An Introduction to Cosmological Arguments for the Existence of God

David W. Agler
6 min readDec 16, 2022


A very brief overview for beginners.

This article was co-written with Ryan Pollock.

We point to causes to explain events. Why is my kitchen floor wet? Because I knocked my cup over. Why isn’t my homework done? Because my roommate distracted me. Why is Jones my senator? Because she won the most votes.

We can ask similar questions on a grander scale: why does the universe exist? Relatedly, why is there something rather than nothing? Supporters of the cosmological argument answer this question: because of God.

Cosmological arguments for God’s existence are arguments that reason from the fact that the universe (or things in the universe) exist to God’s existence. To introduce the most basic form of these arguments, let’s consider two versions of the cosmological argument.

1. The Argument from Causation

St. Thomas Aquinas argued that every physical thing needs a cause, and every cause needs a prior cause that caused that cause, all the way back to a first cause. The computer I am using to type this article was assembled in a factory, the factory itself was constructed by builders, and the builders themselves had parents, the parents had parents, and so on.

A modified version of “St. Thomas Aquinas” by Sandro Botticelli (c. 1482)

What gets these cause-effect chains (“causal chains”) started? Did something within the chain bring itself into existence? That is, is there something that causes its self (“self-caused”)? Aquinas argues this is impossible. Causation involves a cause that is prior to its effect. So, if something caused itself, then that thing would have to exist before it existed, which is absurd.

Could the causal chain be infinite? If the universe were an infinite chain of events, then everything within the chain would have a cause, and there would be no “first cause.” Aquinas also rejects this. If the causal chain did not have a first cause, then how could anything else in the chain come to exist later on? It seems, then, that nothing would exist.

However, Aquinas’ explanation is problematic. If we assume that any causal chain of physical things must have a first cause, then it is true that nothing would exist if there were no first cause. But Aquinas’ job was to prove that causal chains require a first cause. He cannot simply assume it!

2. The Kalām Cosmological Argument

The Kalām Cosmological Argument says that everything that begins to exist has a cause of its existence. The universe began to exist. Therefore, the universe has a cause to its existence.

This argument is minimally persuasive for a few reasons. First, our everyday experience suggests that everything that begins to exist has a cause of its existence. I didn’t simply pop into this world, neither did you, neither did our prehistoric ancestors. We have a beginning. If we have a beginning, then so does the universe.

Second, there is evidence and argument to support the idea that the universe began to exist. First, it is suggested by some of our best scientific theories. The Big Bang theory asserts (contrary to the steady-state or oscillating models) that our expanding universe began in a state of “infinite density” (singularity) roughly 13.82 billion years ago.

Second, not only is it supported by the best science, but also a slew of philosophical arguments. Here is one. Let’s suppose the universe always existed. If so, it has no beginning. If the universe has no beginning, then for any event you choose, there is always an earlier event before that event. And so, there are an infinite number of earlier events before any event you might select. But, there cannot be an infinite number of earlier events. Why? Well, so one argument goes, if there were actual infinite number of earlier events, then there are actual infinites (real-world infinites), and this would imply several absurd results. Let’s mention just one and we will keep it as non-technical as possible.

We can’t count the size of an infinite set but we can compare its size with other infinite sets. One way to do this is by seeing if there is a way of matching up each item from one set with the set of another (a one-to-one-correspondence).

If we can put the sets in a one-to-one correspondence, then the infinite sets are the same size. So, for example, since we can put the positive integers in a one-to-one correspondence with the even integers, the two sets are the same size (or have the same cardinality).

The response is that while this is true of abstract things like numbers, it does not apply to actual (“real world”) objects that occupy space and time like tables, people, and events. Suppose there were an infinite number of apples and this infinite set of apples is composed of two varieties: (1) an infinite number of green apples and (2) an infinite number of red apples. In this case, the total number of apples would be the same size as the total number of red apples. And, if you proceeded to eat thousands and thousands of these red apples (what a stomach ache!), there would remain an infinite number of apples. But, in the real world (not the mathematician’s playground), this is not the case. If collection of apples consists of red and green apples, then the collection of red apples cannot be as large as the collection of apples. And, if you subtract the number of red apples from the total collection of apples, then the size of the collection of apples should decrease.

So, since the idea of actual infinites yields this false result, there cannot be actual infinites. And so, it cannot be the case that the universe always existed. Therefore, the universe began to exist. And so, it must have a cause.

3. Is the First Cause God?

The cosmological argument, at best, only proves that there is a first cause. Why think this first cause is God? Let’s consider some attempts to answer this question.

First, where did the first cause come from? Proponents of these arguments say that the first cause could not be caused by a prior cause because then it would not be the first cause. The first cause cannot cause itself to exist because nothing can cause itself to exist. That leaves just one possibility — the first cause must have existed forever. This does not prove that there is an all-knowing, all-powerful, and all-good being (God), but it does mean that the first cause is utterly unlike anything else since it is eternal (a property typically ascribed to God).

Second, proponents say, an explanation is an answer to a why-question, and there are two kinds of explanation: scientific and personal. A scientific explanation answers why-questions with physical laws and earlier physical states. If asked why my plant has died, one explanation for this is by pointing to the law that plants need water and the events of it not being watered. A personal explanation answers why-questions by appealing to a person’s intentions or desires. Why did my plant die? Because I did not desire to water it. So why did the universe begin? A scientific explanation seems unsatisfactory since scientific explanations appeal to space, time, and physical laws of nature operating in the universe. But such laws don’t exist prior to the universe itself. So, the first cause must be a personal explanation of the universe and, consequently, must be a person (God).

William Lane Craig claims that the universe cannot be infinite because an actual infinite is impossible. Can God be infinite? The traditional attributes of God seem to require this for if God is all-knowing, then God’s knowledge is infinite. God knows everything about this world but also every world God could have created. This would imply that an actual infinite is possible. On this basis, some criticize cosmological arguments for positing a double standard (God can be infinite, but the universe cannot).


Aquinas, Thomas. Summa Theologiae, Questions on God, ed. Leftow, Brian and Davis, Brian. Cambridge, UK: Cambridge University Press, 2006 [1265–1274].

Cheng, Ta-Pei. 2005. Relativity, gravitation, and cosmology. Oxford: Oxford University Press.

Craig, William Lane. 1979. The Kalam Cosmological Argument. New York: Harper & Row Publishers.

Craig, William Lane. 1997. “In Defense of the Kalam Cosmological Argument.” Faith and Philosophy 14: 236–47.

Craig, William Lane, and Quentin Smith. 1995. Theism, Atheism, and Big Bang Cosmology. Oxford: Clarendon Press.

Craig, William, and James D Sinclair. 2009. “The Kalam Cosmological Argument.” In The Blackwell Companion to Natural Theology, edited by J.P. Moreland and William Lane Craig, 101–201. London: Blackwell.

Erasmus, Jacobus and Verhoef, Anne Hendrik. 2015. The Kalam Cosmological Argument and the Infinite God Objection. Sophia 54: 411–427.



David W. Agler

Assistant Teaching Professor - Philosophy. I make logic and philosophy videos at