There is a moral law that is written on our hearts, aka conscience or Natural Law
Thomas Jefferson wrote in the Declaration of Independence, the natural law is self-evident
He knew helping people was the right thing to do but could not explain why without appealing to a standard outside himslef
Without an objective standard of meaning and morality, then life is meaningless. Everything is merely a matter of opinon.
All people are impressed with a fundamental sense of right and wrong:
The sense of moral obligation is something that binds to all people, at all time, in all places
Not every moral issue has an easy answers and moral dilimas exists
Others just denied moral law exist in their lives because it is not what they want to do but know in their heart something is right or wrong
Everyone, everywhere know killing innocecnt humans for no reason is wrong, even serial killers