Lewis - Objective Right and Wrong

There is a real right and a real wrong. Lewis calls this the Law of Nature. He states that every man and every nation believes this - even if they are mistaken about what the real right or real wrong actually is. His evidence is the fact that while many men or nations may state that there is no objective right and wrong, the moment which they feel wronged they undercut their arguments against a real right and wrong. Likewise, he states that the very fact that we make excuses for when we have acted wrongly (or we have acted in a way that other's perceive as wronging them) proves that everyone believes in a real right and wrong. If they didn't have such a belief they would not feel the need to excuse away behavior.