On 27 Oct 2015, at 23:04, Stathis Papaioannou wrote:
On 28 Oct 2015, at 1:30 AM, John Clark <johnkcl...@gmail.com> wrote:
On Mon, Oct 26, 2015 at 5:16 PM, Stathis Papaioannou <stath...@gmail.com
> wrote:
>> From examples in the physical world. You can give as
many botanical definitions of the word "tree" as you want but it
will just be a word defined by other words that are themselves
defined by yet more words that are.... If you tried to dig for
meaning all you'd find is a endless loop, it would just be a game
where words are manipulated according to the rules of botany until
somebody forgot about definitions and pointed to the ASCII string
"t-r-e-e" and then pointed to a large photosynthesizing organism
made largely of cellulose that exists in the physical world. Then
even a martian would notice a correspondence between this game of
manipulating symbols called "botany" that humans had invented and
the way these large photosynthesizing organism made largely of
cellulose live.
> What about a virtual world with trees and observers, and no
I/O devices connecting it to outside trees?
There would still be I/O devices connected to the virtual
trees made by a computer that operated according to the laws of
physics, if not the trees wouldn't even be virtual. And the books
on both virtual botany and real botany would still be more than a
just a symbol manipulation game, they would have semantic content
because there would be a correspondence between the way the
symbols are manipulated and the way the virtual (or real) large
photosynthesizing organism live. Regardless of if they are
virtual or real if you want to know how trees live studying those
botany symbols in virtual (or real) books will help, so they must
have semantic content.
The requirement that a computation be able to interact with the real
world puts a restriction on what qualifies as a computation. You've
challenged Bruno many times to perform a difficult computation using
his Platonic computer. Well, that computation is occurring in front
of you now in the thermal motion of the atoms in your desk, which
under an appropriate interpretation are implementing a Turing machine.
I doubt this. (Even assuming a physical reality in which that make
sense: the part which is digital enough might compute little piece of
programs, but nothing as specific as a brain state. It can do it like
a monkey can type the work of shakespeare.
This might not been important for your argument, though.
But you and Bruno don't have that appropriate interpretation, and if
you did, you would have the result of the calculation already.
But here Clark would say, non problem as "thermal motion of atoms" is
physical.
In other words, the thermal motion computation is not understandable
as such in, and cannot interact with, the world at the level of the
substrate of its implementation; so it would usually be said that
either there is no computation being implemented, or it is being
implemented only in a trivial and useless sense. But remove the
requirement for interaction in the real world, and this objection
falls down.
OK. But no need of lucky thermal atoms. The necessary relations
between natural numbers, if you agree with the laws of addition and
multiplication, guaranties the realization of the computations by
virtue of being true or false.
The computation is being implemented, your difficult calculation has
been completed, and it is being appreciated by the virtual observers
who are clapping and cheering - even though you can't hear them.
OK.
Bruno
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