Mere Christianity - Bk 1 - Ch 1 - The Law of Human Nature

On August 6, 1941, C.S. Lewis broadcast his first BBC talk.  He called it "Common Decency." When Mere Christianity was published in 1952, it was called "The Law of Human Nature."

Though Lewis began to explain Christianity, he opened with the common experience of people quarreling.  According to one account, a bartender, upon hearing this, suddenly stopped in the process of serving a drink,  in order to hear this out.  Lewis wanted to point out that the common experience of quarreling indicated a that people used a usually common standard of right and wrong - of morality - to support their arguments.

Lewis said that while this higher standard used to be called the Law of Nature, he thought it should be called the Law of Human Nature, so as not to confuse it with natural laws such as gravity, etc. While we have no choice whether to observe gravity, or other natural laws, we do have a choice whether to follow the Law of Human Nature, the common morality most observed  for ages.

Lewis said some said different civilizations and ages had different moralities.  Lewis responded that a

true comparison showed most had very similar moralities.  He asked readers to imagine what vast differences would mean - a country where a soldier was admired for running away - or where another was admired for double-crossing those kindest to him.  He compared it to a country where two and two made five.

Lewis acknowledged that not everyone agreed with this view.  But he noticed that those who disagreed usually tended to insist the next moment on a standard of right and wrong to call attention that they had been wronged on some matter or other.

Next, Lewis pointed out that we all know we don't keep the moral law, whatever you might call it.  We know we have not completely kept the moral law we expect others to observe, and tend to accuse others of not keeping.

Lewis summarizes this as the basis for all clear thinking.  First, almost everyone believes others ought to behave in a certain way - the Law of Human Nature - and Second, that everyone who faces the truth has to admit they do not completely observe this standard - and, in fact, have disobeyed it.

Mere Christianity - Preface
Mere Christianity - Overview
Bk. 1 - Ch. 2 - Some Objections