What is the moral argument?
Question 60101
The moral argument begins with something so familiar that it is easily overlooked: human beings make moral judgements and expect them to carry real weight. When we say that torturing children for pleasure is wrong, we do not mean simply that we dislike it, or that our culture happens to disapprove of it. We mean it is actually wrong — wrong in a way that does not depend on anyone’s opinion, wrong in a way that would still be wrong if every person alive thought otherwise. The moral argument asks where that conviction comes from, and whether it can be sustained without God.
The Structure of the Argument
The formal version runs as follows. Objective moral values and duties exist. If God does not exist, objective moral values and duties do not exist. Therefore God exists. The entire weight of the argument falls on the second premise. If the universe is the product of mindless, purposeless physical processes, then human beings are biological organisms shaped entirely by evolutionary pressures. Evolution selects for survival and reproductive success. It has no interest in justice, compassion, or honesty except insofar as these happen to aid survival. Moral sensibilities, on this account, are nothing more than adaptive responses — useful fictions that happened to confer a reproductive advantage on our ancestors.
If that is true, then moral statements have no more objective force than statements about personal taste. “Genocide is wrong” and “I prefer coffee to tea” are, at bottom, both expressions of subjective preference. Most people recognise instinctively that this is not right. There is something about genuine moral claims that reaches beyond preference, beyond culture, and beyond the merely useful. The moral argument takes that intuition seriously and traces it to its source.
Lewis and the Law of Human Nature
C.S. Lewis developed this with characteristic clarity in Mere Christianity. He pointed to the universal human practice of quarrelling. When two people argue with each other, they are not simply expressing conflicting preferences — they are appealing to a standard that both parties are assumed to know and neither has invented. “That’s not fair” only makes sense if fairness is a real thing, not a cultural construct that different societies could define in opposite ways without either being wrong. “You promised” only carries weight if promises create genuine obligations that are not merely conventional.
Lewis called this the Law of Human Nature: a moral standard that human beings know and consistently fail to live up to, and that is not the same thing as the instincts and desires it adjudicates between. Its near-universality across radically different cultures, despite wide variation in what specific actions are thought to fall under it, points toward something that is not invented but discovered — a moral reality built into the structure of things rather than constructed by human societies.
The Biblical Framework
Romans 2:14-15 provides the theological underpinning. Paul writes that Gentiles who do not have the Mosaic law “do by nature what the law requires,” and that “the work of the law is written on their hearts, while their conscience also bears witness.” This is not a claim that all people behave morally. It is the claim that all people carry an awareness of moral obligation — a sense of being measured against a standard they did not invent and cannot simply dismiss. The moral argument in philosophy is working out the implications of what Paul states as anthropological fact.
The existence of a universal moral standard requires a moral lawgiver who transcends the universe. An impersonal universe cannot be the source of binding moral obligations, any more than the law of gravity can be the source of legal obligations. Moral duties require a personal ground — someone to whom obligations are owed, and whose character is the standard against which they are measured.
The Euthyphro Dilemma
A persistent objection is the Euthyphro dilemma, named after Plato’s dialogue: is something good because God commands it, or does God command it because it is good? The first option seems to make morality arbitrary — God could have commanded cruelty and cruelty would then be good. The second option seems to suggest that the standard of goodness is independent of God, making God irrelevant to ethics.
Both options misrepresent the Christian position. God does not command things arbitrarily, nor does He conform to a standard existing outside Himself. God’s nature is the standard of goodness. He commands what He commands because His commands express who He is. He cannot command cruelty because cruelty is incompatible with His character. The dilemma dissolves once the nature of God is properly understood: goodness is not something God imposes by fiat, nor something He conforms to reluctantly — it flows necessarily from who He is.
Can Morality Be Grounded Without God?
The most common secular alternative grounds morality in human flourishing or social contracts. But this simply relocates the problem. Why should human flourishing matter if human beings are biological accidents in an indifferent universe? A social contract can explain why following moral rules might be prudent. It cannot explain why they are genuinely binding on someone who calculates that breaking them would serve their interests and that they can avoid detection. The person who asks “why should I care about anyone else’s flourishing?” receives no satisfying answer from a purely naturalistic framework. The answer “because evolution programmed you to feel that way” is true, perhaps, but does not establish that the feelings track anything real.
So, now what?
The moral argument has immediate pastoral relevance because it addresses one of the most common pieces of cultural mythology: “I don’t need God to be a good person.” This may be true in a behavioural sense — plenty of non-Christians act generously, honestly, and kindly. The argument is not about whether non-Christians can behave well. It is about the metaphysical foundation that makes goodness real rather than merely convenient. The person who takes their own moral convictions seriously — who genuinely believes that some things are right and some things are wrong regardless of what anyone thinks — is already operating on borrowed capital from a theistic universe. The moral argument asks them to follow their own convictions to their proper ground.
“They show that the work of the law is written on their hearts, while their conscience also bears witness, and their conflicting thoughts accuse or even excuse them.” Romans 2:15
Bibliography
- Lewis, C.S. Mere Christianity. Geoffrey Bles, 1952.
- Craig, William Lane. Reasonable Faith: Christian Truth and Apologetics. Third edition. Crossway, 2008.
- Copan, Paul. Is God a Moral Monster? Making Sense of the Old Testament God. Baker Books, 2011.