People often wonder what the cause of the universe was. Some claim that it must have been god, since everything natural has some cause. But under most models of the universe this question is meaningless, for reasons I will explain below.
But first let me detail a theory about the universe’s origin in which the question does have a meaning. In describing this case I am using the term “universe” to denote all observable, or possibly observable, space and time, and not to mean the sum total of all space and time, which is how I will use it later. Given this definition of universe some theorize that the universe we know was originally the extension of another “parent” universe. Consider a flat and uneventful universe. Then suddenly a small region begins to expand at a fast, inflationary rate. (Of course “suddenly” sweeps a lot of complicated detail under the rug, detail that is irrelevant to our investigations here.) If this patch of space expanded fast enough it could form a kind of bubble, in which matter and energy inside could not interact with matter and energy outside because of the newly created distance between them (if two points move away from each other at light speed they cannot interact). It is possible that we are living in such a bubble. And under such a model of the universe it makes perfect sense to ask what the cause of the big bang (the initial burst of inflation that formed the bubble) is, because there are preceding moments in which something must have triggered the big bang.
But this is only one theory about the origin of the universe, and in some ways it leaves the question unanswered, because if we mean by universe the totality of space and time, then we might still wonder about the origin of the parent universe that our bubble sprang from (although, since the parent universe isn’t itself a bubble, it may have no beginning, existing eternally). And there are many models of the universe in which space and time (at least the dimensions that we are familiar with) exist only as part of it (unlike the bubble universe model, in which the dimensions of space and time we are familiar with are simply a part of the parent universe’s space and time dimensions). Given such a model it makes no sense to ask what the cause of the universe (or more particularly, the big bang) was. This is because the notion of causation is essentially defined in terms of time. When we look for a cause we look for states of affairs prior in time without which our effect in question would not have come about. But, if time exists only as part of our universe, then it makes no sense to ask what the cause is because that would require moments of time prior to the creation of the universe, and under such a model there are no such moments. It would be like looking for a point more south than the South Pole.
Now we might still search for the reasons for certain phenomena associated with the beginning of the universe. For example, there are several “cosmological constants” each of which has a certain value. Why do they have one value instead of another? Certainly we can search for a reason why they have these values. Perhaps it is not possible for them to have other values, or perhaps there are a multitude of universes, each with its own set of cosmological constants. But neither of these explanations are causes for the values of the cosmological constants. Likewise we might try to discover why the universe exists. It is hard to imagine where an investigation of this question could even begin, but there are models that attempt to develop some explanation. Again, perhaps all possible universes must exist.
Let me return briefly then3to the “first cause” argument, which is one of the reasons I have developed the above thoughts regarding the cause of the universe. The first cause argument states that everything must have a cause, the universe too, and therefore that god exists, to fill the role of the missing cause for the universe. Now, as I have shown above, this doesn’t make sense under all models of the universe, when we assume that space-time doesn’t exist outside the universe. But, even under a model of the universe where the big bang does have a cause, it isn’t a good idea to call that cause god, since all you know about it is that it is the cause of the universe, not that it has any of the powers usually attributed to god. For all we know the “first cause” (where such a thing makes sense) could be a time-traveling monkey with a barrel of antimatter, and I don’t think you would want to call the monkey god.