Stathis Papaioannou wrote:
On Friday, April 17, 2015, Bruce Kellett <bhkell...@optusnet.com.au <mailto:bhkell...@optusnet.com.au>> wrote:meekerdb wrote: On 4/15/2015 11:16 PM, Bruce Kellett wrote: LizR wrote: On 16 April 2015 at 15:37, Bruce Kellett <bhkell...@optusnet.com.au <mailto:bhkell...@optusnet.com.au>> wrote: Bruno has said to me that one cannot refute a scientific finding by philosophy. One cannot, of course, refute a scientific observation by philosophy, but one can certainly enter a philosophical discussion of the meaning and interpretation of an observation. In an argument like Bruno's, one can certainly question the metaphysical and other presumptions that go into his discourse. Yes, of course. I don't think anyone is denying that - quite the reverse, people who argue /against /Bruno often do so on the basis of unexamined metaphysical assumptions (like primary materialism) And the contrary, that primary materialism is false, is just as much an unevidenced metaphysical assumption. But it's not an assumption in Bruno's argument. As I understand it, his theory in outline is: 1. All our thoughts are certain kinds of computations. 2. The physical world is an inference from our thoughts. 3. Computations are abstract relations among mathematical objects. 4. The physical world is instantiated by those computations that correspond to intersubjective agreement in our thoughts. 5. Our perceptions/thoughts/beliefs about the world are modeled by computed relations between the computed physics and our computed thoughts. 6. The UD realizes (in Platonia) all possible computations and so realizes the model 1-5 in all possible ways and this produces the multiple-worlds of QM, plus perhaps infinitely many other worlds which he hopes to show have "low measure". I leave it to Bruno to comment on whether this is a fair summary of his theory. I have difficulties with several of the points you list. But that aside, one has to ask exactly what has bee achieved, even if all of this goes through? I do not think it explains consciousness. It seems to stem from the idea that consciousness is a certain type of computation (that can be emulated in a universal Turing machine, or general purpose computer.) This is then developed as a form of idealism (2 above) to argue that the physical world and our perceptions, thoughts, and beliefs about that world, are also certain types of computations. But this is no nearer to an explanation of consciousness than the alternative model of assuming a primitive physical universe and arguing that consciousness supervenes on the physical structure of brains, and that mathematics is an inference from our physical experiences. Consciousness supervenes on computations? What sort of computation? Why on this sort and not any other sort? Similar questions arise in the physicalist account of course, but proposing a new theory that does not answer any of the questions posed by the original theory does not seem like an advance to me. At least physicalism has evolutionary arguments open to it as an explanation of consciousness The physicalist model has the advantage that it gives the physical world directly -- physics does not have to be constructed from some abstract computations in Platonia (even if such a concept can be given any meaning.) If you take the degree of agreement with observation as the measure of success of a theory, then physicalism wins hands down. Bruno's theory does not currently produce any real physics at all. The discussion of the detailed steps in the argument Bruno gives is merely a search for clarification. As I have said, many things seem open to philosophical discussion, and some of Bruno's definitions seem self-serving. When I seek clarification, the ground seems to move beneath me. The detailed argument is hard to pin down for these reasons.Physicalism reduces to computationalism if the physics in the brain is Turing emulable, and then if you follow Bruno's reasoning in the UDA computationalism leads to elimination of a primary physical world.
But physics itself is not Turing emulable. The no-cloning theorem of quantum physics precludes it.
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