This could be the most fundamental and difficult-to-answer question of all.
Why is there something rather than nothing?
There is no generally-accepted answer to this question even among those who’ve puzzled over it. Not even among philosophers is there a most-popular answer. Most philosophers have little idea how to answer this question.
Of course many, many, people, perhaps most, think that everything that exists was caused ultimately by God or some other ultimate reality. But why did that exist?
Philosophers going back to at least Aristotle have analyzed what makes for a good explanation, and what different types of explanation there may be. But every successful explanation seems to be either 1) causal or 2) conceptual: We explain something by saying that 1) something caused it. Or we explain it by explaining that 2)—for purely conceptual reasons—it couldn’t have been any other way.
I explain the crack in my windshield by saying that that nasty truck kicked up a stone, which struck my windshield at a high velocity, causing it to crack.
Or I explain why all bachelors are unmarried by saying that it is part of the very concept of being a bachelor that one is unmarried. The concept of bachelorhood is composed of other concepts: the concepts of being an adult, being male, and being unmarried. So one cannot count as a bachelor unless one is adult, male, unmarried. It is “a conceptual truth.” It is just the way the concepts relate to each other. To find out whether all bachelors are unmarried I don’t need to go looking somewhere, or conduct a survey, or conduct an experiment. I can tell that this is true by just thinking about it—just by considering the concepts involved.
All mathematical truths and explanations are like this. I can know that, and explain why, every square has more sides than every triangle, by explaining that “by definition” every square has four sides, and “by definition” every triangle has three sides, and “by definition” four is the next larger whole number after three. So every square must have more sides than every triangle. I don’t need to conduct a survey or go look anywhere. I can tell this just by thinking about it.
We can know such conceptual truths “a priori”—apart from experience, “just by thinking about it.” And when we can tell such things in such a way we can see that they have to be that way—for purely conceptual reasons. But we can only know the truth of causal explanations “a posteriori”—through experience and observation. And these things don’t have to be the way they are; as far as we can tell they could have been different. They are the way they are because something caused them to be that way.
But now what sort of explanation could explain why anything at all exists?
There is very good reason to think that there cannot be an adequate causal explanation:
Suppose that everything that has ever existed has a causal explanation. In other words, suppose that everything that has ever existed existed because something caused it. This is certainly the way we normally explain why something exists. My computer exists because the factory made it. That mountain exists because the tectonic plates crashed into each other causing one to be pushed up over the other. But there is good reason to believe that not everything can have a causal explanation; causal explanations seem incapable of explaining why something-rather-than-nothing exists.
For starters, it seems nonsensical to suppose that something could be the cause of itself. In order to be a cause of anything a thing must already exist. So for a thing to cause itself to come into existence, the thing must already exist. But if it already exists it cannot then bring itself into existence. It is self-contradictory to suppose that a thing exists before it exists. So, nothing can be the cause of itself; everything that is caused to exist must have been caused by something else.
But if everything that exists is caused by something else, then there has to have been an “infinite regress” of causes: Everything that ever existed was caused by a previous thing, which was caused by a previous thing, which was caused by a previous thing, . . . , ad infinitum. There has always been one thing causing another, causing another, etc. This has always been going on. And there was no first thing. (Remember, we’re assuming here that everything has a cause, which cannot be itself. So for everything that ever existed, there was something before it which caused it. So then, given our assumption above, there couldn’t be a first thing.)
But then here’s the million dollar question: Why has that always been going on? Why has there been this infinite regress of causes? What explains its existence? Every link in the causal chain has an explanation—it was caused by the previous cause. But the existence of the whole causal chain seems inadequately explained. If we say that something else caused the whole chain, and continue with the assumption that everything has a cause, then something else must have caused that thing, and we’re off to the races again. We actually end up with an infinite regress of infinite regresses. And we’re still left with our fundamental puzzlement: Why has this always been going on? Why does anything at all exist? Why is there something rather than nothing? That still isn’t adequately explained.
So there does not seem to be an adequate causal explanation of why anything at all exists.
Well, the only other general type of explanation is conceptual. So if there is an answer to our question, it must be a conceptual one. It must be that, for some conceptual reason, something has to exist.
But what is this conceptual reason? Why would anything have to exist?
No one has come up with a convincing answer to this question. So many, many philosophers have rejected this alternative. But since most also see that there cannot be an adequate causal explanation, they opt for a third alternative: There is no explanation. The existence of something rather than nothing is a “brute fact.” It is true, but there is literally no reason why it is true. It isn’t just that we don’t know what the explanation is; there isn’t one.
I find this alternative intellectually repugnant, and, well, I just can’t buy it. I have no difficulty accepting that there are many things whose explanation we don’t know. But I can’t believe that something can be the case and there be utterly no (even unknown) explanation or reason why it is the case. (I accept some version of “The Principle of Sufficient Reason.”)
So I’m left thinking:
There is some conceptual reason why something has to exist.
I don’t know what that reason is.
But I do have a definite opinion about what sort of thing is the most likely sort of thing to have to exist, for conceptual reasons:
A single reality with unlimited causal power.
That entails the concept of God.
But that’s a whole other story.