We start off by saying that the universe that I can sense exists, along with me. I carry on to allow existence to those bits of the universe that I can’t directly sense, but it seems reasonable to infer are present from the physics of the universe.
So existence seems straightforward. But what about non-existence? Particularly in the context of a possible multiverse?
I think what happens is that people figuratively draw out in their minds the whole class IV multiverse that Tegmark talked about, and ask themselves how they would test for the non-existence of a part of it. The answer is that you can’t—experiments can only manipulate and measure existing things using other existing things. You never get to experiment on a non-existent thing.
This means that the whole question “What exists?” is not directly a scientific one at all. Well, partially—you can do science on some of the things that do exist, but you don’t ever get to do science on any of the things that don’t exist. All you can ever confirm is that you can’t see them from where you stand.
I think the right approach is to drop the ‘exists’ word altogether in this context, and instead ask yourself how to describe the universe using the usual approach of looking for the theory which is simplest.
We start off by saying that the universe that I can sense exists, along with me.
I can see no justification whatever for that method. What’s so special about you, that you imbue things with “existing-ness” by sensing them? Surely that’s an egregious Mind Projection Fallacy? “It’s in my map, so it must be in some territory somewhere”?
I wasn’t actually justifying the move—merely saying this is how the concept of existence comes about. My final sentence sums up what I actually think—that ‘exists’ is a deeply misleading concept in situations such as this, and should be confined to folk philosophy, where it’s commonly used meaning is sufficient.
Getting rid of the ‘exists’ concept is more or less what I’m trying to do—or rather, show that if you have an ‘exists’ concept such that ¬exists(infinite sets) then your ‘exists’ concept is incoherent; moreover, that an ‘exists’ defined by exists(our Universe) and ¬exists(everything else) is not an important concept and should be detached from the connotations the savannah brain likes to associate with things that ‘exist’.
Surely can’t be exactly what you mean, as exists(our Univese) and ¬exists(everything else) seems coherent if rather unlikely, and seems consistent at our present state of knowledge with ¬exists(infinite sets).
It seems your ‘exists’ concept is pretty much indistinguishable from ‘logically coherent’, and that that’s the whole point you’re trying to make—that we’re in no position to distinguish these, and should simply abandon the ‘exists’.
Surely can’t be exactly what you mean, as exists(our Univese) and ¬exists(everything else) seems coherent if rather unlikely
I would dispute this, on the grounds that my deductions in formal systems come from somewhere that has a causal relation to my brain—the formal system causes me to be more likely to deduce the things which are valid deductions than the things that aren’t. So, if I ‘exist’, I maintain that the formal systems have to ‘exist’ too, unless you’re happy with ‘existing’ things being causally influenced by ‘non-existing’ things—in which case there’s not a lot of point in asserting that ¬exists(infinite sets). A definition of ‘exists’ which doesn’t satisfy my coherence requirements is, I am attempting to argue, simply a means of sneaking in connotations.
Existence is a bit odd.
We start off by saying that the universe that I can sense exists, along with me. I carry on to allow existence to those bits of the universe that I can’t directly sense, but it seems reasonable to infer are present from the physics of the universe.
So existence seems straightforward. But what about non-existence? Particularly in the context of a possible multiverse?
I think what happens is that people figuratively draw out in their minds the whole class IV multiverse that Tegmark talked about, and ask themselves how they would test for the non-existence of a part of it. The answer is that you can’t—experiments can only manipulate and measure existing things using other existing things. You never get to experiment on a non-existent thing.
This means that the whole question “What exists?” is not directly a scientific one at all. Well, partially—you can do science on some of the things that do exist, but you don’t ever get to do science on any of the things that don’t exist. All you can ever confirm is that you can’t see them from where you stand.
I think the right approach is to drop the ‘exists’ word altogether in this context, and instead ask yourself how to describe the universe using the usual approach of looking for the theory which is simplest.
I can see no justification whatever for that method. What’s so special about you, that you imbue things with “existing-ness” by sensing them? Surely that’s an egregious Mind Projection Fallacy? “It’s in my map, so it must be in some territory somewhere”?
I wasn’t actually justifying the move—merely saying this is how the concept of existence comes about. My final sentence sums up what I actually think—that ‘exists’ is a deeply misleading concept in situations such as this, and should be confined to folk philosophy, where it’s commonly used meaning is sufficient.
Getting rid of the ‘exists’ concept is more or less what I’m trying to do—or rather, show that if you have an ‘exists’ concept such that ¬exists(infinite sets) then your ‘exists’ concept is incoherent; moreover, that an ‘exists’ defined by exists(our Universe) and ¬exists(everything else) is not an important concept and should be detached from the connotations the savannah brain likes to associate with things that ‘exist’.
“exist” doesn’t have a referent. Any attempt to define it will either be special pleading (my universe is special, it “exists”, because it’s the one I live in!), or will give a definition that applies equally to all mathematical structures.
Surely can’t be exactly what you mean, as exists(our Univese) and ¬exists(everything else) seems coherent if rather unlikely, and seems consistent at our present state of knowledge with ¬exists(infinite sets).
It seems your ‘exists’ concept is pretty much indistinguishable from ‘logically coherent’, and that that’s the whole point you’re trying to make—that we’re in no position to distinguish these, and should simply abandon the ‘exists’.
I would dispute this, on the grounds that my deductions in formal systems come from somewhere that has a causal relation to my brain—the formal system causes me to be more likely to deduce the things which are valid deductions than the things that aren’t. So, if I ‘exist’, I maintain that the formal systems have to ‘exist’ too, unless you’re happy with ‘existing’ things being causally influenced by ‘non-existing’ things—in which case there’s not a lot of point in asserting that ¬exists(infinite sets). A definition of ‘exists’ which doesn’t satisfy my coherence requirements is, I am attempting to argue, simply a means of sneaking in connotations.