"Why is there something rather than nothing?" Here is one of the biggest of the Big Questions. But for the all deep philosophizing done in pursuit of answers to this question, it is not usually appreciated that the alternative to there being something is not, in fact, imaginable. I mean imaginable here in its literal sense—we can't form a mental picture of there being nothing at all. But I also mean imaginable in the stronger, and broader sense: it is not thinkable, it is inconceivable.
Suppose, for reductio ad absurdum, that it could have turned out that there is nothing at all, nothing rather than something. Well, then, had it turned out that way, it would be true that there is nothing at all. But what is truth? Or, better, what is a truth? For in that total circumstance in which we are supposing there is nothing rather than something, there turns out to be at least one truth in that circumstance, the truth that there is nothing at all. Now, what about this truth? Is it something, or nothing? Surely it is not nothing. If it were nothing, really nothing, it couldn't have any properties, such as being true. But it does—it's true! So in the circumstance in which there is nothing rather than something, there is in fact something, namely, the truth that there is nothing. But then the truth that there is nothing is not in fact true; it is in fact a falsehood. But if it is false that there is nothing, then there is something. So from the assumption that there is nothing at all, we can derive the contradiction that it is both true and false that there is nothing at all. But whatever is truly contradictory is not possible. So it is not possible that there is nothing at all, and it never has been possible that there could have been nothing at all.
We're stuck with reality, and it's all we've got. But precisely because we're stuck with it, the Big Question about why there is something rather than nothing has never struck me as a very interesting question. The real question is not, after all, why there is something rather than nothing, but why things are such as they are. Why this way, and not some other way? Notice that we can imagine, in both the literal and broad sense, things being otherwise than they are. Thus, that they are this very way seems like the sort of fact which cries out for an explanation.