On 16/10/2015 9:46 am, Jason Resch wrote:
On Thu, Oct 15, 2015 at 5:26 PM, Bruce Kellett
<bhkell...@optusnet.com.au <mailto:bhkell...@optusnet.com.au>> wrote:
On 16/10/2015 8:56 am, Jason Resch wrote:
On Thu, Oct 15, 2015 at 12:34 AM, Bruce Kellett
<bhkell...@optusnet.com.au> wrote:
What evidence do you need to say that something does not
exist? Absence of evidence is, in this case, evidence of absence.
Why is that so in this case, when the standard form of that
phrase is "Absence of evidence is not evidence of absence"?
Because if there is no evidence for something where one would, if
that thing existed, expect evidence, then one is justified in
saying that the thing does not exist.
So what evidence would you expect to see if platonic computations existed?
Evidence of conscious beings independent of any physical substrate. In
other words, ghosts and the other insubstantial beings of popular
mythology and fiction. I see no evidence of such beings where might
expect to see it if they existed, so I conclude that they do not exist.
If there were an elephant in my room at this moment, I would
expect to see it when I turned round. The fact that I do not see
an elephant when I turn round is good evidence that there is no
elephant in my room. Absence of evidence is evidence of absence.
Bruno has shown that one thing we would expect to see is a quantum
reality. And what do we see?
Bruno has shown no such thing.
Also, despite your claims to there being no evidence, there is in
fact evidence of platonic computations. They exist independently of
you, mean, and this physical universe, as surely as "7 is prime" is
true independently of you, me and the physical universe.
The statement "7 is prime" is true by virtue of the axioms of
arithmetic and the definition of a prime number. That does not imply
that "7" exists in any sense whatsoever.
It does if you accept the truth of the axioms. Do you deny the axioms
are true?
As a general matter, yes. Axioms are not true or false, per se. They can
only ever be 'true' in particulr models. They are 'true' in some, and
not in others. I refer you to my concurrent discussion with Bruno.
You confuse "true" being used of a proposition, with "exists".
That is a profound and serious confusion.
The truth of "7 is prime" implies no integer factors of 7 exist
besides 1 and 7. The truth of "8 is composite" implies the existence
of integer factors of 8 besides 1 and 8. I do not confuse truth with
existence. It is the truth of a proof of existence that implies existence.
Perhaps of existence within that formal system. But you must be careful
to distinguish between the notions of 'exist' as meaning that there is a
true proposition in some formal system about that object, and 'exist' as
in physical existence -- there is a physical object corresponding to
that description. So "7" exists in the sense that there is a true
proposition in formal arithmetic which states that "7" is prime. But
there is no physical object corresponding to that abstract notion of
"7". Confusing the two meanings of the word 'exist' lies at the heart of
all your reasoning. And that is why I am so easily able to dismiss it.
In mathematics you have descriptions of Turing machines and
descriptions of computations, but no live machines or
computations.
There are both.
What evidence do you have for this assertion?
The existence of a UD implies a quantum reality, and we observe a
quantum reality.
Accepting the truth of arithmetical systems like the axioms of
Peano/Robinson arithmetic, implies their existence.
But I do not accept the 'truth' of these mathematical structures.
How can you do physics if you cannot count or add one number to another?
I can count without believing that numbers exist independently of their
physical representation.
And, even if taken as a set of axioms upon which one can reason,
they do not imply that anything like a UD actually exists in any
useful sense. The UD is an idea in platonia, and it is totally
without function until it receives a physical implementation.
So then the Bruce Kellet that exist within a platonic calculation of a
simulation of the milky way galaxy on the Planck scale is a zombie?
Too bad for him, that his galaxy is only "abstract", rather than
"concrete".
Ah, but there you betray the essential importance of the physical
substrate. You are simulating a galaxy to support a conscious being. And
that simulation is, of necessity, carried out on a physical computer.
You have not yet given evidence of any consciousness existing without
such a physical substrate.
Substrate independence simply means that you can replace all or
part of the human brain with computer-based equivalents. In
other words, strong AI. No need for platonia in order to say
that consciousness is independent of the substrate.
But if it is independent of substrate, and if computations exist
platonically, then those platonic computations are equally capable
of instantiating consciousness.
You are confusing the meaning of 'substrate'. In the context, I meant
an explicitly physical substrate. Platonia is an idea,
If Platonia is an idea, then so is "The primary physical reality". It
is up to science now, to determine which of these two ideas is more
likely to be true.
Sure. And science has proved many times over that physical reality
exists and can be operated on, while platonia is an idea that has no
useful consequences whatsoever.
Science has never proven that the physical reality is not merely an
appearance to conscious entities that exist as a consequence of
platonically existing computations.
No, but any credibility that that hypothesis might have depends on there
being independent evidence for the possibility of platonically existing
computations. And there is no such evidence.
it is no more 'physically real' than is the idea of a unicorn, or
of Hogwarts School.
Of course it isn't physically real. But why assume physical existence
is the only kind of existence? That seems to be an idea based purely
faith.
Can I take your lack of reply to mean you agree that it is only by
pure faith that you believe physical existence is the only kind of
existence?
I did not reply earlier because no reply to such a comment seemed
necessary. I do not say that physical existence is the only way in which
the word 'exist' is ever used. It is used in the sense of the
mathematical existential quantifier, and it is often used of ideas, and
other non-material things, in a metaphorical sense. It is the failure to
clearly distinguish between these different senses of the word 'exists'
that cause most of your confusion.
Neither unicorns nor Hogwarts can instantiate consciousness.
No more can the idea of platonia.
The idea of platonia doesn't instantiate consciousness, but
objects within platonia do.
Prove it by showing me this magical platonic conscious being.
Look in the nearest mirror.
I know that when I look in the mirror, I cannot see the actual goo
constituting my brain, but that does not mean that I do not believe in
its existence. The object I see in the mirror is the exterior of a
conscious physical being -- the operational word being 'physical'. Not a
platonic idea.
If you want to demonstrate that the idea of platonia can sustain
consciousness of itself, then all you have to do is produce a
conscious being that does not have an accompanying physical
substrate. Until you do that, I think you should shut up about
platonia.
Would you demand of Everett to produce a conscious being from another
branch of the wave function, or else shut up about the other branches
of the wave function?
Yes, of course. The other branches of the wave function are not real
in any useful sense. They are an idea, just as is platonia. And ideas
can have effects in the real world only through the intermediary
action of conscious physical beings, never by magic.
They are consequences of testable theories, mainly QM. You believe in
the existence of galaxies so far away we may never see them, don't you?
Because of the expansion of the universe, galaxies that we once could
see are passing over the Hubble horizon all the time, such that we can
no longer communicate with them. But there is still good indirect
evidence of their existence. But I have no such evidence for the
existence of Everettian many-worlds. They are not necessary consequences
of QM. You seem unaware of the fact that QM can be developed and used,
with complete adequacy, without ever introducing the idea of a wave
function, or of the Schrodinger equation. Both Dirac and Schwinger have
developed such theories. So if the wave function is not a necessary part
of quantum mechanics, then it would be unwise to put too much faith in
the consequences of reifying this abstract calculational tool.
Also, talking of purely theoretical evidence for things, like inflation
and so on, why would cosmologists put so much effort into finding
confirmatory direct evidence for the 'other worlds' predicted by
inflation if everything predicted by a widely accepted theory could be
taken as 'true'? In science, anything that is lacking independent
confirmatory evidence must always be regarded as hypothetical, or
provisional.
If not, then why demand that I shut up about the consequences of
well-accepted theories?
Well-accepted?
Laws of arithmetic. Computationalism.
Why? Arithmetic is system of propositions. Whether it is real
or not has no effect on Church-Turing.
Then you should be equally happy to have your brain implemented by
"unreal computations" as "real computations" :-)
Computations in platonia are 'unreal' -- they do not exist, so
cannot implement anything.
You said earlier that you have no evidence that objects of platonia
do not exist. So why insist so adamantly that they do not?
You should learn to read. I said no such thing. I said that the
absence of evidence for platonia was evidence that it did not exist.
Strange how evidence works. No evidence = evidence?
Yes, funny that. Get used to it!
Are you familiar with Max Tegmark's idea that physical existence is
mathematical existence?
* https://en.wikipedia.org/wiki/Mathematical_universe_hypothesis
* http://arxiv.org/pdf/0704.0646.pdf
*
http://www.amazon.com/Our-Mathematical-Universe-Ultimate-Reality/dp/0307599809
I am familiar with Tegmark's ideas. I do not agree with most of them.
Arguments from authority do not carry weight here. Tegmark is an
outsider in the physics community.
I was not making an argument from authority, only pointing you to some
material that might cast doubt on your belief that physical existence
is somehow different from mathematical existence. Also, "Tegmark is an
outsider in the physics community" is an argument from authority (the
authority of the physicists that have ostracized him).
Tegmark's ideas lack independent evidential confirmation, so they are
not widely accepted. This is an argument from the authority of evidence,
if you like, not just from the authority of the scientific community.
Since you are familiar with his ideas, I ask you, how is physical
existence different from mathematical existence?
Two different meanings of the word 'exist'. Physical existence relates
to physical objects; mathematical 'existence' relates to mathematical ideas.
If you think these are the same thing, then show me the conscious being
that exists independently of any physical substrate. The fact that you
appear unable to do this, and no-one else has ever done it either, is
overwhelming evidence that no such non-physical conscious beings exist.
Bruce
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