The Moral Argument for the Existence of God – Reasonable Christianity

The moral argument for the existence of God is often given a simple deductive form:

1) If there are objective moral values, then God exists.

2) There are objective moral values.

3) Therefore, God exists.

Logicians agree the logical form of this argument is valid. However, this does not guarantee the argument is sound. An argument is sound only when its logical form is valid and when all its premises are true. The crucial step would be to demonstrate premises 1 and 2 are true. Otherwise, the argument fails.


C.S. Lewis therefore does not simply rely on a deductive argument that moves from universal/general to particular. He begins from concrete particulars related to premise 2. He proceeds inductively, that is, he begins by noting some commonly accepted moral values and discussing why some actions are considered praiseworthy or blameworthy. He shows how these moral case studies cumulatively provide clues and supporting evidence that lead to the conclusion that an absolute Moral Law Giver (God) exists.

Lewis begins by demonstrating there must be a universal moral law. He observes that we invariably appeal to an objective moral standard to settle disputes. We insist that a stranger gives us back our seat in a train when he surreptitiously usurps ours when we get up to arrange our baggage. We expect decent behavior and demand fair play. Individuals must keep their promises and nations observe their treatises and are judged if they fail to keep their moral obligations. We are not just being emotional but morally right when we declare, “The Nazis are wrong.”

Moral obligation is all the more curious as often times we don’t quite live up to it. Yet we would not accept excuses for breaking the moral law. Lewis writes, “First, that human beings, all over the earth, have this curious idea that they ought to behave in a certain way, and cannot really get rid of it. Secondly, that they do not in fact behave in that way. They know the Law of Nature; they break it. These two facts are the foundation of all clear thinking about ourselves and the universe we live in.” [MC8]


Lewis refutes several erroneous views on the moral law:

1) The Moral Law Is Not Herd Instinct. It is reasonable to assume our stronger impulse normally wins. We would have instinctively run away (the stronger instinct) rather than face danger to save someone (the weaker instinct). However, when we are caught between two conflicting instincts, we can find ourselves choosing the ‘weaker’ instinct. Somehow, we feel more compelled by a moral imperative to overcome fear and take risk to help the person in danger. If instinct constitutes the moral law it should always be right, but we know from sad experience that there are times when it is moral to restraint our otherwise good instincts like a mother’s love or patriotism. “There are also occasions on which a mother’s love for her own children or a man’s love for his own country have to be suppressed or they will lead to unfairness towards other people’s children or countries.” [MC11] Indeed, an unquestioning obedience to our instinct could lead to inhumane action.

2) The Moral Law Is Not Social Convention.  Lewis argues that simply because we learn something from society does not make it a convention. He has in mind knowledge like math and logic. But someone may disagree, “Isn’t it the case that moral diversity points to context specific rather than universal morality? For example, the ancient Spartans believed in infanticide, but modern societies consider infanticide immoral and murderous.” In short, the moral law is merely social convention.

Lewis asserts that basic moral laws are fundamentally the same for many societies. No society admires selfishness and approves murdering a friend. He gave a list of moral constants at the end of his book The Abolition of Man that includes the law of beneficence that covers duties to parents and children; the law of justice (both court and sexual justice) that requires honesty; the law of good faith and veracity and the law of magnanimity. It turns out that societies have different moral judgment not because of different basic moral values but because they operate with different facts. For examples, witches are no longer treated as murderers not because murder is now right but because as a matter of fact witches are now not thought to be murderers.

3) The Moral Law is Not to be Identified with the (Physical) Laws of Nature. The laws of nature are descriptive (is) which we cannot avoid. For example, we cannot avoid the law of gravity. But moral laws are prescriptive (ought), which can be transgressed. Sometimes factually more convenient situations are morally worse than the less convenient. For example, “A man occupying the corner seat in the train because he got there first, and a man who slipped into it while my back was turned and removed my bag, are both equally inconvenient. But I blame the second man and do not blame the first. I am not angry—except perhaps for a moment before I come to my senses—with a man who trips me up by accident; I am angry with a man who tries to trip me up even if he does not succeed. Yet the first has hurt me and the second has not. Sometimes the behaviour which I call bad is not inconvenient to me at all, but the very opposite.” [MC18]

4) The Moral Law is not Subjective preference. Moral laws are accompanied by the word ‘ought’ as when we say, “you ought to behave decently” or “you ought to be unselfish,” etc. But one may retort, “Why should I bother? For the good of society? But why should I care?” We don’t like moral expectation but somehow we cannot get rid of it. Lewis concludes, “Consequently, this Rule of Right and Wrong, or Law of Human Nature, or whatever you call it, must somehow or other be a real thing—a thing that is really there, not made up by ourselves.” [MC20]

In short, we cannot get rid of objective moral law (opposite of subjective preferences). We did not create it; it is impressed on us from without. If it were merely subjective preference, then morals are matters of personal taste and all value judgments and moral criticism would be meaningless.


Having established premise 2 (the existence of objective moral values), we next seek to establish premise 1 (If there are objective moral values, then God exists).

Establishing premise 1:

1) There must be a universal moral law.

2) Man is the key to understanding this moral law.

3) Conclusion: There is an absolute, universal Moral Law Prescriber from beyond nature or physical reality



1. There must be a universal moral law, or else:

a) Moral disagreements would make no sense.

b) All moral criticisms would be meaningless (e.g., “The Nazis were wrong”).

c) It is unnecessary to keep promises or treaties.

d) We would not make excuses for breaking the moral law.


2) Man is the key to understanding this moral law.

a) Man has an internal moral compass that is more than descriptive (is). It is an imperative (ought). Lewis notes that we know the moral law not by observing external phenomena. Knowledge of the moral law is an inward knowledge, That is to say, the Law of Human Nature, or of Right and Wrong, must be something above and beyond the actual facts of human behavior, “we know that men find themselves under a moral law, which they did not make, and cannot quite forget even when they try, and which they know they ought to obey.” [MC23]

b) The source of this moral law is more like mind than nature, that is, the moral law originates from mind rather than inanimate matter.

Lewis notes that the Moral Law Giver is more like Mind than material Nature, “what is behind the universe is more like a mind than it is like anything else we know. That is to say, it is conscious, and has purposes, and prefers one thing to another. And on this view it made the universe, partly for purposes we do not know, but partly, at any rate, in order to produce creatures like itself—I mean, like itself to the extent of having minds.” [MC22]

c) The source of this moral law cannot be part of the physical reality.

Lewis provides an analogy: Since that power, if it exists, would be not one of the observed facts but a reality which makes them, no mere observation of the facts can find it just as it is. For example, no amount of studying the architecture of the house leads us to find the architect.


3) Conclusion: There is an absolute, universal Moral Law Prescriber from beyond nature or physical reality.

a) Lewis stresses that the moral law is compelling and impresses upon us as a command from a Higher Power. “The only way in which we could expect it to show itself would be inside ourselves as an influence or a command trying to get us to behave in a certain way. And that is just what we do find inside ourselves. Surely this ought to arouse our suspicions… I find that I do not exist on my own, that I am under a law; that somebody or something wants me to behave in a certain way.” [MC24]

One difference is however is that while material objects simply follow the laws of nature, in the case of my moral action “the sender of the letters merely tells me to obey the law of my human nature, he compels the stone to obey the laws of its stony nature. But I should expect to find that there was, so to speak, a sender of letters in both cases, a Power behind the facts, a Director, a Guide.” [MC25]

b) As the Source of the moral law, he expects us to keep his commands and is absolutely good.

If the Moral Lawgiver is not absolutely good, there is no guarantee that our moral effort is worthwhile. We may end up sacrificing our lives for futile purposes. Our moral effort would be in vain if ultimately there is no absolute “right’.

c) The Moral Law Giver must be absolutely good. He can be the standard of all good only if he is absolutely good himself.

The skeptic may protests, “the fact that there is so much imperfection and evil in the human action and the moral order refutes this claim of an absolutely good Moral Lawgiver.” Lewis gives a simple answer: The protest already assumes some standards of just and unjust.  A man declares a line as crooked because he has an idea of a straight line. Likewise, we can declare the world as unjust only because we already operate with an objective, absolute moral standard. “Of course I could have given up my idea of justice by saying it was nothing but a private idea of my own. But if I did that, then my argument against God collapsed too—for the argument depended on saying that the world was really unjust, not simply that it did not happen to please my fancies. Thus in the very act of trying to prove that God did not exist—in other words, that the whole of reality was senseless—I found I was forced to assume that one part of reality—namely my idea of justice—was full of sense.” [MC38]

Lewis concludes, “Consequently atheism turns out to be too simple. If the whole universe has no meaning, we should never have found out that it has no meaning: just as, if there were no light in the universe and therefore no creatures with eyes, we should never know it was dark. Dark would be a word without meaning.” [MC39]

How ironic: rather than disproving a morally perfect Being, judging something as evil in the world presupposes a perfect standard. It is precisely the case that when we judge the world as imperfect that we must presuppose there is a perfect standard by which this is known.


The argument may be summed up as follows:

1) There exists a universal Moral Law. Otherwise, moral disagreements, moral criticism and moral obligations become meaninglessness.

2) A universal Moral Law requires a universal Moral Law Giver as its Source who gives moral commands and to whom we are accountable for our moral behavior.

3) This universal Moral Law Giver must be absolutely good. The ultimate source of moral must be absolutely good. Otherwise, we do not have a standard to judge between good and bad and all moral effort is in vain there is ultimately no absolute right or good.

4) THEREFORE, there must be an absolute Moral Law Giver (God).


An Excursus into Logic

At the simpler level we can reduce the argument so far:

1) If there is a Higher Power or Moral Law Giver, then it would shows itself as an internal command ordering us to behave morally.

2) We find within ourselves such a command.

3) Therefore there is a Higher Power or Moral Lawgiver.


Some skeptics pounce on this formulation and point out that this form is a well-known logical fallacy (fallacy of affirming the consequent):

a) If P, then Q.

b) Q.

c) Therefore, P


But this objection rests on a misunderstanding of C.S. Lewis: that he was presenting a deductive argument. In reality, C. S. Lewis was executing an alternative methodology or set of argument – the abductive argument which goes accordingly:

1) P is true.

2) The best explanation of the truth of P is the truth of T.

3) Therefore T is true.

Logicians accept this as fallacy free form of reasoning. For more see The Philosopher’s Toolkit, pp. 42-43 – “Abduction is a process of reasoning used to decide which explanation of given phenomena we should select, and so, naturally, it is also called ‘argument to the best explanation’”. Some criteria for selecting the best explanation include simplicity, coherence, testability or predictive power and comprehensiveness.


The following formulation of Lewis moral argument for the existence of God should avoid this misunderstanding.


Lewis’s Moral Argument

1. There exists an objective moral order.

2. The best explanation of the existence of the objective moral order is the existence of a Moral Law Giver who created the universe.

3. So: There is a Moral Law Giver who created the universe (from 1and 2).

4. The Moral Law Giver issues moral rules and wants require us to engage in morally right conduct, that is, it is mind-like.

5. If (4), then there is a good, mind-like Moral Law Giver who created the universe.

6. Therefore, there is a good, mind-like Moral Law Giver who created the universe (from 4 and 5)


 Relevant Books:

C.S. Lewis Mere Christianity. Harper Collins 2001.

C.S. Lewis, The Abolition of Man. MacMillan 1955.

Julian Baggini & Peter Fosl, The Philosopher’s Toolkit: A Compendium of Philosophical Concepts and Methods. 2e. Blackwell 2010.


  1. Philip Lyn says:

    Thanks. Great summary! Been working on the “other side” of the apologetics coin a bit last few years: ie creation v evolution, beginnings ie why something rather than nothing etc. I find the classic philosophical arguments explicated in u modern language like those of Lewis, Ravi Zach n Keller strongest. The need to debate the thoughts of rabid atheists like Dawkins, Hitchens etc has been brought to the fore by the popular press n media. Blessed by u bro. Philip Lyn

  2. LOH Soon Choy says:

    TQ again KW. Philip said it all for us who follow you so neatly and clearly. Now how to get all these your pieces out to our church leaders? Network with a dozen possible other websites/scores of friendly churches/church departments and various appropriate NGOs? Besides you eventually publishing all the pieces as a book/series of bite-size booklets?
    (How has been the known response/feedback?) GBU!

  3. Kam Weng says:

    Hi Philip and Soon Choy,

    The secular media and advocates for new atheism like Richard Dawkins, Daniel Dennett and Lawrence Krauss wax eloquent against Christianity, pretending their views are fully backed up by new scientific data. In reality the theories of quantum cosmology, evolutionary processes and human origins remain highly contentious within the scientific community.

    There is currently no conclusive explanation of the mechanisms for the evolution of new species; if we admit we don’t know about the mechanism of a theory, it simply means we don’t have adequate proof. Quantum cosmology many-worlds theory is in principle unverifiable (what kind of ‘science’ is it if it can neither be verifiable or falsifiable?). Cognitive science, the new kid on the block commits the arrogance that besets many new disciplines with its claim of “Nothing but…” fallacy. Finally, there are more than a dozen competing interpretations of quantum mechanics. We are mired in controversy over what constitutes acceptable facts right from the start when attempting to related science to biblical interpretation This should require modesty in cross-disciplinary studies. Unfortunately, you won’t find such modesty among the media propelled scientific ideologues. Christians should keep track of the latest developments in science but they need not be intimidated by critics from new-atheism.

    It is observed that many Christians in Malaysia are presented with a forced and false dilemma in relating science and Christianity. One group advises Christians to give deference to the latest scientific claims which allege the Book of Genesis contains ancient etiological myths, that OT cosmology is outmoded (its construction is actually disputed), and that Adam is merely a symbolic figure or at most representation of some ancient hominids. Jettisoning the historical Adam has become de rigueur for aspiring academics. Another group which follows the home schooling curriculum reacts by insisting the Book of Genesis be accepted as literal without qualification and consideration of its literary genre, that evolution must be totally opposed and that the earth was created 6000 years ago (contrary to the current scientific consensus).

    Capitulation to still contested scientific theories and abandoning classical Christian doctrine is unnecessary. It will certainly undermine confidence in the preaching of the Bible. On the other hand, the pseudo-scientific posture of the home schooling curriculum ill-equips our young Christians to face the atheistic professors when they go to college. Their faith, based on pseudo-scientific views will be overwhelmed when they discover modern scientific enterprise is robust and includes self-correcting procedures to ensure systematic advancement of knowledge.

    Leaders of the Malaysian church need to demonstrate an alternative approach that goes beyond the false dilemma and offer some workable models for integrating science and Christian faith.