Here's a good rule of thumb about morality: Never believe those who say murder or rape may not really be wrong. Such people haven't looked deeply enough into the basis for moral belief-and just aren't functioning properly. (Usually, when personally threatened with murder or rape, they change their tune!) Color-blind persons need help distinguishing red from green. Similarly, morally malfunctioning persons (those denying basic moral truths) don't need arguments; they need psychological and spiritual help. Like logical laws, moral laws and instincts are basic to well-functioning humans.
As part of God's general self-revelation, all people-unless they ignore or suppress their conscience-can and should have basic moral insight, knowing truths, generally available to any morally sensitive person (Rm 2:14-15). We instinctively recognize the wrongness of torturing or murdering the innocent or committing rape. We just know the rightness of virtues (kindness, trustworthiness, unselfishness). A person's failure to recognize these insights reveals something defective; he hasn't looked deeply enough into the grounds of his moral beliefs.
Philosophers and theologians past and present have noted the connection between-God's existence and objective moral values. A moral argument for God's existence goes like this: (a) If objective moral values exist, then God exists. (b) Objective moral values do exist. (c) Therefore, God exists. If objective moral values exist, where do they come from? The most plausible answer is God's nature or character. Even many atheists have admitted that objective moral values (which they deny) don't fit an atheistic world but would serve as evidence for God's existence.
We live in a time when many claim everything is relative, yet ironically they believe they have "rights." But if morality is just the product of evolution, culture, or personal choice, then rights-and moral responsibility-do not truly exist. But if they do, this assumes humans have value in and of themselves as persons, no matter what their culture or science textbooks say. But what, then, is the basis for this value? Could this intrinsic value just emerge from impersonal, mindless, valueless processes over time (naturalism)?
An Eastern philosophical approach to ethics is monism (sometimes called "pantheism"): because everything is one, no ultimate distinction between good and evil exists. This serves to support relativism. A more natural context for ethics is the theistic one, in which we've been made by a good God to resemble Him in certain important (though limited) ways. The Declaration of Independence correctly notes that we've been endowed by our Creator with "certain inalienable rights." Human dignity isn't just "there." Dignity and rights come from a good God (despite human sinfulness).
Can't atheists be moral? Yes! Like believers, they've been made in the image of God and thus have the ability to recognize right and wrong.
Doesn't God Himself conform to certain moral standards outside Himself? No, God's good character is the very standard; God simply acts and naturally does what is good. Universal moral standards have no basis if God doesn't exist.
Extracted from the Apologetics Study Bible.