On 21 Jan 2014, at 15:45, Alberto G. Corona wrote:
It is a phisical definition of computation in the physical world, to
distinguish what physical phenomena are computations and what are not.
I don´t care about mathematical oddities.
But nobody has found such a definition. Physical computation are only
recognized as computation in machine that we can build, from subset of
physical laws, to implement the mathematical definition.
Then it is a theorem that we cannot recognize something as being a
computation, even in the arithmetical reality. We can build one and
recognize those we built, or we can bet that some process computes,
like when saying "yes" to a doctor. But there is no general means to
see if something is a computation or not, and this will depends in
part of we look at it.
Computability is a notion discovered in math. It is related to the key
discovery of Turing (also some others) of the universal (Turing)
machine.
You can defend naturalism, or physicalism, and you have the right to
believe in a primitive physical universe. I am agnostic, and I have to
be, if only because we have not yet decided between Plato and
Aristotle. We are very ignorant, notably on the mind-body question.
I do not defend computationalism. I just show that IF we assume it,
then we get a constructive and testable platonic theology, which
explains physics. And I have done a piece of the derivation and tested
it.
If you are right on metaphysical naturalism, with a real ontological
universe, then comp is wrong. That is all what I say.
Computation in this sense is a manifestation of teleological entities
capable of maintaining his internal structure.
I can accept this as a putative truth about a notion of physical
computation, but this has not yet been defined. "reducing entropy" was
a good try, less wrong than "quantum computation" (despite here Turing
universality is verifiable), but it does not work as nature can
compute without dissipating energy (indeed quantum computers requite
that).
Math do not compute.
That does not make a lot of sense.
Computers do not compute,
Only computers compute. That's almost tautological.
For example universal computers compute anything computable.
I often use the word "computer" in the sense of the french
"ordinateur", which means all purpose computer or universal computer.
Books do not compute.
We agree on this!
Is people that compute
with the help of them.
That makes sense, if only because the Turing machine describe very
well how a person compute with pencil and paper, going through
different state of mind. Yes, people can compute, but computer compute
too, with the standard mathematical definition.
Bruno marchall invoking church thesis to
convince us flooding the list with comp theory
Well, many people agree with the comp axioms, and are interested in
thinking on the conceptual consequences. Then Church thesis is rather
important to understand the generality of the notion.
talking about non
computability does compute too .
I don't understand the sentence.
as well as any living being.
That definition of computation is more restrictive and wider that the
traditional one. Is more restrictive for obvious reasons. It is wider
because it depart from the legomania of digitalism.
But that is the essence of computation. Then it is a beautiful miracle
in AUDA (but implicit in the UDA) that the first person appears not to
be computable or even nameable from her first person point of view.
In fact S4Grz exists by an arithmetical tour de force. It is a formal
logic of the non-formalizable. It explains why, from the 1p view, we
cannot avoid the depart from the legomania of digitalism.
But comp explains the why and the how.
Moreover it is an
operational definition closer to everyday reality and includes all
that is traditionally called computer science and biology (and
sociology) within a wider physical framework.
May be. You did not provide a definition of physical computation. Nor
of "physical", which might help a skeptic like me. The only one you
gave was "reducing entropy". But it does not work. It might work for
life perhaps. It is certainly an interesting idea. But it is not
"computation". You can't change definition at will, or we are talking
about different things. The mathematical notion of computation is NOT
controversial. The physical notion of computation is not even
existing, and most attempts are controversial.
Bruno
2014/1/21, Bruno Marchal <marc...@ulb.ac.be>:
On 20 Jan 2014, at 21:17, Alberto G. Corona wrote:
Computation is understood as whatever made by a digital computer or
something that can be emulated (or aproximated) by a digital
computer.
OK. That's a good definition, and it is correct if ... we assume
Church's thesis.
So everything is a computation.
Goddam! Why. Even just about what is true in arithmetic cannot be
emulated by any computer.
I am afraid you might not really grasp what a computer is,
conceptually. See my answer to stephen yesterday, which shows wahy
Church thesis entails that most attribute of *machines* cannot be
computed by a machine.
Or think about Cantor theorem. The set of functions from N top N is
not enumerable, yet the set of *computable* functions is enumerable.
That is a useless definition. because
it embrace everything.
For a mathematician, the computable is only a very tiny part of the
truth.
Everything is legoland because everything can be emulated using lego
pieces? No, my dear legologist.
Not veything can be emulated by a computer. few things actually in
usual math. Some constructivist reduces math so that everything
becomes computable, but even there, few agree.
In Brouwer intuitionist analysis he uses the axiom "all function are
continuous" or "all functions are computable", but this is very
special approach, and not well suited to study computationalism
(which
becomes trivial somehow there).
What about this definition? Computation is whatever that reduces
entropy.
It will not work, because all computation can be done in a way which
does not change the entropy at all. See Landauer, Zurek, etc.
Only erasing information change entropy, and you don't need to erase
information to compute.
In information terms, in the human context, computation is
whatever that reduces uncertainty producing useful information and
thus, in the environment of human society, a computer program is
used
ultimately to get that information and reduce entropy, that is to
increase order in society, or at least for the human that uses it.
The UD generates uncertainty (from inside).
A simulation is an special case of the latter.
So there are things that are computations: what the living beings do
at the chemical, physiological or nervous levels (and rational,
social
and technological level in case of humans) . But there are things
that
are not computations: almost everything else.
That is the case with the definition you started above, and which is
the one used by theoretical computer scientist.
Bruno
http://iridia.ulb.ac.be/~marchal/
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