Jason Resch wrote:


On Thu, Jan 22, 2015 at 12:48 AM, Bruce Kellett <[email protected] <mailto:[email protected]>> wrote:

    John Clark wrote:

        On 18 January 2015 at 18:27, Jason Resch <[email protected]
        <mailto:[email protected]> <mailto:[email protected]
        <mailto:[email protected]>>> wrote:

                 >  Do you believe that *one and only one* of the following
                statements is true?
                the 10^(10^(10^100))th decimal digit of pi is 0
                the 10^(10^(10^100))th decimal digit of pi is 1
                the 10^(10^(10^100))th decimal digit of pi is 2
                the 10^(10^(10^100))th decimal digit of pi is 3
                the 10^(10^(10^100))th decimal digit of pi is 4
                the 10^(10^(10^100))th decimal digit of pi is 5
                the 10^(10^(10^100))th decimal digit of pi is 6
                the 10^(10^(10^100))th decimal digit of pi is 7
                the 10^(10^(10^100))th decimal digit of pi is 8
                the 10^(10^(10^100))th decimal digit of pi is 9
                Either you answer yes, or no to that question. If you answer
                yes, I don't see how you can escape mathematical realism.


        Seth Lloyd  has estimated that the maximum number of
        computations that could be performed in the visible universe is
        about 10^121 operations on 10^90 bits,  if this is insufficient
        to find your number is it meaningful to say pi has a
        10^(10^(10^100))th decimal digit? I don't know, it depend on if
        mathematics gave rise to physics or physics gave rise to
        mathematics.


    Realist and constructivist approaches to mathematics do not cover
    all the possibilities. You can believe that one of the above
    statements is true without knowing which is true. It is logically
    necessary that one of the statements is true, given the meanings of
    the terms involved. This does not entail mathematical realism.


So one of them is true, but can you (or anyone in this universe) prove:

        the 10^(10^(10^100))th decimal digit of pi is 0   ?
        the 10^(10^(10^100))th decimal digit of pi is 1   ?
        the 10^(10^(10^100))th decimal digit of pi is 2   ?
        the 10^(10^(10^100))th decimal digit of pi is 3   ?
        the 10^(10^(10^100))th decimal digit of pi is 4   ?
        the 10^(10^(10^100))th decimal digit of pi is 5   ?
        the 10^(10^(10^100))th decimal digit of pi is 6   ?
        the 10^(10^(10^100))th decimal digit of pi is 7   ?
        the 10^(10^(10^100))th decimal digit of pi is 8   ?
        the 10^(10^(10^100))th decimal digit of pi is 9   ?

If you answer no to all 10 of those questions, then none of those statements is provable by any entity operating within this universe, yet we know one of the statements is true. So Pi is a mathematical object with properties that don't depend on the physical existence of conceptions/proofs realized by entities or processes operating physically. It follows then that if these properties don't depend on physical processes of this universe, that even if this universe did not exist at all, those properties would not be affected. And from that it follows that mathematical properties and truth statements concerning them have an existence independent of physics, hence mathematical realism.

Jason

No, your conclusion does not follow -- unless you have some non-standard meaning of mathematical realism. It is all quite simple, really. We have a certain set of axioms. Those axioms encompass the definition of pi which can be shown to be a transcendental number. These are simple consequences of the axioms. Nothing at all need exist, or in any sense be /real/, for all of this to be true.

Bruce

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