On 6/1/2016 5:19 AM, Bruno Marchal wrote:

On 01 Jun 2016, at 09:53, Pierz wrote:



On Wednesday, June 1, 2016 at 4:44:33 AM UTC+10, Brent wrote:



    On 5/31/2016 10:08 AM, Bruno Marchal wrote:
    >
    > On 31 May 2016, at 00:36, Pierz wrote:
    >
    >> Clark v Marchal! I love this match-up. I predict it will go 47000
    >> rounds without a knockout!
    >
    >
    > I am interested in the problem why some machine get stuck at
    step 3 of
    > the UDA :)
    >
    > The translation into arithmetic of the reasoning does provide
    light on
    > this, if not an answer to that question. An ideally arithmetically
    > correct machines cannot believe in computationalism, she will not
    > identify her soul with her body or relative Gödel number, that
    is she
    > will not identify herself with any third person description of
    what
    > she really feel to be herself. The soul of the machine is not a
    > machine from the soul's machine point of view.
    >
    > That is well sum up by simple theorem in G and G*. The
    machine's body
    > can be identified with its provability predicate []p. When PA talk
    > about her provability abilities, she derives them from a specific
    > thrid person description of its beliefs and how to generate them.
    > Now, accepting the classical analysis of knowledge, and
    defining it in
    > the Theaetetus' manner, by []p & p (p sigma_1 arithmetical
    > propositions) and "[]" representing Gödel's arithmetical
    beweisbar),
    > we get that
    >
    > 1) G* proves []p <-> ([]p & p)
    >
    > 2) G can't prove in general that []p <-> ([]p & p)
    >
    > and indeed, the logic of []p & p will be quite different from the
    > logic of []p, due to incompleteness.
    >
    > I define the (proper) theology of the machine by G* minus G.
    The local
    > identity of the soul ([]p & p) and the body-brain-program ([]p) is
    > true, but not provable, not even taken as an axiom. It is
    necessarily
    > a non justifiable belief, an hope or a fear.
    >
    > The other very nice thing, also, is that "[]p & p" does indeed not
    > admit any third person description available in its/her/his
    language.
    > Then it also defines an arithmetical interpretation of
    intuitionistic
    > logic (with the solipsist identity of truth and the personal
    mental
    > constructions), and when p is restricted in the sigma_1 (complete)
    > domain (= UD*), we get a quantum logic, which was expected for
    the UDA
    > reson, but still surprising as it marries antisymmetry (related
    to the
    > logic of []p & p (S4Grz)) with symmetry (related to []p & p
    when p is
    > sigma_1).
    >
    > Judson Webb said that Gödel's theorem was a lucky chance for the
    > Mechanist theory of mind, but here we see that (Everett) QM, even
    > formally, is even a bigger chance for Mechanism.
    >
    > Now this remark, that machines cannot believe in Mechanism (and
    its
    > consequences), might apply better to someone like Craig
    Weinberg, (if
    > you remember the conversations here) and less to John Clark, who
    > "accept (and even practice) Mechanism, but still get stuck for
    unknown
    > reason (at step 3). We need another theory, which I think might
    > involve notion of susceptibility and more emotional human
    stuff. Now,
    > if you can make (logical) sense of his refutation of step 3,
    you would
    > help!
    >
    > Note: I have introduced a new term: the surrational. It is,
    like G*
    > minus G, the part of the truth *on* a machine that a sound machine
    > cannot believe/prove/justify.

    In that formulation you take believe, prove, and justify to have the
    same extension.  But that's not a good model of anyone I know.  In
    general believe many things they cannot prove from some set of
    axioms -
    and even if they could, their "proof" is contingent on the axioms.

    Brent

I tend to agree. Indeed the notion of "belief" is a very complex one, psychologically. For example, a person might believe (or more properly, believe they believe) in a doomsday prophecy, and yet as the moment arrives uneventfully, find themselves quite unsurprised. In other words, they were wrong about what they thought they believed. Or a person might believe their husband to be a good person, but upon his being charged with murder, discover that they "knew all along, deep down". And so on. Sometimes I think what we "believe" is merely what we assert to ourselves to be true,

Yes.



and this assertion is in real life often not based upon rational evidence, let alone anything as rigorous or abstract as an "axiom".

OK. But for the derivation of physics, we limit ourselves to simple correct beliefs in arithmetic and (mathematical) induction. If the machines has other beliefs (like the earth is flat) all what counts is that she cannot use such beliefs to get wrong artithmetical propositions. So, in case the machine believes that the earth is flat, and in case we give her evidences or proofs that the earth is not flat, we expect her to revise its beliefs on Earth, and not to conclude "oh, so the earth is flat and not flat, so I can prove A & ~A, so I can prove false, so I can prove that 0 = 1. There is no need for the machine to be more rational than that, nor to have only correct beliefs. Only her beliefs in elementary arithmetic (and thus in elementary computer science) are needed for her to derive the physical laws. And indeed, that is what she does.


I'm not sure where that leaves a theory of humans as arithmetical machines, but the level at which human beliefs about the self and the world are formed and justified seems a long long way from the level at which the "beliefs" of logicians are formed.

For the logicians and philosophers, the only important things about belief (beyond being rational, i.e. close for modus ponens) is that they can be false. The only axioms needed is that B(p -> q) -> (Bp -> Bq) + B('x + 0 = x') + B('x + s(y) = s(x + y)') etc. Note that such beliefs are not assumed, they are derived *in* the theory with axioms x + 0 = x, x + s(y) = s(x + y), etc. (That is NOT obvious, but already done essentially in Gödel 1931).

But in Gödel B stands for "provable", not "believes".

Brent

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