A non-Christian friend of mine once asked me if atheists were better people than Christians because they don’t need someone to tell them what is right and wrong. I’ve seen several atheists make this claim, with greater or lesser degrees of condescension and ridicule. I didn’t have an answer at the time, but after giving it some thought, I do.
First of all, the question completely misunderstands the issue. The issue isn’t whether or not we need someone to tell us what is right and wrong; that’s a different question. The issue is that such categories as right and wrong don’t even exist without the triune God of Scripture.
What this question does is reveal the atheist’s assumption (which is not universal, by the way) that right and wrong exist, and they know it due to various factors: common sense, cultural consensus, and the like. Unlike us Christians, they don’t need someone else to tell them what’s right and wrong; they just know it, because everyone should. The question of “Who’s common sense?” or “Which cultural consensus from which time in history?” remains unanswered to this day, because it’s unanswerable from an atheist worldview. So, from the beginning, the question falls flat on its face.
Second, though, there’s a deeper issue. Without God, how can an atheist — or any unbeliever, for that matter — know right from wrong? Contrary to what the atheist would say, they only know because God has revealed it to them. God’s law is written on their hearts, and their consciences even guide them in moral judgment, though imperfectly (Rom 2:15–16). They are themselves revelation of God (Ps 19:1; Rom 1:19–20), though they lie about him in what they say, think, and do. This is an aspect of a doctrine called common grace. Through these means, God restrains the evil in all of our hearts — Christian and non-Christian alike — lest we destroy ourselves and each other in our wickedness. It is only because of God’s common grace that anyone — atheists, Christian, Muslim, Jewish — can know right from wrong apart from the Bible.
One may object, “Well, God didn’t do a very good job telling people about right and wrong, because people still commit evil acts.” But that isn’t because of any flaw in what God has said; that’s because people choose to ignore God and commit those evil acts instead (Rom 1:32).
Of course, none of this is a substitute for Scripture. Only God’s word reveals his law perfectly. But even those who have never cracked open a Bible have heard from God on some level.