Cosmological fine-tuning

The idea of fine-tuning is not a recent invention of apologists. It emerges progressively from cosmology itself over the course of the 20th century, contrary to researchers' initial expectations.

Robert Dicke (1916-1997): the founding intuition

It was at Princeton, where he joined the faculty in 1946 after his Rochester doctorate (1941) and MIT radar research during the war, that the physicist Robert Dicke formulated the intuition that the universe presents “settings” strangely adapted to the appearance of life, notably in his 1961 article on Dirac's cosmology and Mach's principle^[3]. He pointed out that no other science can explain why the age that the standard cosmological model attributes to the universe (≈ 13.8 billion years) corresponds precisely to the time needed to allow stellar evolution, carbon nucleosynthesis, and ultimately the emergence of intelligent life capable of contemplating the universe. Dicke concluded that an “infinitesimal variation in a single one of the dozens of cosmological parameters” would have prevented the universe as we know it from existing^[4].

Brandon Carter (1942-): the “anthropic principle”

It was the Australian physicist Brandon Carter who coined the term “anthropic principle” in 1973 to designate this phenomenon^[5]. He distinguishes two versions:

• Weak anthropic principle: the universe as we observe it must be compatible with the existence of observers (a truism)
• Strong anthropic principle: the universe must possess the properties allowing life to develop within it (the apologetic argument)

John D. Barrow & Frank Tipler: the reference work (1st ed. 1986)

The founding book is The Anthropic Cosmological Principle (Oxford, Clarendon Press, 1st ed. 1986), by John D. Barrow (professor of mathematics at Cambridge) and Frank Tipler: xx + 706 pages presenting a vast documented inventory of examples of fine-tuning, which leave no doubt about the reality of the phenomenon^[6].

Stephen Meyer (2021): the contemporary synthesis

In 2021, the philosopher of science Stephen C. Meyer (PhD Cambridge) published Return of the God Hypothesis (HarperOne, 2021), which synthesises three scientific discoveries of the 20th century pointing toward theism: the Big Bang model as proposed by standard cosmology (formulated in 1927, confirmed in 1964-1965), cosmological fine-tuning (1973-1986), and information in DNA (1953-2003)^[7].

Physicists have identified some thirty fundamental constants whose precise value determines the very nature of the universe. Matthieu Lavagna sums up the stakes well: scientists are not speaking only of present terrestrial life, but of the very possibility of organisms capable of feeding themselves, extracting energy, growing and reproducing; without these settings, no general form of life could arise^[8].

The cosmological constant Λ

This is the most extreme case. The cosmological constant (denoted Λ, lambda) governs the accelerated expansion of the universe and the vacuum energy density. Since Weinberg (1989), the reference formulation is a discrepancy of about 120 orders of magnitude between the predicted vacuum energy and the observed value, that is, a precision of the order of 1 in 10¹²⁰, as taken up by Susskind^[14][15]; Lavagna, according to a slightly different Planck unit convention, gives 1 in 10¹²¹^[16]. Bolloré-Bonnassies speak of contributions that cancel out to the 122nd decimal place^[17].

This precision is such that it has been described by physicists as the “worst fine-tuning problem in physics”, not because it is suspect, but because no theory manages to explain it naturally. The slightest variation in one direction: the universe explodes and no galaxy forms. In the other: it collapses before even the first stars form.

The four fundamental forces

• Strong nuclear force: precision of 0.5%. At +2%, no stable proton; at −9%, no element heavier than hydrogen would ever have existed.
• Electromagnetic force: precision of 4%. Otherwise: no carbon or oxygen.
• Weak nuclear force: governs radioactive decay, a fine balance between stability and evolution.
• Gravitational force: if it were stronger by a factor of ~10⁴⁰, stars would burn out in a few million years (too short a time for biological evolution).

The electron / proton mass ratio

The proton is about 1,836 times heavier than the electron. This precise proportion is what makes complex chemistry possible: formation of covalent bonds, stability of DNA molecules, cellular biochemistry. A variation of a few percent would make DNA structurally unstable^[18].

The initial density of the universe: Dicke's precision

The parameter Ω₀ (omega zero) measures the ratio between the actual density of the universe and the critical density needed for a universe in controlled expansion. Its observed value is extremely close to 1. A deviation of one part in 10⁵⁵ at the Big Bang would have sufficed to collapse the universe in a few seconds or to disperse it without galaxy formation.

According to the chronology of the standard cosmological model, the orders of magnitude reported by Bolloré-Bonnassies (op. cit., p. 173) are staggering:

• 180 seconds after the Big Bang, the ratio had to differ from 1 “to the thirteenth decimal place”, that is, 1.0000000000001 (calculation attributed to George Gamow and Steven Weinberg)^[19]
• 1 second after the Big Bang, “the expansion rate had to be really and exactly adjusted to the 15th decimal place” (calculation attributed to Robert Dicke himself)^[20]
• At Planck time (10⁻⁴³ second after the Big Bang), this precision was even more extreme, a figure that cannot be written down

The cosmologist Alan Guth (MIT, father of the theory of cosmic inflation) explains, in paraphrase, that if, at that moment, the expansion of the universe had been very slightly weaker, the nascent cosmos would have collapsed on itself under the effect of gravitation long before reaching its present size, and that, conversely, with a slightly faster expansion, atoms and stars would not have had time to form and the Universe would have remained purely gaseous^[21].

Initial entropy (Penrose)

The mathematician and Nobel laureate Roger Penrose calculated the probability that a universe would have an initial entropy as low as ours, a necessary condition for any ordered structure. The result is dizzying: 1 in 10^(10^123), a number whose decimal expansion exceeds human imagination^[22].

“The precision needed to produce a universe like ours, in terms of the second law of thermodynamics, is of the order of 1 in 10^(10^123).” — Roger Penrose, The Emperor's New Mind, Oxford University Press, 1989^[23]

The apologetic argument takes the form of a four-branched dilemma: faced with this extreme precision, the explanations discussed in the literature are chance, physical necessity, the multiverse or intelligent design^[24][25].

1. Chance

The most naive hypothesis: “it is simply like that, by chance”. But as Penrose showed, the probability is so tiny (1 in 10^(10^123) for initial entropy alone) that speaking of chance is no longer rational; it is an act of faith in the improbable. Lavagna gives the analogy of the red marble: if a bag contains billions of billions of deadly blue marbles and a single red marble that saves, drawing precisely the red one demands a stronger explanation than “improbable events happen”^[26].

2. Physical necessity

A “theory of everything” would show that the constants could only take these values, by mathematical necessity. But no such theory has ever been found despite a century of research, and nothing indicates that it exists. It is a science-fiction promise.

3. The multiverse

The hypothesis of the existence of an infinity of universes: if all possible universes exist, then it is inevitable that at least one (ours) has the perfect constants for life. But this hypothesis presents three major problems:

• Non-testability: by definition, one cannot observe the other universes; it is metaphysics disguised as science
• The Borde-Vilenkin-Guth theorem (2003) also applies to multiverses: they themselves must have a beginning, and therefore a cause
• The Boltzmann Brain problem: in a multiverse, spontaneously fluctuating brains are statistically infinitely more probable than ordered universes like ours, which makes all rational observation absurd^[27]
• The universe generator: even if a mechanism produced a multitude of universes, it would still be necessary to explain why this mechanism possesses precisely the laws capable of varying the constants in the right space of possibilities^[28]

4. Intelligent design

The fourth option, and the most rational according to Bolloré, Bonnassies, Meyer, Craig and Lennox, is that an intelligent Designer, transcendent and personal, chose the values of the constants because He intended to produce a universe capable of harbouring life. It is the classic argument from design, but this time supported by the most precise scientific data of the 20th and 21st centuries.

Objection: the “God of the gaps” argument

The most frequent objection against apologetic fine-tuning is that of the “God of the gaps”: whenever science does not yet have an explanation, believers place God there, and the next physical theory may suffice to fill that gap^[29].

This objection confuses two radically different types of reasoning:

• Argument from ignorance (God of the gaps): “Science does not yet have an explanation → therefore God.” It does indeed rest on a provisional gap.
• Positive argument from specified complexity: “Current, precisely measured scientific data point toward a Designer.” This is not ignorance; it is an inference founded on what we know.

Fine-tuning is not a gap in our knowledge: it is a precisely measured fact. The cosmological constant Λ has been measured at 10⁻¹²² in natural Planck units, and it is precisely because we know it that we can calculate how finely tuned it is. As William Lane Craig puts it: “The fine-tuning argument is based on what we know about physics, not on what we do not know”^[30]. John Lennox adds^[31]: if God exists, He is not “where science stops”; He is also there where science advances, that is, where the precision of the constants, far from being explained, becomes more dizzying with each decade.

The syllogism of fine-tuning, in its clearest form (cf. William Lane Craig)^[32]:

1. The universe presents extreme fine-tuning compatible with life.

2. This fine-tuning is due either to chance, or to necessity, or to design.

3. Chance is statistically irrational; necessity is not demonstrated and is highly improbable; the multiverse is unverifiable and engenders logical absurdities.

4. Therefore, fine-tuning is very probably due to intelligent design.

Conclusion: The universe was designed by a transcendent Mind, which the Catholic tradition names God.

Matthieu Lavagna devotes a whole development of Soyez rationnel, devenez catholique ! (pp. 85-93) to formulating and then refuting the main objections against the fine-tuning argument^[33]. The rule of honest apologetics is always to present objections in their strongest version, not to caricature them, but to show that the argument withstands even the most rigorous criticisms. Here are the seven main objections formulated without straw men.

Objection 1: The cosmic lottery: “every combination is equally improbable”

The objection in its strongest form: Every particular combination of physical constants is, a priori, equally improbable. If the constants had had different values, the inhabitants of that universe (if there were any) would have asked the same question, marvelling at their “luck”. The fine-tuning argument commits a classic error: it presupposes that our result is special when it is so only retrospectively, like a poker player stunned before a particularly improbable hand, when any other hand would have been just as improbable. Lavagna sums it up: any particular combination of constants was just as improbable, so there is nothing to explain^[34].

Response: The poker analogy precisely reveals its insufficiency. Fine-tuning is not surprising because our particular result occurred, but because the result belongs to the extremely restricted set compatible with life. Out of all possible combinations of physical constants, those allowing the existence of stable atoms, long-lived stars, organic chemistry and life represent a tiny fraction; Bolloré and Bonnassies estimate that the probability of a life-bearing universe by pure chance is less than 1 in 10⁵⁰ ⁰⁰⁰^[35].

The British philosopher John Leslie formulates the decisive analogy of the firing squad^[36]: if fifty elite marksmen aim at you at point-blank range and all miss, it would be absurd to conclude “any result was possible, so I should not be surprised”. The real question is: why did all fifty miss? The fine-tuning argument does not say “why am I alive?”; it says “why did all fifty marksmen miss?”, and this question demands a causal answer.

Objection 2: The weak anthropic principle: “we can only observe a universe compatible with us”

The objection in its strongest form: The weak anthropic principle (Weak Anthropic Principle) stipulates: every observable universe must necessarily be compatible with the existence of observers. It is therefore not a coincidence that we exist in a fine-tuned universe; it is a logical triviality. The only observers capable of asking the question of fine-tuning are those who exist in a universe that permits them. The cosmologist Sean Carroll (Johns Hopkins University since 2022, previously Caltech) defends that this anthropic selection dissolves the appearance of the problem without recourse to any additional explanation^[37]. Richard Dawkins, in The God Delusion (2006)^[38], adds that the WAP alone suffices to explain the appearance of fine-tuning.

Response: The WAP is a valid truism, and that is precisely why it explains nothing. It says why we cannot observe a universe incompatible with life, but not why this compatible universe exists. Lavagna formulates the distinction with precision^[39]: the WAP explains why observers are necessarily in a compatible universe, but not why this compatible universe exists rather than none.

Anthropic selection only works as an explanation if one already presupposes an ensemble of several universes among which to select. In a single universe, it explains nothing: there is nothing to select from. Leslie formulates the limit^[40]: the WAP specifies where observers can be; it does not say why the conditions of their existence are met, and these two questions are radically distinct.

Objection 3: The life zone would be wider than believed

The objection in its strongest form: Fine-tuning calculations presuppose that carbon-based life, water and organic chemistry are the only criterion. If one envisages alternative structures, based on silicon, ammonia, or radically different forms of complexity, the zone of universes compatible with some form of complexity might be much vaster. The atheist physicist Victor Stenger (University of Colorado, 1935-2014) argued in The Fallacy of Fine Tuning (Prometheus Books, 2011) that improbability calculations rest on unjustified biological assumptions^[41].

Response: This objection has received a precise empirical answer. The astrophysicist Luke Barnes (Western Sydney University) published in 2012 a refutation of Stenger's thesis in Publications of the Astronomical Society of Australia^[42], then in A Fortunate Universe (Cambridge, 2016)^[43]. Barnes demonstrates that Stenger commits several methodological errors: he varies the constants one by one while holding the others fixed (which erases real correlations) and uses incoherent definitions of “possible life”. The conclusion of Barnes and Lewis, atheist and theist together, is unambiguous: even with generous definitions of complexity, the zone of compatible parameters remains extraordinarily restricted. Robin Collins quantifies: in Bayesian analysis, the fine-tuning of the cosmological constant alone represents an improbability of at least 1 in 10⁵³^[44].

Objection 4: A future “Theory of Everything” will make the constants inevitable

The objection in its strongest form: The physical constants seem free today because our physics is incomplete. A unified theory, string theory or loop quantum gravity, could show that these constants are necessary consequences of the underlying mathematical structure, as the value of π is of Euclidean geometry. Fine-tuning would then be only a provisional appearance linked to our ignorance. Hawking evokes this possibility in The Grand Design (Bantam Press, 2010)^[45].

Response: This objection is intellectually honest but presents fundamental difficulties. (1) It remains purely speculative: after more than a century of fundamental physics, no theory has reduced the constants to mathematical necessities. String theory has on the contrary produced a landscape of 10⁵⁰⁰ possible solutions, increasing the space of free parameters instead of reducing it^[46]. (2) It displaces the question: even if the constants followed from a mathematical structure, it would be necessary to explain why this mathematical structure exists and is instantiated in a real universe rather than remaining an abstraction. Hawking himself acknowledges in A Brief History of Time that even a perfect theory cannot alone “breathe fire into the equations”^[47]. (3) Initial entropy remains intact: Penrose's precision (1 in 10^(10^123)) concerns the initial state of the universe; a Theory of Everything about the constants does not explain why the universe began in a state of such dizzying precision.

Objection 5: The argument from divine complexity

The objection in its strongest form: This is the philosophically most elaborate objection, formulated by Richard Dawkins in The God Delusion (Houghton Mifflin, 2006)^[48]. It is formalised thus: (1) To design a universe so precisely tuned, a Creator must possess an intelligence of prodigious complexity. (2) Every complex being requires a causal explanation. (3) Postulating a Creator therefore solves nothing: it creates a problem even more difficult than the one it claims to solve. Dawkins asks the question: “Who designed the designer?”; any God capable of tuning the universe would be statistically more improbable than the universe itself.

Response: This objection rests on a precise philosophical error, identified by Alvin Plantinga (Where the Conflict Really Lies, Oxford University Press, 2011)^[49] and by John Lennox^[50]: it treats God as a complex physical object, composed of material parts, whose complexity calls for the same causal explanation as natural things. But in the classical philosophical tradition, from Aristotle to Thomas Aquinas, God is not complex in the material sense: He is pure act, simple in the metaphysical sense (not composed of parts), necessary and not contingent. The complexity that Dawkins presupposes is precisely the definition of what God is not, according to the theologians he claims to refute.

Lennox formulates the counter-argument with precision^[51]: a simple intelligence can generate immense complexity. An elementary algorithm can produce fractals of infinite mathematical richness; a composer is certainly “simpler” than the totality of his work. The complexity of the effect does not imply the proportional complexity of the cause. Moreover, for Dawkins' reasoning to work, it would first be necessary to demonstrate that every thinking and acting being is necessarily physically complex; this is precisely what classical theism contests with the notion of a necessary and simple being.

Objection 6: “Who created God?”: the regression of causes

The objection in its strongest form: If the fine-tuning argument concludes to a Designer, it remains to explain why this Designer exists. If everything precisely configured requires an explanation, God Himself requires one. The argument displaces the problem by one step without solving it. And if one posits God as an arbitrary exception to the causal rule, one could just as well posit the universe itself as that exception, making God useless^[52].

Response: The fine-tuning argument, in its rigorous Bayesian formulation (Collins, Craig), does not say “everything requires a cause, therefore God”; it says “which hypothesis makes fine-tuning most probable?” This comparative reasoning is not cancelled by the question of God's origin, just as “who forged this knife?” is not refuted by “who made the craftsman?”: the two questions are legitimate and distinct.

The Catholic philosophical tradition distinguishes contingent beings (which could not exist) from necessary beings (whose non-existence is impossible). The physical universe, whose constants could have taken other values, is clearly contingent. God, in Thomism, is posited as necessary: not by arbitrary decree, but because the regression of contingent causes logically requires a being not itself contingent, what Aristotle called the unmoved prime mover. This distinction is not ad hoc; it results from an independent metaphysical reflection prior to fine-tuning, and it precisely prevents the infinite regression that the objection fears.

Objection 7: The multiverse: natural selection on a cosmic scale

The strengthened objection: If a physical mechanism generates an infinity of universes with variable constants, like the landscape of string theory with 10⁵⁰⁰ solutions according to Leonard Susskind (The Cosmic Landscape, Little, Brown, 2005)^[53], it becomes inevitable that some universes have constants compatible with life. We find ourselves in one of them by simple anthropic selection. Fine-tuning is then no more surprising than the fact that we live on a habitable planet rather than in interstellar void. This position is defended by physicists such as Lee Smolin (The Life of the Cosmos, 1997) and Max Tegmark (Our Mathematical Universe, Knopf, 2014)^[54].

Response: The multiverse is a physically respectable hypothesis, but its use as a response to fine-tuning presents structural difficulties. (1) Non-testability: the other universes of the landscape are not observable by definition; it is metaphysics disguised as physics, precisely what sceptics reproach religion with. (2) Measure problem: for the multiverse to constitute a probabilistic explanation, a probability measure must be defined on the space of universes; no coherent measure has been proposed without circularity^[55]. (3) Generator problem: the universe-generating mechanism (eternal inflation, string theory) itself requires precisely calibrated physical laws; fine-tuning is simply displaced by one level. (4) Boltzmann problem: in an infinite space of random universes, brains fluctuating spontaneously in the void (Boltzmann Brains) are statistically incomparably more numerous than ordered universes like ours^[56], which would make all coherent scientific experience absurd. The philosopher Richard Swinburne (Oxford) thus sums up the balance, in paraphrase of his argumentation: postulating an infinity of unobserved universes to explain fine-tuning costs ontologically far more than postulating a single Creator God^[57].

The academic study of fine-tuning has developed considerably in the 21st century. Four works constitute the current university references on the subject:

Luke Barnes & Geraint Lewis: A Fortunate Universe (Cambridge, 2016)

Co-written by an atheist cosmologist (Geraint Lewis, University of Sydney) and a theist cosmologist (Luke Barnes, Western Sydney University), this work published by Cambridge University Press has become the academic reference on fine-tuning^[58]. Its central conclusion, signed by both authors despite their metaphysical divergences:

“The fundamental properties of the Universe appear to be fine-tuned for life.”^[59]

Martin Rees: Just Six Numbers (1999)

Lord Martin Rees, British Astronomer Royal, former president of the Royal Society, identifies six critical constants which alone suffice to explain the nature of the universe:

• N ≈ 10³⁶: ratio between the electromagnetic force and the gravitational force. If N were significantly smaller, no star could shine long enough.
• ε ≈ 0.007: efficiency of hydrogen-helium fusion. At 0.006: no complex chemistry. At 0.008: no stable hydrogen.
• Ω ≈ 0.3: actual density / critical density.
• λ ≈ 0.7: cosmological vacuum energy (cosmological constant).
• Q ≈ 10⁻⁵: amplitude of primordial density fluctuations.
• D = 3: number of spatial dimensions. With D = 2 or D = 4, life could not exist.

“Cosmic evolution is surprisingly sensitive to the values of these numbers. If one of them were not tuned, there would be neither stars nor life.” — Martin Rees, Just Six Numbers, 1999^[60]

Robin Collins: Blackwell Companion to Natural Theology (2009)

The philosopher Robin Collins (Messiah University, Pennsylvania), world expert on fine-tuning, authored chapter 5 (“The Teleological Argument: An Exploration of the Fine-Tuning of the Universe”) of the Blackwell Companion to Natural Theology, an academic reference work. His Bayesian formalisation shows that fine-tuning makes the existence of life 10⁵³ times more probable under the theistic hypothesis than under the naturalistic hypothesis^[61].

Frank Tipler: The Physics of Christianity (2007)

The physicist Frank Tipler (Tulane University), co-author with Barrow of The Anthropic Cosmological Principle, extends his work through a theistic physics developed in The Physics of Christianity (Doubleday, 2007)^[62].

The most astonishing historical episode of fine-tuning is the theistic prediction made by Fred Hoyle in 1953. For carbon, the essential element of life, to form in stars via triple-alpha fusion (three helium nuclei fusing), there must exist a nuclear resonance at a very precise energy. Hoyle theoretically predicted this energy at 7.68 MeV, and the experimental measurement, carried out at Caltech by William Fowler, gave 7.65 ± 0.03 MeV^[63].

This prediction is so precise and improbable that it led Hoyle, then a militant atheist and defender of the steady-state universe, to publicly evoke a “super-intellect” at work in nature. His famous statement follows this discovery:

“Would you not say to yourself: ‘A calculating super-intellect must have designed the properties of the carbon atom’?” — Fred Hoyle, on the carbon-12 resonance^[64]

The fine-tuning argument is not limited to cosmology. The discoveries of molecular biology in the 20th century revealed a second level of fine-tuning, distinct and independent of the cosmological one: the tuning of the conditions necessary for the emergence of life itself, in particular the problem of biological information.

DNA: a library of four billion characters

In 1953, Francis Crick and James Watson discovered the double-helix structure of DNA^[65]. This discovery reveals that DNA is, in its essence, a digital information medium: a sequence of nitrogenous bases (adenine, thymine, guanine, cytosine) that encodes the instructions for building and operating every living organism. The simple bacterium Escherichia coli possesses 4,288 genes and a genome of 4.6 million base pairs, the computer equivalent of a 600-page technical book. Yet the critical question is not how to read this book, but to explain how it could have written itself spontaneously in a primitive chemical soup, without intelligence or intention.

Stephen Meyer, philosopher of science at Cambridge, devotes his work Return of the God Hypothesis (HarperOne, 2021) to demonstrating that biological information constitutes the third pillar of the theistic argument after the Big Bang and cosmological fine-tuning^[66]. His fundamental argument: all known complex and specified information comes from an intelligence; no observation has ever shown a functional information system emerging spontaneously from chemical chance.

The improbability of the first functional protein

Bolloré & Bonnassies devote chapter 11 of Dieu, la science, les preuves to the origin of life and its improbabilities^[67]. A minimal functional protein requires about 150 amino acids in a very precise order, out of 20 possible amino acids at each position, with a chirally homogeneous constraint (left only). The combinatorial calculation is pitiless: the probability of obtaining by chance a functional protein of this size exceeds 1 in 10¹⁹⁵.

The information biologist Hubert Yockey (a nuclear physicist converted to bioinformatics), in Information Theory, Evolution, and the Origin of Life (Cambridge University Press, 2005)^[68], formalises this calculation with the rigour of Shannon theory. He establishes that the probability of spontaneous appearance of a single functional polypeptide chain among the simplest is 1 in 10¹⁶⁴. Yockey, who is not a believer, nevertheless concludes:

“One must conclude that, contrary to established and current wisdom, a scenario describing the genesis of life on earth by chance and natural causes, which can be accepted on the basis of fact and not faith, has not yet been written.”^[69]

Convergence: Christian de Duve, Nobel laureate

The Nobel Prize in Physiology or Medicine 1974, Christian de Duve (1917-2013), one of the great cell biologists of the 20th century (discoverer of the lysosome), devotes a late work to reflecting on the meaning of biological complexity. In Singularities: Landmarks on the Pathways of Life (Cambridge University Press, 2005)^[70], de Duve acknowledges an irreducible difficulty in the materialist explanation of the origin of life:

De Duve argues there, in paraphrase, that life belongs to a cosmic imperative inscribed in the very structure of the Universe, rather than to an extraordinarily improbable product of chance^[71].

This thesis reflects a profound teleological conviction: the complexity of living things does not arise from an accidental combination of molecules; it reflects a prior inscription in the very laws of the cosmos. Bolloré & Bonnassies connect this position to that of a Creator who designed the laws so that life would inevitably emerge^[72].

What biological fine-tuning adds to the argument

Biological fine-tuning strengthens the cosmological argument on two distinct points:

It is independent: even if one accepted that the cosmic constants are necessary or explicable by a multiverse, the problem of information in DNA and the improbability of the first protein subsist in full. The two levels of fine-tuning converge toward the same conclusion without depending on each other.

It is quantifiable differently: cosmological fine-tuning concerns probabilities of continuous parameters; biological fine-tuning concerns combinatorial probabilities of discrete sequences. Both approaches lead to improbability figures that astronomically exceed the number of atoms in the observable universe (estimated at 10⁸⁰), making any explanation by chance alone rationally untenable.

Beyond the figures and constants, the fine-tuning of the Universe has been recognised, commented on, and sometimes confessed with astonishment by the greatest physicists of the 20th century, including by notoriously materialist or agnostic scholars. It is this concert of testimonies that Michel-Yves Bolloré and Olivier Bonnassies bring together in chapter 8 of Dieu, la science, les preuves^[73] and in chapter 12 (“100 essential quotations”)^[74]. Here are some of the most striking.

Lee Smolin: 1 chance in 10²²⁹ that a randomly drawn universe would contain stars

The materialist physicist Lee Smolin (Perimeter Institute, Waterloo) himself acknowledges:

“How is it that the parameters governing the elementary particles and their interactions are arranged with such a balance that a cosmos as complex and diverse as ours appears? If the Universe is created by a random choice of parameters, the probability that it will contain stars is one chance in 10²²⁹.”^[75]

Richard Feynman: “we do not understand where the numbers come from”

Nobel laureate Richard Feynman (1965), a notorious atheist, admits it without detour:

“We use numbers in all our theories, but we do not understand them, what they are, or where they come from.”^[76]

Paul Davies: “I refuse to believe that the Universe is a fortuitous accident”

The physicist Paul Davies (Arizona State University), laureate of the 1995 Templeton Prize, an agnostic by training, confesses:

“I belong to the group of scientists who do not subscribe to a conventional religion but nevertheless deny that the universe is a purposeless accident. The physical universe is put together with an ingenuity so astonishing that I cannot accept it merely as a brute fact. There must, it seems to me, be a deeper level of explanation. Whether one wishes to call that deeper level ‘God’ is a matter of taste and definition.”^[77]

Paul Dirac: “then there must therefore be a God”

One of the founders of quantum mechanics, Nobel laureate Paul Adrien Maurice Dirac, declared in 1971:

“If physical laws are such that the starting of life has an excessively low probability, so low that it would not be reasonable to suppose that life could have begun by pure chance alone, then there must therefore be a God.”^[78]

Allan Sandage: “There must exist an organising principle”

The American astronomer Allan Sandage (1926-2010), former assistant to Edwin Hubble, laureate of the 1991 Crafoord Prize in Astronomy:

“I find it quite improbable that such order came out of chaos. There has to be some organizing principle. God to me is a mystery but is the explanation for the miracle of existence, why there is something instead of nothing.”^[79]

Steven Weinberg: the admission of a militant atheist

Nobel laureate Steven Weinberg (1933-2021), militant atheist, author of the famous “the more the Universe seems comprehensible, the more it also seems pointless”, is nevertheless forced to concede:

“Life as we know it would be impossible if any one of several physical quantities had slightly different values.”^[80]

Arno Penzias: “a Universe which has an underlying plan”

The 1978 Nobel Prize in Physics, Arno Penzias, co-discoverer with Robert Wilson of the cosmic microwave background, relic of the Big Bang, moved from an agnosticism of Jewish upbringing to an affirmed theistic position:

“Astronomy leads us to a unique event, a universe which was created out of nothing, one with the very delicate balance needed to provide exactly the conditions required to permit life, and one which has an underlying plan.”^[81]

Fred Hoyle: “a super-intellect has monkeyed with physics”

The great British cosmologist Fred Hoyle (1915-2001), historic defender of the steady-state universe and militant atheist, was led by his own prediction of the carbon-12 resonance (see previous section) to publicly evoke a “super-intellect” at work in nature:

“A common sense interpretation of the facts suggests that a superintellect has monkeyed with physics, as well as with chemistry and biology, and that there are no blind forces worth speaking about in nature. The numbers one calculates from the facts seem to me so overwhelming as to put this conclusion almost beyond question.”^[82]

Stephen Hawking: “very finely adjusted to make possible the development of life”

The most famous cosmologist of the 20th century, Stephen Hawking (1942-2018), director of the Centre for Theoretical Cosmology at Cambridge, never became a believer in the confessional sense, but he explicitly acknowledges fine-tuning in A Brief History of Time (1988):

“The values of these numbers seem to have been very finely adjusted to make possible the development of life.”^[83]

Hawking would later propose the multiverse hypothesis and quantum “sum over histories” as an alternative explanation, which does not eliminate the fine-tuning problem (cf. the Boltzmann Brain and universe generator objection above).

George Smoot: “finely orchestrated”

Nobel laureate in Physics George Smoot (Nobel Prize 2006 for the COBE mission, which mapped the fluctuations of the cosmic microwave background and confirmed the existence of the Big Bang) writes, with Keay Davidson in Wrinkles in Time:

“The big bang, the most cataclysmic event we can imagine, on closer inspection appears finely orchestrated.”^[84]

Antony Flew: the conversion of the most famous atheist of the 20th century

One of the most significant cases in contemporary philosophy is the late conversion of Antony Flew (1923-2010), for fifty years reputed as the most influential atheist philosopher in the English-speaking world, author of God and Philosophy (1966) and foundational articles of analytic atheism. In 2004, he publicly announced that he had become a deist, citing cosmological fine-tuning and information in DNA as determining reasons. In There Is a God (HarperOne, 2007), co-written with Roy Abraham Varghese, he writes:

“I have been compelled to acknowledge that the fine-tuning of the universe provides the most convincing empirical evidence I have ever seen that behind the order and complexity of the universe is a creator who must be acknowledged.”^[85]

Flew's conversion is particularly significant because he had no personal interest in changing his mind, and resolved to do so exclusively on the basis of rational arguments, against his own lifelong philosophical tradition.

John Lennox: the analogy of Russia covered with coins up to the Moon

To convey the order of magnitude 1 in 10⁴⁰ that characterises the ratio between the electromagnetic force and the gravitational force, John Lennox (professor of mathematics at Oxford) proposes this pedagogical analogy:

“At the beginning of the Universe, for the chemistry that allows life to exist, the ratio between the electromagnetic force and the force of gravitation had to be adjusted to within 1/10⁴⁰. To give an idea of the precision 1/10⁴⁰, imagine that we covered all of Russia with small coins; then that we built piles of coins over all this territory up to a height equal to the distance to the Moon; then now, let us take a billion systems like this one, finally paint a single coin red, then blindfold a friend and ask him to find it in a single try. The probability that he ‘lands on it’ is of the order of 1/10⁴⁰. It is really a tiny probability.”^[86]

Max Planck: “a conscious and intelligent mind”

The founder of quantum mechanics Max Planck (Nobel Prize 1918), in his 1944 text Das Wesen der Materie (The Nature of Matter):

“All matter originates and exists only by virtue of a force. We must assume behind this force the existence of a conscious and intelligent mind.”^[87]

Freeman Dyson: “the Universe knew we were coming”

The great theoretical physicist Freeman Dyson (1923-2020), of the Institute for Advanced Study at Princeton:

“The more I examine the Universe and the details of its architecture, the more evidence I find that the Universe, in some sense, must have known that we were coming.”^[88]

The accumulation of these testimonies, coming for the most part from Nobel laureates or leading academic figures, a majority of them agnostics or materialists, is in itself one of the most singular scientific phenomena of the 20th century. As Bolloré sums it up: “The fine-tuning of the Universe is no longer disputed by anyone. The only question that remains is that of its interpretation.”^[89], a formula which aims at the existence of the phenomenon in the reference academic literature, not unanimity of interpretations, as the seven objections treated above show.

Contemporary Catholic authors see in these scientific advances a convergence with the doctrine of creation. The defined point of the Church on which they rely is that of the First Vatican Council (constitution Dei Filius, 24 April 1870, ch. 2 and canon 1): God can be known “with certainty by the natural light of human reason from created things”^[90]. It is this rational knowability of God that is defined; the magisterium has, on the other hand, not pronounced by any act on the fine-tuning argument itself. The judgement according to which the atheist position would have become “scientifically untenable” is that of the essayist Olivier Bonnassies, not an act of the magisterium^[91].

Concordist prudence: Fr. Georges Lemaître himself, Catholic priest and father of the Big Bang model, warned against all hasty concordism: cosmology proposes a rational convergence, not a proof of faith, and the two orders must not be confused.

The numerical chronologies cited in this article (age of the universe, seconds after the Big Bang) are those of the current standard cosmological model, presented as such; the position held on the age of the world remains that of the short chronology received from Tradition.

• The existence of God: overview of the rational proofs
• The Kalam cosmological argument: the complementary argument founded on the beginning of the universe
• Did Jesus really exist?: historical proofs
• The resurrection of Jesus: the central event of Christianity