On 08 Jan 2017, at 03:16, John Clark wrote:
On Sat, Jan 7, 2017 at 5:23 AM, Bruno Marchal <marc...@ulb.ac.be>
wrote:
>> How can anything be "used" by anything if matter that obeys
the laws of physics is not involved somewhere along the line ?
> because with the standard definition of computation, they
exist
A definition can't make something exist!
Wrong.
Coiunterexample. I define a glodlyrapicul by a cat. That makes the
glodlyrapiculs existing (assuming you are OK that cat exists, for the
sake of the argument at least).
> and are realized in all models of Robinson Arithmetic.
And dragons are realized in all the Harry Potter books,
Now in the sense of computer science, which is relevant here.
but none of them can burn my finger.
If you are emulated at the right level in a finger burning situation,
you will feel the pain, and that will not depend locally from the fact
that the emulation is made by this or that universal system. Globally,
for the lasting aspect of the pain, some physics arise, but the theory
explains why. It is not invoked like a god who could select a
computation as more real than another.
And without matter that obeys the laws of physics Robinson
Arithmetic can't balance my checkbook, or do anything else
either.
That sentence is ambiguous. I can agree, but in the sense I can agree
with, this does not make matter needed to be assumed in the axiom of
the fundamental theory.
> The definition of computation does not involve matter
You can make any definition you want but if that's what you call
"computation" then I don't see why anybody would be interested in it.
Many people are interested. It is a branch of math, and it makes us
able to show that some problem are not algorithmically solvable. It is
used to study our limitations, which is indeed the key of the negative-
like machine theology, like the neoplatonist one.
Without that definition, we would not say that Hilbert 10th problem
has been solved (in the negative), etc. recursion theory, and machine
theology is full of negative result, like universal machine cannot
named their god, or know if they halt or not, etc.
> You do the same mistake than the people who say that a
(physical) simulation of a typhoon cannot make us wet. The usual
answer to this is that a simulation of "you + the typhoon" will make
a "you" feeling being wet in a relative way.
I agree but there is a difference. I could ask the simulated person
if the simulated typhoon makes him feel wet, but I don't know how to
ask 3 if Robinson Arithmetic makes it feel like it's half of
6.
Me neither.
But you can ask the John Clark simulated together with the typhoon at
the right level in arithmetic if he feels wet, and he will give the
same answer, not depending if you simulated this in a fortran itself
on a physical computer, or you trace by hand the theorem in arithmetic
saying the equivalent situation. Then the feeling itself, of that John
Clark does not depend of having made the simulation, if you agree that
the truth of 24 is composite does not depend on you verifying that fact.
> No universal Turing machine can distinguish the following
situations:
A physical device simulating Robinson arithmetic simulating a Lisp
universal program simulating that universal Turing machine,
and
Robinson arithmetic simulating a physical device simulating Robinson
arithmetic simulating a Lisp universal program simulating that
universal Turing machine.
That is incorrect, It's extraordinarily easy to distinguish between
the two, one will produce an output and one will not. If you start
with Robinson arithmetic rather than a physical device you'll end up
with nothing, not even the null set.
How could that be possible? We interrogate the machine *in*
arithmetic. The output are given by relative input. You are telling me
that 3 does not divide 6 when nobody do the physical computation, but
the even physicist can no more use arithmetic without a justification
in physics that 3 divides 6. But that does not exist, because physics
does not even address such question, and borrow from math the useful
truth. String theory is happy that "1+2+3+4+5+ ... = -1/12" makes
mathematical sense, so that the photon as a mass zero. They did not
say "we have proven that 1+2+3+4+5+ ... = -1/12 in the theory string
+photon-has zero-mass".
> Is this OK for everybody?
No I don't believe we are.
I know. You are quite "religious" about this.
>> A definition is NOT a construction!
> Yes, that is exactly the point. We can define the set of
arithmetical true statements, and so we can *talk* about it, without
being able to construct it, or to generate it mechanically.
Talk is cheap. We can talk about Faster That Light Spaceships,
Star Trek does it all the time, but we can't build one and that's
why it's called "fiction".
Except that star strek is fiction. Arithmetical truth, or the halting
set, are mathematical concept on which all mathematician agrees. You
have mention some of them yourself like Chaitin non algorithmic
compressible number.
And the notion of arithmetical truth is so intuitive and simple that
it took a Gödel and a tarski to succeed in showing it is not definable
nor amenable to a complete theory.
Hlibert thought the arithmetical reality was mechanical, unlike the
analytical, the surprise was it was not, but that did not make it
disappear.
Nothing can be explained without matter and the laws of physics
because there would be nothing doing the explaining and nothing
doing the understanding.
How do you know? You are just stating your assumption/theory. If you
are right, then in your theory computationalism is false. Just say no
to the doctor. Oops, you have already say yes.
Also there is an ambiguity, which you play with a lot. I cannot
explain you the number without using our physical environment, but
that does not mean that the notion of number depends on the existence
of that physical environment.
No theories in math assumes anything in physics.
>> A personal God who might grant us immortality if we
flatter Him enough is the only type of God that 99.9% of the 1.2
Billion Catholics are interested in. That's why they go to Mass on
Sunday, to butter Him up. If He's not personal then God is about
as useful to them as a screen door on a submarine.
> Who care?
1.2 Billion Catholics care and they care very much! When they
use the word "God" they mean something RADICALLY different from what
you mean when you use the same word, and that
makes communication almost impossible, and yet you insist on
using that same damn word. And people wonder why philosophy
gets so muddled.
Right answer, the catholics care.
So you are catholic? or you care, for some reason to what the catholic
thinks.
Well, thanks for making my point so transparently true. You care more
about the god of the politician than to the god of the self-inquirer.
Yesterday the clergy burned alive the skeptics. Today the clergy let
the atheists burry alive the same skeptics.
(I mean the gnostic atheist here, of course, not the modest agnostic).
You care about what catholic means by god, only because it is easier
to mock them.
You are attaching a poor dog to a wall, throw the ball, and then mock
the dog because it can run to the ball. That's what you seem to do.
And by the way, the modern catholic have no problem writing paper on
the god of Plato, and many christian theologian disbelieve completely
in the naïve conception that gnostic atheists seem to care so much
about.
bruno
John K Clark
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