The ability to discover the natural law is by using your conscience , as Catholics would call it
Catholics believe the conscience has two parts of it :
the knowledge part is our minds ability to know the difference between right and wrong
the action part is the internalimpulse to do what is right and avoid doing what is wrong . This is the part that gives humans their sense of moral duty
Catholics believe that the conscience is unique to humans - only humans have a conscience - further proof that God created humans in Hisimage
If humans obey their conscience more there would be lessmoral evil and lesssuffering