Mere Christianity. I am not entirely convinced that every one of his arguments holds or is presented in the best way possible, but I am nevertheless struck by how much the content of this work, now seventy years old, continues to speak to the questions posed by modern men, both believers and non-believers. Here are a few paragraphs I thought particularly forceful (but too long for Facebook statues), from the seventh chapter "The Invasion."
It is no good asking for a simple religion. After all, real things are not simple. They look simple, but they are not. The table I am sitting at looks simple: but ask a scientist to tell you what it is really made of-all about the atoms and how the light waves rebound from them and hit my eye and what they do to the optic nerve and what it does to my brain-and, of course, you find that what we call "seeing a table" lands you in mysteries and complications which you can hardly get to the end of. A child saying a child's prayer looks simple. And if you are content to stop there, well and good. But if you are not-and the modern world usually is not-if you want to go on and ask what is really happening- then you must be prepared for something difficult. If we ask for something more than simplicity, it is silly then to complain that the something more is not simple.
Very often, however, this silly procedure is adopted by people who are not silly, but who, consciously or unconsciously, want to destroy Christianity. Such people put up a version of Christianity suitable for a child of six and make that the object of their attack. When you try to explain the Christian doctrine as it is really held by an instructed adult, they then complain that you are making their heads turn round and that it is all too complicated and that if there really were a God they are sure He would have made "religion" simple, because simplicity is so beautiful, etc. You must be on your guard against these people for they will change their ground every minute and only waste your tune. Notice, too, their idea of God "making religion simple": as if "religion" were something God invented, and not His statement to us of certain quite unalterable facts about His own nature.
Besides being complicated, reality, in my experience, is usually odd. It is not neat, not obvious, not what you expect. For instance, when you have grasped that the earth and the other planets all go round the sun, you would naturally expect that all the planets were made to match-all at equal distances from each other, say, or distances that regularly increased, or all the same size, or else getting bigger or smaller as you go farther from the sun. In fact, you find no rhyme or reason (that we can see) about either the sizes or the distances; and some of them have one moon, one has four, one has two, some have none, and one has a ring.
Reality, in fact, is usually something you could not have guessed. That is one of the reasons I believe Christianity. It is a religion you could not have guessed. If it offered us just the kind of universe we had always expected, I should feel we were making it up. But, in fact, it is not the sort of thing anyone would have made up. It has just that queer twist about
it that real things have. So let us leave behind all these boys' philosophies-these over-simple answers. The problem is not simple and the answer is not going to be simpler either.
The full text of Mere Christianity is available here. Thanks to Wikia for the image.