The Kalam cosmological argument is a modern formulation of the cosmological argument for the existence of God. It is named after the Kalam (medieval Islamic scholasticism) from which many of its key ideas originated. Philosopher and theologian William Lane Craig was principally responsible for revitalising these ideas for modern academic discourse through his book The KalÃÂm Cosmological Argument (1979), as well as other publications.
The argument's central thesis is the metaphysical impossibility of a temporally past-infinite universe and of actual infinities existing in the real world, traced by Craig to 11th-century Persian Muslim scholastic philosopher Al-Ghazali. This feature distinguishes it from other cosmological arguments, such as Aquinas's , which rests on the impossibility of a causally ordered infinite regress, and those of Leibniz and Samuel Clarke, which refer to the principle of sufficient reason.
Since Craig's original publication, the Kalam cosmological argument has elicited public debate between Craig and Graham Oppy, Adolf Grünbaum, J. L. Mackie and Quentin Smith, and has been used in Christian apologetics. According to Michael Martin, the cosmological arguments presented by Craig, Bruce Reichenbach, and Richard Swinburne are "among the most sophisticated and well-argued in contemporary theological philosophy".
The most prominent form of the Kalam cosmological argument, as defended by William Lane Craig, is expressed in two parts, as an initial syllogism followed by further philosophical analysis.
The Kalam cosmological argument is a deductive argument. Therefore, if its premises are true, the conclusion follows necessarily.
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Craig argues that the cause of the universe necessarily embodies specific properties, in being:
Based upon this analysis, he appends a further premise and conclusion:
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Craig appraises the theological significance of the final conclusion:
The origins of the cosmological argument can be traced to classical antiquity, rooted in the concept of the prime mover, introduced by Aristotle. In the 6th century, Syriac Christian theologian John Philoponus (c. 490âÂÂc. 570) presented the first known version of the argument based on the impossibility of an infinite temporal regress, postulating that time itself must have had a beginning.
Like other early Christian commentators, Philoponus disputed the Greek doctrine of the eternity of matter, noting that this was inconsistent with the Judeo-Christian doctrine of creatio ex nihilo. Furthermore, he examined the contradiction between Greek conceptions of past eternity and Aristotle's repudiation of the existence of actual infinities. In 529, he presented his critique, On the Eternity of the World Against Proclus, categorising arguments for the finitude of the past, which underpinned his arguments for the existence of God.
Philoponus's ideas would be developed substantially within the proceedings of medieval Islamic scholasticismâÂÂor kalamâÂÂthrough the 9th and 12th centuries, refined in the 11th century by Al-Ghazali and in the 12th by Ibn Rushd. In his landmark thesis, The Incoherence of the Philosophers, Persian Muslim theologian Al-Ghazali characterised the absurdity of a beginningless universe and of the existence of actual infinities, articulating a prototypical formulation of the modern Kalam cosmological argument:
In the 13th century, the cosmological argument was introduced to medieval Christian theology, wherein it would be examined by St. Bonaventure as well as Thomas Aquinas in his Summa Theologica (I, q.2, a.3) and Summa Contra Gentiles (I, 13). Conceptions of temporal finitism that had been substantiated in Philoponus'sâÂÂand later, Al-Ghazali'sâÂÂwritings inspired energetic debate between Aquinas and Bonaventure, as well as further generations of scholars up until the 18th century. Craig writes:
According to Quentin Smith:
The Kalam cosmological argument has received criticism from philosophers such as J. L. Mackie, Graham Oppy, Adolf Grunbaum, Michael Martin, Quentin Smith, Wes Morriston and Alex Malpass as well as physicists Sean M. Carroll, Lawrence Krauss and Victor Stenger.
Modern discourse encompasses the fields of both philosophy and science (e.g. the fields of quantum physics and cosmology), which Bruce Reichenbach summarises as:
Since the temporal ordering of events is central, the Kalam argument also brings issues of the nature of time into the discussion.
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Craig and James Sinclair offer three reasons to support the first premise, proposing that it is more plausibly true than its negation:
Graham Oppy, J. L. Mackie and Wes Morriston have objected to the intuitiveness of the first premise. Oppy states:
Mackie affirms that there is no good reason to assume a priori that an uncaused beginning of all things is impossible. Moreover, that the Causal Principle cannot be extrapolated to the universe from inductive experience. He appeals to David Hume's thesis (An Enquiry Concerning Human Understanding) that effects without causes can be conceived in the mind, and that what is conceivable in the mind is possible in the real world. This argument has been criticised by Bruce Reichenbach and G.E.M. Anscombe, who point out the phenomenological and logical problems in inferring factual possibility from conceivability. Craig notes:
Morriston asserts that causal laws are physical processes for which we have intuitive knowledge in the context of events within time and space, but that such intuitions do not hold true for the beginning of time itself. He states:
Craig responds that causal laws are unrestricted metaphysical truths that are "not contingent upon the properties, causal powers, and dispositions of the natural kinds of substances which happen to exist", remarking:
Paul Davies is unconvinced that the Causal Principle can be defined consistently in fundamental physics, proposing that the phenomenon of quantum indeterminacy contradicts a deterministic model of cause and effect. Craig concedes that quantum indeterminism contradicts the proposition that every event has a cause. Nonetheless, he maintains it is consistent with the causal premise that "everything that begins to exist has a cause", encompassing the more modest view that objects cannot come into existence entirely devoid of causal conditions. Even if quantum events arise without sufficient prior conditions, he affirms at least some necessary conditions are present:
Wes Morriston inquires whether necessary conditions alone are adequate in defining causation, suggesting further substantiation is necessary when contemplating the causal origin of the universe. For Bruce Reichenbach, the strength of the first premise is grounded in the ontology of quantum indeterminacy. If indeterminism is a fundamental feature of the real world, rather than an epistemic artefact of incomplete knowledge or hidden variables, he suggests its implications for the Causal Principle would be substantially negative.
Craig stresses that the phenomenon of indeterminism is specific to the Copenhagen interpretation of quantum mechanics, remarking that this is only one of several interpretations, some of which are fully deterministicâÂÂmentioning Bohmian mechanicsâÂÂand none of which are as yet known to be true. He concludes that subatomic physics is not a proven exception to the first premise.
Quantum vacuum phenomena are often expounded to be uncaused in origin, referring to quantum indeterminacy governing the vacuum state and semantics that define the zero-point field as nothing, in an ontological sense. Quentin Smith illustrates the example of virtual particles, which appear and disappear through fluctuations in the quantum vacuum, as evidence of uncaused natural phenomena. In his publication, ', Lawrence Krauss proposes that quantum fluctuations can explain how space, time and matter can emerge from 'nothing' (referring to the vacuum state). Michael Martin writes:
David Albert deems the term 'nothing' to be misleading when defining the quantum vacuum. In a critique of Krauss's book, he remarks:
Craig describes the vacuum state as a quantifiable, energetic medium that qualifies as something rather than nothing, rejecting the view of quantum vacuum phenomena as uncaused. On quantum fluctuations, he writes:
Alexander Vilenkin determines that, even in the "absence of space, time and matter", the laws of physics are still present and require explanation, though this state would be "as close to nothing as you can get". He continues:
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For scientific confirmation of the finitude of the past, Craig refers to evidence in cosmology and theoretical physics:
Alexander Vilenkin describes the BordeâÂÂGuthâÂÂVilenkin theorem:
According to Vilenkin and co-author Alan Guth, the past boundary described by the BordeâÂÂGuthâÂÂVilenkin theorem does not necessarily represent a cosmic beginning, instead the beginning of cosmic inflation. Though it "opens the door" for theories other than an absolute beginning, in a 2012 lecture, Vilenkin would discuss problems with alternative theories that would claim to avoid a cosmological beginning (including eternal inflation, cyclic and emergent models) concluding: "All the evidence we have says that the universe had a beginning". In publications, he would conclude that the BordeâÂÂGuthâÂÂVilenkin theorem is sufficient evidence for a beginning of the universe.
Sean Carroll observes that the theorem assumes a classical spacetime, determining it to be incompatible with the extreme energies and densities that define the Planck era of the early universe, where quantum effects become dominant. Instead of describing a cosmic beginning, he remarks that the theorem's boundary defines the point at which classical mechanics of the universe no longer apply:
Craig responds that, if anything exists before the past boundary described by the theorem, it would be a non-classical region described by a yet-to-be-determined theory of quantum gravity. This quantum gravity region must also have a beginning, he stipulates, given that its inherent instability would render any quantum regime impossible to endure indefinitely or exist timelessly and changelessly:
He draws on arguments from Anthony Aguirre and John Kehayias, who write:
As a purely kinematic theoremâÂÂrelying solely on the geometric properties of expanding classical spacetimeâÂÂthe BordeâÂÂGuthâÂÂVilenkin theorem assumes an average rate of cosmic expansion greater than zero (H<sub>avg</sub> > 0) on the basis of a linear arrow of time.
Craig and James Sinclair identify 4 exception conditions that bypass this requirement and evade the theorem:
They contend that these models contradict observational cosmology or confirm the cosmic beginning they were devised to disprove.
According to the emergent universe model, the universe existed in a static phase for an infinite duration, then transitioned spontaneously via quantum tunneling to a dynamic expansion phase. The static phase is metastable and, because it endures over infinite time, the universe overall has an average expansion rate of zero (H<sub>avg</sub> = 0) thereby avoiding the BordeâÂÂGuthâÂÂVilenkin theorem.
Metastability in this context refers to a false vacuum state, which is stable according to classical physics, but unstable at the quantum mechanical level in that it can transition spontaneously via quantum tunneling to a more stable true vacuum state. This transition may trigger cosmic inflation, or conversely, collapse of the universe to a hyperdense state. Vilenkin and Audrey Mithani maintain that the metastable state cannot endure indefinitely. Though an event such as cosmic collapse is highly improbable, they argue that over an infinite duration it becomes a mathematical certainty. If the emergent universe cannot exist indefinitely, then it must have had a beginning.
Responding to Vilenkin and Mithani, Rube Goldberg cosmology postulates an emergent model of spacetime that is fully classical, avoiding a quantum gravity era as well as the problems associated with quantum instability. However, the author notes that its composition comes at the cost of a "long chain of highly ad hoc assumptions, akin to a Rube Goldberg machine".
Bounce cosmology refers to any theoretical framework in which the universe rebounds from a preceding phase of contraction to the current phase of expansion, substituting the initial singularity predicted by classical general relativity with a big bounce.
Cyclic universes proceed through an infinite cycle of expansions and contractions. Though the earliest models proposed no net expansion or contraction (H<sub>avg</sub> = 0), they were noted to be in violation of the second law of thermodynamics given that the universe would eventually reach a state of heat death, rendering an infinite cycle impossible. Paul Steinhardt and Neil Turok suggest that cosmic volume could increase with each cycle, causing entropy dilution sufficient to avert heat death. Vilenkin notes, however, that this would put the universe in a state of net expansion, rendering it subject to the BordeâÂÂGuthâÂÂVilenkin theorem, therefore finite into the past.
De Sitter cosmology describes a universe that contracts for infinite time prior to a point of minimum size, followed by expansion. Though it avoids the BordeâÂÂGuthâÂÂVilenkin theorem by averaging net contraction through time (H<sub>avg</sub> < 0), George Ellis maintains that initial conditions must be inexplicably precise for contraction to rebound into uniform expansion characteristic of the observed universe. This extraordinary fine-tuning must be acausal and assumed as brute fact, he argues, given that it originates in an infinite past. Vilenkin writes:
The AguirreâÂÂGratton model postulates a reversal of time at , with spacetime structured as two cosmic expansions evolving in opposite time directions from a point of minimum size. The universe resembles a de Sitter 'bounce', but classifies as a model of eternal inflation by maintaining an inflationary state at every point in time. Among the model's proponents are Victor J. Stenger, as well as Sean Carroll, who presents it as "proof by construction" that a universe without a beginning is conceivable. Vilenkin pronounces a reversal of time at to make the moment "no less special than a true beginning of the universe." He elaborates to Stenger:
For philosophical evidence of the finitude of the past, Craig refers to:
Correspondingly, he argues:
Variations of these arguments have been presented by philosopher Andrew Loke, who refers to a modified version of Hilbert's Hotel, and Ben Waters, who has published the story of Methuselah's Diary as a refinement of the diary of Tristram Shandy.
Craig maintains that, though it is metaphysically impossible for actual infinities to exist in the real world, they (and the absurdities that attend their existence in the real world) are describable via mathematics, therefore logically possible. He also distinguishes between actual infinities and potential infinities, stating that it is fully possible for potential infinites to exist in the real world, in contrast to the former:
Edward Feser observes that the Kalam cosmological argument is based upon a presentist theory of time in which past and future events do not exist, remarking that this would be incompatible with objections against an eternal past based upon Hilbert's Hotel:
Craig affirms that the simultaneous existence of the enumerated objects is irrelevant, so long as past events have been real, thus instantiated in reality, they can be counted. He refers to a narrative by Aquinas of a blacksmith who, from an eternal past, has used and broken successive hammers. He writes that the discarded hammers need no longer exist to be counted as an actual infinite. Furthermore, that the absurdities attending the existence of actual infinites in reality still apply if the enumerated objects no longer exist:
Feser contends that past events are more analogous to abstract objects than concrete objects, such as rooms and guests relevant to Hilbert's Hotel, noting that it is fully tenable for mathematicians to deal with infinite sets of abstract objects, such as natural numbers. For this, he refers to Aristotle's postulate that denies the existence of time independent of objects that change:
Craig proposes that, though a beginningless past would qualify as an actually infinite series of past events, an endless future would qualify only as a potential infinite, given that future events, unlike past events, are yet to be actualised and merely potential.
Wes Morriston and Alex Malpass argue that this asymmetry is arbitrary. They pronounce that future events that will be actual satisfy the same reality condition as past events that are deemed actual in that they have been. Furthermore, they stipulate that natural numbers can be representative of moments in time. Since the set of natural numbers greater than any given value, x, is always an actual infinite, so too, they argue, must future events beyond any given moment in time be actually infinite. They conclude that, if the Hilbert's Hotel paradox disproves an eternal past, so too must it negate an endless future, contradicting the Judeo-Christian doctrine of eternal life.
Commenting in agreement that future events cannot be actually infinite, Craig responds that this objection begs the question and fails to address the ontological distinction between past and future qualified by the objectivity of temporal becoming under presentism. He writes:
In a critique of Craig's book The KalÃÂm Cosmological Argument, published in 1979, Michael Martin writes:
Martin adds that Craig has not justified his claim of creation ex nihilo, remarking that the universe may have been created from pre-existing material in a timeless or eternal state. Moreover, that Craig takes his argument too far beyond what his premises allow in stating that the creator is greater than the universe. For this, he cites the example of a parent creating a child who eventually becomes greater than he or she.
In the Blackwell Companion to Natural Theology, published in 2009, Craig and James Sinclair present a philosophical analysis of the properties of the cause of the universe, indicating that they follow by entailment from the initial syllogism of the Kalam cosmological argument:
Based upon their conceptual analysis, Craig concludes:
He remarks upon the theological significance of this union of properties:
The Kalam cosmological argument is based on the A-theory of time, also known as the "tensed theory of time" or presentism, in which past and future events do not exist in reality (they have existed, or will exist, but do not exist now) and only the present exists. This is opposed to the B-theory of time, also known as the "tenseless theory of time" or eternalism, in which past, present and future events co-exist and there is no privilege to the present other than as a frame of reference.
Under the A-theory, the passage of time and temporal becoming are objective and real features of the universe, with objects coming into being and going out of being. In the B-theory, temporal passage and becoming are illusions of consciousness. Craig explains:
Craig has defended the A-theory against objections from J. M. E. McTaggart and hybrid AâÂÂB theorists. He refers to the neoâÂÂLorentzian interpretation of the Special Theory of Relativity, which he contends has become tenable in light of recent findings in quantum mechanics concerning Bell's theorem. Similar to Einstein's original interpretation, the Lorentzian view describes a 3-dimensional universe existing through time, with objects in motion demonstrating time dilation and length contraction. However, these relativistic distortions occur relative to a privileged rest frame (an absolute frame of reference for the universe) rather than relative to each observer.
He writes that the Lorentzian interpretation, in postulating an absolute space and absolute time, resolves the fragmentation of reality that characterises Einsteinian relativity, in which observers in relative motion occupy different spaces and times. Importantly, Lorentz's view of time as dynamic, and distinct from space, renders it compatible with the A-theory conception of a tensed universe.
Philosopher Yuri Balashov asserts that both consensus and evidence support Minkowski's interpretation of relativity, which posits a 4D geometric universe inhabited by objects extended in time as well as space. In spurning the notion of a 3D universe existing in time, Minkowskian relativity rejects the A-theory, correlating instead with the B-theory conception of a tenseless spacetime. Balashov remarks:
Craig suggests that Balashov underestimates the challenge to Minkowskian relativity presented by recent findings. He criticises Balashov for adopting a verificationist method that overlooks important metaphysical and theological foundations for the A-theory, declaring that correct interpretation of Special Relativity involves not merely scientific, but also metaphysical, inquiry.
In a 2020 interview, Craig proposed that the Kalam cosmological argument could be adapted to the B-theory of time by:
Under the B-theory, scientific evidence for the finitude of the past would still be valid and the argument as a whole would be tenable, though requiring reformulation to correct for the negation of temporal becoming. Craig articulates a B-theory version of its syllogism:
Philosopher Ben Waters has also argued that the Kalam cosmological argument does not require a commitment to the A-theory.