Some objections

This chapter is a little more difficult to interpret.  While I understand his reasoning while I'm reading it, I'm not sure I understand it enough to expound on it.  But I will try.

Some things in this world are subjective... given to opinion.  Morality of a culture is subjective.  Each one a little different from the other because of how we see the world.  The difference is this.  When we look at the morality of several cultures, we judge how "good" that is based not on our own morality but on the Law of Human Nature.  There is a plumb line that we are trying to match as close as we can and some are closer than others.  So the Law of Human Nature would be an objective thing, not given to change.

Lewis compares it to a piano piece.  There are notes that one ought to play, different notes at different times.  It is not that one note is always wrong and another one is right but that each when played at their proper time are correct.  Our instincts to do one thing is not always right but it is also not always wrong.  It is not always wrong to kill (as in a war) and it is not always right to allow sexual desire to be satisfied. 

Sometimes one instinct will tell us to do one thing and another instinct will tell us to do something else.  The Law of Human Nature tells us which instinct we OUGHT to listen to.  The instincts are the merely the keys, but the Law is the composition.  We can have an instinct to help someone but also have an instinct of self-preservation.  The Law will tell us which one we should obey.

Yes, we can learn this from our parents and teachers but not all will to the same extent.  This doesn't make it any less true as not learning your multiplication facts doesn't make them not true, it just makes you less aware of it.

This boggles my mind a bit. I do not think like Lewis does about things, which means it's a stretch for me to attempt to explain them.  This is my best effort!