The Kalam Cosmological Argument

By David P. Diaz, Ed.D.



Spiral galaxy

There are few, if any, subjects more contentious than that of the existence of God. Either God exists and created the universe, or he does not and can be safely disregarded. To commit one’s life to a God who is not there is, at best, a salve for one’s fear of the unknown and, at worst, a delusion of epic proportions.

Skeptics have mostly believed that the universe has either always existed or sprang up without cause from nothing.[1] They often suggest that the notion that a supernatural entity could have caused the universe is suspect thanks to the principle of sufficient reason. This principle affirms that everything that exists must have a reason, cause, or ground.[2] In other words, if everything needs a reason, cause, or ground, the skeptic might well ask, “What caused God?”

Thomas Aquinas (1225–1274 AD), perhaps the most influential theologian of the Middle Ages, argued that only finite, limited, contingent[3] things need a cause.[4] According to Aquinas, a regression of causes can legitimately stop at an uncaused Causer of all finite things: God. For Aquinas, God is a necessary being[5] that needs no cause.[6] However, many skeptics think they can simply circumvent this line of reasoning by assigning the title of necessary being to the material universe itself. Thus, one could say that, like God, the material universe is eternal, uncaused, and, therefore, serves as its own sufficient reason. Indeed, atheists often regard the universe as a necessary being, and thus claim that the universe needs no other cause. In other words, there is no need for the God hypothesis.

One way to address this counterclaim is to demonstrate that the universe likely had a cause for its existence. This would mean that all phenomena in the universe, including the universe itself, need a cause. The rest of this essay presents an argument that the universe had a cause of its existence.

The Kalam Cosmological Argument

The kalam cosmological argument does not attempt to prove the existence of God, let alone the existence of the Christian God. Instead, the kalam argument endeavors to demonstrate the likelihood that the universe began to exist a finite time ago.[7] In other words, the argument aims to show that the universe is conditional; its existence depends on something other than itself. Therefore, the universe must have been caused by, or arisen from, something else.

The kalam argument is a response to the claim that any appeal to God is unnecessary because the universe has always existed. For those who believe the universe has always existed (or those who think it came into existence uncaused from nothing), the kalam argument represents a crucial first step in understanding the rational implications of such a view. If it can be shown that the universe had a beginning, we can move on to “what” or “who” was responsible for its coming into being.

The kalam cosmological argument is nothing if not simple. It goes like this:[8]

  1. Whatever begins to exist has a cause for its existence.
  2. The universe began to exist.
  3. Therefore, the universe had a cause for its existence.

Defense of the First Premise

Causality is a universal part of human experience, a rational norm that seems to be self-evident or reducible to the self-evident. Premise 1 tells us that everything that comes into existence has a cause. But what could have caused the universe? Could it have simply sprung into existence from nothing whatsoever? No! And it is essential to understand why the universe cannot arise from nothing.

Though nothingness may be an idea that we can think about and perhaps even formulate a concept of in our minds, it has no existential reality, no properties that would mark it as something that exists in the real world. Indeed, the principle of negative causality tells us:

Nothing cannot cause something. Only being can cause being. Nothing does not exist, and only what exists can cause existence since the very concept of “cause” implies an existing thing that has the power to affect another. From absolutely nothing comes absolutely nothing.[9]

Scientists who claim to have generated something from nothing in a lab are mistaken. The “nothing” in these experimental settings is always “something” in disguise. Fields, forces, waves, vacuums, energy, etc., are all part of the physical world and represent different types of “something” rather than “nothing.”

Some will tell us that quantum indeterminacy suggests that subatomic particles pop into existence from nothing. However, indeterminacy in this sense does not mean that the particles are uncaused. Since the process appears to be guided by the laws of quantum mechanics, it seems plausible to assume a causal principle at work.

David Hume had doubts about causality. He thought that since one can imagine circumstances where something can come into existence without a cause, then it must be possible in reality. Hume concluded: “Therefore, one might conclude that it is possible that a brick pops into existence uncaused.”[10]

However, the defender of causality can question that mere imagination can be responsible for actual existence. As Alexander Pruss points out, there is a difference between imagining something without its cause and imagining something along with its cause.[11] For example, when we imagine an empty room, we conceptualize it in a way that approximates how it would generally appear in our world. So, we might imagine a room with four walls, a ceiling, a floor, and without furniture. But it is unlikely that we would imagine an empty room without air or as a quantum vacuum state. As Pruss suggests, there is no reason to think we can imagine a vacuum.[12]

Therefore, we might also question whether someone could imagine a brick that suddenly appears without cause. To do that, one must imagine every possible cause (including those that are impossible or missing). Even if one imagines a series of possible images, this says “little or nothing about the ontological possibility of things materializing out of nothing.”[13]

In the end, even Hume had to acknowledge that his academic denial of causality couldn’t remove his belief that it was true. Said Hume: “But allow me to tell you that I never asserted so absurd a Proposition as that anything might arise without a cause: I only maintain’d, that our Certainty of Falshood of that Proposition proceeded neither from Intuition nor Demonstration; but from another Source.”[14]

The notion that something can be caused by nothing not only contradicts human experience and intuition but is also contrary to science, which seeks causal explanations for all events. For every effect, there must have been some action (cause) that moved or changed an existing thing from an initial state of affairs into some other state. Therefore, the idea that something (i.e., that which exists) can be caused by nothing (i.e., that which does not exist) is fanciful.

Defense of the Second Premise

Did the universe have a beginning? Many believe that our universe is infinite—that it has always existed and, therefore, needed no cause. In support of premise 2, the kalam argument puts forth two independent philosophical arguments and two scientific confirmations.

Actual versus Potential Infinite

To fully appreciate the kalam argument’s second premise, one must first understand the concepts of potential and actual infinity. An understanding of these two concepts will explain whether an infinite or eternal universe is actually possible.

A potential infinite is a set of things (e.g., numbers, days, events, etc.) that continue incrementally toward infinity but never arrive. A potential infinite represents a counting process that is finite at any point along the way but never reaches a final (or initial) cause. So, if you are counting the days into an infinite past, you will never finish counting back to the first day because a potential infinite never becomes an actual infinite. Of course, this simply won’t do as an explanation for an infinitely existing universe because it leads to an infinite regress of causes, which does not concur with the findings of either current science or rational thought (as explained below).

On the other hand, an actual infinite is a (hypothetically) completed group of things with an infinite number of members. In other words, the set is complete; it always and everywhere consists of an infinite number of items. While this concept appears in certain types of mathematics (i.e., set theory), an actually infinite number of things most likely cannot exist in the real world because this outcome would reduce to an absurdity—the implication of which will be explained in the arguments below.

The First Supporting Argument

The first supporting argument is this: An actually infinite number of things cannot exist. To explain why this is true, it helps to assume—for the sake of argument—that an actual infinite can exist and then show why this results in absurd consequences.

Consider a hypothetical library with an assumed actual infinite number of red and black books.[15] The number of members can never change in an actually infinite set because it is always infinite. Therefore, no matter what happens, the library will always have a completed infinite set of books. While it may seem contradictory to say that there are as many red books as red and black books combined, this is the claim for an actually infinite set of red and black books. Moreover, if one removes all the black books from the library, there will still be an infinite number of books in the collection.

Let us now say that each book in the library has an infinite number of pages. In an actually infinite library, there would be just as many pages in the first book as in the entire collection. One can readily see that it makes no sense to say there is the same number of pages in one book as in all the others combined, but such an outcome would be guaranteed in an actually infinite set.

The above examples demonstrate the futility of the concept of actual infinity for describing things in the real world, especially when proposed as an explanation of an infinite universe. While it may serve as an accepted concept in set theory, it is unlikely that an actually infinite set has a complement in the physical world we experience. In other words, it is most likely impossible for an actual infinite to be instantiated in the real world.

The Second Supporting Argument

The second supporting argument is this: It is impossible to form an actual infinite by successive addition. If one starts by adding one number at a time or working our way backward one day, one month, or one year at a time, one can never reach an actual infinite through successive addition; one can always add another number (i.e., day, month, year). As mentioned above, this leads to an infinite regress or a never-ending series of causes (i.e., a potential infinite).

So, what is the practical problem of never arriving at an actual infinite through successive addition? Picture this: For each event occurring at the present moment, (1) There was a cause, and for that event, (2) there was another cause, which resulted from (3) another cause, which was brought about by (4) another cause, and so on into the never-ending stream of past events. The chain of antecedent causes can be traced backward but never reaches the first cause because there will always be one more cause to add to the chain. But the problem is this: If just one of these past events has not already happened (i.e., been caused or actualized), then the present moment could never have occurred. Any chain of events must have a first member because, without a first cause, there could be no second, third, or nth cause. To actualize an event in the present, each past event has to have already occurred. But this is impossible because an infinite regression of causes can have no first cause.

Thus, based on the two philosophical arguments above, the universe could not be actually infinite; it must have had a beginning. But the kalam argument does not end there. Two scientific confirmations add explanatory scope and power to the two philosophical arguments.

The First Scientific Confirmation

The first scientific confirmation that the universe began to exist comes from expansion theory. This theory has its roots in the works of Alexander Friedmann and Georges Lemaître, who, applying the general theory of relativity, predicted that space, as it continues to expand, will become less and less dense. For our purposes, the implication of this finding is this: If you reverse the expansion process, you will eventually arrive at a fully contracted beginning where the universe would be compressed into the highest possible density in the smallest possible space. This condensed state of matter, the initial singularity, constituted the universe’s beginning.[16]

In 1929, Edwin Hubble—an American astronomer—added experimental support to expansion theory by demonstrating that the light at the far end of galaxies is shifting toward the red end of the spectrum, which indicates that the light sources are receding from view. No matter which direction one looks, distant galaxies are racing apart. And, if the universe is expanding, it must have once existed in a contracted state. Hubble’s observations pointed to a time in the distant past when the universe was incredibly small and dense. The subsequent eruption has been referred to as the big bang.[17] Thus, expansion theory provides evidence that the universe had a beginning and hence, a cause.

One spinoff of expansion theory points to a contracting universe that starts with a big bang and ends with a “big crunch.” In this scenario, the universe will stop expanding and eventually collapse. In this case, the universe will suffer death by sudden obliteration, or as Davies puts it: “The big crunch is like the big bang in reverse.”[18] While we may find out in the future that such a theory is true, this would not change the likelihood that our universe had a beginning, and if and when it crunches, this will represent the end of space, time, and matter.

A more recent update to expansion theory—the theory of dark energy—asserts that the expansion rate is now speeding up. Dark energy, which is thought to permeate all of space—comprising approximately 70 percent of the universe’s total energy—acts like a vacuum force that allows space to expand more and more rapidly. If true, this would mean that the universe will likely expand forever and with increasing speed.[19] And yet, this theory, too, points to a universe that had a beginning.

Finally, the Borde-Guth-Vilenkin theorem proves that classical space-time, under a single, very general condition, cannot be extended to past infinity but must reach a boundary at some point in the finite past. In an article titled “The Beginning of the Universe,” physicist Alexander Vilenkin states: “if the universe is, on average, expanding, then its history cannot be indefinitely continued into the past.”[20] In answering the question, “Did the universe have a beginning?” Vilenkin says, “It probably did.” At least, he concludes, “We have no viable models for an eternal universe.”[21]

The Second Scientific Confirmation

The second scientific confirmation that the universe began to exist comes from the second law of thermodynamics. In a closed system, all substances will eventually reach a state of maximum disorder (i.e., entropy) and thermodynamic equilibrium.[22] One of the implications of this theory is that the universe will eventually run out of thermodynamic free energy, and, in that case, the universe will end in heat death.[23] In other words, our universe not only had a beginning at a finite point in the past but will eventually become inert at some point in the future. In this scenario, if the universe extended infinitely into the past, it would have long since reached heat death, and we would not be around to contemplate it. The fact that it hasn’t yet reached maximum entropy means that the universe must have had a beginning.

According to theoretical physicist Sabine Hossenfelder, the central problem with studying our own universe is observation and testing.[25] There is a limit to how far we can see in our universe; nothing can travel through space faster than the speed of light. However, while nothing can travel through space faster than the speed of light, space itself has no such limit. Thus, the edges of our universe could be expanding away from us at faster-than-light speed. If so, it would mean that the light at the outer boundary of observation would never reach us. This boundary is called the “cosmological horizon” and represents the furthest possible limit from which we could retrieve information about the universe.

Many physicists have noted accumulating evidence supporting multiple parallel universes (“many-worlds” or “multiverse”). Many worlds and other multiverse theories have one glaring feature in common; they take us far afield from the historical foundations of science.[24] As a result, it may be difficult, if at all possible, to prove the truth of the existence of the multiverse. Says Hossenfelder, proposed multiverses are “causally disconnected from us.”[26] Thus, there is simply no way to observe them and, therefore, no way of testing the validity of the theories. After all, how would one test a hypothesis regarding other possible universes when there would be no data forthcoming? Hossenfelder concludes: “The vast majority of multiverse ideas are presently untestable, and will remain so eternally.”[27] Thus, purely theoretical constructs, like the multiverse, can never be explained scientifically. Instead, they must be based on numerous experimentally unsupported assumptions and, ultimately, accepted solely by trusting the predictive power of the theory in question.

Even if some theory of a multiverse turns out to be proven true, it would not only be compatible with theism, but theism may provide a better explanation for the multiverse than naturalism. The multiverse may be more compatible with theism because an unlimited set of universes is more commensurate with an unbounded cause (i.e., God) than with a cause that is random. Since there is no evidence or reason to believe that the multiverse must be randomly ordered, and since our own universe is finely tuned for life, it seems more likely that God has created a world ensemble that is designed to support life.

In summary, based on philosophical arguments and scientific confirmations, there is good reason to believe that the universe had a beginning. If the premises of the kalam cosmological argument are true, the conclusionthe universe had a cause for its existencefollows necessarily.


The limited scope of the present essay will allow me to go no further. The reader should nevertheless reflect on and appreciate the magnitude of the conclusion that the universe was caused to exist. That something caused the vastness of what we know as the “universe” should tell us something about the nature of that cause. It means that something transcendent to the universe brought it into existence. The universe couldn’t have caused itself, nor could it have always existed, nor did it suddenly materialize out of nothing, but it must have been caused by something other.

The kalam argument proper doesn’t address the question of who or what caused the universe. Nevertheless, its conclusion—the universe must have been caused—is consistent with the claim that God created the universe. In other words, there is nothing in the philosophical or scientific evidence that precludes the existence of God, and there is good reason to believe that something outside the universe caused the universe.

About the Author

David P. Diaz, Ed.D. is an author, retired college professor, and the publisher of the Things I Believe Project. His writings have spanned the gamut from peer-reviewed technical articles to his memoir, which won the 2006 American Book Award. Dr. Diaz holds Bachelor’s and Master of Science degrees from California Polytechnic State University and a doctoral degree in education from Nova Southeastern University.


[1] For this paper, I am defining “nothing” as precisely that—no-thing. It is the complete opposite of something (substance); it has no essence, form, and/or properties and, therefore, does not exist.

[2] Yitzhak Y. Melamed and Martin Lin, “Principle of Sufficient Reason,” The Stanford Encyclopedia of Philosophy (Summer 2021 Edition), Edward N. Zalta (ed.),

[3] Contingent or finite things are those that could not have existed on their own (i.e., have the potential to not exist) and are, therefore, dependent on something else for their existence.

[4] Thomas Aquinas, Summa Theologica. Vol. 1. Translated by Fathers of the English Dominican Province (Westminster, MD: Christian Classics, 1981), Pt. 1 Q2 Art. 3 (third way).

[5] A necessary being is one that could not have failed to exist. In other words, a necessary being is one that cannot not exist and, therefore, serves as the cause of all other things that exist.

[6] Aquinas, Summa Theologica, Pt. 1 Q2 Art.3.

[7] The kalam cosmological argument saw its foundations in the work of Christian philosopher John Philoponus (AD 490–570) and became popular among Arabic philosophers in the late Middle Ages. More recently, it has been developed further by William Lane Craig, The Kalam Cosmological Argument (Eugene, OR: Wipf and Stock Publishers, 2000).

[8] There are different statements of the kalam argument; this is, I think, its simplest form. This formulation of the argument comes from Craig, The Kalam Cosmological Argument, 63.

[9] Norman L Geisler, The Big Book of Christian Apologetics: an A to Z Guide (Grand Rapids, MI: Baker Books, 2012), 171.

[10] As cited in Alexander R. Pruss, “The Leibnizian Cosmological Argument,” in The Blackwell Companion to Natural Theology, ed. William Lane Craig, and James Porter Moreland (Malden, MA: Wiley-Blackwell a John Wiley & Sons, Ltd., Publication, 2012), 47.

[11] Ibid.

[12] Ibid.

[13] Douglas Groothuis, Christian Apologetics: A Comprehensive Case for Biblical Faith (Downers Grove, IL: Intervarsity Press, 2022), 208.

[14] As cited in Craig, The Kalam Cosmological Argument, 168.

[15] From J. P. Moreland, Scaling the Secular City: A Defense of Christianity (Grand Rapids, MI: Baker Book House, 1987), 23.

[16] A singularity is “a point at which a function takes an infinite value, especially in space-time when matter is infinitely dense, as at the centre of a black hole” (Oxford Living Dictionaries, s.v. “singularity”). Infinite, in this sense, refers to the point where the laws of physics break down. That point represents the boundary of time in which space no longer exists. Some quantum cosmology models introduce “imaginary numbers” for the time variable in the Standard gravitational equations. This effectively eliminates a singularity in the model. However, it does not contradict the assertion that the universe had a beginning. There would still be a beginning, albeit without a singularity. For further discussion of a singularity, see William Lane Craig and James D. Sinclair, “The Kalam Cosmological Argument,” in The Blackwell Companion to Natural Theology, ed. William Lane Craig, and James Porter Moreland (Malden, MA: Wiley-Blackwell a John Wiley & Sons, Ltd., Publication, 2012), 129–30.

[17] Although English astrophysicist Sir Fred Hoyle (1915–2001) coined the term big bang on a BBC radio program, he rejected the theory as an unlikely explanation of the beginning of the universe.

[18] Paul Davies, God and the New Physics (New York, NY: Simon & Schuster, 1984), 205.

[19] K. R. Dienes, “Rethinking the Rules of Reality,” presented at University of Arizona lecture series 2017 Rethinking Reality, June 12, 2017.

[20] Alexander Vilenkin, “The Beginning of the Universe,” Inference: International Review of Science 1, no. 4 (2015),

[21] Ibid.

[22] A closed system refers to a universe that has no mass being fed into or out of it. The universe has finite mass and contains sufficient density/gravitational force to stop (or perhaps reverse) the expansion that commenced at the big bang.

[23] For more on the heat death of the universe, see “Heat Death of the Universe,” Wikipedia,

[24] Four levels of the multiverse have been distinguished: Level 1: space beyond the observable universe. Level 2: “bubble” universes spawned in inflationary cosmology. Level 3: parallel “many-worlds.” Level 4: an all-encompassing version where mathematically possible existence is equivalent to actual physical existence. See W. David Beck and Max Andrews, “God and the Multiverse,” Philosophia Christi 16, no. 1 (2014): pp. 101-115,, 104–06.

[25] Sabine Hossenfelder, Lost in Math: How Beauty Leads Physics Astray (New York, NY: Basic Books, 2018).

[26] Ibid., 101.

[27] Hossenfelder appropriately qualifies her statement: “The existing predictions demonstrate that the multiverse is in principle amenable to experimental test, but these tests are useful only for very specific scenarios” (p. 107).

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