Why do you believe in objective moral values?
The Bible makes it very clear that God set moral laws—the standards of right and wrong. People are not given this option (Isaiah 45:19, Romans 1:25). The penalty for challenging God on this is severe in a very ultimate sense (Genesis 2:17, Isaiah 5:20, Romans 6:23, Jude 7).
But we can also intellectually defend objective moral values over moral relativism. First, relativism is always self-contradictory. The statement that "there are no absolutes" is a self-contradictory statement, because it itself expresses an absolute. It is therefore an internal contradiction and thus it cannot be true. In other words, relativism is nonsense.
To be a relativist, one must believe that (a) There is no truth, (b) Nothing is knowable, and (c) Nothing is meaningful. Yet the fact is that all people live their lives with some moral absolutes. If all life were truly relative, the cry for "fairness" would disappear. If all life were relative, there would be no definition of "abuse," or "racism," etc. The avid relativist will scream as loud as anyone else if his car is stolen!
The best example of a moral relativist—when taken to its logical conclusion—is a sociopath.
Actually, it is fairly easy for most people to see that objective moral standards do exist. We might ask, do you think it is acceptable to burn people at the stake because we think they are witches? Or what if the Christian Coalition suddenly started rounding up homosexuals and torturing them? Or what about the ancient Chinese custom of crippling women for life by tightly binding their feet from childhood to resemble lotus-blossoms? Do you think it's okay for Catholic priests to sexually abuse little boys and that the Church did nothing wrong in trying to cover it up? Certainly, you find these things abhorrent! Should we impose our values of women's rights on a culture that does not afford women rights? Most professing relativists would say yes, not thinking about the inconsistency in their worldview.
If you are a student, let's say you turned in "A" work all semester and when you got your report card you see that you got an "F" in the course. Or if you are an employee, would it be right for the boss to fire you without cause? If there were no such thing as objective moral standards, you would have no right to complain in such situations. You would be obligated to accept anything and everything.
The idea of no absolutes is often expressed today with the word tolerance. Tolerance, in today's usage, proposes that all ideas are morally equivalent—that truth is relative, that everything we have learned about morality in 4,000 years of recorded human experience is now negotiable.
If tolerance is a stand-alone virtue, then we must tolerate everything. Following that logic, then, we must be tolerant of, for example, slavery or a South American drug cartel, etc. Is whoever wields the most power the most moral? Of course not. But the relativist cannot avoid ending up with that view.
We submit that tolerance and love are not the same thing. Jesus calls us to a standard higher than mere tolerance. He calls us to compassion. While Jesus reached out to prostitutes, tax collectors, and the downtrodden, he did not preach "tolerance." He helped people see truth. Jesus loved the adulteress who was going to be stoned. He loves us even though we also deserve the eternal death penalty. Jesus saves us and tells us, as the adulteress, to "leave your life of sin" (John 8:11). And his message changes the lives of people he touches forever.
Atheists insist that morality is either genetically acquired through evolution, or is strictly matter of utilitarianism to survive among our neighbors. But this misses the point. The essence of morality is doing what one ought to do without regard to what one is inclined to do or what is in one's best interest to do. The essence of morality is to operate against self-interest.
Tim Keller in his book, The Reason for God, challenges us: "Aren't there people in the world who are doing things you believe are wrong—things that they should stop doing no matter what they personally believe about the correctness of their behavior? If you do (and everyone does!), doesn't that mean you do believe that there is some kind of moral standard that people should abide by regardless of their individual convictions?...We all have a pervasive, powerful, and unavoidable belief not only in moral values but also in moral obligation."
The relativist at this point may amend their original statement by saying, "As long as you're not hurting others, you're free to do and believe what you like." But this is an arbitrary distinction (as well as another absolute statement). Who says I can't hurt others? What constitutes "hurt." Where does this rule come from? If this statement is made based on a personal preference, it means nothing for anyone else. "Do no harm" (a common statement by libertarians) is in itself an appeal to something greater—a sort of universal dignity for the human person. But again, the question is where does this dignity come from? The atheist/relativist cannot logically answer the question: "If I can harm someone to better myself today, and not get caught, why not do it?"
As you can see, the further you delve into these questions, the closer you come to understanding that our concepts of right and truth are not arbitrary but are based in some greater, universal truth outside ourselves—a truth written in the very nature of our being. We may not know it in its entirety, but it can't be denied that this truth exists.
Evidence also supports the view that there are moral absolutes just as there are physical absolutes. If we continually challenge the physical laws of nature, for example, driving recklessly, sooner or later it will catch up with us. In the very same way, if we regularly challenge God's moral laws, we can expect to suffer the consequences.
It is important to recognize that God did not give us moral laws, i.e. rules by which to live, because He is mean or hateful or arbitrarily restrictive. He gave us rules precisely because he loves us so much that he wants us to be safe and happy.
Again, we call on evidence. There are many statistics to verify the validity of the effects of following the lifestyle espoused in the Bible. For example, studies show that monogamous married heterosexual couples report greater happiness and "overall life satisfaction" as well as greater sexual fulfillment than any other lifestyle. And people living a Christian lifestyle are significantly healthier and live significantly longer on average than other groups.
Check out these links:
And this short video: Morality Without God
See also the next two questions: If it feels good for me isn't it right? and Why can't I live my life as an agnostic?