On 25/04/2017 6:59 pm, Bruno Marchal wrote:
On 25 Apr 2017, at 01:13, Bruce Kellett wrote:
On 24/04/2017 6:07 pm, Telmo Menezes wrote:
On Mon, Apr 24, 2017 at 6:08 AM, Russell Standish
<[email protected]> wrote:
On Sun, Apr 23, 2017 at 11:49:51AM +0200, Telmo Menezes wrote:
Ok, so you are rejecting computationalism. Computationalism is the
hypothesis that our mind supervenes on computations (sorry Bruno,
it's
easier to write for the purpose of this discussion :). You are
declaring that mind supervene on the physical brain.
That is not it at all. We've clarified with Bruno many times that
computational supervenience is compatible with physical
supervenience. Which is just as well, as otherwise it would be so much
the worse for computationalism.
I have no doubt that the brain is a physical computer, and that
computations performed by the brain are no different from any other
computations.
We are discussing physicalism and computationalism, and if they are
compatible or not, correct?
Bruce repeatedly makes variation of the claim: "look, the brain is
physical and the brain generates consciousness, these are the facts".
This is what I am replying to. It's an argument from authority that
leaves no space for debate or reasoning.
First, it is not an argument from authority, it is an argument made
on the basis of all the available evidence -- consciousness
supervenes on the physical brain.
Second. An argument from authority is not necessarily a reason to
reject that argument. Because life is short and we cannot be experts
in absolutely everything, we frequently have to rely on authorities
-- people who are recognized experts in the relevant field. I am
confident that when I drive across this bridge it will not collapse
under the weight of my car because I trust the expertise of the
engineers who designed and constructed the bridge. In other words, I
rely on the relevant authorities for my conclusion that this bridge
is safe. An argument from authority is unsound only if the quoted
authorities are themselves not reliable -- they are not experts in
the relevant field, and/or their supposed qualifications are bogus.
There are many examples of this -- like relying on President Trump's
assessment of anthropogenic global warming, etc, etc.
Third, since it is now clear that the term "physicalism" refers to
the belief in primary matter, I have never ascribed to "physicalism".
Usually I use "Weak materialism" for the "assumption/belief" in
primary matter.
The change in terminology from post to post is very confusing. Recently,
"physicalism" was defined as the belief in primary matter. If these are
the same, do not use two terms -- it merely causes confusion.
primary means "in need to be assumed"; Something is "primary" if to
get its existence we need to assume it, or something equivalent.
OK, so in those terms the working hypothesis is that the physical
universe is primary, because we assume the existence of an external,
objective, physical world. The nature of that world is the subject of
study, and we do not start by assuming that either matter or arithmetic
is primary: because they might be emergent from something more
fundamental, who knows. Agnosticism on metaphysical matters is the usual
scientific stance.
For example, we know since the failure of logicism that numbers are
primary. We cannot derive them from logic.
But we can derive them from physics.
Of course, we can derive them from the combinators theory, but
combinators are Turing equivalent to the numbers.
Weak materialism is just the belief in some matter, and that matter
cannot be explained by something non material.
I must used "weak" before materialist, because the term "materialist"
has a special meaning in philosophy of mind: it means that only matter
"really" exist, ad is opposed to dualism (matter and mind exists) and
immaterialism monism (only immaterial objects exist)
Physicalism is the assumption, in metaphysics/theology, that physics
is the fundamental science to which all other sciences can be, in
principle, reduced.
This is what is more usually defined as strong reductionism; which has
nothing to do with the belief in any "primary matter".
We can conceive some forms of physicalism which are immaterialist, for
example Tegmark is close to this. But usually, most physicalist are
weak materialist, and often I use weak materialism and physicalism as
being quasi the same thing.
And that confusion of terminology is most unhelpful.
I am an empirist, indeed, I extracted "computationalism" from biology,
well before I knew about Church and Turing. And I take physics very
seriously, and as the ultimate judge. Indeed, my point is that if
mechanism is correct, the physical reality is "in the machine's head",
and that is what makes mechanism testable: by comparing the physics in
the head of the machine with the physics inferred from the observation.
And that is the point of my scepticism regarding computationalism -- you
say the theory is to be tested against observation, or physics, but yet
you cannot give any serious account of the physics of the external
world. Any objective assessment of your achievements, in your own terms
as measured against physics, is a resounding "Fail".
I do not know what "primary matter" is supposed to mean, and it
certainly has never been a subject of study that I have encountered
in my lifetime of work in physics.
The expression "primary matter" comes from Aristotle, which is the
first to clearly assume it as a metaphysical assumption/theory. It has
no role in physics at all, except helping the physicists to sleep and
not to be too much perturbate by the mind-body problem, which since
day one is the trouble maker for those who want to be physicalist or
weak-materialist.
It is a completely useless term as far as current science is concerned.
And, although a metaphysical term, I suspect that it is of little
relevance to the mind-body problem.
What I have argued for is the existence of an external, objective,
physical world about which there is intersubjective agreement.
No problem with this, even if the "cosmos" (not the universal wave,
but the branch we are in) will appear eventually to be much plausibly
a first person plural construct (of numbers, not machine).
That is your hope, but it has yet to be demonstrated.
Whether the matter in this world is primary or emergent from
something more fundamental is an open question, and still the subject
of active debate in the physics community: I have no commitment to
either side of this argument. Likewise, there is an ongoing debate
among physicists about realist or anti-realist interpretations of
quantum mechanics, alongside more general debates about realism in
the philosophy of physics in general.
So I do not take kindly to attempts to silence me, or put me down, by
categorizing my views in simplistic terms, or in ways that I have
never entertained.
My problems with computationalism arise from the fact that I do not
believe in mathematical platonism,
I prefer to use "platonism" for Plato's theology, and use "realism"
here. I also do not believe in mathematical realism. But arithmetical
realism is needed by any one willing to give sense to the
Church-Turing thesis, or number theory.
Yes, I know that mathematical platonists often prefer to be called
mathematical realists. But you split too fine a hair by distinguishing
arithmetical realism from mathematical realism.
Arithmetical realism is neutral on finitism/not-finitism. It is just
the agreement with Robinson arithmetic. It is even consistent with
ultrafinitism. You can believe in a biggest natural number. To be
sure, the proof of the consistency of RA + "there is a biggest natural
number" cannot be done by ultrafinitist means, but since Gödel we know
that the proof of consistency of a theory usually use more than the
theory.
and the fact that computationalism has not produced any concrete
results about the physical world -- it is all speculative --
There is noting speculative in showing that physicalism is
incompatible with mechanism, and mechanism has been the motor of
basically all progress in science since Diderot (who defined
rationalism by Mechanism).
Since your definitions of terms seems to change with context, I am not
at all sure what you mean here by "mechanism". Is this the same as
computationalism? Or something quite different? Whatever you mean by
this, I would dispute that this has been any sort of motor for progress
in science since the 18th century -- you seem to disregard the empirical
content of science.
But you have not shown incompatibility of anything with physicalism (or
strong reductionism). You certainly haven't shown anything to be
incompatible with "primary matter", because none of us knows what that
might be.
Usually, non-mechanism is judged speculative, as it speculates on
actual infinities (from personal god(s) to substantial soul) for which
we have no evidence at all.
Then mechanism reminds us that primary matter is also speculative.
So, most would agree that mechanism is the less speculative theory of
mind that we have. Indeed, it even shows that physicalism and weak
materialism are incoherent, and reminds us that indeed, there are
never been any evidences for it.
It shows no such thing. We have repeated asked for this contradiction
between computationalism (mechanism) and physicalism (weak materialism),
and you are always forced to concede that there is no such
contradiction. The best you can come up with is that you cannot believe
anything else. But, i am sorry, but what you can or cannot believe has
no place in a scientific discussion. It is less that helpful for you to
continue to claim results that you are unable to substantiate.
It is just an extrapolation of our local feeling, similar to
extrapolate that the earth is flat from very local measurement.
there is not even a proof of the existence of an acceptable physical
solution. When you have derived Newton's laws from computationalism,
then we might have something to talk about.
The goal is to progress on the mind-body problem, and expose the
metaphysical prejudice. Then, criticizing a metaphysics because it
does not give result in physics, is like criticizing physics because
it does not give a recipe for the pizza.
Who says physics does not have a recipe for pizza? If your goal is to
progress the mind-body problem, you should not in that endeavour make
all sorts of extravagant claims about physics -- such as the reversal
between physics and arithmetic -- and repeatedly state that the test of
your theory is its agreement with physics. As you say, if all you are
doing is metaphysics, then you should stay clear of the hard science
and not attempt to replace physics by something else. But, in so far as
you make claims about physics, it is perfectly legitimate to criticize
you for the content of those claims.
Today, mechanism seem to be the only theory which propose an
explanation why the average universal numbers develop some physical
beliefs, and is the only one capable of explaining the difference
between quanta and qualia.
I think neuroscience, with its reliance on the undisputed concept of the
supervenience of the mind (consciousness) on the physical brain, might
be a more productive path to follow. You are like a man with a hammer,
for whom everything seems like a nail. You are a man who is fascinated
by logic, so you seen everything as a problem in logic. Others might see
things a little more clearly.
Bruce
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