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!
- 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.
- Does anything else exist? Look around. Do you have sensory organs? Yup, other stuff exists.
- 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.
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.
- 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.
- 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.
- 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.
- 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.
- 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).
- Does Mickey Mouse exist? Rev has four correct answers for this one.
- …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]
15 thoughts on “What Exists?”
I think your most controversial statement is actually in (3) when you say “those things still exist in the simulation’s memory (object permanence!), so the answer is still yes.”
Pointed to by your “practice problems” – we can only rely on our own memories to verify that objects are permanent within the system, and we have no way to check our memories. System behaviors that are inconsistent with object permanence often fail to surprise us in dreams; we only hope that’s not the case when we’re awake!
Re: 4) A light beam traveling away from you toward a mirror will affect you again in the future.
Otherwise, this list is Correct.
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Directly relevant to the question of mathematics and the overloading of the word “exists”: http://st-rev.livejournal.com/395798.html
I will probably rewrite this for Carcinisation at some point.
“Things that don’t exist: consciousness, persistent identity, the passage of time”
Death to this philosophy. It is a comprehensive denial of reality. Every one of those things exists.
We’ve had a similar conversation before on LessWrong (I used to post as WrongBot). What definition of “exists” are you using?
Before I try to answer, can you tell me something. Do you think that those three items are not real in any sense at all, or do you just think they have a type of reality that shouldn’t be called “existence”?
Sorry, the point I’m trying to make is that the everyday concept of “reality” or “existence” is hopelessly confused. “The passage of time is real” is not a proposition with a truth value.
‘“The passage of time is real” is not a proposition with a truth value.’
According to the timestamp on that comment, it was written in August. Where I am, it is now September. How does your philosophy accommodate these facts?
So why don’t you just say “The passage of time is not real”?
And indeed, you said as much in your original tweet. So then why did you go on to say in our discussion, that “The passage of time is real” has “no truth value”, i.e. is neither true nor false?
Because “real” is overloaded, which is kind of the point of this post.
Does Mickey Mouse exist? http://st-rev.livejournal.com/103259.html