On 14 Nov 2014, at 08:46, LizR wrote:

In case anyone isn't acquainte with the library of Babel, it contains all possible books of a particular length (I think it's around 400 pages) which use a certain number of characters, say 30. If we assume there are, say, 2000 characters per page, we get (I think) 30 to the power of 800,000 books, a large but finite number of the sort I think Daniel Dennett called "Vast" (meaning ridiculously larger than any numbers that could be used to count anything in the observable universe. The LOB would dwarf the observable universe). It's similar to Russell's TON in that it contains essentially no information - or certainly no useful information. As Borges mentioned it contains the accurate catalogue of the Library (presumably occupying many lightyears of shelves, if assembled in one place) together with a "Vast" number of innaccurate catalogues. It also contains every book ever written, including the one in which the short story in question appears. This is rather similar to the multiverse, in which every story ever written is being played out somewhere (in the case of Harry Potter, with the help of an awful lot of quantum uncertainty happening to come out in just the right way).


But note that the UD* contains all programs books, but also all execution of the programs, and all relative state of the "readers" of all book. Russell does not use computationalism, so he needs some absolute sampling in his theory. Don't confuse a book, or a description of a computation (in arithmetic), and an execution of a computation (in arithmetic). Those are quite different, and that play some role in the step 8, to graps for example that a movie does not implement a computation. You really need the truth of some number relation, which does not exist in the description of computation. It is a subtle but very important point. In particular, the counting algorithm 0, 1, 2, 3, ... contains all books, but with addition and multiplication, you still don't get the UD nor UD* (the execution of the UD).

To get the UD, and UD*, you cannot start from nothing, you will need some non-zero information initializing the theory, like the axiom of arithmetic & logic, of the axioms on combinators and equality. Like you need the SWE in physics, even if you start from the vacuum. The UD is a dynamical object (in the math sense, not the physical).

A theory must say what is assumed as initial objects (like the numbers, the sets, or the particles), and give the basic laws (addition and multiplication) Then a notion like "nothing" is theory dependent. The hard part is the choice of the "thing" we need to get the epistemologies (where physics resides when we assume computationalism). But then comp shows that physics is theory independent, so you can assume any theory you want, as long as it is Turing complete. You should better not take a theory like string or QM, because it will be confusing when deriving physics from it.

Bruno





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