On 7/2/2012 4:10 AM, Bruno Marchal wrote:
On 01 Jul 2012, at 20:20, meekerdb wrote:
On 7/1/2012 4:59 AM, Bruno Marchal wrote:
Except neither fortran nor Turing machines exist apart from
physical realizations.
Of course they do. Turing machine and fortran program are
mathematical, arithmetical actually, object. They exist in the same
sense that the number 17 exists.
Exactly, as ideas - patterns in brain processes.
That would contradict the Arithmetical realism, and thus Church
thesis, comp, etc.
Hi!
A big carve out of the preceding thread... We need an exact definition
of Realism!
Brent
We can implement them in physical system, but this does not make
them physical.
They are abstractions.
If you want. This changes nothing.
There is no need of step 8, here. It is just a mathematical fact
that arithmetic emulates all programs, in the mathematical sense
of "emulate".
That's a metaphorical sense.
Not at all.
"Arithmetic" doesn't act or perform anything,
Acting and performing are the metaphor here. Computation is a purely
mathematical notion discovered before the building of physical
computer. Some could even argue that the physical reality can only
approximate them.
Right. They are idealizations.
And with comp we have to define eventually notion like acting and
performing from the relation between numbers, and this is rather
easy to do.
That doesn't follow. Comp only says that we could substitute some
different physical structure for part (or all) of a brain, and so
long as the input/output functions were always
At some level,
But is this level reachable by finite means?
the same consciousness would be unchanged.
OK.
But how exactly would we measure this invariance of consciousness? How
do we deal with the parochial nature of the encodings of the diaries
that the various observers write such that we have something like a 3p
account of the experience? What I write in my diary might be in a code
that only I might understand, so how do we compensate for this
variability of language?
So comp allows that we may still need a physical realization of the
functionality.
In which case physical inactive object, with respect to a particular
computation, must be physically active. That is a contradiction. Cf
step 8.
In the case of a Mach–Zehnder interferometer we see that what appears to
be physically purely passive and inactive arms can and does play a real
and causal part such that its removal makes a difference.
That this can be described by relations between numbers does not
entail that it is replaceable by the abstraction.
Indeed, and that is why there is a step 8.
But Step 8 makes a leap too far. It mistakes the relative independence
of computations for complete separation from physical systems.
What is difficult is to get the right measure on the computations,
not to define action and performance.
I am explaining what is a computation on the FOAR list, but you can
find it also in any textbook on theoretical computer science. No
notion of physics are involved at all in the definition.
But those definitions are concerned with abstracting away the physical,
If you want.
We do!
since the physical realization can be different for (approximately)
the same function.
You are confusing a computation with its implementation in a physical
reality. Computations have been discovered in the mathematical
reality, before we implemented them in the physical reality. They
exist independently of us, once you agree that 17 is prime is true
independently of us. And "17 is prime independently of us" is
obligatory to explain what Church thesis is, so we assume that
implicitly when saying "yes" to the doctor.
There simply is not such thing as a computation if we remove its
implicated connection to the possibility of actual physical
implementation. To remove the possibility is to disconnect it completely
from the ability to be communicated. Purely abstract statements by your
definition cannot cause any change in a physical system nor be
correlated with any particular configuration of brain states, thus they
are perpetually beyond our ability to apprehend them.
It is no different than abstracting apples and oranges as fruit so
that we can add one apple to one orange and get two fruit. It doesn't
make apples and oranges the same thing.
Sure. But it makes both of them being incarnation of fruit, showing
that fruit can exist even without apple or without orange.
Nope, sorry. That simply doesn't work. Categories cannot be defined from
the inside that do not have non-labelable members. To claim otherwise is
to refute your entire result. How can you communicate its significance
if you cannot write it down?
--
Onward!
Stephen
"Nature, to be commanded, must be obeyed."
~ Francis Bacon
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