On 29 Oct 2012, at 17:03, John Clark wrote:
On Mon, Oct 29, 2012 Bruno Marchal <[email protected]> wrote:
>> We now know that computing or thinking is physical,
> We don't know that.
We know that as well as we know anything about physics.
This is not valid. A priori we can be dreaming in some world based on
a different physics. Or, as with comp we might belong only to
sophisticated computations, which are entirely emulated already by
degree four diophantine polynomials.
And computation is a the start a purely mathematical, indeed
arithmetical, concept. All physical computations are defined by the
physical incarnation of the corresponding mathematical computation.
> We deduce that in the Aristotelian's theories.
I have no idea what if anything that means.
There are two main rational conception of reality.
1) the Aristotelian one, in which the ultimate reality is a physical
world, and the erst emerges from it.
2) the Platonist one, in which the physical reality is the border, or
the shadow of a vaster invisible reality.
The idea that today science has solved the question of deciding
between those two conception is a crackpot idea of sunday type
philosophers.
The UDA illustrates this, by showing that if we take computationalism
seriously enough, the Platonist conception of reality is about
unavoidable, and that the physical reality is no more a primitive
notion, but a derivative of an ability owned by complex relation
between some numbers. This makes also comp testable, as the derivation
is constructive (albeit technically difficult).
>> it takes energy to do it and it gives off heat;
> Actually computation can be made reversibly, without dissipation
of energy.
With reversible computing you can make the amount of energy used for
a calculation arbitrarily small and thus the heat emitted
arbitrarily close to zero BUT, as I said before, only at the price
of slowing down the computation;
I give a good energy at the start, and I can sped the non dissipating
process at the speed limited by light.
we were talking about the theoretical feasibility of making a
prediction and making a forecast of yesterday's weather is not of
much use.
No. We were talking on something else.
Bruno
http://iridia.ulb.ac.be/~marchal/
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