I have just started reading this book and already it has spoken into my life. The very first chapter is about what he calls the 'law of human nature'. It's all about the standard of which you treat other human beings and how you expect them to treat you. Basic right and wrong. I like how he put it [comparing right and wrong to notes on a piano]:
Think once again about a piano. it has not got two kinds of notes on it, the 'right' ones and the 'wrong' ones. Every single note is right at one time or another. The moral Law is not any one instinct or set of instincts: it is something that makes a kind of tune (the tune we can call goodness or right conduct) by directing the instincts.
He earlier in the passage wrote regarding how every human instinct has a right time and a right place. Such as [Lewis suggests] the instinct to fight and the instinct to have sex, in the right situation they are perfectly fine, but outside of that they are the 'wrong notes'. The right situation he gives for both examples is as follows: for fighting it is proper to increase that instinct when going to fight for your country and in reference to sex he says it is proper for a married man to increase his sexual desire, but of course, only with his wife.
I have been really struggling with wanting to please God, being blameless before others and being a good example of Christ to those who do not know him, and this chapter eased my fear slightly. The reminder that every action has a proper time and place is very comforting. Now the challenge is, through prayer and supplication, let God do all the work he needs to so that I play my song in tune.