On 25/06/2016 1:36 am, Bruno Marchal wrote:
On 24 Jun 2016, at 08:42, Bruce Kellett wrote:
On 24/06/2016 3:32 am, Bruno Marchal wrote:
On 23 Jun 2016, at 03:01, Bruce Kellett wrote:
..... if physics can be seen as possible a simulation run by some
alien civilization, then physics is certainly Turing emulable.
Which is not the case. The alien can fail us only for a finite time.
Prove that without assuming computationalism. What in our physical
world is not Turing emulable?
Consciousness, and the appearance of primary matter (probably the
phenomenological "collapse").
Comnsciousness is not Turing emulable? You had better say "No" to the
doctor, then. Primary matter might be a problem only if you assume
computationalism. But if you don't assume computationalism, you have no
problems.
What could not be simulated by an alien running a simulation on a
physical computer? Prove that we are not brains-in-a-vat.
If Nature satisfies qZ1*, then we can take that as an evidence we are
at the physical bottom, which means we are in infinitely many "brain
in a vat" in arithmetic.
Rubbish. I thought it was part of your argument that we can't know what
substrate our computations are running on -- there is no difference
between the physical brain and the computer simulation (at the correct
level). In that case, we can never know that we are not a BIV, or that
we are not part of a simulation run by some alien civilization.
If Nature violate qZ1*, then: either computationalism is wrong, of we
are in a brain in vat made by people closer to the bottom.
Computationalism could well be wrong,and we could still be BIVs.
Or maybe computationalism is the same as brains-in-a-vat --
consciousness and the physical world are both merely illusions.
Consciousness is certainly not an illusion, as it is a form of
knowledge, linked to truth by definition. And that mirrors the fact
that we cannot doubt being conscious, given than a genuine doubt
require consciousness. Consciousness can be defined by []p & p, with p
= t, at least for a first approximation, and this makes it non
definable in arithmetic, yet unavoidable for all universal numbers,
and this knowingly so for the Löbian numbers. The physical is an
illusion, if you want, but a lawful persistent one, and we can compare
its structure with what we actually observe.
So you grant priority to what we observe? Just as well, because that is
what is basic. As Brent says, consciousness in isolation is nothing --
we have to be conscious of something, and the only thing we can be
conscious of is the physical world. The external world is, therefore,
essential for the existence of consciousness, and it is logically prior.
One is necessarily as sure of the external world as one is of being
conscious, the external defines the conscious state: 1p does not exist
without the corresponding 3p.
Bruce
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