peterdjones wrote:
> Georges Quénot wrote:
>> peterdjones wrote:
>>> Georges Quénot wrote:
>>>> peterdjones wrote:
>>>>> [...]
>>>>> (To put it another way: the point is to explain
>>>>> experience. Physicalism explains non-experience
>>>>> of HP universes by saying they don't exist. MM appeals
>>>>> to ad-hoc hypotheses about non-interaction. All explanations
>>>>> have to end somewhere. The question is how many
>>>>> unexplained assumptions there are).
>>>> I would like to understand your view. How do *you* solve
>>>> the "HP universe" problem? In your view of things, amongst
>>>> all the mathematical objects to which a universe could be
>>>> isomorphic to, *what* does make only one (or a few) "exist"
>>>> or "be real" or "be physical" or "be instanciated" and all
>>>> others not?
>>> In your view, what means that only mathematical objects exist ?
>> I can try to answer to this but I do not see how it helps
>> to answer my question. It is hard to explain what it means
>> to someone that resist the idea (that must be like trying
>> to explain a mystic experience to a non believer).
>> It is just the idea that there could be no difference between
>> mathematical existence and physical existence.
> Then why do we use two different words (mathematical and physical) ?

For various historical and practical reasons and because
identity is still a conjecture/speculation. Just like we
used to consider "inertial mass" and "gravitational mass".

>> I would say that it
> "it" meaning mathematical existence IS different to physical existence.
> ?

No "it" referred to "IS NOT different from". I meant that
"mathematical monism" is likely to make sense only if
"physical monism", "mathematical realism" and "Tegmark's
hypotesis" also make sense and can possibly be true.

>> makes sense only in the case in which the three other
>> mentionned conjectures also make sense and could be true.
> I don't see why the mathematical realism needs to be true.
> The difference between mathematical existence and physical
> existence could consist in physical things exisitng, and
> mathematical objects not exisiting.

That would not be "mathematical monism" or it would be a
"mathematical monism" in which one and only one particulat
"mathematical object" would exist. This seems logically
difficult and then: why just this one?

>> I believe that we have a diffculty here because we have very
>> different intuitions about what mathematical objects can be
>> and about what a mathematical object corresponding to a
>> universe hosting conscious beings could look like. I already
>> mentionned three possibilities to deal with the HP universe
>> "problem" in this context. I understood that it did not make
>> it for you because of this difference between our intuitions.
>>> All explanations stop somewhere. The question is whether they
>>> succeed in explaining experience.
>> Do you mean that it is "just so" that the "mathematical
>> object" that is isomorph to our universe is "instantiated"
>> and that the "mathematical objects" that would be isomorph
>> to HP universes are not?
> We can go some way to explaining the non-existence
> of HP universes by their requiring a more complex
> set of laws (where "we" are believers in physical
> realism).

Whether HP universes require or not a more complex set
of laws is a very good question but it seems unlikely
that it can be easily answered. For some physicists,
the currently known (or freseeable) set of rules and
equations for our universe *is* compatible with "HP
events". Such events might appear in other portions of
our universe. For others, it is just the opposite, it
might well be that there do not exist any set of rules
and equations that would correspond to a "HP universe".

> However, we are bound to end up with
> physical laws being "just so".

Not really. What is "just so" is that a conscious being
has to live in only one universe at once just as he has
to live in only one place and in only one period of time
at once. It is no more mysterious that I do not live
Harry Potter's life that I do not live Akenaton's life.
And lots of "HP-like" events have also been reported in
*this* world.

> However -- so every
> other explanation ends up with a "just so".

At some point, yes. The question is just what "just so"
one is willing to accept or to resist to.

> In physical
> MWI it is just so that the SWE delimits the range of possible
> universes. In Barbour's theory it is just so that Platonia
> consists of every possible 3-dimensional configuration of
> matter, not every 7-dimensional one, or n-dimensional one.
> In Mathematical Monism, it is just so that, while very mathematical
> object exists, no non-mathematical object exists.

Oh yes. All of the five conjectures I mentionned can be
perceived as "just so". It just so happens too that they
do make sense to some people and do not to other people.

>> Isn't that a bit ad'hoc? Does it explain anything at all?
>>>> Also, you reject "mathematical monism" as not making sense
>>>> for you but what about the ohter conjectures I mentionned?
>>>> Do you find that "physical monism" ("mind emerges from
>>>> matter activity"), "mathematical realism" ("mathematical
>>>> objects exist by themselves") and "Tegmark's hypothesis"
>>>> ("our universe is isomorphic to a mathematical object",
>>>> though Tegmark might no be the first to propose the idea)
>>>> make sense? Have some chance of being true?
>>>> Do you find that "physical monism" ("mind emerges from
>>> matter activity"),
>>> All the evidence points to this.
>> OK. So in your view this makes sense and is likeky to be true.
> Those are two different claim: it is likely to be true,
> but seeing *how* it is true, making sense of it is the Hard Problem.
> IMO the hardest part of the hard problem is seeing how mind
> emerges from mathematical description -- from physics in the
> "map" sense, rather than the "territory" sense. Switching to
> a maths-only metaphysics can only make the Hard Problem harder.

As I perceive it, this is the hard problem even starting
with a (classical) physical context. A I perceive it also
placing it in a mathematical context doesn't make it harder
or easier. But this is just from my viewpoint indeed.

>> Evidence is also that a lot of people resist physical monism
>> just as you resist mathematical monism.
> Under my analysis the problem with physical monism is
> reification (confusion of map with territory) of the maths!

Yes. I understood that you resist the idea of a possible
identity between map and territory.

>>>> "mathematical realism" ("mathematical objects exist by themselves")
>>> Not supported by empirical evidence; not needed to explain
>>> the epistemic objectivity of mathematics.
>> That could be a language problem. In my view, what I was
>> thinking of is likely to be equivalent to the "epistemic
>> objectivity of mathematics" in your view.
> "Epistemic objectivity of maths" means "every competent mathematician
> gets the same answer to a given problem". It doesn't say anything about
> the existence of anything (except possibly mathematicians).

Well, if "every competent mathematician gets the same answer
to a given problem", "competent mathematicians" do not have
much freedom about what they might find as an answer to some
given problems. So there must "exist" "something" that
"constrain" them. And "this" might even exist in the absence
of "competent mathematician".

>>>> and "Tegmark's hypothesis"
>>>> ("our universe is isomorphic to a mathematical object",
>>> Must be at least partially true, or physics would not work,
>> Partially is not of much help in this context. Th question is
>> whether it can/could be *fully/absolutely* true.
> Even if it is *fully* true,

Of course, it can/could be not fully true (and if it happened
to be true, that would probably be "just so" too) but in case
it would no be fully true, all the discussion we have here
would be pointless.

> isomorphism is **not** identity!

This is obviously untrue: it might well be that not all
isomorphisms are identity but, indeed, identity is always
an isomorphism and, hence, at least *some* isomorphisms
*can* be the identity.


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