What are Cosmological Arguments?

Cosmological arguments are probably the most discussed and most intriguing area of natural theology. While there are a great variety of areas of philosophy that point towards God’s existence – we find that, for whatever reason, the realm of cosmological arguments seems to bring the most interest from both defenders and opponents of the arguments. Since these arguments are so interesting, it is worthwhile to lay out in detail what exactly these arguments are and what kinds of evidence and argument they draw on.

What Are Cosmological Arguments?

The idea behind cosmological arguments is well-expressed in the book of Romans:

“For since the creation of the world God’s invisible qualities—his eternal power and divine nature—have been clearly seen, being understood from what has been made, so that people are without excuse.” – Romans 1:20, NIV

The key point here is the phrase ‘being understood from what has been made’. The apostle Paul is making the point that by observing the created world, there is a very real sense in which you ought to recognize the handiwork of God.

To see this point more clearly, consider an analogy. Look at the painting below:

“Starry Night,” by Vincent van Gogh, 1889.

Recognize this? This is the famous Starry Night. Now, we know this was painted by Vincent van Gogh. Now, look at the next painting:

“Wheatfield with Crows,” by Vincent van Gogh, 1890.

Now, I think it fairly likely you haven’t seen this painting before. But if you already know Vincent van Gogh from his painting Starry Night, I think you can instantly see that this too is a painting by the same man. You can see the artist in the painting. Van Gogh has a unique style, a style that is instantly recognizable. Even if you didn’t know who he was, you could probably put two paintings of his side by side and immediately know that the same person painted both.

This is the idea Paul is conveying about God. As God is the Creator of the universe, we can see many of God’s qualities by observing the things He has made – just like we can see the qualities of an artist by the paintings they produce. And this is the basic idea behind cosmological arguments. Cosmological arguments are arguments that infer from observations we can make about the structure of the world around us that there must be a being very much like God behind it all.

So, what do these look like? There are several very different types of examples. I’ll go over a few in the rest of the article. Even if you don’t find them convincing, I hope this overview will help convey the very sensible intuitions that lay behind these arguments.

Kalam Cosmological Argument

The atheist philosopher Quentin Smith, writing in The Cambridge Companion to Atheism (2006), observed about what is now called the Kalam cosmological argument (put into its current form by philosopher William Lane Craig):

“A count of the articles in philosophy journals shows that more articles have been published about Craig’s defense of the Kalam argument than have been published about any other philosopher’s contemporary formulation of an argument for God’s existence. Surprisingly, this even holds for Plantinga’s ontological argument and Plantinga’s argument that theism is a rationally acceptable basic belief. The fact that theists and atheists alike “cannot leave Craig’s Kalam argument alone” suggests that it may be an argument of unusual philosophical interest or else has an attractive core of plausibility that keeps philosophers turning back to it and examining it again.”

So this is quite the famous debate! What, then, is the debate about?

The Kalam cosmological argument is named after medieval Islamic theology, within which the argument was developed to a high degree of philosophical sophistication before the modern time. The argument has a shockingly simply formula:

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

How much simpler can it get! Well, the first step is essentially to point out that, as the entirety of science and philosophy show us again and again, events that we observe are caused by something else (even if, as in quantum mechanics, you can’t fully determine what that cause is). Well, if everything in our experience only starts existing when something causes it to exist – and in fact this principle is a fundamental principle is science – then what of the universe? Science appears to point us in the direction of the universe having an absolute beginning in time – the Big Bang. There are also independent philosophical reasons to think that time had a beginning grounded in the paradoxical nature of past infinite timelines, but the point is still the same – it really looks like the universe began. Then if the first point is right this means the universe must have a cause.

The first objection might be that this doesn’t seem to say anything about God… but slow down and think. The conclusion of the argument is that the entire cosmos has a cause outside of itself. When you think about what it means to be a Cause of the universe, you end up with a concept that looks a lot like God – such a Cause would need to, for example, exist beyond space and time and yet have such immense power that the being can cause time itself to come into existence. The sounds a lot like the divine attribute of omnipotence. There are more sophisticated conceptual arguments that show that this Cause must look even more like a monotheistic God, but going in depth into those would bring us too far afield.

Discussing the Kalam argument leads to lots of interesting conversations about the nature of time, science, and the relationship between cause and effect. Lots of interesting stuff to talk about!

The Leibnizian Contingency Argument

The Leibnizian cosmological argument is, like the Kalam and other cosmological arguments, based on observations about the universe in which we live. But unlike the Kalam, this cosmological argument – put forward famously by the co-inventor of calculus Gottfried Wilhelm Leibniz – has as its starting point the distinction between contingent existence and necessary existence. For example, I exist contingently because I could well have not existed. It is entirely possible that my parents never met or never even existed – and so I don’t have to exist. I am contingent. A being that exists necessarily would be the opposite. A thing that exists necessarily (if there are any such things) would be a thing that must exist – it cannot not exist.

Leibniz’ basic insight is that if something exists contingently (if it didn’t have to exist) then there should be some reason why it exists rather than not. The wide variety of ways to express this idea go under the title of the Principle of Sufficient Reason. Leibniz, starting from this idea, observes that the universe appears to be a contingent thing. Attempting to say that the universe could only exist exactly the way it does is very strange – even saying that the must be a universe at all seems rather strange. Leibniz reasons then that for a contingent universe, there should be a reason outside of itself for why it exists. This explanation, Leibniz would say, is God, who exists necessarily.

From the Stanford Encyclopedia of Philosophy article on this version of cosmological arguments, we find the following presented as one form the argument might take:

  1. If it is possible that it is necessary that a supernatural being of some sort exists, then it is necessary that a supernatural being of that sort exists.
  2. It is possible that it is necessary that a supernatural being of some sort exists.
  3. Therefore, it is necessary that this being exists.

Here is a different way of phrasing the same idea, the phrasing used by William Lane Craig:

1. Anything that exists has an explanation of its existence (either in the necessity of its own nature or in an external cause).
2. If the universe has an explanation of its existence, that explanation is God.
3. The universe exists.
4. Therefore, the universe has an explanation of its existence. (from 1, 3)
5. Therefore, the explanation of the existence of the universe is God. (from 2, 4)

Thomistic Cosmological Argument

There are, again, many variations on the idea behind Thomistic cosmological arguments. The general idea goes back to Aquinas’ Five Ways – the five major proofs of God’s existence that the great philosopher and theologian Thomas Aquinas offered. Several of them fall into the category of cosmological argument, but they take a different flavor than the Kalam or Leibnizian arguments. The basic idea of a Thomistic argument is something like this:

“Change is always the effect of a cause. It would stand to reason then that, on the basic principle that all effects have causes, all change has a cause. Since the idea of an infinite regress of causes is senseless, there must be an Uncaused First Cause that is the sufficient reason for why changing things exist at all.”

Aquinas is a bit hard to read, as he uses a very sophisticated and hard to penetrate philosophical jargon. So instead of presenting one of Aquinas’ formulations and his defense, I’ll present an argument based on the nature of cause and effect put forward by modern philosopher Alexander Pruss in his book Infinity, Causation, and Paradox that I have been reading – which is a deeply fascinating book on the philosophy of mathematics, infinities, and causation. Here is how Pruss formulates his argument.

  1. Nothing has an infinite causal history.
  2. There are no causal loops.
  3. Something has a cause.
  4. Therefore, there is an uncaused cause.

What is Pruss’ idea here? For context, this argument is written down in Chapter 9 of his book. What is he doing in the previous eight chapters? He is explaining, analyzing, and defending a position he calls causal finitism. Causal finitism, as Pruss defines it, is the view that if I trace the causes of some event back in time, the total list, which he calls the causal history of the event, is never infinitely long. Pruss reasons that there are only three possible causal histories an even might have – you could have a loop, an infinite backward chain, or a finite backward chain. Pruss argues extensively that there are no infinite backward chains or loops. To understand these arguments, consider the example of loops. An example of a causal loop would be a statement like

X was caused by Y, which was caused by Z, which was caused by X.

If you take things like this seriously, you end up with insane situations like a human being their own great grandparent – which surely is not possible. So, since all causal loops involve something like this, there are no causal loops. The arguments Pruss presents against the infinite histories are more technical and would take much longer to explain – but Pruss puts forward compelling paradoxes and outright contradictions that show up in situations like these as well. Therefore, Pruss, reasons, the only type of causal history that is valid is the finite causal history. This reasoning explains (1) and (2).

Now, certainly the idea of cause and effect is real – so (3) is true. Since all causal chains must come to an end, and since there are such things as causal chains, there exists an end to all causal chains. The end of the chain has to be uncaused – otherwise the chain wouldn’t be at its end yet. Therefore, an uncaused cause exists – and we could argue separately that God seems to be by far the best candidate for what an Uncaused Cause would be like.


Here, I’ve laid out some of the main categories of cosmological argument. To see a much more extensive list of cosmological arguments, check out this video, which goes over 20 different cosmological arguments that are discussed to varying degrees in the philosophy of religion today.

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