On 24 Aug 2014, at 22:43, meekerdb wrote:
On 8/24/2014 4:44 AM, David Nyman wrote:
On 23 August 2014 23:50, meekerdb <[email protected]> wrote:
You're saying it may be incoherent to reduce consciousness to
computation, if computation is reducible to physics? Why would
that be incoherent? Must 'reduction' necessarily be reduction to
the bottom to be coherent? Or are you assuming consciousness can't
be reducible to physics therefore it can't be reducible to some
intermediate (computation) that risks be reducible to physics?
No, I'm definitely not saying, in principle, that consciousness
couldn't be reduced to physics. Indeed my whole point has been that
if computation is, in the end, nothing over and above physical
action, any theory that links consciousness to computation is
tacitly a claim that consciousness is itself nothing over and
above physical action. That claim may be true, but it
can't be a claim about computation, only one about physics.
Why can the relationship not be (and I'm not claiming it is) that
1) Everything is physical.
2) Some physical actions constitute computations
3) Some computations instantiate consciousness.
Then, as you say "tacitly, consciousness is physical action", but
it's not "nothing over and above physical action"; it's particular
kinds of physical action. Being a particular kind is over and above
simply being a physical action. I realize that saying just what
makes this particular kind is problematic. But I think the same
problem arises for saying what computations instantiate
consciousness under CTM - whether it's reducible to physics or not.
Indeed, your own "engineering-level" analogies exploit precisely
this ambiguity.
You have yourself expressed the view (re Tegmark's ideas, as I
recall) that mathematics is a human invention: i.e. a collection of
abstractions from physical reality. On that basis, the very notion
of computation *could only be* a meta-mathematical metaphor
approximated by certain classes of physical action.
Well, I'd have said, "a constraining definition" instead of
"metaphor", but I guess I take your point.
I'm grateful to Bruno for pointing out that CTM, taken seriously,
rather than being merely a "psychological" theory riding on the
coat-tails of physics, must entail a profound "reversal" of
explanatory priority.
That's because Bruno rejects the link between 1) and 2) and takes
computation to exist in Platonia, independent of physics. So of
course with that assumption physics needs to either be explained
from computation (Bruno's program) or have it's own dualist basis.
I'm not so sure Platonia exists. Look up the old archive debates
between Bruno and Peter Jones.
I don't remember that Peter Jones have any problem with
"Platonia" (the sigma_1 complete, yet tiny part of arithmetic we need
for the ontic level).
Peter Jones was just thinking that this was not enough, and that some
primitive matter was needed to select some subcomputations in the
space of all computations (which is given by that sigma_1 complete
part).
It is the move still possible at step 7, to postulate a "small or non-
robust" primitive physical universe. Then I argue that the movie-graph-
argument, step 8, (MGA), shows that he still has to endow that
"primitive matter" with non-Turing emulable elements to make sense of
the selection, without too much magic, so that in any case, it rises a
doubt on saying yes to the doctor and believing that we can survive
through the "correct", at some "right" substitution level. It makes
Peter Jones argument into a "creationist" argument to prevent the
testing of an hypothesis. If that "magic matter" exists, let us test it.
Bruno
Brent
I have no idea whether this insight will lead, in the end, to a
correct TOE, but it seems clear that it does require computation to
take explanatory priority over physics.
David
On 8/23/2014 9:09 AM, David Nyman wrote:
On 23 August 2014 05:02, meekerdb <[email protected]> wrote:
What we observe in practice are physical devices of various kinds
(indeed, in principle, indefinitely many kinds) that we accept
FAPP as adequately instantiating particular classes of computation
within certain fairly stringent limits.
What we observe, aside from observing our own thoughts and maybe
even then, is always theory laden. Partly we see the world
through a theory of objects that evolution has provided us, sort
of naive physics, but a theory nonetheless as optical illusions
demonstrate.
And the relevance of this remark to my point is what, precisely?
Just a cautionary remark that observing a physical device already
involves assumptions that it is an experience that can in principle
be shared and agreed on by other observers - i.e. that it assumes
some physics.
To put it another way, we are prepared to interpret the normal
physical behaviour of such devices *as if* it instantiated the
mathematical notion of computation.
Right, because it usually (modulo a dropped bit or so) does.
Obviously. And your point is...?
These considerations should make it clear that any description of
the normal behaviour of a physical device as computation can only
be in a sense that is, ultimately, metaphorical.
I think you are too hung up on ontology. You denigrate everything
that's not in terms of the ur-stuff of (some unknown) true
ontology as metaphor or fiction. Why not accept that knowledge,
including knowledge of ontology, is always provisional and
uncertain and it's best to think of it as a model summarizing our
best idea - but not necessarily the one TRUE idea.
Maybe you are getting a little too hung up on what you imagine me
to be hung up on. If that is the case, it might make you somewhat
unreceptive at the outset to what you assume to be my line of
argument. I'm not trying to grind any axe in particular but only
to articulate what I suspect are sometimes unrecognised
assumptions as clearly as I can and then examine the consequences.
Of course I may well be wrong on any point and so my aim is to
encourage discussion from which I might learn.
In this particular case what I'm driving at isn't that either
matter or computation need be considered as some kind of mystical
"ur-stuff" (whatever that would be). What I'm questioning is
whether it is really coherent to attribute *first-person*
consciousness to "computation" against the background of any
theory that is committed to a physically primitive level of
explanation.
You're saying it may be incoherent to reduce consciousness to
computation, if computation is reducible to physics? Why would
that be incoherent? Must 'reduction' necessarily be reduction to
the bottom to be coherent? Or are you assuming consciousness can't
be reducible to physics therefore it can't be
reducible to some intermediate (computation) that
risks be reducible to physics?
I know you cross swords with Bruno over the meaning of primitive
in this context, but I don't see why this has to be problematic.
Primitive simply means the level of explanation to which it is
*assumed* every other level can be reduced.
I think we only "cross swords" when Bruno implies that any
reduction of consciousness to physical processes is the same as
asserting that some (undefined) physics is primitive. The way
theoretical physics has developed over the last century I wouldn't
be surprised if someone developed a fundamental theory of physics
based on homotopy theory or knots or numbers. But it wouldn't
affect the reduction of chemistry to physics and it might not
affect the reduction of computation to physics. I take "physics"
to mean the most fundamental science of what we can empirically
agree on - whatever it's ontology is. I think Bruno only differs
in that he thinks we can agree on things that are not empirical,
like arithmetic.
The point is not that we can know any particular theory of this
sort to be TRUE, but only that we should rigorously pursue its
consequences *as if it were*.
My point then is that we should start by treating a theory of
physical primitivism "as if true". If so, it is only consistent to
suppose that any phenomenon under consideration in terms of that
theory must be assumed to be adequately and fully accountable (at
least in principle) at its lowest level of physical reduction. You
persistently demur from this line of argument, but I think you
miss my point, which is entirely harmless in every case except (I
contend) that of the "1p part" of consciousness. It is entirely
possible to understand a physically-instantiated computation (and
hence, on CTM, an associated state of consciousness) to be the
same physical process regardless of the "level of reduction" at
which it is considered. After all, any such "level" is, in the
end, merely a term of art associated with the theory in question.
But what I'm questioning is whether it is coherent to (tacitly)
treat the 1p part as merely such a term of art.
?? Does "term of art" imply a third person description?
My sense is that you equivocate on this, because if we only
consider the 3p part (as in your analogy of the Mars Rover) the
point (i.e. 3p-reducibility) is indeed harmless. But the 1p part
resists 1p-reduction. It stubbornly is what it is. Hence my
question essentially is about the kind of theory required to make
sense of associating an irreducible 1p part with a reducible 3p
part. AFAICS such a question cannot even be posed coherently in
terms of physical primitivism.
Suppose that you have a theory which reliably tells you which 1p
qualia go with which 3p brain processes (the engineering level
solution to the mind-body problem). Does that "make sense of
associating an irreducible 1p part with a reducible 3p part."? Or
are you saying that such an association can't be a brute fact?
Indeed you have suggested that it is unreasonable to ask for this.
What inclines me to Bruno's ideas (assuming CTM of course) is that
this particular question may be better posed in terms of a theory
that takes computation, not physics, as its primitive.
Yes, I agree that it might be. But even if it provides a better
answer to the relation of qualia to brains, that doesn't make it a
better TOE if it can't solve the "white rabbit" problem. It will
just have traded one problem for another.
I think the remainder of your remarks equivocate on precisely this
3p-1p distinction, so I won't comment on them specifically. If
I've read you wrongly on this I'd be grateful for clarification.
No, I think that's a fair reading. As you note, I don't think it's
possible to have a 1p-reduction of the 1p part (if I understand
what you mean by 1p-reduction). I think the engineering level
solution may be the best that can be done.
Brent
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