Well, if everyone behaved selfishly, and took it to its natural conclusion, you would logically deduce that murder would be common, as someone else’s gain might well be my loss. Since a society (or lack thereof) where murder is common will not allow me to sleep peacefully at night in fear of becoming a victim, then yes, we can agree that we creation, even apart from Divine Law, needs a moral order. From murder, you can similarly deduce many faults against charity, albeit less grave, that likewise society must proscribe. In the end, you will basically end up with the Ten Commandments and love thy neighbor as thyself. Short of that, you get chaos. That’s why the Church teaches that the Ten Commandments are inscribed upon each of our hearts as part of the natural law.
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