An argument for God's existence from the reality of objective moral values and duties. Classical formulation: (1) If God does not exist, objective moral values and duties do not exist; (2) Objective moral values and duties do exist; (3) Therefore, God exists. Defenders: C. S. Lewis (Mere Christianity, Book I), William Lane Craig (Reasonable Faith), Paul Copan. The argument draws on Romans 2:14-15 — "the work of the law is written on their hearts, while their conscience also bears witness" — the universal moral awareness that even those without Scripture possess.
The moral argument is perhaps the most powerful contemporary argument for God in a secular culture that is simultaneously passionate about morality (social justice, human rights, racial equality) and committed to naturalistic metaphysics (no God, just matter). The contradiction is the opening. (1) If naturalism is true, morality is reducible. On pure naturalism, moral feelings are evolutionary survival strategies (what felt good to our ancestors spread in the gene pool); social constructions (whatever our tribe decided); or personal preferences. None of these produces obligations binding on others. But contemporary moral discourse treats rights — e.g., "racism is wrong, always, everywhere, for everyone" — as objective. The atheist who claims this has borrowed Christian capital to say it. (2) C. S. Lewis's opening in Mere Christianity. Lewis argues that the human sense of "fair play" and "the way things ought to be" reveals a Moral Law — independent of any individual or society — that presupposes a Moral Lawgiver. (3) Counter-arguments and responses. Atheists respond with "evolutionary ethics" or "contractualism"; careful analysis shows these do not generate binding obligations, only explanations of moral feelings. The Euthyphro dilemma (does God command it because it is good, or is it good because God commands it?) is resolved in Christian theism by grounding moral goodness in God's unchanging nature, not His arbitrary will. (4) Pastoral usefulness. When someone says "I'm spiritual but not religious; I just try to be a good person," press on what "good" means. Most people assume objective moral standards without realizing those standards presuppose the God they deny.