The Kalam Cosmological Argument

The term "Kalām" (كلام) means in Arabic "words" or "discourse" — it designates medieval Islamic speculative theology, which sought to articulate Quranic revelation with philosophical reason.

John Philoponus (6th century) — Christian origin

The argument is Christian first. John Philoponus of Alexandria (c. 490 — c. 570), a Christian theologian and philosopher, was among the first to formulate it — the first preserved Christian formulation — in his writings criticising Aristotelian cosmology^[1]. Against Aristotle, who defended the eternity of the world, Philoponus demonstrates, through mathematical arguments about the impossibility of the actual infinite, that the world must have had a beginning. This is the Christian root of the argument — with this sober reservation: his tritheist interpretation of the Trinity led to his condemnation as a heretic, during his lifetime at Alexandria and then during a disputation held at Constantinople before Patriarch John Scholasticus, with an imperial edict against the sect; scholarly tradition further reports a posthumous condemnation, without any precise conciliar act naming him being established^[2].

Al-Kindi (9th century) — finitude demonstrated

The Arab philosopher Al-Kindi, in Baghdad, demonstrates in his treatise On First Philosophy (Fi al-falsafa al-ula) that body, time and motion cannot be actually infinite: the world is therefore finite in time and requires a cause of its beginning^[3]. This is the Islamic link of the argument between Philoponus and Al-Ghazali.

Al-Ghazali (1058-1111) — Islamic formulation

The Persian theologian Al-Ghazali takes up this argument and gives it its classic formulation in the Kitab al-Iqtisad fi'l-I'tiqad (The Book of Moderation in Belief) — the source indicated by Craig himself, and not the first discussion of the Tahafut al-Falasifa. In substance — a paraphrase of the English formulation quoted by William Lane Craig —: whatever begins has a cause of its beginning; now the world is a being that begins; therefore the world has a cause of its beginning^[4].

This formulation was discussed in the 13th-century scholastic West through the Arabo-Latin translations; Saint Bonaventure develops an argument of the same type — the impossibility of an actually infinite temporal succession (an infinite number of past celestial revolutions, an infinite multitude of souls) and the necessity of a temporal beginning of the world — in his Commentary on the Sentences of Peter Lombard (Book II, distinction 1, on the production of things)^[5].

William Lane Craig (1979) — contemporary reformulation

In the 20th century, the analytic philosopher William Lane Craig (born 1949) devoted his doctoral thesis to this argument, published by Macmillan in 1979^[6]. Craig enriched it with two new scientific confirmations — Big Bang cosmology and thermodynamics — which make it today one of the most discussed arguments in the analytic philosophy of religion.

The argument takes the form of a rigorous syllogism in two premises followed by a philosophical analysis of the cause:

Premise 1 — Causality: Whatever begins to exist has a cause.

Premise 2 — Cosmology: The universe began to exist.

Logical conclusion: Therefore, the universe has a cause.

To this conclusion is added the analysis of the nature of the cause: it must necessarily be uncaused, outside time, outside space, immaterial, extremely powerful, and personal — that is, the monotheistic God.

The first premise is the most universally accepted metaphysical axiom in the history of thought: ex nihilo nihil fit — nothing comes from nothing. It rests on three foundations:

1. Universal philosophical intuition: No culture, no philosophical tradition has ever accepted that a thing could spontaneously emerge from absolute nothingness, without any cause. If we accept that, nothing can be explained any more.

2. Empirical experience: We never see objects pop out of nothing. This stands as universal inductive testimony.

3. Principle of sufficient reason: everything that exists must have a reason for existing — either in itself (a necessary being), or in an external cause.

This premise does not say: "everything has a cause". It says: "whatever begins to exist has a cause". The distinction is crucial. An eternal and necessary being does not fall under the premise; an event or a reality that comes into existence does. That is precisely why the popular objection "who created God?" misses the target: it turns the Kalam into a thesis its defenders do not hold.

The quantum objection

The most discussed contemporary objection comes from quantum mechanics: "vacuum fluctuations" would allow particles to pop up spontaneously without a cause. But this objection rests on a confusion: the quantum vacuum is not absolute nothingness. It is an energetic medium governed by the laws of quantum mechanics. As Craig points out, fluctuations require a pre-existing quantum field — so they are not uncaused in the absolute sense^[7].

The philosopher of physics David Albert, though a critic of religious apologetics, makes the same remark against Lawrence Krauss: if one invokes relativistic quantum fields, one must still explain where those fields come from and why there are physical laws rather than nothing^[8]. The quantum objection thus shifts level: it can discuss an initial physical state, but it does not replace the metaphysical explanation of the very being of space-time.

The radical denial of the causality principle

A more radical philosophical objection against premise 1 comes from the Australian philosopher Graham Oppy (Monash University), one of the leading defenders of analytic non-theism. In Arguing About Gods (chapter 3, "Cosmological Arguments", pp. 97-173 — chapter 4 being devoted to the teleological argument)^[9], Oppy disputes that the causality principle can be extended a priori to the universe as a whole: he envisages uncaused beginnings and makes the universe a legitimate exception to a premise that would be only an empirical generalisation.

Reply: Oppy does not abandon all causal inference in science — he restricts its scope. But making the universe an exception to the causal principle without independent justification is precisely an ad hoc exception: the defender of the Kalam replies that the premise rests on metaphysical intuition (ex nihilo nihil fit) confirmed by uniform experience, and that it is up to whoever postulates an uncaused beginning to give a reason for it. If the most fundamental object — the universe itself — can pop up without a cause, the demand for causal explanation loses its foundation exactly where it matters most.

It is significant that David Hume himself — often cited as the father of causal scepticism and invoked in support of this objection — never in fact denied that events have causes. In a letter to John Stewart in 1754, he wrote explicitly:

"I never asserted so absurd a Proposition as that any thing might arise without a Cause: I only maintain'd, that our Certainty of the Falsehood of that Proposition proceeded neither from Intuition nor Demonstration; but from another Source." — David Hume, letter to John Stewart, 1754^[10]

Hume does not deny causality: he questions its epistemological foundation. (The idea that this "other source" means experience and habit is the standard interpretation of the commentators — it is placed here outside the quotation marks, since it does not appear in the text of the letter.) Invoking Hume to deny premise 1 of the Kalam is therefore a frequent historical misunderstanding.

Stephen Hawking proposed in The Grand Design (2010) that the universe would have created itself spontaneously from nothing through the laws of gravitation alone:

"Because there is a law such as gravity, the universe can and will create itself from nothing." — Stephen Hawking and Leonard Mlodinow, The Grand Design, Bantam Books, 2010^[11]

The philosopher and mathematician John Lennox (University of Oxford) replies that this claim contains a fundamental confusion: the law of gravitation is not nothing, and a physical law is not an acting entity capable of creating anything. As he writes in God and Stephen Hawking:

"Nonsense remains nonsense, even when talked by world-famous scientists." (p. 32)

"Physical laws cannot create anything. They are a description of what normally happens under given conditions." (p. 40) — John Lennox, God and Stephen Hawking, Lion Hudson, 2011^[12]

This is the most contested premise. It is defended by three converging lines: philosophical, cosmological, thermodynamic.

A. Philosophical argument: impossibility of the actual infinite

If the universe had no beginning, then there exists an actually infinite series of past events. But actual infinities generate logical absurdities.

The classic illustration is Hilbert's Hotel paradox^[13]: a hotel with infinitely many rooms, all occupied, can take in a new guest by moving each guest one room along. It can take in infinitely many new guests by moving each guest to the room with the doubled number. But then, infinity + 1 = infinity, and infinity × 2 = infinity: the arithmetic of infinity contradicts intuition and reveals the metaphysical impossibility of an actual infinite in the real world.

If the series of past events were infinite, one would have had to "traverse" infinitely many events before arriving at the present — which is impossible. So the universe had a beginning.

Al-Ghazali's paradox: planetary orbits

Al-Ghazali offers a further argument based on planetary cycles^[14]. Jupiter completes one revolution around the Sun in 12 years, Saturn in 30 years. If the universe had no beginning, both planets would have completed, since eternity, infinitely many orbits each — yet Jupiter would have completed 2.5 times more than Saturn. Both totalities could then be put into one-to-one correspondence with a proper part of themselves: the whole would be no greater than the part (reasoning by bijection and by parity, see Lavagna, pp. 55-56). This contradiction reveals the metaphysical absurdity of an actual infinite in the real world. As David Hilbert himself put it — Hilbert being the father of the modern theory of transfinite infinity, Cantor remaining its founder —:

"The infinite is nowhere to be found in reality. It neither exists in nature nor provides a legitimate basis for rational thought. The role that remains for the infinite to play is solely that of an idea — if one means by an idea, in Kantian terminology, a concept of reason which transcends all experience and which completes the concrete as a totality." — David Hilbert, lecture of 4 June 1925 at Münster, "Über das Unendliche"^[15]

The Pruss-Koons paradox: impossibility of the infinite causal series

The philosopher Robert Koons (University of Texas) developed a paradox showing that an actually infinite causal series with no first term is logically impossible^[16]: the Grim Reaper Paradox. Imagine infinitely many reapers numbered 1, 2, 3, …, each programmed to strike unless a higher-ranked reaper has already struck. With no first reaper in the series, each action is indefinitely blocked by the next one — yet, at the end of the series, a determinate result must have been obtained (such paper bears such number, the victim is dead) without anyone having acted to produce it. The contradiction proves the logical impossibility of an infinite causal series with no initial term.

In Infinity, Causation, and Paradox (Oxford University Press, 2018), Alexander Pruss (Baylor University) defends a more general thesis, causal finitism: no event can have more than a finite number of events in its causal history — an infinite causal history is metaphysically impossible^[17].

Philosophical objections to the actual-infinite argument

Objection A — Comparison with Zeno of Elea

The objection consists in likening the actual-infinite argument to Zeno's paradox: "To go from A to B, one must first cover half, then half of the half, ad infinitum — so motion is impossible." If Zeno is refuted (motion does exist), why would the Kalam argument hold?^[18]

Reply: the comparison is mistaken, because the two infinities are not of the same nature.

Motion through space is divisible in thought to infinity (potential infinite), but the distance remains finite and the subdivisions are never all simultaneously actualised. The series of past events, by contrast, would be a completed set of real events — an actual infinite whose contradictions (Hilbert's Hotel, Al-Ghazali's paradox) are not resolved by a convergent limit.

Objection B — Saint Thomas, Mackie and Sobel: traversal by finite portions

Saint Thomas Aquinas held that one cannot demonstrate by reason alone that the world had a beginning — for him it is a revealed fact. In the Summa Theologiae (Ia, q. 46, art. 2), he observed that "from any past day whatever to today, there is only a finite number of days"^[19], suggesting that each finite portion is traversable. This position is taken up by the analytic philosophers John Mackie (The Miracle of Theism, Oxford, 1982, p. 93) and Jordan Howard Sobel (Logic and Theism, Cambridge, 2004, p. 182): if each finite segment of the past series can be crossed, the whole series could be too.

Reply: this argument commits a fallacy of composition. Just because each brick of a wall is light does not mean the whole wall is light — the property of the parts does not necessarily transfer to the whole. Likewise, the fact that each finite portion is traversable does not mean that the infinite series as a whole is: a series with no first term has no starting point from which to begin the traversal^[20].

Objection C — Kant's antinomy

Immanuel Kant presents in the Critique of Pure Reason a cosmological antinomy: the thesis (the world has a beginning in time, A426/B454) and the antithesis (the world is eternal, A427/B455) would both seem demonstrable, revealing reason's inadequacy to decide about the cosmic infinite^[21]. Important clarification: the definition of beginning as "that which is preceded by an empty time" belongs to the proof of the antithesis (A427/B455) — it is not an objection by Kant against the proof of the thesis. The antinomy thus shows that the Kantian definition of beginning leads to indecision; it does not refute the beginning argument as such.

Reply: the objection rests on Kant's own definition of beginning, which is not the only possible one. A more rigorous definition proposed by Craig: X begins to exist at t if and only if X exists at t, and t is the first instant at which X exists. This formulation requires no time prior to t — it asserts only the existence of a first instant, with no reference to a prior void. Kant's antinomy does not refute the Kalam: it refutes his own inadequate definition of beginning^[22].

B. Cosmological argument: the Big Bang

In 1927, the Belgian abbé Georges Lemaître published in the Annales de la Société scientifique de Bruxelles his expanding-universe model^[23] — the first rigorous formulation of the expansion of the universe (a model without a beginning, starting from a static universe at t = −∞^[24]); in 1931, he proposed the primeval atom hypothesis (Nature, "The Beginning of the World from the Point of View of Quantum Theory")^[25]. In 1929, the astronomer Edwin Hubble observationally confirmed the expansion (the redshift of galaxies). In 1964, Arno Penzias and Robert Wilson accidentally discovered the cosmic microwave background — the residual thermal radiation of the Big Bang, theoretically predicted two decades earlier; their measurements were published in 1965^[26]. They received the Nobel Prize in Physics in 1978.

Big Bang theory implies that the observable universe has been in a state of expansion from an extremely hot and dense state, which the standard cosmological model places — by reconstructing the past from its own presuppositions, not by direct measurement (on the short chronology of about 6,000 years received here, see Is the World Only 6,000 Years Old?) — at about 13.8 billion years (NASA, USGS) — a figure on which the argument does not depend. Lemaître was not merely offering a pious hypothesis: his 1927 paper linked Friedmann's dynamic solutions for the first time to the already observed radial velocities of the extragalactic nebulae, and discovered what is now called the Hubble-Lemaître law^[27].

C. The Borde-Guth-Vilenkin theorem — BGV (2003)

The major objection is that cyclic-universe or multiverse models escape the Big Bang. But in April 2003, in Physical Review Letters (exact title of the paper: "Inflationary Spacetimes Are Incomplete in Past Directions"), the cosmologists Arvind Borde, Alan Guth and Alexander Vilenkin published a decisive mathematical theorem^[28] — whose substance is given here in paraphrase, presented as such:

Any space-time whose average rate of expansion is positive over its history is past-incomplete: it must have a past space-time boundary. (paraphrase)

This theorem does not depend on the classical energy conditions used by the older singularity theorems: the authors stress that they offer a simple kinematic argument and that an inflationary model must invoke physics other than inflation to describe its past boundary^[29]. Its power comes precisely from its minimal generality: it does not claim to describe what is at the boundary, but it forbids treating inflation as a past-eternal explanation. In other words: if we rewind the film of expansion — the galaxies moving away from one another — the trajectories do not extend indefinitely into the past: they stop at a boundary, a beginning, which inflation alone cannot erase.

Alexander Vilenkin, himself an agnostic cosmologist and a historic defender of multiverse theories (director of the Institute of Cosmology at Tufts University), drew his own conclusions — with the caution of "probably":

"The answer to the question "Did the universe have a beginning?" is: probably yes. We have no viable models of an eternal universe."^[30] Original text: "The answer to the question, "Did the universe have a beginning?" ... is, "It probably did." We have no viable models of an eternal universe. The BGV theorem gives us reason to believe that such models simply cannot be constructed." — A. Vilenkin, "The Beginning of the Universe", Inference: International Review of Science, vol. 1, no. 4, 23 October 2015. The theorem itself, Vilenkin specifies, says nothing about the existence of God: it establishes a past limit, not a cause.

This conclusion, coming from a declared defender of the multiverse, is significant for the apologetic argument: it is not a Christian theologian who judges the beginning of the universe probable, it is a cosmologist — a strong support, but not a demonstration.

Limits to be stated honestly. The BGV theorem holds in the classical regime: it does not describe what is at the boundary and does not settle the physics of quantum gravity, which could modify the picture at the most remote times. Alan Guth himself, co-author of the theorem, judges that a universe without a beginning remains probable: during the Craig-Carroll debate of 22 February 2014, Sean Carroll brandished placards held by Guth stating that the universe probably did not have a beginning and is very likely eternal — a position reported by Carroll on 24 February 2014^[31]. This article therefore retains the real degree of certainty: data compatible with a beginning, a strong but non-demonstrative support — Vilenkin's own "probably".

D. Testimony of Robert Wilson (1978 Nobel Prize)

Robert Woodrow Wilson, co-discoverer (with Arno Penzias) of the cosmic microwave background in 1964 — a discovery that won them the 1978 Nobel Prize in Physics — wrote the preface to the work Dieu, la Science, les Preuves (2021). Here is his testimony — excerpts restored in the exact order of the preface, each cut marked:

"[…] if, on the contrary, as Big Bang theory suggests, the Universe had a beginning, then we cannot avoid the question of creation. […] It so happens that at the start of my career, like most of my colleagues, I thought the Universe was eternal. […] Our discovery definitively shattered the belief that the Universe had neither beginning nor end. […]" — Robert W. Wilson, 1978 Nobel laureate in Physics, preface to Dieu, la Science, les Preuves^[32] Wilson accompanies his remarks with express reservations, however: this general thesis, he writes in substance, does not give him a sufficient explanation — "I certainly do not know the explanation".

The 20th-century historical reversal

Beyond the mathematical and experimental arguments, the history of 20th-century cosmology is itself an indirect argument for the beginning of the universe: it was precisely because the idea of an absolute beginning disturbed the metaphysical presuppositions of the scientific community so profoundly that its discovery was slow, conflictual, and sometimes persecuted^[33]. As Bolloré and Bonnassies write in chapter 6 ("Le roman noir du Big Bang") of Dieu, la science, les preuves: "Never would there have been such an outburst of violence against the theorists of the expansion of the Universe and the Big Bang if the materialists had not thought that this was strong proof of the existence of God. The use of force is, here more than ever, an admission."^[34]

Einstein and Lemaître (1927). Lemaître, present at the fifth Solvay Congress in Brussels in October 1927, did not "present" his cosmology in session: it was on the margins of the congress, during a walk in Leopold Park, that Einstein discussed his expansion paper with him^[35]. According to Lemaître's own account in French^[36], Einstein first made favourable technical remarks, then judged the physical interpretation "quite abominable" — the commonly quoted English form ("Your calculations are correct, but your physics is abominable") is a later relay of this account. The anecdote of "priestly physics", which rests on no verified primary source, is withdrawn.

Arthur Eddington and the beginning. Sir Arthur Eddington wrote in 1931, in Nature (vol. 127, pp. 447-453): "Philosophically, the notion of a beginning of the present order is repugnant to me. […] I should like to find a genuine loophole."^[37] — and he called the expanding universe absurd and unbelievable. But making Eddington an opponent of expansion would be wrong: Lemaître's former teacher, he adopted the expanding model and had the 1927 paper translated (Monthly Notices of the Royal Astronomical Society, 1931)^[38]. To speak here of a "reversal" is therefore improper: it is a documented evolution, not a sudden turnaround.

Einstein's reversal (1931). After the observational confirmation of the expansion by Edwin Hubble in 1929 (redshift of galaxies at the Mount Wilson telescope), Einstein travelled to Pasadena in January 1931. He returned transformed. According to the sole testimony of George Gamow (My World Line, 1970) — a private remark, unverifiable elsewhere — Einstein is said to have called his own 1917 introduction of a cosmological constant to force his equations to describe a static universe the "biggest blunder" of his life^[39]. Science thus had to rid itself of a mathematical artefact introduced for metaphysical reasons — not for scientific ones.

John Wheeler — the physicist's enthusiasm. The eminent American physicist John Archibald Wheeler (Princeton, mentor of Richard Feynman and Hugh Everett), summed up the event with this exclamation:

"Of all the great predictions that science has ever made over the centuries, was there ever one greater than this, to predict, and predict correctly, and predict against all expectation a phenomenon so fantastic as the expansion of the universe?"^[40]

Arthur Eddington on entropy. Eddington's position is also expressed in the face of the second law of thermodynamics, which implies a beginning of the universe. His provocative formula has remained famous:

"The law that entropy always increases holds, I think, the supreme position among the laws of Nature. If someone points out to you that your theory is in disagreement with Maxwell's equations — then so much the worse for Maxwell's equations. […] But if your theory is found to be against the Second Law of Thermodynamics I can give you no hope."^[41]

The Soviet persecution of the Big Bang pioneers. Chapter 6 of DSP (Dieu, la science, les preuves: "Le roman noir du Big Bang") presents the reaction of Marxism-Leninism to the cosmology of the beginning as a threat against the materialist axiom of the eternity of matter — the authors themselves announcing a narrative "at times touching on spy fiction": this is their thesis, not a fact established by historiography^[42]. Lenin made the eternity of matter an axiom of dialectical materialism (Materialism and Empirio-criticism, written in 1908); according to Bolloré and Bonnassies, he perceived in it the philosophical danger of a science that would establish a beginning of the world, opening the way to the idea of a Creator^[43]. Under Stalin, the state-atheism campaign was accompanied by purges that struck Soviet astronomers: the facts are documented by historiography, notably by R. McCutcheon on the 1936-1937 purge of the Soviet astronomical community^[44]. Matvei Bronstein (executed by firing squad in 1938 at 31), Vsevolod Frederiks (deported, died in the Gulag), Lev Landau (arrested in 1938, freed after Piotr Kapitsa's intervention)^[45]; Nikolai Kozyrev, arrested in the Pulkovo affair (1936), was detained at Norilsk (Norillag)^[46]. The mathematician Alexander Friedmann, author in 1922 of the expansion solutions, died on 16 September 1925 at the age of 37 — before the purges, which he therefore never knew^[47].

According to the thesis defended by Bolloré and Bonnassies, the remarkable fact of 20th-century cosmology's history is that the idea of an absolute beginning of the universe prevailed against the philosophical presuppositions of part of the scientific community and against the dominant ideologies (Marxist materialism, post-Newtonian positivism). This is what in Popperian epistemology is called "the strongest corroboration": a thesis imposed by the facts against researchers' expectations is worth far more than a thesis confirming what those researchers already wanted to believe.

E. Thermodynamic argument: entropic death

The second law of thermodynamics states that the entropy of a closed system increases irreversibly over time. If the universe had existed for an eternity, it would long ago have reached its thermal equilibrium — "heat death", where no more useful energy circulates, no more stars shine. Yet this is manifestly not the case. So the universe has a beginning.

Matthieu Lavagna takes up the thermodynamic argument for the beginning (p. 59): without God, the material universe ends in a thermal death with no more stars, no more usable heat, no more life; this cosmic end forces the question of the beginning instead of letting the universe play the role of an eternal absolute^[48]. (Pp. 34-35 of the same work concern the absurdity of a life without God, not thermodynamics.) Bolloré and Bonnassies formulate the same reasoning more technically: if the material universe were closed and eternal, entropy would already have reached its maximum; the fact that the cosmos is still structured and energetically differentiated indicates a finite past^[49].

The Catholic Church does not base faith on any particular cosmological theory. It does teach, however, that human reason can know God from the created world. The First Vatican Council solemnly defined, in the dogmatic constitution Dei Filius (24 April 1870):

"If anyone says that the one true God, our Creator and Lord, cannot be known with certainty from the things that have been made, by the natural light of human reason, let him be anathema."^[50]

The Catechism of the Catholic Church (§§ 31-35) continues this teaching. § 31 states that the "proofs of God's existence", in the sense of "converging and convincing arguments", "allow us to attain true certainties"; § 35 specifies that "the proofs of God's existence can predispose one to faith and help to see that faith is not opposed to human reason"^[51].

Pius XII explicitly applied this principle to the cosmological discoveries of his time in his address of 22 November 1951 to the Pontifical Academy of Sciences:

"Creation in time, therefore; and therefore a Creator; therefore God!"^[52]

Saint John Paul II, in the encyclical Fides et Ratio (14 September 1998), recalls that philosophy and human reason retain their full place in the search for God:

"By arguing from sense data, [reason] can also reach the cause which lies at the origin of all sensible reality."^[53]

Prudence comes from Lemaître himself: a Catholic priest and cosmologist, he refused to turn the Big Bang into an easy concordism. The Kalam therefore does not say: "physics directly proves the Creed". It says more soberly: contemporary physics makes it highly rational to hold the premise that the universe is not past-eternal; philosophy then draws from it the necessity of a transcendent cause. The Church receives this argument as coherent with her faith, not as its foundation.

Once the two premises and the conclusion "the universe has a cause" are granted, the philosophical analysis of this cause reveals that it must possess very specific attributes:

• Uncaused: otherwise, an infinite regress of causes — already excluded by the arguments above
• Outside time: it precedes the initial instant when time itself begins
• Outside space: it precedes the creation of space
• Immaterial: otherwise it would be material, hence in space
• Extremely powerful: capable of creating the entire universe from nothing (ex nihilo)
• Personal: capable of choosing to create rather than not create, at a precise instant — which presupposes a free will

These attributes converge precisely on the classic definition of the monotheistic God — eternal, immaterial, omnipotent, personal. The philosophical conclusion of the Kalam is therefore the rationally demonstrated existence of a transcendent Creator.

Why the cause must be personal

The attribute of personality deserves particular development, since it is the most contested. Craig offers the following argument: the cause is timeless and immaterial from eternity. But the universe began to exist a finite number of years ago. How can an eternal cause produce a temporal effect that begins?

For natural causes, the effect is simultaneous with the cause: fire always burns as long as it is there, the sun always warms as long as it shines. An eternal natural cause should therefore produce an eternal effect. Only a free will — capable of choosing to create at one moment rather than another — can produce a temporal effect from an eternal condition. This is the argument of William Lane Craig, taken up from the medieval analysis of Al-Ghazali himself: a timeless cause without a freely determining will would have produced a universe from all eternity^[54].

Craig concludes in Reasonable Faith that the first cause must therefore be non-physical and personal — only a freely determining will can produce a temporal effect from an eternal condition^[55].

Objection 1 — "Who created God?"

Answer: This is the most frequent objection, and it rests on a quite natural misunderstanding: premise 1 is often quoted in the truncated form "everything has a cause", whereas it says "whatever begins to exist has a cause". Hence the decisive distinction between two types of beings: contingent beings that begin to exist (and therefore require a cause — that is premise 1), and the necessary being that never began to exist (and therefore requires no cause). God, by definition, is eternal and uncaused — He does not begin to exist, so premise 1 does not apply to Him. The classic image illustrates this — without targeting anyone: asking "who created the Uncreated?" is like asking "which married man is still a bachelor?" — the question assumes, in its own terms, the opposite of what it asserts.

Objection 2 — "The multiverse escapes the beginning"

Answer: This is the most sophisticated objection. But the BGV theorem (2003) applies also to multiverses: any multiverse with positive average expansion must have a past boundary — hence a beginning, and hence a cause beyond it. This is precisely the scientific irony that Vilenkin himself acknowledges (Many Worlds in One, p. 176): "There is no escape". The multiverse does not solve the problem of the beginning; it merely moves it up one level.

Objection 3 — "The universe is cyclic: it bounces eternally"

Answer: The BGV theorem also applies to cyclic or bouncing models, as long as their average expansion is positive. The classic thermodynamic objection adds that each cycle would increase total entropy: an infinite cyclic past would already have exhausted all usable energy — and we would not be here to debate it.

Objection 4 — "The Hartle-Hawking model: a universe with no initial boundary"

The physicist Stephen Hawking and the physicist James Hartle proposed, in a paper published in 1983 in Physical Review D, a quantum-cosmology model in which the universe presents no sharp temporal boundary in the classical sense^[56]. Hawking draws the famous conclusion in A Brief History of Time (1988): "If the universe is really self-contained, having no boundary or edge, it would have neither beginning nor end: it would simply be."^[57]

Answer: This argument does not remove the problem of the beginning, for three converging reasons:

First, the Hartle-Hawking model rests on imaginary time (τ = it), a mathematical device introduced to make the equations tractable. In imaginary time, there is no singularity; in real time — the only one that counts physically — the initial singularity reappears. The philosopher Robin Collins stresses in substance, in his study of fine-tuning (paraphrase, presented as such): Hartle-Hawking imaginary time would be a calculation technique, not an ontological description of the real world^[58].

Second, even a "no-boundary" universe still requires that the wave function of the universe and the physical laws governing it be given. Removing the initial singularity does not remove the metaphysical question: why is there something — even a quantum field and equations — rather than nothing?

Third, Hawking himself implicitly acknowledges that the why question remains open. In the conclusion of A Brief History of Time, he writes that even a complete unified theory would be only a set of rules and equations, and asks "what breathes fire into the equations and makes a universe for them to describe?"^[59] — acknowledging that physics cannot answer the metaphysical question of being.

Vilenkin: "There is no escape"

The cosmologist Alexander Vilenkin (Tufts University, Institute of Cosmology) sums up the scope of his 2003 theorem thus:

"It is said that an argument is what convinces reasonable men and a proof is what it takes to convince even an unreasonable man. With the proof now in place, cosmologists can no longer hide behind the possibility of a past-eternal universe. There is no escape: they have to face the problem of a cosmic beginning." — Alexander Vilenkin, Many Worlds in One, Hill and Wang, 2006, p. 176^[60]

This statement, signed by one of the leading defenders of the multiverse, strengthens the apologetic argument: it is not a Christian theologian who judges the beginning probable, it is a cosmologist — data compatible with a beginning, a strong but non-demonstrative support, as throughout section C.

Plantinga: Where the Conflict Really Lies

The analytic philosopher Alvin Plantinga (Notre Dame), in his landmark work Where the Conflict Really Lies: Science, Religion, and Naturalism (Oxford University Press, 2011)^[61], does not strictly speaking defend the cosmological argument: the work deals with evolution, divine action, fine-tuning, design, then deep concord and deep conflict between science and religion. His thesis — summarised here in paraphrase, presented as such — is that the real conflict would not be between science and religion, but between science and philosophical naturalism, an undemonstrated metaphysical presupposition rather than a scientific result.

Spitzer: New Proofs for the Existence of God (2010)

The Jesuit philosopher Robert J. Spitzer (founder of the Magis Institute), in New Proofs for the Existence of God: Contributions of Contemporary Physics and Philosophy (Eerdmans, Grand Rapids, 2010)^[62], devotes his book to the physical and philosophical proofs of God's existence, including Kalam-type cosmological arguments.

Refutation of Krauss and the ill-defined "nothing"

The atheist physicist Lawrence Krauss, in A Universe from Nothing (2012), claims to solve the question of the beginning by showing how the universe can emerge "from nothing". But as the philosopher David Albert (Columbia University) points out in his review in the New York Times Book Review (23 March 2012)^[63]:

"Krauss's physical theories have absolutely nothing to say about where those fields came from… or why there should have been a world in the first place. Period."

Krauss's "nothing" is in reality not absolute nothingness but the quantum vacuum — a physical field governed by mathematical laws. Yet explaining the appearance of the universe from a pre-existing field does not solve the question: the origin of that field and of its laws must then be explained.

The Kalam argument, while not specific to Catholicism, is a rational formulation particularly compatible with it. It matches the second way of Saint Thomas Aquinas (Summa Theologiae, Ia q. 2, a. 3) — the way of efficient causality, which ascends from observed causality in the world to an "uncaused first cause"^[64]. Saint Bonaventure formulates it explicitly in his Commentaries on the Sentences of Peter Lombard (Book II, distinction 1): the universe cannot be the author of its own beginning, and an actually infinite temporal succession is impossible — so the world must have begun in time, through a first cause^[65].

Today, Matthieu Lavagna presents the Kalam argument in the first part "Theism" of his work Soyez rationnel, devenez catholique ! (2023)^[66].

The Kalam is not an isolated argument that should carry the whole Christian edifice on its own. It is rather one piece of the apologetic bundle: it establishes a transcendent first cause; cosmic fine tuning examines the intelligibility and precise adjustment of nature's constants; the argument from contingency asks why there is something rather than nothing; the moral argument establishes the existence of an objective Lawgiver; the story of Jesus, of the Resurrection and of the Church finally identifies this first cause with the living God of Revelation.

• Cosmic Fine Tuning — the complementary scientific argument
• The Existence of God — overview of the rational proofs
• The Five Ways of Saint Thomas Aquinas — the classic way of causality