Mere Christianity

In 1941, in the middle of World War II, the BBC invited an Oxford literature professor to speak at night about a subject that seemed out of place during the bombings: right and wrong. C.S. Lewis accepted, and the talks aired between 1941 and 1944. Years later he gathered and revised that material into a single book, published in 1952 under the name Mere Christianity.

Lewis's plan was strange by the standards of the time: he didn't start by quoting the Bible or asking listeners for faith. He started by asking why even people who have never opened a sacred book argue using phrases like that's not fair or you promised. This way of defending the faith with logic and everyday examples is what we now call apologetics.

The book has four parts, like steps: the moral law as a clue to something behind the universe, what Christians claim about that something, how it would change everyday behavior, and finally the Christian idea of God as Trinity. This summary follows the same steps, and marks when an idea is the author's interpretation.

Lewis observes something simple: in any everyday quarrel, whether on a packed bus or in an argument over who pays for the round at the bar, people appeal to a standard they expect the other person to recognize. Nobody says only I don't like that, they say that's not done, as if there were a yardstick common to both sides.

Comparing different peoples across history, Lewis notes that the content of that yardstick varies less than you would think: almost everywhere values courage, honesty and care for family. To him, this suggests a human moral law, not just a personal taste of each culture.

The most uncomfortable part comes next: everybody recognizes this yardstick and, at the same time, almost nobody lives up to it. The person who demands honesty from a neighbor is the same one who cheats his own boss on the payroll when he can get away with it. That contrast is the real clue, more revealing than the law itself.

Lewis anticipates two objections. The first says the moral law is just herd instinct, like the instinct to protect offspring. He answers that instincts push in one direction only, but morality sometimes asks for the opposite of the strongest instinct: someone can feel like running from danger and still feel they ought to help a person who is drowning.

The second says morality is just social convention, changing with no criterion at all. Lewis pushes back by asking: if morality were only local taste, how can anyone say one country's morality is worse than another's? Every comparison of that kind already presupposes a standard above both.

The argument doesn't yet prove the existence of God, and Lewis himself is honest about that: it only shows that reducing morality to custom explains less than it seems to at first glance.