In my previous post, I linked to seven Closer to Truth videos of me spouting about free will, Gödel’s Theorem, black holes, etc. etc. I also mentioned that there was a segment of me talking about why the universe exists that for some reason they didn’t put up. Commenter mjgeddes wrote, “Would have liked to hear your views on the existence of the universe question,” so I answered in another comment.
But then I thought about it some more, and it seemed inappropriate to me that my considered statement about why the universe exists should only be available as part of a comment thread on my blog. At the very least, I thought, such a thing ought to be a top-level post.
So, without further ado:
My view is that, if we want to make mental peace with the “Why does the universe exist?” question, the key thing we need to do is forget about the universe for a while, and just focus on the meaning of the word “why.” I.e., when we ask a why-question, what kind of answer are we looking for, what kind of answer would make us happy?
Notice, in particular, that there are hundreds of other why-questions, not nearly as prestigious as the universe one, yet that seem just as vertiginously unanswerable. E.g., why is 5 a prime number? Why does “cat” have 3 letters?
Now, the best account of “why”—and of explanation and causality—that I know about is the interventionist account, as developed for example in Judea Pearl’s work. In that account, to ask “Why is X true?” is simply to ask: “What could we have changed in order to make X false?” I.e., in the causal network of reality, what are the levers that turn X on or off?
This question can sometimes make sense even in pure math. For example: “Why is this theorem true?” “It’s true only because we’re working over the complex numbers. The analogous statement about real numbers is false.” A perfectly good interventionist answer.
On the other hand, in the case of “Why is 5 prime?,” all the levers you could pull to make 5 composite involve significantly more advanced machinery than is needed to pose the question in the first place. E.g., “5 is prime because we’re working over the ring of integers. Over other rings, like Z[√5], it admits nontrivial factorizations.” Not really an explanation that would satisfy a four-year-old (or me, for that matter).
And then we come to the question of why anything exists. For an interventionist, this translates into: what causal lever could have been pulled in order to make nothing exist? Well, whatever lever it was, presumably the lever itself was something—and so you see the problem right there.
Admittedly, suppose there were a giant red button, somewhere within the universe, that when pushed would cause the entire universe (including the button itself) to blink out of existence. In that case, we could say: the reason why the universe continues to exist is that no one has pushed the button yet. But even then, that still wouldn’t explain why the universe had existed.