Everyone believes in right and wrong not merely as words we us to describe the things of which we approve or disapprove, or what we like or dislike, but as real standards that somehow exist in the real world. We demonstrate this belief continually in the way we speak.
Everyone has heard people quarrelling, they say things like...'That's my seat, I was there first'...'Leave him alone, he isn't doing you any harm'...'Give me a bit of your apple, I gave you some of mine'...'Come on, you promised.'... The person who makes these remarks is not merely saying that the other person's behaviour does not happen to please him. He is appealing to some kind of standard of behaviour which he expects the other person to know about. Your companion seldom replies, 'To hell with your standard.' He nearly always tries to make out that what he has been doing does not really go against the standards, or that if it does, there is some special reason for it. It looks as if both parties had in mind some kind of Law or Rule of fair play or good behaviour about which they agree. If they had no agreement about the 'rule of fair play' they might fight like animals but they would not be quarrelling in the human sense of the word.
Quarrelling means trying to show that the other person is in the wrong. There would be no sense in trying to do that unless you both had some sort of agreement as to what Right and Wrong are; just as there would be no sense in saying that a soccer player had committed a foul unless there was some agreement about the rules of soccer.
Christians believe that a personal God exists and has a particular nature and moral character. Moral laws reflect that nature of who God is. His character provides the source of morality as well as the standard for moral laws in the universe. Since every person is made in God's image, like God, we are moral beings. It's no wonder we know intuitively that right and wrong exist. It's no wonder we sense to the very core of our being that right and wrong are somehow "real things," not simply words we use to express our personal preferences. God has written these fundamental moral laws on our very souls.
From "The Godless Delusion" by Patrick Madrid and Kenneth Hensley