OK, so I've read the UDA and I 'get' it, but at the moment I simply can't accept that it is anything like a 'proof'. I keep reading Bruno making statements like "If we are machine-emulable, then physics is necessarily reducible to number psychology", but to me there remain serious flaws, not in the logic per se, but in the assumptions.
Bruno says that "no science fiction devices are necessary, other than the robust physical universe". He also claims that to argue that the universe may not be large or robust enough (by robust I assume he means stable over time) to support his Universal Dovetailer is "ad hoc and disgraceful". I think it is anything but. To describe such an argument as "disgraceful" is to dismiss with a wave of the hand the entirety of modern cosmology and physics, disciplines which after all have managed to produce a great deal more results in the way of prediction, explanation and tangible benefits than Bruno's theory (I insist it is a theory and not a 'result'). As a computer science expert, I assume Bruno is aware of modern computational approaches to physics. Such approaches explicitly forbid any kind of 'infinite informational resolution' as is required by Bruno's theory. The information content of the universe is seen as being a fundamental quantity much like energy, constantly transforming but conserved over the whole system in the same way energy is. This computational approach indeed seems to be the *basis* for much of Bruno talks about (computability, emulability and so on are all fundamental ideas), but then he flies in the face of it by proposing some kind of automated, Platonic computation devoid of any constraints in terms of state memory or time. Let's take a look at the UD. Obviously this is not an 'intelligent' device, beyond the intelligence implicit in the very simple base algorithm. It just runs every possible computer program. Random computer programs are made of and produce *static*, they are a random arrangement of bits. Now clearly, we know that if you look at a large enough field of static, you will find pictures in it, assemblies of dots that happen to form structured, intelligible images. Likewise in the field of random computed algorithms, very very occasionally one will make some kind of 'sense', although the sense will naturally be entirely accidental and in the vast, vast majority of cases will give way a moment later to nonsense again. So when the UD runs through its current sequence of programs, what it is really doing is just generating a vast random field of bits. Nonetheless, each of these individual programs needs to have potentially infinite state memory available to it (the Turing machine tape). Now the list of of programs run by the machine continues to grow with each iteration as it adds new algorithms, so it takes longer and longer to return to program 0 to run the next operation. As it needs to run *all* programs, a necessarily infinite number, it requires infinite time, but for some reason Bruno thinks this is not important. Either it has infinite processing speed as well as memory, or it has infinite time on its hands. Fine. But then we can simply dispense with the UD altogether and just gather up its final results, which is an infinite field of static, a giant digital manuscript typed by infinite monkeys. Everything capable of being represented by information will exist in this field, which means it is capable of "explaining" everything. And nothing. We have to deconstruct the notion of "computation" here. Computation is the orderly transformation of information. But the UD's orderliness is the orderliness of the typing monkey. If it is orderly at all, it is by mistake. By talking about it the UD as performing computation more intelligence is implicitly imputed than this hypothetical device possesses. Yes, it would generate every possible information state, and would therefore create me and all my possible futures, but these 'pictures' would have no coherence, would immediately dissolve back into the static they emerged from. The UD, as a generator of static, cannot explain coherence in my experience. There is a fundamental circularity here. Something must explain the coherence of 1p and 3p accounts (laws of physics). Because the UD must exist (someone please explain this to me!), the explanation must lie in the UD. Because the UD is pure computation, the laws of physics (the coherence) must be reducible to principles of computation. But why no earth must the UD exist? And if it did exist, the reduction of the UD to an infinite static field shows that it is devoid of such explanatory power. Only if there is something about the UDA that confines it to meaningful, orderly algorithms (whatever that might mean), can Bruno's argument follow. But the UD's algorithm is a few lines of code, there is no hidden magic to allow it to select such algorithms. We have to throw out the UD, not the laws of physics. The whole notion of the 'teleporting consciousness' is obviously fundamental to the argument. It is assumed by 'yes doctor' (and argued for in step 8) that consciousness is not bound to any physical substrate, but is a function of certain computational states - ie arrangements of bits. What again is deeply unclear is how a boundary is formed around such arrangements to give them coherence in the overall field. In an infinite field of transforming information - the output of the UD - there will be areas of apparent coherence, but the coherence is apparent, not real. Such a coherent region could only be identified by a mind (or computer) capable of recognizing coherence or pattern. The UD does not possess such intelligence, or only as yet another algorithm which is on the same level as the other algorithms, and not capable of accessing the states of all other computational threads. You'd need to posit some new level of meta-computation picking out the coherent results of the UD from the incoherent ones, but how does *it* recognise coherence? It's an infinite regress. And how do these coherent areas of the field which we call consciousnesses (or 1p) connect with their self-similar regions in the UD output? There may be pictures of me in all possible states within this field, but they will be completely disconnected from one another. How does the consciousness apparently implicit in the picture of me 'join the dots' between these random images to make a timeline which defines my history? The argument that it is 'machine psychology' or 'laws of arithmetic' merely begs the question - or obfuscates it. In the end, the UDA merely asserts the results of its own assumptions, but the assumptions are profoundly doubtful. You can dress the emperor's nakedness up in a lot of fancy mathematical formulism and obscure verbal manoeuvres, but he is still naked. Infinite randomness is a 'powerful' explanation because you can find anything you like inside it. But when you see how vast the sea of surrounding meaninglessness is, you realise the bankruptcy of that mode of explanation. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to firstname.lastname@example.org. To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/everything-list?hl=en.