The Moral Argument

The moral argument is often misunderstood because it is turned into a psychological accusation: "Atheists would be incapable of being good." That is not its thesis. It concerns the real status of obligation, not the moral quality of persons. An atheist can recognise the good, act courageously, defend the weak and sincerely condemn injustice; the philosophical question remains: in a universe without God, what makes this condemnation objectively true and binding?

This clarification echoes the Catholic doctrine of conscience: in the words of the Second Vatican Council (Gaudium et Spes 16) taken up by the Catechism (§ 1776), conscience is "the most secret core and sanctuary of man. There he is alone with God, Whose voice echoes in his depths"; this same conscience must be informed and moral judgment enlightened (§ 1783)^[7][8].

Immanuel Kant and the "postulate of practical reason"

It is in the Critique of Practical Reason (1788) that Immanuel Kant gives the moral argument its first systematic philosophical formulation. For Kant, the moral law felt by every man as a categorical imperative requires, in order to be genuinely binding, three postulates: the freedom of the subject, the immortality of the soul, and the existence of God. Without God, the promise of an ultimate coincidence of virtue and happiness (the highest good) remains suspended in a void^[9].

Kant does not claim to demonstrate God the way one demonstrates a theorem of mathematics — on the contrary, he thinks speculative reason is incapable of it. But he maintains that practical reason, the reason that acts morally, cannot operate coherently except by assuming the existence of a God who guarantees it.

Fyodor Dostoevsky: "if God does not exist, everything is permitted"

In The Brothers Karamazov (1880), Dostoevsky lends Ivan Karamazov the now-famous thesis: without immortality, there is no virtue — and so, in practice, "everything is permitted". Ivan states it as early as Book II, in the starets's cell (chapters VI-VII: "there is no virtue if there is no immortality" — translator's translation), and develops it in Book V ("Rebellion" and "The Grand Inquisitor")^[10]. Lavagna recalls that this literary intuition forms the matrix of the contemporary moral argument^[11].

It is Dmitri, the eldest, who seizes upon it with passion as early as Book III ("Confession of an Ardent Heart") — and it is from this intuition that a modern reconstruction by contemporary apologetics, taken up by Lavagna, unfolds the reasoning in tight form:

1. If God does not exist, man is the only master on board.
2. If man is the only master on board, it is he who defines virtue.
3. If it is man who defines virtue, then virtue is relative (to different cultures and civilisations).
4. If the definition of virtue is relative, then there are no objective moral obligations.
5. Therefore if God does not exist, there are no objective moral obligations^[12].

C. S. Lewis and Mere Christianity

C. S. Lewis opens Mere Christianity (1952) with a long meditation on the moral law (Moral Law) as a pointer to the existence of a Lawgiver — Book I, chapter 1, "The Law of Human Nature" (the passages summarised below come from this chapter). His central thesis: we would be compelled to believe in a real right and wrong — we can be mistaken about them as in a calculation, but they would be neither a matter of taste nor of opinion, any more than the multiplication table^[13].

Lewis shrewdly remarks that anyone professing to believe in neither true good nor true evil would contradict himself as soon as he felt wronged^[14] — in other words: the moral relativist is incapable of holding his own position in practice.

William Lane Craig: the contemporary analytic formulation

The American analytic philosopher William Lane Craig — professor of philosophy at Houston Christian University from 2014 to 2024, then visiting professor of philosophy at the Talbot School of Theology (Biola) — gave the moral argument its most rigorous form in Reasonable Faith (3rd ed. 2008, chap. 4, "The Moral Argument" section, pp. 172-182)^[15]. It is this formulation that Lavagna takes up in French.

Craig insists on a crucial distinction: in this argument, the word objective does not mean universally accepted. A value is objective, in his view, if it holds independently of what human beings believe about it^[16]. Disagreement between cultures therefore does not invalidate objectivity — it merely signals that at least one culture is mistaken.

Matthieu Lavagna and French-language diffusion

In 2022, Matthieu Lavagna publishes Soyez rationnel, devenez catholique ! — a French-language synthesis that takes up, in substance, Craig's argument (pp. 172-182 of Reasonable Faith) while adapting it to a French Catholic readership^[17]. The edition cited in this article is the new edition (MDN Productions, distributed by Salvator, April 2023): the chapter devoted to the moral argument occupies pages 95 to 107 there (p. 94 closes the previous chapter). It is this source that structures the present article.

Cardinal Newman and the argument from conscience

Alongside the Kantian tradition and Craig's analytic formulation, Cardinal John Henry Newman (1801-1890) developed a distinct and complementary version of the moral argument, based not on deductive logic but on the experience of conscience. In the 2nd of his sermons preached before the University of Oxford — "The Influence of Natural and Revealed Religion Respectively" (preached on 13 April 1830, published in Fifteen Sermons Preached before the University of Oxford, 1843) — he shows that conscience resembles no natural instinct and no aesthetic feeling:

"Conscience implies a relation between the soul and a something exterior, and that, moreover, superior to itself; a relation to an excellence which it does not possess, and to a tribunal over which it has no power."^[18]

For Newman, conscience accuses and approves with an authority that imposes itself on man — and this imposing exteriority points to a person, not to an abstract law. A sense of imperative as powerful as shame or remorse is fully explained only if someone is watching us: in other words — and this is the writer's paraphrase, not a quotation from Newman — conscience teaches us that we are not our own masters^[19].

Newman takes up this conviction in his Letter to the Duke of Norfolk (1875): if conscience commands, it is because there is a Voice behind it — echoing Saint Paul's words on "the law written on hearts" (Rom 2:15)^[20]. This convergence between the Thomist formulation of natural law, the Kantian intuition of the practical postulate and the Newmanian argument from conscience constitutes the threefold tradition on which Craig and Lavagna implicitly rely.

The precise meaning of the premise

This premise is often caricatured. Lavagna is careful to clarify its meaning: it does not deny that an atheist can lead a virtuous life — sometimes more so than some theists —; it concerns the objective foundation of moral obligations, not persons^[21].

The argument therefore concerns neither individual moral psychology ("can atheists be good?"), nor moral knowledge ("can one know the good without faith?"), but the ontological foundation of moral objectivity.

Guillaume Bignon's analogy (volleyball)

The French philosopher Guillaume Bignon (author of La foi a ses raisons, BLF Éditions, 2018) offers, according to Lavagna, a limpid analogy: the rules of volleyball would hold objectively because a game-creating authority fixed them — a player who juggled the ball instead of sending it over the net would be objectively wrong, not merely of a different opinion. But without an official creator of the game, there would remain only players in jerseys with a ball and a net, with no objective goal: in case of disagreement about the goal, none would be more right than another, for lack of an authoritative privileged opinion^[22].

This analogy captures the central intuition: every normative rule presupposes a lawgiver. And for a rule to be objectively binding on all players, that lawgiver must transcend the players themselves.

The materialist argument against itself

If one adopts a coherent atheistic materialism, Lavagna observes, human beings would be nothing but products of biological evolution — slightly more developed animals — with no special moral status^[23]. Yet the animal kingdom knows, strictly speaking, neither murder nor theft: a bird that kills a fish or seizes it with its talons commits neither murder nor theft, for no prohibition weighs on these acts — even if they harm their victims, they are neither unjust nor immoral^[24].

This observation, which goes back to the atheist philosopher Richard Taylor (Ethics, Faith and Reason, Prentice-Hall, 1985), highlights a dilemma for atheism: either man is an animal like any other, and there is no reason for him to have moral obligations that other animals lack; or man is morally special, and then one must explain why — which materialism cannot do without introducing something that transcends it.

The "hundred-million-euro button" (Bolloré-Bonnassies)

To convey the scope of the problem intuitively, Michel-Yves Bolloré and Olivier Bonnassies propose in Dieu, la science, les preuves (Guy Trédaniel, October 2021) a thought experiment, taken up by Lavagna: if you were offered a fortune to press for an instant a button that would kill, with total impunity and in secret, an unknown family on the other side of the world, what would you do^[25]?

From a coherent materialist standpoint, observing that one is genetically disposed to empathy provides no obligation not to press that button. At most a statistical preference, which one may well decide to overcome in order to enjoy the immediate gain.

In the corresponding chapter of Dieu, la science, les preuves (chap. 21, "La conscience morale"), the experiment is preceded, in substance — what follows is the writer's paraphrase, not a quotation from the authors —, by another question: could a parliamentary majority make it just to gas the Jews, to restore slavery or to authorise paedophilia? The authors aim to provoke not a vague emotion, but the recognition of a moral prohibition that resists voting, interest and impunity^[26]. It is precisely this resistance that the moral argument seeks to explain.

Why evolution does not suffice to ground duty

The evolutionist objection often replies: our moral sentiments come from group altruism, cooperation and natural selection. Such an explanation may illuminate the psychological origin of certain inclinations; it does not ground their normative authority. Observing that man tends to protect his kin does not prove that he must protect the innocent when it costs him everything.

This distinction is classic in moral philosophy: moving from a biological fact (we often feel empathy) to a moral duty (we must respect the dignity of others) requires a norm that the fact alone does not contain.

The confessions of atheist philosophers

The elegance of the moral argument is that it does not need to be conceded by its opponents: several 20th-century atheist philosophers are said to have recognised its first premise as an inescapable consequence of their atheism. The passages below are summarised by the writer from the quotations given by Lavagna (references indicated in footnotes): no original having been checked against a copy, they are presented as paraphrases, not as verbatim quotations.

For Jean-Paul Sartre (L'existentialisme est un humanisme), man would be freedom: without God, no pre-existing value or order would legitimate our conduct^[27]. The existentialist would even judge, according to Sartre, this absence of God very embarrassing: no a priori good any more, no infinite consciousness to think it, nothing written anywhere — man would be abandoned, with no support either within or outside himself, and everything would be permitted^[28].

For Albert Camus (L'Homme révolté, Gallimard, 1951), without an affirmed value, everything would become possible and nothing would matter: the murderer would be neither right nor wrong, the world would be divided not between the just and the unjust but between masters and slaves, and the only rule would be effectiveness — being the strongest^[29].

The Oxford biologist Richard Dawkins (River Out of Eden, 1995) would describe, at the most elementary level, a universe without purpose and without good or evil — nothing but blind indifference — in which men would be machines for propagating DNA^[30].

The atheist philosopher of science Michael Ruse would hold that human moral conscience is explained by its biological advantage: viewed as a set of rationally justifiable assertions about something objective, ethics would be illusory — morality would be nothing but an aid to survival and reproduction^[31].

The atheist philosopher Richard Taylor (Ethics, Faith and Reason, 1985) would judge it perfectly intelligible to say that a thing is wrong because God forbids it, but unintelligible to declare a thing morally wrong with no God to legislate: the notion of moral obligation would be unintelligible apart from the idea of God^[32].

Lavagna draws the conclusion that atheist philosophers themselves concede, in their writings, the first premise: their atheism would be incapable of grounding an objective morality^[33].

The weight of moral intuitions

The second premise — there are objective moral obligations — by no means requires maintaining that all of morality is objective. It suffices that at least some moral obligations are — which, Lavagna writes in substance, would seem obvious: a normally constituted man recognises that torturing babies, rape, slavery or paedophile acts are objectively atrocious crimes^[34].

Remarkably, even the atheist philosopher Michael Ruse would recognise this: for him, saying that it would be morally acceptable to rape small children would be an error comparable to saying that 2 + 2 = 5^[35].

And David Brink, another atheist philosopher (The Cambridge Companion to Atheism, 2006), would hold moral objectivity to be the position to be revised only in the face of a substantiated and convincing argument showing it to be indefensible^[36].

In other words: moral objectivity is the default position of our intuitions, and the burden of proof lies with the sceptic.

Lavagna's pedagogical test

The author of Soyez rationnel, devenez catholique ! proposes a practical application when facing a relativist interlocutor: asking him whether he would really hold as morally neutral the gulag for homosexuals, torturing babies for pleasure, or paedophile abuse in keeping with its perpetrators' vision — these violent examples would, according to Lavagna, awaken moral intuitions, and this instinctive disgust would reflect the moral law inscribed in the heart^[37].

"Human rights" as an involuntary confession

Lavagna notes a cultural paradox: atheist Western society would brandish human rights as an ultimate weapon against evil, without being able to say where these rights or this human dignity come from — could they really emanate from atoms^[38]?

The confession would come, paradoxically, from the atheist Australian philosopher Raimond Gaita (A Common Humanity, Routledge, 2002): only a believer could speak seriously of the sacred, of man as an end in himself, of unconditional respect and of inalienable rights^[39].

Objection 1 — Cultural relativism

According to the first objection, the disagreement of cultures and civilisations on moral matters would show that morality cannot be objective.

This objection, Lavagna writes in substance, would confuse the objectivity of moral values with their universality^[40]. To say that a value is universal is to say that it is in fact recognised by all. To say that it is objective is to say that it is true independently of what people think of it. A truth can be objective without being universally known: moral obligations might be objective by nature while some civilisations err in their access to moral knowledge^[41].

The Catholic theologian would add, according to Lavagna, that moral disagreement would be a consequence of original sin darkening human reason in its access to these obligations^[42].

Objection 2 — "Morality based on fear of punishment"

A common objection holds that grounding morality in fear of divine punishment — or conversely in hope of reward — corrupts virtuous action at its root, by making it self-interested.

Lavagna replies that this objection misunderstands the argument: theists ground morality neither in fear of punishment nor in hope of reward — which would indeed make action self-interested — but in God himself as the source of the good: one acts well out of unconditional respect for the absolute good that is God^[43].

Objection 3 — "Evolution explains altruism"

This objection is stronger than cultural relativism, because it does not deny the moral fact as felt: it seeks to explain it through biological history. But it still confuses causal explanation with normative justification. That a behaviour helped a group survive does not prove it is just; natural history also explains aggression, domination, sexual rivalry and the elimination of the weak. If morality is but a biological tool, it loses precisely what we want to save: its right to judge our instincts.

Objection 4 — The Euthyphro dilemma

The most classic objection comes from Plato, in the dialogue Euthyphro: either something is good because God wills it (in which case the good becomes arbitrary — God could have made hatred good), or God wills something because that thing is good (in which case the good pre-exists God and no longer depends on him).

The classic answer, already given by Saint Thomas Aquinas and taken up by Craig and Lavagna, consists in introducing a third option: God's nature being goodness itself, God could not command evil — his commandments necessarily express his just and loving nature, without arbitrariness^[44].

God does not decree the good arbitrarily, nor does he observe a good external to himself. God is the good, and his commandments necessarily express his nature. This answer makes the Euthyphro dilemma a false dilemma.

Objection 5 — Utilitarianism: objective morality without God?

"Mill's utilitarianism suffices to ground an objective morality: the good is the greatest happiness for the greatest number, and that requires no God."

The objection is serious: John Stuart Mill (Utilitarianism, 1863) does propose an ethics claiming to define the good objectively — maximising happiness and minimising suffering — with no reference to the divine^[45]. This objection directly targets the first premise of the moral argument.

Two replies are in order. First, utilitarianism itself presupposes an anterior norm: why would happiness be objectively good to maximise? This question cannot find an answer in the same terms — it presupposes a normative principle that utilitarianism cannot ground itself without infinite regress or arbitrary postulate. Second, utilitarianism collapses in the face of limit cases — torturing an innocent person if it maximises the happiness of the greatest number, eliminating a troublesome minority for the well-being of the majority. These conclusions revolt our most solid moral intuitions. Yet if a moral theory prescribes what our deepest moral intuitions unanimously condemn, it is the theory that must be revised, not the intuitions. This is what philosophers call the modus tollens of ethical refutation — in plain words: one discards the hypothesis because what it predicts contradicts a certainty^[46].

Objection 6 — Error theory (Mackie): there are no moral facts

"The philosopher J. L. Mackie maintains that moral judgments are systematically false because there are no objective moral facts in a purely natural universe. The first premise of the moral argument is therefore but a category mistake."

John Leslie Mackie's error theory — in plain words: the idea that all our moral judgments ("this is wrong") are false, because nothing in the world corresponds to them — set out in Ethics: Inventing Right and Wrong (Penguin, 1977), deserves a precise reply, for it represents the most radical and most coherent critique of moral objectivity^[47]. Mackie himself recognises that moral language claims objectivity — and he deems this claim erroneous: objective moral properties, if they existed, would be so strange ("queer": of a strangeness at odds with everything else in the universe) in a purely material universe that they must be denied.

But this recognition is, paradoxically, a confession in favour of the first premise: Mackie admits that without a transcendent ground, there is no objective morality. He chooses to conclude that objective morality should be eliminated; the theist concludes that a transcendent ground exists. The disagreement is no longer over the first premise — it is over the plausibility of the second. And faced with the second premise (there are objective moral obligations), Mackie's argument stumbles on the force of fundamental moral intuitions: torturing innocents is objectively evil, and this intuition resists every theoretical revision.

The atheist philosopher Derek Parfit (1942-2017, On What Matters, vol. II, Oxford University Press, 2011) attempted, against Mackie, to defend a non-theistic non-naturalist moral realism — in plain words: moral truths true in themselves, being neither material things nor commandments of God. Objective moral truths would thus exist without God, just as objective mathematical truths would exist without a physical substrate^[48]. His "Triple Theory" does not reduce to "Mill": it is the convergence of three schools — Kantianism (revised categorical imperative), contractualism (Scanlon) and rule consequentialism. Parfit's position is respectable and complex. It does not refute the moral argument, but shifts the debate: even if objective moral truths existed in an atheist universe, one would have to explain how they have normative authority over biological beings issued from blind evolution — and why these truths would be accessible to our reason. Parfit himself recognises that his project leaves open questions about the nature of the relation between practical reason and the cosmos^[49].

The moral argument is not merely an apologetic strategy: it naturally extends the Catholic doctrine of natural moral law, formally taught by the Catechism in paragraphs 1954-1960:

§ 1954 — "Man participates in the wisdom and goodness of the Creator who gives him mastery over his acts and the ability to govern himself with a view to the true and the good. The natural law expresses the original moral sense which enables man to discern by reason the good and the evil, the truth and the lie."^[50]

§ 1956 — "The natural law, present in the heart of each man and established by reason, is universal in its precepts and its authority extends to all men. It expresses the dignity of the person and determines the basis for his fundamental rights and duties."^[51]

§ 1958 — "The natural law is immutable [...] and permanent throughout the variations of history; it persists under the flux of ideas and customs, and supports their progress."^[52]

The moral argument can thus be read as the contemporary philosophical formulation of what Catholic theology calls natural law: an objective moral norm, accessible to the reason of every man, and grounded ultimately in the very nature of God.

Saint Thomas Aquinas gives the classic formula: the first principle of natural law is that "good is to be done and pursued, and evil is to be avoided"; all other moral precepts attach to this first principle of practical reason^[53]. The contemporary moral argument therefore does not replace the Catholic tradition: it reformulates it in the face of modern materialism.

Saint Paul already wrote to the Romans:

"When Gentiles who have not the law do by nature what the law requires, they are a law to themselves, even though they do not have the law. They show that what the law requires is written on their hearts, while their conscience also bears witness [...]"^[54]

To conclude, Lavagna would judge the argument solid: the sceptic remains free to deny all objective goodness or badness, but at the price of a radical nihilism contradicting our intuitions; most people concede that at least some actions are morally vile in an objective way — and, atheism being unable to account for this objectivity, it would follow that atheism is false, whereas theism grounds this objectivity in God, the absolute good^[55].

The argument does not claim to demonstrate that the Christian God exists: it establishes that a transcendent Lawgiver, source of the good, exists. It is only through convergence with the other theistic arguments — the Kalam cosmological argument, fine tuning, the resurrection — that one arrives at the Christian identification of the God of Abraham, Isaac and Jacob, manifested in Jesus Christ.

• The existence of God — overview of the arguments
• The Kalam cosmological argument
• Cosmological fine tuning
• The free-will argument
• Did Jesus really exist?
• The resurrection of Jesus as a historical event

Principal sources

• Matthieu Lavagna, Soyez rationnel, devenez catholique !, 1st ed. 2022; cited ed.: MDN Productions (distributed by Salvator), April 2023 (ISBN 978-2-491255-51-0), pp. 95-107 (chapter checked page by page against the digital copy of the April 2023 edition on 4 October 2026).
• William Lane Craig, Reasonable Faith: Christian Truth and Apologetics, Crossway, 3rd ed. 2008 (1st ed. 1984, 2nd ed. 1994), chap. 2 "The Absurdity of Life without God" and chap. 4 "The Existence of God (2)", pp. 65-91 and 172-182. French translation: Foi raisonnable, transl. Christiane Pagot and Gérald Pech, Éditions la Lumière, 2012.
• C. S. Lewis, Mere Christianity, Geoffrey Bles, London, 1952 (1st ed.), Book I "Right and Wrong as a Clue to the Meaning of the Universe", chap. 1. French translation cited: Voilà pourquoi je suis chrétien, Empreinte Temps Présent, 2020.
• Guillaume Bignon, La foi a ses raisons : Confessions d'un athée surpris par Dieu, BLF Éditions, 2018 (passage summarised from Lavagna, p. 96).
• Michel-Yves Bolloré & Olivier Bonnassies, Dieu, la science, les preuves : l'aube d'une révolution, Guy Trédaniel, October 2021 (ISBN 978-2-8132-2585-6), chap. 21 on the moral conscience.
• Catechism of the Catholic Church, §§ 1954-1960 (natural law) and §§ 1776-1783 (moral conscience).
• Saint Thomas Aquinas, Summa Theologiae, I-II, q. 94, a. 2 (first principle of natural law).