Often when discussing morality or the aspects thereof with both teenagers and adults, one will hear someones life philosophy in the form of, "hey, what is right for you may not be right for me." These "relativists," as we call them, do not have a clue. Mostly but not always, relativists are atheists or extremely weak believers in God, or a god, or some type of god, and so on. After their typical catch phrase stated above, discussions with them often turn to this question: does absolute moral truth exist? How do we measure it? What is its nature?
How do we find goodness and truth? If one believes that truth is truly relative, then one can believe whatever one wishes, and there one has truth. Under that principle, Hitler did what he thought was right by killing Jews. That does not constitute "right." Assume that Bill Clinton believes that gravity will now go up rather than down. Even if everyone in the entire world agreed with him, gravity, as a natural scientific law, would still go down. It does not matter what people think, people's thoughts and ideas would not change gravity. Natural scientific law transcends human opinion; natural moral law does as well.
Laws of the United States government prohibit manslaughter. If someone wants to murder an individual, the law happens to side with the protagonist. Is truth, then, defined by a government? Ancient governments used to condone, and in some cases demand, child sacrifice and slavery. Does that make slavery and child sacrifice morally acceptable? We like to think that since we do not demand these things currently, we have a "better" form of government than in ancient times. "Better" implies a "best," which also implies a measurement of the government by an objective standard outside of the human race. Truth, then, also transcends government.
Some people define right as "what feels right" or what brings the most amount of pleasure and the least amount of pain to the greatest amount of people. This returns to the original relativist theory of "what is right for you may not be right for me." What "feels good" to one person may make another miserable. If two people do separate opposite actions (for example, one person who steals and one person who does charity work) and both "feel good" to each individual, are they both right? Surely everything cannot be right and vice versa.
Moral truth, which we have concluded is transcendent of the human race, may appear extremely elusive, but in reality one can discover it by human reason. We call this the "natural law" in the moral sense, because God has "written it in [our] hearts..." (Rom 2:15). Thinking atheists can use honest "cause and effect" reasoning to discover this. Essentially, The Ten Commandments embody and clearly define this law. Besides the third commandment, God did not impose any new laws on mankind. Parents ought be honored. Possessions of one person should not be taken by another. Murder is a gargantuan offense with extreme consequences, and so on.