On 12/12/2018 3:19 AM, Bruno Marchal wrote:

On 10 Dec 2018, at 20:26, Brent Meeker <[email protected] <mailto:[email protected]>> wrote:



On 12/9/2018 11:38 PM, Philip Thrift wrote:


On Sunday, December 9, 2018 at 8:43:59 PM UTC-6, Jason wrote:



    On Sun, Dec 9, 2018 at 2:02 PM Philip Thrift <[email protected]
    <javascript:>> wrote:



        On Sunday, December 9, 2018 at 9:36:39 AM UTC-6, Jason wrote:



            On Sun, Dec 9, 2018 at 2:53 AM Philip Thrift
            <[email protected]> wrote:



                On Saturday, December 8, 2018 at 2:27:45 PM UTC-6,
                Jason wrote:


                    I think truth is primitive.

                    Jason



                As a matter of linguistics (and philosophy), *truth*
                and *matter* are linked:

                "As a matter of fact, ..."
                "The truth of the matter is ..."
                "It matters that ..."
                ...
                [ https://www.etymonline.com/word/matter
                <https://www.etymonline.com/word/matter> ]


            I agree they are linked.  Though matter may be a few
            steps removed from truth.  Perhaps one way to interpret
            the link more directly is thusly:

            There is an equation whose every solution (where the
            equation happens to be */true/*, e.g. is satisfied when
            it has certain values assigned to its variables) maps
            its variables to states of the time evolution of the
            wave function of our universe.  You might say that we
            (literally not figuratively) live within such an
            equation.  That its truth reifies what we call matter.

            But I think truth plays an even more fundamental roll
            than this.  e.g. because the following statement is
            */true/* "two has a successor" then there exists a
            successor to 2 distinct from any previous number. 
            Similarly, the */truth/* of "9 is not prime" implies the
            existence of a factor of 9 besides 1 and 9.

            Jason



                Schopenhauer 's view: "A judgment has /material
                truth/ if its concepts are based on intuitive
                perceptions that are generated from sensations. If a
                judgment has its reason (ground) in another
                judgment, its truth is called logical or formal. If
                a judgment, of, for example, pure mathematics or
                pure science, is based on the forms (space, time,
                causality) of intuitive, empirical knowledge, then
                the judgment has transcendental truth."
                [ https://en.wikipedia.org/wiki/Truth
                <https://en.wikipedia.org/wiki/Truth> ]


            I guess I am referring to transcend truth here. Truth
            concerning the integers is sufficient to yield the
            universe, matter, and all that we see around us.

            Jason




        In my view there is basically just *material* (from matter)
        truth and *linguistic* (from language) truth.

        [
        https://codicalist.wordpress.com/2018/06/18/to-tell-the-truth/
        <https://codicalist.wordpress.com/2018/06/18/to-tell-the-truth/>
        ]

        Relations and functions are linguistic: relational type
        theory (RTT) , functional type theory (FTT) languages.

        Numbers are also linguistic beings, the (fictional) semantic
        objects of Peano arithmetic (PA).

        Numbers can be "materialized" via /nominalization /(cf.
        Hartry Field, refs. in [
        https://en.wikipedia.org/wiki/Hartry_Field
        <https://en.wikipedia.org/wiki/Hartry_Field> ]).


    Assuming the primacy of matter assumes more and explains less,
    than assuming the primacy of arithmetical truth.

    Jason




In today's era of mathematics, Joel David Hamkins (@JDHamkins <https://twitter.com/JDHamkins>) has shown there is a "multiverse" of truths:

*The set-theoretic multiverse*
[ https://arxiv.org/abs/1108.4223 ]

/The multiverse view in set theory, introduced and argued for in this article, is the view that there are many distinct concepts of set, each instantiated in a corresponding set-theoretic universe. The universe view, in contrast, asserts that there is an absolute background set concept, with a corresponding absolute set-theoretic universe in which every set-theoretic question has a definite answer. The multiverse position, I argue, explains our experience with the enormous diversity of set-theoretic possibilities, a phenomenon that challenges the universe view. In particular, I argue that the continuum hypothesis is settled on the multiverse view by our extensive knowledge about how it behaves in the multiverse, and as a result it can no longer be settled in the manner formerly hoped for.
/
/
/
/
/
What this means is that for mathematics (a language category), truth depends on the language.

I think Hamkins could say the same thing in French.  His example of the continuum hypothesis just says that by adding as axioms different undecidable propositions we get different sets of theorems.  He doesn't use the word "truth" and I think with good reason.  Theorems in mathematics aren't "true" in any normal sense of the word.  What is true is that the axioms imply the theorem...given the rules of inference.

By incompleteness truth is bigger than what *any* consistent can prove. Of course you can say that the meaning of

      [Exyz(x^3 + y^3 + z^3 = 33) v ~ (Exyz(x^3 + y^3 + z^3 = 33))

Is true because it is an substitution instance of the tautology A v ~A.

Which is exactly what I'd say; and is the only way that you can know it is true.

But you can also reflect on this, and believe it is true, because either such numbers do exist, or they don’t.

The phrase following "because" is just rephrasing A v ~A.

But "Exyz(x^3 + y^3 + z^3 = 33) “ is an open problem. Such open problem would not make sense if you define truth by proof.

Many mathematicians would say you have */discovered/* it.  But you could only discover it by finding a proof  I don't define truth by proof.  You can prove what is false just by choice of axioms.  So having a proof doesn't prove the conclusion is true; it only shows that it is true that the conclusion follows from the premises.


Recently I have proven that TOT (the set of Gödel numbers of the codes of the total computable function is not recursively enumerable. That proofs would have no meaning if truth = proof. Intuitionism is recovered in Mechanism as the particular first person solipsistic view ([]p & p, S4Grz1).

Many mathematicians would say you have */discovered/* it.  But you could only discover it by finding a proof.


In mathematical logic, we study since long the difference between proof and truth (satisfied by a reality).

Yes, you create a whole theology around not all truths are provable.  But you ignore that what is false is also provable. Provable is only relative to axioms.

Brent


Bruno

PS I will use the word “reality" instead of “model", as most physicisst continue to use “model” for theories.





Brent

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