• Re: Professor Eric Hehner's brilliant work

    From Richard Damon@21:1/5 to olcott on Mon Apr 21 18:43:14 2025
    On 4/21/25 4:27 PM, olcott wrote:
    WST Workshop on Termination, Oxford, 2018
    Objective and Subjective Specifications
    Eric C.R. Hehner
    Department of Computer Science, University of Toronto

    (6) Can Carol correctly answer “no” to this (yes/no) question? https://www.cs.toronto.edu/~hehner/OSS.pdf

    Is the perfect example of isomorphism to the halting problem's
    pathological input. The halting problem input D derives a self-
    contradictory question for H the same way that Carol's question
    is self-contradictory for Carol.

    No it isn't, as Carol is a voltional being while a decider is deterministic.

    Thus, the decider has effectively already made its decision on the input
    before the input is actually made, and thus the input can use that
    answer to thwart it.

    This just shows a category error in your logic. You don't seem to
    understand the deterministic behavior of programs, and the fact that all
    their behavior is created as soon as the program is created, even if
    they are never actually run or simulated. We just don't know what that
    behavior is.

    This goes back to another of your confusions, about the difference
    between Truth (which just is or isn't) and Knowledge, which might not be
    yet.


    Credit to Richard Damon for finding the loophole in the original question.

    Professor Eric Hehner PhD put the finishing touches on an
    earlier idea in serial collaboration with  Daryl McCullough.
    I quoted Daryl's work many many times without attribution
    before I finally found this original post:

       You ask someone (we'll call him "Jack") to give a truthful
       yes/no answer to the following question:

       Will Jack's answer to this question be no?

       Jack can't possibly give a correct yes/no answer to the question.

       https://groups.google.com/g/sci.logic/c/4kIXI1kxmsI/m/hRroMoQZx2IJ



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  • From Richard Heathfield@21:1/5 to olcott on Fri May 2 06:40:39 2025
    On 21/04/2025 21:27, olcott wrote:
    WST Workshop on Termination, Oxford, 2018
    Objective and Subjective Specifications
    Eric C.R. Hehner
    Department of Computer Science, University of Toronto

    (6) Can Carol correctly answer “no” to this (yes/no) question?

    Undecidability isn't restricted to Turing Machines.

    --
    Richard Heathfield
    Email: rjh at cpax dot org dot uk
    "Usenet is a strange place" - dmr 29 July 1999
    Sig line 4 vacant - apply within

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