On 7/7/2011 12:11 AM, Colin Geoffrey Hales wrote:


You have missed the point. When you feel pain in your hand your are feeling it because the physics of specific specialized small regions of the cranial central nervous system are doing things. This includes (1) action potentials mutually resonating with (2) a gigantic EM field system in extremely complex ways. _Exactly how and why this specific arrangement of atoms and behaviour delivers it is irrelevant. It is enough to know that it does_. More than that it is the ONLY example of natural cognition we have.

The whole point of this argument is that unlike any other time in the history of science, we are expecting the particular physics (that we know delivers cognition) can be totally replaced (by the physics of a computer or even worse, a non-existent Turing machine) , yet still result in cognition.

It's not the "totally" that is the problem. Bruno asks if you can replace a part of a brain with something that does the same computation (at some level) and have no effect on the conscious (or unconscious) life of that person. This certainly seems plausible. But it relies on the remaining world to continue interacting with that person. So in his idea of replacing physics with computation he has to suppose replacing all of the brain plus everything that interacts with the brain. In other words a simulation of the person(s) and the universe. Then within the simulation EM fields are computed and supply computed illumination to computed eyes and brains. He invites us to consider all this computation done by a universal dovetailer, a computer which also computes all possible computable universes as it goes. But to me it seems a great leap from computing what a piece (or even all) of a brain does to computing a whole (quantum) universe. I'm not at all sure that the universe is computable; and it's certainly a different question than whether I would say yes to the doctor.

If you believe that computed physics equations is indistinguishable from physics, to the point that a computed model of the physics of cognition is cognition, then why don't you expect a computed model of combustion physics to burst into flames and replace your cooker? Why can't you go to work in a computed model of a car that spontaneously springs into your life? Why don't you expect to be able to light your room with a computed model of the physics of a lightbulb? Why can't you compute Maxwell's equations and create a power station?

You can within a simulation.

Here's the mantra (a) "COGNITION IS COMPUTATION"

Well if so, then why isn't ILLUMINATION BY LIGHT a result of COMPUTATION OF LIGHTBULB PHYSICS? That would be the prediction if (a) were true. A computation of hurricane physics is not a hurricane. But then nobody wants to create a hurricane, nor do we expect the computation to produce one!..... _But_ we _do_ want to literally create cognition...and we do then, for no valid reason, assume that computation delivers it. We are being inconsistent and a fundamental level. We build Pinocchio the computational puppet and kid ourselves it's somehow a boy.

A computer is not a set of resonating action potential/electromagnetic fields of the kind found in a brain, not matter what the program is. I know this because I am an electrical engineer+neurobiophysicist. You cannot argue that the result is cognition without making a dramatic presupposition/conflation about computing of the kind that creates this mess in the first place.

Those action potential and EM fields are all computable. So why would it not be possible to recreate their interface with the rest of the brain by a computer controlled artificial neuron or other artificial structure?

This is the logical result of that belief. We have the natural world to work with (atoms and space). That's our computer. Either the (Turing) computational equivalence applies everywhere or it doesn't apply at all. Therefore it doesn't apply at all.

_We can't have it both ways_.

That's sort of what Bruno argues. Once he concludes that the universe can be computed he says that means material bodies can't exist (but he really means they can't be fundamental). Implicit in this though is that computations "exist" with material instantiation, i.e. Platonism.




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