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    Kreisel's squeezing argument and Shapiro's categoricity r... — Carmelics
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    Challenges→Truth in second-order logic ('M ⊨_s φ') is not an absolute property relative to ZFC.

    Kreisel's squeezing argument and Shapiro's categoricity results suggest second-order logical consequence has a determinate extension fixed by the standard semantics, independent of set-theoretic indeterminacy.

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    Key Terms

    Categoricity results(as mathematical results Shapiro proved)
    Mathematical theorems showing that a particular description or set of rules picks out exactly one structure, with nothing left ambiguous.
    Kreisel(as a historical figure in logic and philosophy of mathematics)
    Georg Kreisel (1923–2015), a mathematical logician who studied how mathematical reasoning works and whether we can be certain about mathematical truths.
    Second-order logic(as used in mathematical logic)
    A formal system that goes beyond basic logic by allowing you to quantify over (talk about) properties and relations themselves, not just individual objects.
    Set-theoretic indeterminacy(what Shapiro claims explains AC-independence)
    A genuine lack of determinedness or definiteness in the basic mathematical objects (sets) themselves, not just in how we talk about them.

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    Shapiro(The statement refers to her specific theoretical requirements)
    A philosopher (Laurie Shapiro) who studies the philosophy of mind and cognitive science; she has argued specific criteria for when we should consider something a real scientific category.
    Standard semantics(as a way of interpreting logical systems)
    The most straightforward interpretation of what logical statements mean in terms of the real world—basically, the 'normal' way of understanding truth.
    determinate extension(as used in philosophy of language and metaphysics)
    Having clear, definable boundaries—knowing exactly what things count as examples of something and what doesn't.
    logical consequence(WL II, 391–395; noted as similar to Tarski 1956, 419)
    A proposition s is a logical consequence of a set of premises σ if and only if s follows from σ with respect to the sequence of all extra-logical simple ideas contained in σ or s.
    squeezing argument(philosophy of logic)
    Kreisel's argument that uses proof theory to support the model-theoretic definition of logical consequence, depending on the language having a sound and complete proof system

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    Truth & Knowledge1 linkedPhilosophy of Language1 linked

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    Truth in second-order logic ('M ⊨_s φ') is not an absolute property relative to ...

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