This is the hardest question in philosophy. I’ve written little on the topic before, so I wanted to go ahead and put my thoughts out there…
I’ll assume that physics is not eternal. If it is, we’ve got an easy answer to philosophy’s central question.* It may not be, and if so we have got some serious explanatory work ahead of us.
What is existence? St. Augustine once said that he knew what “time” was… Until someone asked him to define the word. Existence is like that. We all know at the gut level what it is, but if pressed for a definition we’d be stumped. I once looked up “exist” in the dictionary, and it said “to be actual.” I looked up “actual,” and it said “to be real,” I looked up “real” and it said “to exist.” The dictionary offered nothing except an ultimately circular definition. However, another dictionary defined “exist” as “to occupy space and time.” But isn’t that definition also troublesome? I’d say that space and time are real, that they exist, but under the definition we just read saying space and time exists is tantamount to simply saying space and time occupy space and time. Richard Carrier points out that this is true; space and time are at every spatiotemporal location, and he draws the conclusion that space and time necessarily exist (personal correspondence). I don’t know about you, but I feel like that might be like the ontological argument, pulling a fast one with mere words. However, if we want to reject Carrier’s conclusion, we have to find a better definition of “existence.”
A sea monster isn’t real, but the sun is. What is the difference between the two that makes one real and the other imaginary? Well, the sun has detectable effects on ourselves and other things, but a sea monster doesn’t. One might say that sea monsters had an effect on superstitious sailors of the middle ages; but that wouldn’t be right: it is really the idea of a sea monster that made them afraid. “The ability to interact with other beings” seems like a decent definition of existence. But, what if there were extra-terrestrials on the other side of the universe that will never interact at all with us? Would they still exist according to the above definition? Sure, just as long as we understand “the ability to interact…” as meaning “the theoretical ability to interact with other beings.” Those ETs may never meet with us, but just as long as it remains a theoretical possibility (meaning: we would interact with them if we had a way of being transported over to their planet) then those ETs could be said to exist. It might be said that this definition of existence is circular: we’re defining existence as the theoretical ability to interact with other beings (beings = things that exist). Well, this definition doesn’t capture the core notion of what it means to exist, but it is fair to say that a necessary property of existence is the ability to interact with other things, at least in theory.
So, if you agree with me that “theoretical ability to interact” is a fingerprint of existence, something that must go hand in hand with it, where does that take us in our journey to answer the question “Why Something rather than nothing?”?
In order to interact with other beings, or have effects on things, you must be within time.**An effect takes place at a certain point in time, and you can’t act at a certain point in time if you aren’t within it. Even if there were a God outside the space-time continuum, and he attempted to reach into our space-time at a certain point to work a miracle, his action would entail an order of actions, an order in which God did things, which is time (time = the order in which things occur).
To interact with other beings, it is probably the case that you must also exist within space: If it is true that you must have a point of contact with something to effect it, then you must be inside space to effect anything.
Under our working definition of existence, space and time do not exist, strictly speaking. Space and time don’t have effects on things, space and time are a framework in which effects, actions, and reactions reside. As such, it makes no sense to ask whether the framework of existence exists. We might ask “why is there filled space instead of empty space?” why the framework has a painting instead of just blank canvas, but can’t ask questions about the framework itself. This is a question we’ll return to later, but for now I just want to secure the point that the “framework” of space and time cannot “not exist” – such a statement wouldn’t even make sense.
Let’s look at the problem of existence from another angle: When we say “Why is there something rather than nothing?” We’re saying that there are two basic possibilities: there is (a) something and (b) nothing. If we take “nothing” as word meaning one and the same thing as “nonexistence” then we are asking “why doesn’t nonexistence exist?” It’s self-evident why not: it’s a contradiction. Notice how difficult it is to talk about this question without referring to some hypothetical “place” or “state of affairs” where “nothing exists” which is self-contradictory: if you want to define nothing as an absence of space and time itself, you can’t discuss any “state of affairs” (which is a moment of time) or any “place” (a particular position within space) that has no time and space. Space and time define existence. In other words, that’s what existence is: space and time.
What I’ve been saying so far bodes well with other things philosophers have noticed over the centuries: there are only two categories of things that some (not all) philosophers have believed have thought had some sort of non-spatiotemporal existence: abstract objects and minds. Abstract objects can be accounted for in fully material, spatiotemporal terms (nominalism) and so can minds (mind-body physicalism).
I think the problems with mind-body physicalism, like the hard problem of consciousness, are completely solvable. I don’t feel that way about the problems with mind-body dualism. There are deep paradoxes within the view that a mind could even possibly exist without a body. Stephen Law goes over one in his book Believing Bullshit. Richard Carrier goes over an argument to that effect in “The God Impossible.” The same thing can be said about the immaterialist view of abstract objects: deep paradoxes. If abstractions are supposed to be non-spatiotemporal things, and humans are spatiotemporal, then how do we humans know about these non-spatiotemporal abstractions that cannot effect anything within the temporal realm?
So, the view that space and time are define existence itself is not only defensible and in and of itself (with the arguments I gave earlier) but it is also deeply congruent with other philosophical arguments against individual cases of purported non-spatial existence and with the vast scientific evidence against disembodied minds (if you think non-spatial existence is impossible, you’d predict that observation would show the human mind to be fully physical and that exactly zero instances of disembodied minds would ever be found).*** The convergence of different arguments from different sources of knowledge (science and philosophy) to the same conclusion is a strong mark of truth.
At this point you must be wondering: if my argument only shows that empty space must be, then why is it the case that filled space exists instead of empty space? Physics has already answered this question: quantum fluctuations. Lawrence Krauss has an excellent online talk about this very subject, and a book too. Empty space regularly and observably produces equal amounts of positive and negative energy, matter is a form of energy, and thus empty space can produce the energy and matter filled universe in which we live. As Krauss explains, it also happens to be the case that the vacuum fluctuation theory explains several odd features of our universe, such as why our universe has equal amounts of positive and negative energy and equal amounts of positive and negative electric charge. One may still wonder why the laws of quantum mechanics hold true, that is, why space-time has a tendency to produce particles of energy. As has been discovered elsewhere in Quantum mechanics, when there are two possibilities as to what can happen, each possibility is actualized fifty-percent of the time. The energy of space-time could be (zero) or (one plus negative one) [a quantum fluctuation], and so each scenario unfolds half of the time.****
For more information:
Stephen Law gave an interview about the question “Why there is something rather than nothing?” In which he explains the same basic answer I have given. Bede Rundle explores several arguments for my conclusion in his book Why There is Something Rather Than Nothing.
“Mr Deity and the Really Hard Time” amusingly explores several paradoxes surrounding the creation of the universe. My hat goes off to the writers of that one, it’s amazing to see good philosophy summarized and told light-heartedly in a skit that will make you chuckle.
* If physics has existed for infinite time in the past, then we have an easy answer to the question, “Why is there something rather than nothing?” Something exists at each moment of time because matter cannot be created or destroyed and because matter existed in a previous moment of time. Why is there something now? Because there was something a second ago, and matter cannot vanish out of existence from one moment to the next. Why was there something exactly 13.7 billion years ago? Same reason. The same answer goes for any moment of time. Why has there been matter for all eternity? Because there was matter at every individual moment, and there was matter at every individual moment because there was matter in the previous moment, ad infinitum.
** It might be objected that time has effects on things: it is often said, for example, that “time has changed me.” It’s a common way of speaking, but to be exact time doesn’t change anyone: what changes people is processes that go on within time. Example: An alcoholic isn’t led to give up his drinking by “time,” he is led to give it up by events that occur within time, like becoming disgusted with his lifestyle, concerns about health, family interventions, and so on.
**** What I wrote here is not confirmed science: it is just my speculative explanation about why quantum fluctuations happen.