Natural laws, yes, there are laws of gravity, laws of action and reaction, laws of science. But why, then, should we reject a natural law of morality or the way in which human beings are meant to act. Maybe it’s because these laws can be broken, but that only contributes to our free will. If I chose to fly, could I do it? Would that not conflict with the law of gravity? Yet it says that if you have faith you can move mountains – that transcends natural law.
Onto civil laws and the difference between war and murder:
“Could there be anything more absurd than that a man has the right to kill me because he lives on the other side of the water, and his prince has picked a quarrel with mine, though I have none with him?” Pascal, Pensees 60. It seems that the difference is only in politics and the laws that civil governments make. Laws are a reflection of the people. People are corrupt, so the laws will be corrupt. Therefore, an argument for moral relativity on this basis (that the laws of men vary according to custom and heritage) is not convincing. We all know people are corrupt. There is no more truth in all of this than the laws. The only sense in which we have the truth revealed in our laws is to that extent that we are united with God – in his image and likeness – because God is truth.