On Wednesday, May 10, 2017 at 6:40:19 AM UTC+10, Brent wrote:
On 5/8/2017 10:16 PM, Bruce Kellett wrote:I find Barbour's idea of time capsules quite helpful here. Each time capsule is a self-contained conscious moment. There is no progression necessarily involved, so the computation that gives one conscious moment is complete in itself, and independent of other such conscious moments. (In Barbour's picture, these moments are points in configuration space that are related physically, but we do not use that aspect here.) In the moment, you are self-aware, and aware of memories that give you a concept of self. But in that moment there is no way that you can know whether these memories are veridicial or not -- they could well all be completely false, in which case there is no "you" that continues through time as a related series of experiences. Each experienced moment is complete in itself, and there is no continuation. If all you have is the moment of consciousness, you can go no further than this. It is all an illusion, and there is no physics to extract. Of course, this is a solipsistic conclusion, but there is nothing in our experience of consciousness that shows solipsism to be false. The "I" is the "I" of the moment, nothing more. Now consider the UD in arithmetic. It dovetails all possible programs -- does all possible computations -- but most computations have nothing to do with consciousness. If we use Boltzmann's thermodynamics as an illustration of the situation, the computations of the dovetailer represent a state of thermal equilibrium, a state of maximum entropy. The characteristic of thermal equilibrium is that every microstate is equally likely -- a state of complete chaos. Similarly, in the dovetailer, every computation is equally likely and there is no order whatsoever. Occasionally, in Boltzmann's thermal equilibrium there are fluctuations to states of lower entropy in which some order emerges, but according to the second law of thermodynamics, these always return to equilibrium. Similarly, in the computations of the dovetailer, there are occasionally computations that make some sort of internal sense. Some of these correspond to conscious moments. But, as in the thermal case, these rapidly return to meaningless noise. Small fluctuations to momentary order are overwhelmingly more likely than larger fluctuations to order that persists over time -- or computations that correspond to an extended sequence of (consistent) conscious states. In fact, within the dovetailer there are undoubtedly sequences of computations that correspond to the entire history of the observable universe, from the big bang through to the final heat death. But such calculations are of measure zero in the overall picture. So, if one is to take the statistics of computations that pass through one's instantaneous conscious state in order to extract meaningful physics, one will find that the overwhelming majority of these computations are of short-lived conscious moments that rapidly return to meaningless chaos, nothing more. The dovetailer would then say that no consistent physics can ever be extracted from the statistics over conscious moments, because these statistics are dominated by chaotic continuations.I agree with that except I think you are not recognizing a drastic difference of scale. A human conscious thought is something with duration, something on the order of tens of milliseconds. The substitution that you say "yes, doctor" to, must operate at a much higher frequency. So I conceive of the UD producing threads of computation consisting of many successive states within one "thought" and there will be threads in other programs being executed by the UD which are sufficiently similar over this sequence of states as to constitute the "same thought" because thoughts are classical level emergent things. In Barbours metaphor this a kind of stream of fog. If you take this view of thoughts having duration then they can overlap and form a kind of continuum. Bertrand Russell gives this analysis of time as a perception in one of his more technical papers. But a consequence of this is that what picks out a "thought" from just noise is this persistent coherence over the duration of many (countably infinitely many) thread of UD computations. This persistence is what constitutes physics in that consciousness because it must account for all interactions that are perceived as external and it must make them more coherent than just noise. So a happy solution to the measurement problem would be to show, purely as a matter of arithmetic, that such coherent threads of significant length have high measure. Brent
I agree that I did not pay much attention to the duration of a "conscious moment". I think what you say about thoughts having duration, and the overlap giving a sense of continuity reflects our own experience of consciousness, and the possibility of an 'internal narrative' gives our sense of identity cohesion. But this comes from our embedding in a physical world, where there are clocks and an external time, with durability given by universal conservation laws and the like. The question is, can this be extracted from the UD in arithmetic?
If we look in more detail at how the dovetailer operates, it executes all possible programs in a 'dovetail' fashion -- stepwise as it were, not by executing each program in sequence. The question arises as to what each step consists of -- what is executed before the dovetailer moves on to the next program (or back to previous programs)? A step could be something like a single assembler instruction, but that is processor dependent, and could involve many hundreds of individual 'gate' operations. I think it is probably more useful to think in terms of a basic Turing machine, so each step is a single Turing operation -- read the tape, mark or erase or move, according to the current machine state, and update the machine state. The trouble is that the machine state will then not be correct for the next step of another program, so we have to have some way that the TM can ready its necessary ready state at each step of each program. I think this is necessary whatever processor one imagines -- registers and the like must all be updated before the next program step is executed.
But let us imagine that we have some way of solving this problem. It is then clear that the steps of the dovetailer are essentially random. The rules governing each operation in each program are deterministic, but, as in an ideal gas, after a sufficient period of operation, the sequence of steps is indistinguishable from random. Also, I have not specified any notion of time at this point. There is no time in arithmetic, so we can make do with the machine stepping rate as a clock, which may not have anything in common with a physical clock, such a thing has to emerge when we get some physics.
So what might constitute a conscious moment in this random sea of TM operations? There is a question here that I have not seen clearly answered: Does the 'program' that constitutes a conscious moment correspond to a consecutive sequence of dovetailer steps? Or does consciousness reside in one of the programs themselves -- so that separate steps making up the conscious moment may be separated by an arbitrarily large number of machine steps? Given the random nature of the programs themselves, and the randomness of the sequence of machine steps, I don't think it actually makes any difference which picture you have in mind. For definiteness, I will say that whatever computation underlies consciousness is made up of a sequence of machine steps -- time can then be related to the number of elementary steps involved.
Given the random nature of individual steps, the emergence of a coherent conscious moment is akin to a chance fluctuation in a gas (or in the state of maximum entropy characteristic of thermal equilibrium). The longer the sequence of steps required to elicit consciousness, the less likely it is that such a fluctuation will occur. The vast majority of partial conscious moments will be fleeting chance coincidences, and more extended fluctuations will also rapidly dissolve into chaos.
Given that the dovetailer in arithmetic is infinite, then anything of non-zero probability will occur somewhere, so there will undoubtedly be computational sequences that render conscious moments of any particular duration. And every part of those extended sequences will also occur, many more times, as fragmentary sequences. But since those fragmentary sequences relapse into chaos, the idea of consistent continuations of computations arising from the measure over these fragments seems somewhat illusory.
My conclusion from this is that the prospects for deriving a coherent picture of consciousness in this way, much less a coherent physical world, is quite small. We must remember that the "Yes, doctor" scenario, from which the computationalist journey starts, takes place in a physical world -- the computer that is to replace your brain is a physical computer, with a physical clock and a coherent series of computational steps that can render a simulation of the brain processes at whatever level is required. I suspect that anything that reproduces such a computer will have zero measure in the UD
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