in fact, one man who claimed to be God, and who claimed to forgive sins. He might have been lying, he might be a demon, he might be crazy, or he might be have been telling the truth. If so, we are very fortunate to be given the opportunity to repent of our rebellion before God invades for real and it is too late.

The next section is a discussion of various Christian morality, which seem to have little relation to each other, so are presented as a list of ideas here:
Lewis now observes that theology is important, because we will acquire some ideas of God, and if we do not study theology, we will be filled with the world’s ideas of God. The theology of interest to Lewis is what God is doing in humanity at large. Currently humans are primarily natural, so we will die because nature always runs down. But God is making us sons of God, sharing His divine nature with us somehow. This new type of life began with Jesus, and if we come close to Jesus, we will catch the infection from him. This change involves killing the old nature, which of course we are apt to not want. And at the moment, we do not have this new nature, so we are doing a bit of “dress-up”. However, if we think about what we would be like if we really were sons of God, we would find things that we are not or should not be. As God fixes this, it will be painful. But God is not out to make nice men, but sons of God and will stop with nothing less.

However, some people look at the Church and see a lot of hypocrites and people whose behavior is worse than some non-Christians. The first problem with this is that we cannot compare people’s personality; our personality is affected by a large number of things outside our control, including upbringing and even health or whether we slept well. If God gave us good upbringing and health so that our personality is naturally inclined to be nice, He expects much more of us than someone who is perhaps not very healthy and not naturally inclined to be nice. Given what they have to work with, perhaps they are being far better than the person who does not have to work to be nice. A second consideration is that you would expect to find unhealthy people in a church; you do not need a doctor if you are not sick.

Lewis ends by saying that if we want to find ourself, we must give it to God. We do not realize how much of our ideas are simply what we have acquired from our culture or other sources and not really our own. When we give them to God, He will bring out our real nature. “Sameness is to be found most among the most ‘natural’ men, not among those who surrender to Christ. How monotonously alike all the great tyrants and conquerors have been: how gloriously different are the saints.”

Mere Christianity is a good introduction to the ideas and principles of Christianity. It is not intended to be a bullet-proof argument, although since Lewis is highly intellectual, there is a good deal of logical argument. His explanations are clear and well illustrated; Lewis explains Christianity in a way that is understandable to everyone, yet deep enough that long-time Christians will see things in a new way. Because Lewis tends to write intellectually, readers with an intellectual bent will find this to be a superb book, but readers who value other things may find the book a little difficult and dry. In either case, it is well worth reading, and will enhance all readers’ understanding of God and what He is doing in our lives.
Review: 9.5
Definitely a book that will last 100 years. Strikes a good balance between making things simple enough for readers new to Christianity and those who are well-versed; indeed, perhaps the simplicity is part of the value.