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STEELMANNING the Kalām Cosmological Argument

Written By: Ryan Leonesio

In the 1970s, American theologian and philosopher William Lane Craig dedicated his doctoral dissertation to reviving an ancient argument for the existence of God, one that seemed particularly resonant amid the scientific advancements of the 20th century. Upon earning his PhD, he expanded this work into his seminal 1979 book, The Kalām Cosmological Argument.1 A cosmological argument, derived from the Greek word kosmos meaning “universe” or “order,” seeks to demonstrate the necessity of a first cause for the cosmos’s existence. The term “kalām,” rooted in Arabic for “speech” or “discourse,” refers to the medieval Islamic theological tradition from which Craig traced the argument’s origins, drawing on insights from long-overlooked philosophers. The argument unfolds deductively as follows: 

As a deductive syllogism, its conclusion logically follows if the premises hold true—though in scientific contexts, premises are often supported by their explanatory power over alternatives rather than absolute proof. What renders the kalām argument particularly compelling is that neither premise explicitly invokes God; instead, they can be evaluated through empirical and philosophical analysis of the material world, with the conclusion implying a transcendent, divine creator. Thus, the argument’s validity hinges on rigorously scrutinizing these two foundational premises.

Whatever Begins to Exist Has a Cause

The first premise of the kalām cosmological argument—that whatever begins to exist has a cause—is by far the less contested premise of the two, as it stands as a bedrock principle of physics and metaphysics. The ancient Greek philosopher Parmenides termed the axiom ex nihilo nihil fit, “out of nothing, nothing comes.”2 In his treatise on metaphysics, The Critique of Pure Reason, Immanuel Kant outlines the groundwork of the universe and necessary principles based on intuitive reasoning and empirical observation, and among these is that every effect has a cause. Kant identifies that “whatever follows or happens, must follow in conformity with a universal rule upon that which was contained in the foregoing state.”3 This is a self-evident truth that aligns with human experience: we never observe objects or events emerging uncaused from absolute non-existence. To deny this would invite absurdity, as it implies that a sports car, for example, could spontaneously appear in one’s garage. Any critique suggesting that quantum fluctuations demonstrate something arising from nothing is misguided. Quantum fluctuations occur within a quantum vacuum, a dynamic system containing quantum fields, vacuum energy, and governed by physical laws—far from being absolute non-existence. To insist that something may arise from nothing, despite this notion having no evidence and directly contradicting the foundational laws of reality, undermines both science and reason. Such epistemic implications would render any disagreement in chemistry, cosmology, logic, etc. valid, simply because anyone could invoke inductive uncertainty. Ultimately, the premise not only withstands scrutiny but offers itself as a coherent foundation absent in rivals.

The Universe Began to Exist

Premise two is by far the most contentious of the two, but is nevertheless strongly substantiated. There are two types of evidence to argue that the universe began to exist: philosophical and scientific. We will begin with the philosophical.

Philosophical Arguments for “The Universe Began to Exist”

Craig’s philosophical arguments address whether the universe can logically be infinite or must have a beginning. They set aside all scientific or religious suppositions and ask, given our understanding of time and laws like causality that govern the natural world, whether the universe must have a beginning or if space, time, matter, and energy could theoretically have existed eternally into the past. Aristotle famously argued that the universe must be eternal because every effect needs a cause, and if we trace this backward, we will never reach a point where an event didn’t have a cause; thus, the universe must stretch eternally into the past. Others, including Craig, argue that implying the universe could extend infinitely into the past is logically absurd. Since the regressive chain of cause and effect holds true and one cannot go infinitely into the past, there must be a cause, and that cause must lie outside the confines of time, space, matter, and energy. This, of course, raises the question: What are the arguments that assert an eternal temporal regress is logically invalid?

Argument #1: In an Infinite Past, We Could Reach the Present

If we examine the way we move through time, it happens as a series of events unfolding one after the next. Each moment, no matter how small, leads sequentially to a subsequent moment. Therefore, if the past were infinite, the present moment could never have been reached. An actual infinite cannot be completed, making the existence of the current moment impossible if it were preceded by an infinite series of successive events. Al-Kindi, a medieval Arab philosopher, argued that “the infinite can neither be traversed nor brought to an end; then the temporally infinite can never be traversed so as to reach a definite time.”4 Similarly, Saadia Gaon, a Jewish philosopher who came shortly after al-Kindi, also emphasized that it is “impossible for existence to have traversed infinity in descending fashion so as to reach us. But if existence had not reached us, we would not have come into being.”5 The argument can be formally represented in a Modus Tollens syllogism as:

Imagine planning a road trip to a specific destination, only to find that the journey requires traversing an infinite number of miles. No matter how fast you drive or how long you travel, you would never arrive at your destination because there would always be an infinite distance left to cover. Similarly, if the past were infinite, it would be akin to an endless journey. No matter how much time has passed, the present moment could never be reached because an infinite amount of time would still need to be traversed. 

Argument #2: An Actual Infinite Cannot Exist

An infinite regress lacks cogency on another similar, yet more general principle—resting on the distinction between potential and actual infinities. Potential infinity refers to a process that could continue indefinitely, such as the addition of numbers, whereas an actual infinite implies a completed totality. 

Since we exist in the present and with each passing second the timeline expands, logical errors naturally arise when fusing these self-evident facts with an infinite temporal expansion. Infinity plus one is. . . infinity? But does that mean before adding one it wasn’t actually infinity? Another absurdity comes to light when comparing different sizes of infinity. For instance, the infinite numbers that range between zero and one are twice as small as the infinite range of numbers between zero and two. But what does that even mean to consider an actual infinite series of numbers to be smaller than another actual infinite series of numbers? Al-Ghazali, an Islamic philosopher during the 11th century, offered a thought experiment, proposing that if all of the planets in the solar system have been in motion for eternity, yet because Earth for example revolves around the sun faster than Mars, how can they both have revolved around the sun infinitely if one moves faster than another? “How could it be,” al-Ghazali writes, “that that which is infinite lacked just one. . . we must call it a self-evident absurdity.”6 While we can conceptualize infinity in a potential sense, al-Ghazali intuitively grasped that differential quantities in actual infinites is by definition absurd. The categorical syllogism is outlined as: 

When Aristotle articulated his laws of causation in his work Physics, he thoroughly established the fundamental principle that every effect requires a cause, a deduction that remains valid. However, it seems that his extension of causality to an infinite temporal regress led to a conflation of potential and actual infinity. By tracing the chain of cause and effect from the present into the past, we encounter a potential infinity. In contrast, positing an infinite past and extrapolating infinitely towards the present, as previously surveyed, commits a categorical error.   

A finite temporal series necessitates an origin, a first cause that is itself uncaused and transcendent, as it cannot be part of the series it initiates.

Scientific Arguments for “The Universe Began to Exist”

Whereas the philosophical arguments for an absolute beginning of the universe rely on logic and reasoning, the scientific arguments focus on observation and theoretical astrophysics to infer, based on current scientific data, that the universe had an absolute beginning in the relatively recent past.

The cornerstone of the scientific case for a cosmic beginning is the observed expansion of the universe. Scientists like Isaac Newton originally proposed in the 18th century that the universe was static.7 However, in the early 20th century, American astronomer Vesto Slipher identified a phenomenon within galaxies known as the Doppler effect.8 A direct example of the Doppler effect can be observed in the changing sound frequencies of a moving police car’s siren. As a police car approaches you, the sound waves from the siren are compressed, resulting in a higher frequency. As the police car drives past, and you now stand behind it, the sound waves expand, creating a lower frequency as the car drives away. Essentially, you can stand the exact same distance in front of or behind a moving police car, and the siren’s sound frequency will always be lower when standing behind, strictly because the car is moving away from you. Slipher detected a similar effect in galaxies, but rather than analyzing frequencies of sound, he analyzed the frequency of light.

Light frequencies propagate as waves, much like sound waves in the Doppler effect. Spectroscopists—scientists who, among other things, study the properties of light—employ various tools to capture and disperse light from distant celestial objects across a spectrum. The composition of observed objects determines where specific light frequencies appear on the spectrum.

As Slipher gazed through his telescope, perhaps anticipating the wavelengths corresponding to the galaxies he was observing, the spectrograph unveiled a revelation that defied a fundamental axiom of the universe. Nearly every light frequency absorbed had shifted from its natural placement on the spectrum—the galaxies were moving. When light shifts toward the blue end of the spectrum, it signifies high frequencies (standing in front of a moving police car). Conversely, light shifted toward the red end of the spectrum indicates a lower frequency (standing behind the moving police car). To Slipher’s astonishment, the frequencies of almost every galaxy had shifted toward the red end of the spectrum—a phenomenon known as the redshift—signifying that not only were the galaxies in motion, but they were moving away from Earth.

By incorporating observational data on redshifts and drawing from the mathematical insights of astrophysics, it was a Belgian priest, Georges Lemaître, who proposed that the universe is expanding.9 It wasn’t long before Lemaître’s model was confirmed. American astronomer, Edwin Hubble, made a series of groundbreaking observations using his state-of-the-art telescope that provided compelling evidence for the expansion of the universe through a correlation between the distance of galaxies and their recessional velocities.10

While the expansion of the universe can be observed, and by back extrapolation it can be inferred that the universe was once much smaller, whether or not the universe had a complete beginning remained unknown. If there was an absolute beginning, known as the Big Bang, the theory predicts two key observations: (1) residual radiation from the initial explosion, like lingering campfire heat; and (2) traces of galaxy formation in that radiation. In 1964, radio astronomers Arno Penzias and Robert Wilson accidentally discovered the Cosmic Microwave Background (CMB), an afterglow matching the first prediction—radiation from some kind of onset “explosion” persisted everywhere.11 Later, in 1989, NASA’s Cosmic Background Explorer (COBE) satellite mapped the CMB, revealing tiny temperature fluctuations—“great galaxy seeds”—that matched predictions for galaxy formation.12 These findings confirmed the Big Bang as the universe’s origin.

Despite widespread acceptance that the universe had a beginning, the topic remains contentious due to debates over whether the Big Bang marked an absolute origin of time, space, matter, and energy. Some argue that the Big Bang was merely the start of our universe, emerging from unknown prior conditions. However, this view simply shifts the question: if time, space, matter, or energy existed before the Big Bang, their origin still requires explanation, deferring the question. One might claim that, while our universe has a beginning, we cannot know if pre-Big Bang time, space, matter, and energy were eternal. This, however, reintroduces the philosophical challenges of an eternal universe, such as the logical impossibilities of an infinite regress. Moreover, compelling scientific evidence supports the Big Bang as an absolute beginning.

Black holes, regions where gravity is so intense that even light cannot escape, help us understand the universe’s beginning. When massive stars exhaust their fuel, they collapse, compressing mass into a tiny volume. According to general relativity, as volume shrinks while mass remains constant, density (mass/volume) skyrockets, approaching infinity at a singularity—a point of infinite density and spacetime curvature where physics breaks down. Stephen Hawking proposed in his PhD thesis that the universe’s origin resembles a black hole singularity. Rewinding cosmic expansion, all matter compresses, volume shrinks, and density soars. By 1973, Hawking, Roger Penrose, and George F. R. Ellis proved mathematically that, despite asymmetries, the universe traces back to such a singularity. Paul Davies notes, “If we extrapolate this prediction to its extreme, we reach a point when all distances in the universe have shrunk to zero.”13

The most definitive evidence comes from a 2003 discovery—the Borde-Guth-Vilenkin (BGV) theorem—which extends beyond standard Big Bang models.14 The theorem proves that any universe with an average expansion rate greater than zero cannot be past-eternal. When you follow the paths of objects, like stars or galaxies, backward through time in our expanding universe, these world-lines—think of them as GPS tracks showing where things move through space and time—reach a starting point after a finite amount of time. Just as it is physically impossible—not due to technological limitations but due to the laws of physics—so too is it impossible for the universe to be extrapolated backward infinitely. This point of impossibility marks the universe’s absolute beginning, not a transition from a prior state.

Therefore, the Universe Has a Cause. 

The kalām cosmological argument concludes that the universe has a cause, as its two premises—whatever begins to exist has a cause, and the universe began to exist—proove to be robustly substantiated. If the premises are true, it necessrialy follows that the universe’s finite beginning demands a transcendent, uncaused cause. In a concluding remark, Craig writes, “On the basis of a conceptual analysis of the conclusion implied by the kalām cosmological argument, we may therefore infer that a personal Creator of the universe exists, who is uncaused, beginningless, changeless, immaterial, timeless, spaceless, and unimaginably powerful. This, as Thomas Aquinas was wont to remark, is what everybody means by ‘God.’”15

  1. William Lane Craig, The Kalām Cosmological Argument (London: Macmillan, 1979). ↩︎
  2. Parmenides’ axiom ex nihilo nihil fit (“out of nothing, nothing comes”) is referenced in his philosophical fragments. See John Burnet, Early Greek Philosophy ↩︎
  3. Immanuel Kant, Critique of Pure Reason, trans. J. M. D. Meiklejohn (London: Henry G. Bohn, 1855). ↩︎
  4. Peter Adamson, Al-Kindi (Oxford: Oxford University Press, 2007).
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  5. Saadia Gaon, Book of Beliefs and Opinions, trans. Samuel Rosenblatt (New Haven: Yale University Press, 1948).
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  6. Al-Ghazali, The Incoherence of the Philosophers, trans. Michael E. Marmura (Provo, UT: Brigham Young University Press, 2000).
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  7. Isaac Newton, Mathematical Principles of Natural Philosophy, trans. I. Bernard Cohen and Anne Whitman (Berkeley: University of California Press, 1999).
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  8. V. M. Slipher, “The Radial Velocity of the Andromeda Nebula,” Lowell Observatory Bulletin 2, no. 58 (1913).
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  9. Georges Lemaître, “A Homogeneous Universe of Constant Mass and Increasing Radius Accounting for the Radial Velocity of Extra-Galactic Nebulae,” Monthly Notices of the Royal Astronomical Society 91 (1931).
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  10. Edwin Hubble, “A Relation between Distance and Radial Velocity among Extra-Galactic Nebulae,” Proceedings of the National Academy of Sciences 15, no. 3 (1929).
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  11. A. Cliff Penzias and R. W. Wilson, “A Measurement of Excess Antenna Temperature at 4080 Mc/s,” Astrophysical Journal 142 (1965).
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  12. George F. Smoot et al., “Structure in the COBE Differential Microwave Radiometer First-Year Maps,” Astrophysical Journal Letters 396, no. 1 (1992).
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  13. Craig, pp. 101-102, quoting P.C.W. Davies, “Space-time Singularities in Cosmology,” in The Study of Time III, eds. J.T. Frase, N. Lawrence, and D. Park (Berlin: Springer, 1978), pp. 78-79. ↩︎
  14. Arvind Borde, Alan H. Guth, and Alexander Vilenkin, “Inflationary Spacetimes Are Not Past-Complete,” Physical Review Letters 90, no. 15 (2003).
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  15. William Lane Craig, Reasonable Faith: Christian Truth and Apologetics, 3rd ed. (Wheaton, IL: Crossway, 2008). ↩︎

Further Resources

Books

  1. Al-Ghazali, The Incoherence of the Philosophers, trans. Michael E. Marmura (Provo, UT: Brigham Young University Press, 2000).
  2. William Lane Craig, The Kalām Cosmological Argument (London: Macmillan, 1979).
  3. William Lane Craig, Reasonable Faith: Christian Truth and Apologetics, 3rd ed. (Wheaton, IL: Crossway, 2008).
  4. William Lane Craig and J. P. Moreland, eds., The Blackwell Companion to Natural Theology (Oxford: Wiley-Blackwell, 2009).
  5. Paul Davies, The Mind of God: The Scientific Basis for a Rational World (New York: Simon & Schuster, 1992).
  6. Stephen C. Meyer, Return of the God Hypothesis: Three Scientific Discoveries That Reveal the Mind Behind the Universe (New York: HarperOne, 2021).

Online Resources

  1. Reasonable Faith (www.reasonablefaith.org).