What Exists?

Wrong question.

A few months ago I pointed out something on twitter that is worth expanding on. (Thanks @sarahdoingthing for reminding me!)

While there’s plenty to go into on each of these topics, they all kind of hinge on the last one. What does it mean for something to “exist”? What does it mean for something to be “real”? The answer is nothing. It doesn’t mean anything.

As usual, our language is broken. The word “exist” can mean many things in different contexts. “What exists?” is 10-20 different questions, and some of those are themselves wrong questions. I’m going to go ahead and answer as many of those questions as I can, taking “exists” to mean “is part of my web of cause and effect”. Note that this definition is observer-relative; for the purpose of these questions I’ll be assuming that you are a human being on earth who can read English. (If you are outside this target audience, I recommend running a copy of the author of this article, he can explain it better in person.)

It is my intent here to convince you that this definition is more useful than the blurry haze of connotation and denotation that currently surrounds most use of the word.

Now, to specifics!

1. Does anything exist? The answer is always yes due to anthropic bias. If you can sit around and ask questions, yes, stuff exists. Descartes covered this like 400 years ago.
2. Does anything else exist? Look around. Do you have sensory organs? Yup, other stuff exists.
3. Do things I can’t see exist? So, what, things ripple in and out of existence as you turn your head? Actually, that would be consistent with being in a computation-bound simulation, but those things still exist in the simulation’s memory (object permanence!), so the answer is still yes.
4. Do things travelling away from me at lightspeed exist? Objects travelling away from you at the speed of light are objects you will never, ever be able to acquire information about or interact with ever again. If you’ve interacted with them in the past, they exist. Otherwise no. Rev has kindly pointed out that mirrors exist. There is no number 4.
5. Does God exist? This is a question that’s actually like 1000 questions, depending on what you mean by “god”. If you’re talking about an extremely powerful non-physical agent who has the ability to interact with our universe but rarely does so, well, probably not. Supernatural mythological figures? Sorry.
6. Do other universes exist? That would depend on whether or not it is possible, in principle for us to interact with those universes. There are some universes that definitely don’t exist, and some that might depending on future math/physics discoveries.
7. Does math exist? No. (This is where we get slightly controversial.) When I think about math, my thoughts are real. When I write an equation on a blackboard, the chalk is real, the symbols are real, your mental interpretation of the symbols is real. But there’s no abstract math stuff that either of us is interacting with. There are merely symbol manipulations that are or are not consistent, as judged by us.
8. Does justice exist? Justice is like math, so no. To the extent that I’m talking about anything coherent when I use the word “justice”, I’m talking about a particular kind of algorithm for evaluating outcomes. You probably use the word to refer a to a slightly (or very!) different algorithm of the same general class. Justice is a part of my values, but it is not an outside force which acts upon us or upon which we can act.
9. https://twitter.com/jamesmcn/status/495119712028590080This is a bad question, and I am a bad person for answering it. “Nothing”, the word, exists. “Nothing exists.” is a false statement (see answer #1). ‘Nothing’, the concept, exists as a concept (in the minds of people who think about it, not in any kind of hazy extradimensional space).
10. Does Mickey Mouse exist? Rev has four correct answers for this one.
11. …What other types of things might or might not exist? I’ll expand this list based on your comments. (There are three practice problems hidden at the top of this article.)

[Last updated 8/2]