a thoroughly bad man thinks he is all right
Remember that, as I said, the right direction leads not only to peace but to knowledge.
When a man is 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 and less.
A moderately bad man knows () he is not very good:
a thoroughly bad man thinks () he is all 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.
You can understand the nature of drunkenness /when you are sober, not when you are drunk.
Good people know about both good and evil: bad people do not know about either.
From Mere Christianity
Compiled in A Year with C.S. Lewis