The atheist asking this question is rarely a mean person. He is usually a good one. And the question presses harder than he realizes — because his goodness is the very evidence the question is trying to explain.
Knowing morality vs. grounding morality
A child does not need to know who the lawmaker is in order to obey the law. Likewise, atheists know — and live by — moral truths. The question is not epistemological; it is ontological. What grounds objective moral truths? On naturalism, what makes cruelty wrong rather than merely unfashionable?
This distinction is everything. Christians are not claiming atheists cannot be good. They are claiming that on the atheist's own terms, "good" loses its anchor.
Honest atheists have admitted the problem
Friedrich Nietzsche saw clearly that the death of God meant the end of all the moral furniture inherited from Christianity. Bertrand Russell wrote that without God, human aspiration is the result of "an accidental collocation of atoms." Jean-Paul Sartre admitted that, without a God, "all is permitted." Richard Dawkins has written that the universe has "no design, no purpose, no evil, no good — nothing but pitiless indifference."
These are not slips. They are the consequences of the position. And they are honest.
The moral argument runs
- If objective moral values and duties exist, then God exists.
- Objective moral values and duties do exist — we know this directly (the wrongness of torturing children for fun is not a preference).
- Therefore, God exists.
C. S. Lewis on this is decisive
"My argument against God was that the universe seemed so cruel and unjust. But how had I got this idea of just and unjust? A man does not call a line crooked unless he has some idea of a straight line."
The Orthodox emphasis: the moral law and the image of God
St. Paul wrote that the Gentiles "show the work of the law written on their hearts" (Romans 2:15). This is the doctrine of natural law — but for the Christian East it goes deeper. We know right from wrong because we bear the image of God. Even the most distant person from the gospel carries within him the trace of his Maker. His conscience is not a social adaptation. It is the ruined echo of the One who made him.
The invitation
This is not a gotcha argument. It is an invitation. The atheist's goodness is itself a clue. The moral law he lives by is not an embarrassment to be explained away. It is a signpost. If he is willing to follow it, it points home.
As Frank Turek calls it: the atheist is "stealing from God" — using a moral framework that only Christianity can ground. The good news is that he is welcome to keep using it. He just has to find out where it actually came from.