On the Origin of the Universe: A Survey of Explanations

How many explanations are there for the origin of the universe? Not many, it turns out. I'm going to suggest that there are three basic explanations. I'm not going to argue in favor of any one of these; I just want to survey the ontological landscape in regards to the origin of the universe. To do this, I'm going to present three dilemmas and comment on each one.

Note that I'm taking for granted that our universe isn't eternal, i.e., that it didn't always exist. This is consistent with the view that the universe began with a big bang nearly 14 billion years ago. Let's begin, then, with our first dilemma: given that the universe came into being, it either (a) came into being uncaused or (b) came into being from a prior cause. Option (a) seems to be nonsensical; if nothing existed in the past, then nothing would exist now, because nothingness has no potential to cause anything. Nonetheless, David Hume argued that the idea of something coming into being uncaused cannot be demonstrated to be false or logically incoherent. In fact, he argued that it is logically possible for something to come into being from nothing, because we can conceive of, for example, a rabbit simply popping into existence without an antecedent cause. Points in favor of (b) are that it is consistent with our understanding of cause-and-effect and that "whatever begins to exist has a cause of its existence" is a key principle of rational thought. We make intellectual progress by investigating the causes of things, and it seems arbitrary to suggest that the universe should be an exception.

Assuming, then, that the universe has a cause, here is our second dilemma: either (c) the cause of the universe is itself uncaused or (d) the cause of the universe had a cause. Option (c) leads us back to our points about (a). Option (d) leads us to the problem of infinite regress. Suppose that the cause of the universe itself had a cause; does the cause of the cause of the universe have a cause? If so, then does it, too, have a cause?

Indeed, this sets up our third dilemma: either (e) the chain of causes leading to the origin of the universe goes on forever or (f) the chain of causes leading to the origin of the universe does not go on forever. Since Georg Cantor's work in set theory and infinity in the 19th century, no one argues that (e) is logically impossible, that is, no one argues that the idea of an actually infinite set entails a contradiction. Nonetheless, one objection to (e) is that even if we can explain the existence of any member of an infinite set by pointing to a prior member, we do not have an explanation for why the entire set exists. This was Gottfried Wilhelm von Leibniz's critique of (e). He held strongly to the Principle of Sufficient Reason: for every fact F, there must be an explanation why F is the case. Suppose PSR is true and that it is a fact that our universe is preceded by an actually infinite set of causes. Leibniz would say that such a fact needs a sufficient reason, i.e., an explanation for why it is the case. Not surprisingly, criticisms of Leibniz's argument hinge on the question of why we should accept PSR. No one disputes that PSR is a rational principle with intuitive appeal, but the key issue is whether or not it can be demonstrated to be true.

A second objection to (e) is that although an actually infinite set of causes is logically possible, counter-intuitive paradoxes would result if such a set physically existed. Saint Bonaventure tried to demonstrate this with an argument similar to the following.

Let's first think about non-physical infinite sets. In particular, let's think about the set of all odd numbers and the set of all even numbers. Each of these sets is actually infinite, that is, each set is made up of an infinite number of numbers. It's not hard to imagine that every odd number in the odd set can be paired with an even number in the even set, ad infinitum. So 1 can be paired with 2, 3 with 4, 5 with 6, and so on. What's important here is that no counter-intuitive paradoxes occur because of this.

Now let's think about infinite sets that might physically exist. For example, imagine the existence of a solar system with a planet and moon such that the planet revolves around the sun once for every three times that the moon revolves around the planet. So each revolution of the planet pairs up with three revolutions of the moon. So the set of moon revolutions would seem to have more members than the set of planet revolutions. However, suppose that the number of revolutions of both the planet and moon are actually infinite. This means that every single revolution of the moon can be paired off with a single revolution of the planet, ad infinitum. No moon revolution is without a member that it can pair up with in the set of planet revolutions. Why is this counter-intuitive? Because it seems that the number of moon revolutions should exceed the number of planet revolutions. Whether or not these counter-intuitive paradoxes mean that an actually infinite set cannot physically exist is a key question in the philosophy of infinity.

If (f) is the case, then it follows that there is a first cause that stops the infinite regress of cause-and-effect. Moreover, if it's not the case that this first cause came into being from nothing and it's not the case that the first cause was preceded by an infinity of causes, then this first cause has always existed. Hence, when all is said and done, there are three explanations for the origin of the universe:

1. There is an infinite regress of causes-and-effects leading to the origin of our universe.
2. The universe came into being uncaused.
3. There is a first cause of the universe (or of the finite set of causes leading to the origin of the universe).

The main issues in regards to 1 are whether or not an infinite regress can physically exist and whether or not such a regress, if it does physically exist, requires an explanation. The key issue in regards to 2 is whether or not it makes sense to say that something can come into existence without a cause. Finally, 3 hinges on 1 and 2 not being the case; hence, proponents of 3 will want to show that 1 and 2 are not plausible.

What I think is interesting about this is that it demonstrates the power of philosophy. The origin of the universe seems like a daunting problem, but it is not an intractable one; we can understand the basic positions, as well as the key issues in defending each position. If nothing else, philosophy maps the logical terrain of any given problem, highlighting the major positions and arguments in regards to that problem.