C.S. Lewis

When a man getting better he understands more
and more clearly the evil that is still left in him.

When a man is getting worse,
he understands his own badness less
ansd less.A moderately he is right.

This is common sense,really.
You understand sleep when you are awake,
not while you are sleeping.

You can see mistakes in arithmetic
when your mind is working properly;
while you are making them you cannot see them.

Good people know about bad and evil;
bad people do not know about either.5