The Argument from Contingency

A being is contingent if it exists, but might not have existed. There is no contradiction in conceiving a world in which a given man was never born, in which a given mountain does not exist, in which a given galaxy never formed, in which the physical constants have different values, or even in which our material universe does not exist at all.^[2]

Conversely, a necessary being is a being that cannot not exist. Its non-existence would be impossible, not through external constraint, but because it carries within itself the reason for its being. Logical truths provide a limited analogy: 2 + 2 = 4 needs no temporal cause to become true; its contrary is impossible. But the argument from contingency does not conclude to a mere abstract truth: it concludes to a concrete necessary being, capable of grounding the existence of concrete realities.

This distinction avoids a frequent confusion. The argument does not say: "everything has a cause, therefore God has a cause". It says: whatever is contingent calls for an explanation outside itself. God, if he exists as a necessary being, therefore does not fall into the class of contingent beings to be explained by something else.

A distinction inherited from Aristotle, Avicenna and Maimonides

Long before Latin scholasticism, the distinction between the possible and the necessary already structured Greek, Arabic and Jewish metaphysics. Aristotle, in the Metaphysics (books V and IX), distinguishes dunamis (potency, possibility) and energeia (act): a being in potency can be or not be; a pure act cannot not be.^[3] The Persian philosopher Avicenna (Ibn Sīnā, 980-1037) refines this distinction in the Kitab al-Shifa by opposing wajib al-wujud (being necessary through itself) and mumkin al-wujud (possible being): every being that is not necessary through itself calls for an external cause that makes it exist.^[4]

Moses Maimonides (1138-1204), in the Guide for the Perplexed, takes up this distinction in the service of Jewish theology and transmits it to Christian scholasticism.^[5] Thomas Aquinas, who discusses Avicenna's position on the distinction of essence and existence by name (De ente et essentia, ch. 4), integrates this heritage into his third way. The contingent / necessary distinction is therefore not an ad hoc invention of Catholic apologists: it is the outcome of a metaphysical reflection shared by the three great monotheistic traditions of the Mediterranean basin.

A distinction confirmed by contemporary modal logic

Modal logic, formalised in the 20th century by Saul Kripke, made it possible to specify the technical meaning of contingent and necessary on the basis of the notion of a possible world. A proposition is necessarily true if it is true in all possible worlds; it is contingent if it is true in some possible worlds and false in others.^[6] The argument from contingency can then be restated with new rigour: if God exists, he exists in all possible worlds; if the universe exists, it exists only in some possible worlds. Modal logic has therefore not weakened the classical argument; on the contrary, it has strengthened its conceptual precision.

In the Summa Theologiae, Saint Thomas presents five ways of demonstrating the existence of God. The third is precisely the way drawn from the possible and the necessary. Thomas observes in nature beings that come to be and pass away; they are therefore possible to be and not to be. If they were all of this kind, it would have to be admitted that at some point there would have been nothing. But if nothing had existed, nothing could have begun to exist, since nothing comes from nothing.^[7]

The exact text of the third way

The central passage of Thomas deserves to be quoted in its medieval rigour:

« La troisième voie se tire du possible et du nécessaire. Nous trouvons dans les choses des êtres qui peuvent être et ne pas être, puisque certains naissent et disparaissent, et par conséquent peuvent être et ne pas être. Or il est impossible que tous les êtres soient tels : car ce qui peut ne pas être, à un moment donné n'est pas. Si donc tous les êtres pouvaient ne pas être, à un moment donné il n'y aurait rien eu dans la réalité. Mais s'il en est ainsi, même maintenant il n'y aurait rien : car ce qui n'est pas ne commence à être que par quelque chose qui est. Si donc rien n'avait été, il aurait été impossible que quoi que ce soit commençât à être, et ainsi maintenant il n'y aurait rien — ce qui est manifestement faux. » — Saint Thomas d'Aquin, Somme théologique, Iᵃ pars, q. 2, a. 3^[8]

The logic of the demonstration

The Thomist conclusion is sober: there must exist at least one necessary being. Then Thomas specifies that necessary beings can receive their necessity from another; but it is impossible to go back to infinity in a series of received necessities. We must therefore posit a being necessary through itself, which does not receive its necessity but communicates it.

The structure of the argument can be summed up in five steps: (1) there exist possible beings, that is, beings that can be or not be; (2) what can not be, at some point is not; (3) if all beings were possible, there would have been a moment when nothing existed; (4) but then nothing would exist now, which is manifestly false; (5) there must therefore exist a necessary being, either necessary through another or necessary through itself — and going back up the series of received necessities, we arrive at a being necessary through itself, "whom all call God".

A present dependence, not merely a temporal one

The strength of the third way does not depend on a naive picture of the universe as a temporal chain in which God would simply be the first chronological link. In Thomas, the question is more radical: what presently sustains the existence of that which has not in itself what it takes to exist?

The classical analogy of Thomism distinguishes causes in an accidental series — a grandfather begets a father who begets a son, without the grandfather having to subsist for the son to exist — and causes in an essential series: a chandelier hanging depends presently on the ceiling; a melody depends presently on the musician playing it; a train of wagons depends presently on the locomotive pulling them. It is in this second series, and not in the first, that the argument requires an uncaused first: not in chronology, but in the metaphysical order of present dependence.^[9]

Four centuries after Thomas, Leibniz restates the argument in more systematic terms with the principle of sufficient reason. It is he who poses, in the Principles of Nature and Grace (1714), the founding question of all metaphysics: "why is there something rather than nothing?"^[10]

The principle of sufficient reason

In the Monadology (1714), Leibniz lays down two principles at the foundation of all knowledge: the principle of contradiction and the principle of sufficient reason.

« Et celui de la raison suffisante, en vertu duquel nous considérons qu'aucun fait ne saurait se trouver vrai ou existant, aucune énonciation véritable, sans qu'il y ait une raison suffisante pourquoi il en soit ainsi et non pas autrement, quoique ces raisons le plus souvent ne puissent point nous être connues. » — G. W. Leibniz, Monadologie, § 32 (1714)^[11]

This formula does not mean that we always know the reason for each thing; it means that reality is not a brute chaos in which events arise without intelligibility. Science itself silently presupposes this principle: a researcher who said "the result of this experiment is what it is, for no reason" would renounce all possible inquiry. The principle of sufficient reason is therefore, as Leibniz stresses, a presupposition of all rationality.

The argument of the infinite series

Leibniz distinguishes necessary truths, whose contrary is impossible — like mathematical truths —, and truths of fact, which are contingent.^[12] Truths of fact can be analysed into particular reasons, but this analysis can continue indefinitely through the series of natural causes. That does not yet give the ultimate reason for the series itself.

His decisive point is this: even an infinite series of contingent beings would remain contingent. Explaining each member by the preceding one is not enough to explain why the entire series exists. Leibniz illustrated this point with an image that has remained famous: an infinite series of books copied from one another would explain why each copy reproduces the preceding one; it would never explain why there is this collection of books, with this content, rather than nothing.^[13]

From the series to the necessary substance

Leibniz therefore concludes that the sufficient reason of contingent things must be outside the series of contingent things, in a necessary substance:

« Ainsi, la dernière raison des choses doit être dans une substance nécessaire, dans laquelle le détail des changements ne soit qu'éminemment, comme dans la source : et c'est ce que nous appelons Dieu. » — G. W. Leibniz, Monadologie, § 38 (1714)^[14]

The step is narrow, but decisive. The question "why is there something rather than nothing?" is not a mere speculative curiosity: it is the fundamental metaphysical question, to which only the existence of a necessary being can give a rational answer.

The analytic philosophy of the 20th and 21st centuries has taken up and restated Leibniz's argument with great logical rigour. The Stanford Encyclopedia of Philosophy summarises its general structure.^[15]

The logical structure in six steps

The argument can be presented concisely:

1. There exist contingent beings.
2. Every contingent being calls for a sufficient explanation of its existence.
3. The totality of contingent beings is itself contingent.
4. This totality cannot ultimately be explained by another contingent being included in it.
5. Its ultimate explanation must therefore be a non-contingent, that is, necessary, being.
6. This necessary being is what the philosophical tradition calls God.

Each step can be debated, but the strength of the argument is cumulative: to reject it, one must either deny the existence of any contingent reality (which is absurd), or suspend the principle of sufficient reason at the precise moment when it becomes metaphysically awkward.

Pruss and the Big Conjunctive Contingent Fact

Alexander R. Pruss, in The Principle of Sufficient Reason: A Reassessment (Cambridge University Press, 2006), names BCCF — Big Conjunctive Contingent Fact — the conjunction of all contingent facts.^[16] This conjunction cannot receive its explanation from a member of the conjunction, since every member is already part of it: its explanation must therefore come from a necessary fact, which implies the existence of a necessary being.

Pruss also shows that the argument can be restated in modal logic, without recourse to a strong version of the principle of sufficient reason: it suffices to admit that contingent facts can have an explanation, to obtain, with the help of the modal system S5, the existence of a necessary being.^[17]

Feser, Rasmussen, Guillaud, Lavagna

Edward Feser, in Five Proofs of the Existence of God (Ignatius Press, 2017), devotes a whole chapter to the Leibnizian argument, which he defends as the most rigorous version of the cosmological proofs.^[18] Joshua Rasmussen, in How Reason Can Lead to God (IVP Academic, 2019), offers a pedagogical version accessible to the non-specialist reader, starting from elementary metaphysical foundations.^[19]

In French, Frédéric Guillaud, in Dieu existe. Arguments philosophiques (Cerf, 2013), takes up the argument with a solid Thomist apparatus and devotes more than seventy pages to it.^[20] Matthieu Lavagna, in Soyez rationnel, devenez catholique ! (2023, 1st ed. 2022), gives a recent French-language presentation, articulating the Thomist and Leibnizian versions.^[21]

The most immediate objection consists in saying: "perhaps the universe itself is necessary". But this answer only holds if one grants the word universe a necessity that it manifestly does not possess.

The marks of contingency of the observable universe

The observable universe has determinate physical characteristics: according to the standard cosmological model (Lambda-CDM), its age is estimated at about 13.8 billion years on the basis of interpreted measurements (cosmic microwave background, Hubble's law, presuppositions of the constancy of laws), fundamental constants with precise values, determinate laws of physics, catalogued elementary particles, particular initial states, an unevenly structured distribution of matter. No logical contradiction appears when we conceive a universe with different constants, different laws, or without galaxies. What can be otherwise is not necessary in the strict metaphysical sense.^[22]

The cosmological fine-tuning argument reinforces this point: the physical constants are adjusted with extraordinary precision to allow the existence of complex structures and life. Such fineness of adjustment is precisely what one expects of a contingent product, determined by a choice, and not of a metaphysical necessity.

The multiverse hypothesis

If we extend the word universe to the whole of all possible universes in a hypothetical multiverse, the question remains entirely open. A multiverse, if it existed, would still be a set of determinate, structured realities, mathematically governed by a generating meta-mechanism. We would still have to ask why this multiverse exists rather than another, or rather than nothing. The regress does not disappear by multiplying universes; it is merely pushed back one step.

Moreover, as the physicist-philosopher Bernard Carr has stressed, the multiverse hypothesis hardly resolves the problem of fine-tuning: it itself presupposes a meta-level of laws rich enough to generate viable universes, and this meta-level in turn calls for an explanation.^[23]

Why adding up contingents is not enough

Another objection consists in saying that the totality of contingents could be necessary even if each of its members is contingent. This is the composition fallacy argument: one would wrongly confuse the properties of the parts with those of the whole.

The classical answer is threefold. First, all intensive properties — being material, being limited, being contingent — are transmitted from the fact that each part possesses them to the fact that the whole possesses them too. Second, a sum of realities that might not have existed does not become, by mere addition, a reality that cannot not exist: a pile of bowls, even an infinite one, does not become a plate. Finally, the conjunction of all contingents is itself a contingent fact: one could conceive another conjunction, or none; so this conjunction itself calls for an external explanation.^[24]

The argument from contingency does not conclude first to the God of Christian Revelation, nor directly to the Trinity, nor to the Incarnation, nor to the sacraments. It concludes to a necessary being that already possesses several classically divine attributes.

Seven philosophically deduced attributes

This being must be outside the totality of contingent beings, hence not included in the material universe. It must be non-composite, for every composition would call for a reason explaining why these parts are united in this way. It must be without arbitrary limits, for every finite limit would raise the question: why this limit and not another? It must be concrete, for an abstraction causes nothing: it must therefore be spiritual or personal, not a mere mathematical law.^[25]

Beyond abstract deism

Some philosophers — Spinoza in particular — concluded from the argument to a purely immanent God, identified with nature or with the single substance. But this identification runs up against the marks of contingency of nature: observable nature precisely does not have its reason for being in itself. The argument therefore leads indeed to a transcendent God, distinct from the world, the principle of its existence and not the mere totality of the world.^[26]

This conclusion rejoins classical Catholic teaching: reason can attain the existence of a creator God, origin and end of the universe, even if it cannot discover by itself the supernatural mysteries that God reveals in Jesus Christ.^[27]

The argument from contingency is not only a piece of Catholic apologetics; it is integrated into the solemn teaching of the Church.

The First Vatican Council and the constitution Dei Filius

In 1870, the First Vatican Council dogmatically defined the capacity of human reason to know God:

« La sainte Église, notre Mère, tient et enseigne que Dieu, principe et fin de toutes choses, peut être connu avec certitude par la lumière naturelle de la raison humaine à partir des choses créées. » — Concile Vatican I, constitution dogmatique Dei Filius, chap. 2, 24 avril 1870^[28]

This is not one theological opinion among others: it is a dogmatic teaching, accompanied by a canon explicitly condemning the contrary position. The argument from contingency is not the only way envisaged by the Fathers of the council, but it is one of the ways that this constitution explicitly makes possible.

The Catechism and the rational ways to God

The Catechism of the Catholic Church (§§ 31-36) takes up this teaching and explicitly cites contingency among the rational paths that lead to God:

« Le monde : à partir du mouvement et du devenir, de la contingence, de l'ordre et de la beauté du monde, on peut connaître Dieu comme origine et fin de l'univers. » — Catéchisme de l'Église catholique, § 32^[29]

The Catechism situates these ways within a cumulative approach: "converging and convincing arguments" that make it possible "to arrive at true certainties" (§ 31). It is therefore not a demonstration of the mathematical type, but a convergence of rational ways, of which contingency is one of the principal ones.

Saint John Paul II and the encyclical Fides et Ratio

The encyclical Fides et Ratio (1998) recalls that the Catholic faith does not oppose reason to belief, but presupposes a reason capable of God. Saint John Paul II defends therein the metaphysical capacity of human reason, against the modern currents that would confine philosophy to linguistic analysis or transcendental critique. The argument from contingency is precisely one of the metaphysical approaches that this encyclical intends to defend.^[30]

The argument from contingency has been debated for more than seven centuries. Five principal objections deserve a precise answer.

Objection 1 — Hume and the critique of causality

In the Treatise of Human Nature (1739) and the Enquiry Concerning Human Understanding (1748), David Hume maintains that the notion of cause is only a psychological habit: we see B constantly follow A, and we wrongly infer a necessary connection. If causality itself is without necessity, the argument from contingency seems to lose its driving force.^[31]

Answer. The Humean critique, taken literally, is suicidal: it also forbids experimental science, everyday reasoning and memory. Hume himself admits that he cannot live according to his own scepticism. Above all, classical metaphysics does not invoke a mere regular succession, but the present dependence of a being that has not in itself what it takes to exist upon a being that has in itself what it takes to exist. This dependence is not a repeated empirical observation: it is a rational requirement of the very intelligibility of being.

Objection 2 — Kant and the inaccessible unconditioned

In the Critique of Pure Reason (1781), Immanuel Kant maintains that reason cannot reach the unconditioned: every cosmological argument would illegitimately presuppose the ontological argument, and any claim to ground the existence of a necessary being would be a transcendental illusion.^[32]

Answer. The Kantian critique presupposes a theory of knowledge — phenomenalism — that arbitrarily limits reason to what is conditioned by the forms of sensibility. But this theory is itself metaphysical, and it raises precisely the question it intends to forbid: why would reason have these limits? Contemporary neo-Thomism (Étienne Gilson, Jacques Maritain, Charles De Koninck, Edward Feser) has shown that classical metaphysics does not depend on the presuppositions that Kant criticises: it starts not from an analysis of our concepts, but from an analysis of observable being. The argument from contingency does not deduce existence from a concept; it goes back from an existing fact to its real condition.^[33]

Objection 3 — The universe as a brute fact (Russell)

During the famous 1948 BBC radio debate between Bertrand Russell and Father Frederick Copleston, Russell asserts: "I should say that the universe is just there, and that's all."^[34] The objection consists in saying that the contingent universe exists without an ultimate reason; one would admit the principle of sufficient reason for realities internal to the world, but refuse to apply it to the world as a totality.

Answer. This exception is gratuitous. If one wishes to suspend a universal rational principle at the precise moment when it becomes metaphysically awkward, one must give a reason. But giving a reason why the universe would need no reason already reintroduces the very principle one wanted to deny.

Alexander Pruss formulated the danger of this denial: « si certains états de choses contingents peuvent n'avoir aucune explication, alors il devient possible que nos propres états perceptifs arrivent sans raison ».^[35] Confidence in rational inquiry, whether scientific or historical, implicitly rests on the idea that reality is intelligible. Withdrawing the principle of sufficient reason is undermining science itself.

Objection 4 — A necessary cause would make everything necessary

Another objection, formulated notably by Peter van Inwagen, asserts: if God is necessary and causes the universe, then the universe ought to be necessary too. But the universe is contingent; therefore God cannot be its cause.^[36]

Answer. The answer lies in a simple distinction: a necessary personal cause can freely produce a contingent effect. Effects do not follow from a personal cause as theorems follow from axioms. If God created by impersonal necessity, the universe would indeed be necessary; but classical theism affirms that God creates freely. His essence is necessary; his creative act is free.^[37]

This distinction is decisive for the Catholic theology of creation. God does not create because he would lack something. He creates gratuitously, out of goodness. The world is therefore neither a necessary emanation of God, nor an absurd accident: it is a gift.

Objection 5 — The argument does not prove the Christian God

That is true, if by that one means that the argument does not demonstrate the whole Creed. But it is a poor objection if one demands of a metaphysical argument that it accomplish the entire work of Christian apologetics.

The argument from contingency establishes a limited but fundamental conclusion: the contingent world depends on a necessary, transcendent, immaterial, free and unique being. Other arguments then complete the case: fine-tuning shows the mathematical order of the universe; the moral argument interrogates the foundation of the good; the resurrection of Jesus moves from philosophical theism to historical Christianity; Catholic apologetics finally examines the Church, the sacraments and authority.

A rational inquiry often advances in this way: not by a single argument that would prove everything, but by cumulative convergence. Contingency does not replace the other ways; it lays the metaphysical foundation upon which they rise.

The argument from contingency is not only a logical exercise. It obliges us to look at the world as received. Nothing of what we are has in itself the ultimate reason for its existence: our body, our soul, our history, the persons we love, light, time, space, the very possibility of thinking. All of this exists, but might not have existed.

« Tu nous as faits pour Toi, Seigneur, et notre cœur est sans repos tant qu'il ne demeure en Toi. » — Saint Augustin, Confessions, livre I, chap. 1, n° 1^[38]

Saint Augustine expressed in one sentence the spiritual fruitfulness of metaphysics. If contingent being is not absurd, if it is suspended upon a necessary being that gives existence without receiving it, then the whole of reality becomes a sign. Creation is not a neutral decor; it is participation.

Pascal, in his Pensées, experienced the vertigo of this contingency:

« Quand je considère la petite durée de ma vie, absorbée dans l'éternité précédente et suivante, [...] je m'effraie et m'étonne de me voir ici plutôt que là, car il n'y a point de raison pourquoi ici plutôt que là, pourquoi à présent plutôt que lors. » — Blaise Pascal, Pensées, fragment Brunschvicg n° 205^[39]

The experience of human fragility and the metaphysics of contingency converge: only the existence of a necessary being that wills and sustains the existence of contingent beings can give this fragility a meaning other than the absurd. As the Catechism teaches, the material world, by its motion, its contingency, its order and its beauty, can lead to God as the origin and end of the universe.^[40]

The argument from contingency therefore answers one of the most radical questions of the human mind: why is there something rather than nothing? The Catholic answer is that the contingent does not rest upon the void. It rests, at every instant, upon Him who is.

• Does God exist? — a synthesis of the great rational ways to God.
• The Kalam cosmological argument — why the universe has a beginning.
• Fine-tuning — the physical constants adjusted for life.
• The moral argument — the objective foundation of the good.
• The ontological argument — the modal way starting from necessary being.