• Moliere
    4.2k
    To that I'd say that logic excludes temporality. Not that it should do so -- but that's the idea. Temporality is introduced through the power of English semantics. (We get the liar's paradox as well, with that)
  • Michael
    14.6k
    In Tarski's case, by separating the metalanguage from the object language, so that such self-referential sentences cannot be constructed.Banno

    So it has limited applicability to natural languages as self-referential sentences can be constructed in English.

    What theory of truth is able to make sense of the English sentence "this sentence has thirty one letters" being true then?
  • Banno
    23.6k
    "this sentence is false" is true iff this sentence is falseMichael

    Remember this?

    a) "snow is white" is true iff snow is white
    b) "snow is green" is true iff snow is green
    Michael

    Whatever happens with liar, true or false, the T-sentence is true.

    Indeed, if one adopts a third truth value, between true and false, the T-sentence remains true.
  • Banno
    23.6k
    I started a thread specifically on Tarski and the formal logic of truth.
  • Banno
    23.6k
    You are tying a knot where one is not needed.

    "this sentence has thirty one letters" is in the object language.

    In the metalanguage, we name that sentence "Fred". Fred is true if Fred had thirty one letters.

    Fred has thirty one letters.

    Fred is true.
  • creativesoul
    11.6k


    Sure. I situate logic differently in that logic is an accounting practice. When taking account of that which already existed in its entirety prior to being taken into account, different sort of considerations arise... Such considerations are only established more along the lines of a priori reasoning.

    Banno calls me an anti-realist as a result of the stance I take regarding what sorts of things can be true and what makes them so. A prediction is neither true nor false at the time it is made because it is about what has not yet happened. Correspondence to(consistency with) what has happened(fact, in the original sense of "true") plays a major role in my thinking. Seems to me that most academic circles realize that any substantial notion of truth needs to be able to account for or be amenable to correspondence... somehow.
  • Banno
    23.6k
    The liar's paradox is not capable of being true or false.creativesoul

    And yet, amusingly, even if this is so, because it is a conditional, ("this sentence is false" is true iff this sentence is false) is true.
  • Michael
    14.6k
    You are tying a knot where one is not needed.

    "this sentence has thirty one letters" is in the object language.

    In the metalanguage, we name that sentence "Fred". Fred is true if Fred had thirty one letters.

    Fred has thirty one letters.

    Fred is true.
    Banno

    OK, but this is no longer deflation/disquotation/the T-schema, which are all just "p" is true iff p.

    Your account now is "p" is true iff q.
  • creativesoul
    11.6k


    The reason why the Liar is not truth apt is because it has no truth conditions.
  • Moliere
    4.2k

    I entertain dialethism, but actually the liar's paradox is one of the things I think I've come around on in saying it's not dialethic. Or, it can be, but that depends on the rules of logic we're willing to allow.

    Not like that's a definite belief, as @Sam26 pointed out. Still thinking through that one.

    But unsurprisingly, I'm not opposed to dialethism.
  • Banno
    23.6k
    Sure. But if it were true, the T-sentence would be true.
  • Banno
    23.6k
    Well, do that and you get antirealism thrown in for free.
  • Banno
    23.6k
    Your account now is "p" is true iff q.Michael

    It always was. Putting p on both sides is a special case.


    Edit: See here.
  • Moliere
    4.2k
    Yeh, an unsatisfactory result, though. A kind of anti-realism that no one would really want.
  • Sam26
    2.6k
    "The whole is greater than the sum of the parts" is true ≡ The whole is greater than the sum of the parts.
    To what does this correspond?

    "Frodo walked in to Mordor" is true ≡ Frodo walked in to Mordor.
    To what does this correspond?

    "Frodo walked in to Sydney" is true ≡ Frodo walked in to Sydney.
    To what does this correspond?

    "No bachelor is married" is true ≡ No bachelor is married.
    To what does this correspond?

    "All bachelors are married" is true ≡ all bachelors are married.
    To what does this correspond?

    "This sentence is false" is true ≡ this sentence is false
    To what does this correspond?
    Banno

    Each of these can be answered, I don't see a problem. But to think that "p is true, if and only if p" is some kind of answer, is to say nothing meaningful, it's tautological, and that's being kind. Is this how you learned to use the concept true? I took a philosophy class by Tarski and now I know what truth is. Most of that theory is just so convoluted. I get much more out of Wittgenstein's ideas, even if there are some problems, than theories like Tarski's.
  • Michael
    14.6k
    Your account now is "p" is true iff q.Michael

    It always was. Putting p on both sides is a special case.Banno

    Then it just seems to be saying that "p" is true iff its truth conditions obtain which is a pretty vacuous theory. So as I said earlier, a more substantial account of truth is needed. Correspondence, coherence, verificationism, etc.
  • Luke
    2.6k
    The reason why the Liar is not truth apt is because it has no truth conditions.creativesoul

    "This sentence" is true iff this sentence.
  • creativesoul
    11.6k
    ...logic excludes temporality. Not that it should do so -- but that's the idea.Moliere

    That's a flaw in my view for what it is attempting to take into account does not always exclude temporality.
  • Moliere
    4.2k
    "this sentence" is not well formed. It does not fit the form of a proposition. It is only a subject, and contains no predicate.
  • creativesoul
    11.6k


    Not even sure what you're trying to do there...
  • Moliere
    4.2k
    Ah, OK. I misread.
  • Sam26
    2.6k
    There is no fact of the matter in that sentence. Many of these kinds of paradox's don't amount to a hill of beans.
  • Moliere
    4.2k
    One advantage of excluding temporality is that we can then discuss what we mean by temporality. If the logic we employ uses temporality, then there are views that are likely to be ignored, given that people think of that differently.

    It is a kind of game. But, then, I am saying logic is a kind of game, more or less.
  • Luke
    2.6k
    Just using "is true" as we normally do.
  • Sam26
    2.6k
    You also find this in the Gettier examples, a bit different, but essentially same.
  • Banno
    23.6k
    Two very different questions that keep being mixed up:

    • What is "true"?
    • What sentences are true?

    T-sentences answer the first.

    @Sam26 answered the second, but few noticed.
  • Banno
    23.6k
    logic excludes temporalityMoliere

    That's a flaw in my viewcreativesoul

    It needn't. See Indexicals and Temporal Logic

    So that criticism of logic falls flat on its face.
  • Moliere
    4.2k
    Heh. Well, I have more reading assignments then.
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