On 09 Jan 2014, at 05:55, meekerdb wrote:

Bruno writes Bp & p, where "Bp" ambiguously means "Proves p" (Beweisbar?) and "Believes p".

What is ambiguous? I said that I limit the interview to Platonist *correct* machine, believing in arithmetic or in recursively enumerable extension of arithmetic. And the fact that the machine cannot prove Bp -> p for all p, suggest that provability obeys to the axioms I gave for belief, and not for knowledge (where Bp->p is not just true but believed as well).



"Believes p and P" is then a belief that is "true".

OK. That's correct.


I put scare quotes around "true" because I think it just means "is a consequence of some (Peano's) axioms", which is not necessarily the same as "expresses a fact".

At the meta-level (G*), that is true, but the machine does not know that, and for correct machine, this change nothing. We have Bp -> p (as a theorem of G*, not of G).

Bruno





Brent

On 1/8/2014 2:11 PM, John Mikes wrote:
Bruno and Brent:

did you agree whether "TRUE BELIEF" means in your sentences

1. one's belief that is TRUE, (not likely), or
2. the TRUTH  that one believes in it (a maybe)?
(none of the two may be 'true').

JM


On Wed, Jan 1, 2014 at 5:50 AM, Bruno Marchal <marc...@ulb.ac.be> wrote:

On 31 Dec 2013, at 21:09, meekerdb wrote:

On 12/31/2013 1:07 AM, Bruno Marchal wrote:
only rules to extract knowledge from assumed beliefs.


?
I answered "no" to your question. Knowledge is not extracted in any way from belief (assumed or not). knowledge *is* belief, when or in the world those beliefs are true, but this you can never know as such.

Since your theory to an infinite number of semi-classical worlds with different events (and even different physics) it seems that "true belief" is not a very useful concept.

It is, because by incompleteness, we will have that Bp & p (true belief) obeys a different logic (an epistemic intuitionist logic) despite G* knows that it is the same machine, having the same action. The machine just dont know that, although it can infer it from comp + a sort of faith in herself.



Every belief is going to have probability zero of being true.

neither Bp nor Bp & p is a priori related to probability. For this you need []p -> <>p, which is ocrrect for Bp & p, though, and indeed a physics appears already there, but that is a sort of anomaly (which confirms what I took as an anomaly in Plotinus, but the machine agrees with him). Now, Bp, when present in the nuances, gives the logic of the corresponding "certainty", so it is trivially a probability one. We need to extract the logic, and the probability different from 1 are handled by the mathematics, and is related to the Dp (not Bp). The probability bears on the accessible "worlds".



The interesting concept is the probability of future events relative to one's current state.

That's exactly why we need to go from Bp to Bp & Dt (or Bp & Dt & p, or actually Bp & p). This gives the relevant notion of relative consistency together with some temporal interpretation.

Bruno


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