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    Skolem's paradox reveals that 'truth in all models' is mo... — Carmelics
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    Challenges→Sentences proved from first-order axioms are true in all models of those axioms, including countable models and non-standard models

    Skolem's paradox reveals that 'truth in all models' is model-relative: a sentence about uncountability can be true in the intended model yet satisfied in a countable model via different satisfaction relations.

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    Key Terms

    Countable(as describing the size of these unintended models)
    Able to be listed or matched up with the counting numbers (1, 2, 3...), even if the list is infinite; basically, not too large or weird to count in principle.
    Model (in logic)(in formal logic and semantics)
    An imaginary scenario or description of a possible world where certain statements are true or false—used to test whether logical arguments work.
    Satisfaction relation (in logic)(explaining that different models satisfy the same sentence in different ways)
    The relationship between a logical statement and a model that determines whether the statement is true in that model—it's the 'way' in which something makes a statement true.
    Skolem
    # Skolem Skolem refers to Thoralf Skolem, a Norwegian mathematician (1887-1963) who made important discoveries in logic and the foundations of mathematics. He's best known for the "Löwenheim-Skolem theorem," which essentially states that if a mathematical statement can be true in one infinite structure, it can also be true in a simpler, countably infinite structure—a surprising result that challenged assumptions about the nature of mathematical truth. His work fundamentally shaped modern logic and showed surprising limitations in how precisely mathematical languages can describe reality.

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    Skolem's Paradox(mathematical logic / set theory)
    The apparent paradox that arises because a countable model of ZFC can internally satisfy the theorem that uncountable sets exist, despite the model's domain being countable from an external perspective
    Uncountability(as the property being discussed in the sentence)
    A quality of infinite sets that are so large they can't be listed or matched up with regular counting numbers, no matter how hard you try (like the infinity of all real numbers).
    intended model(Model theory / philosophy of mathematics)
    The canonical structure that a theory is meant to describe; for ZFC, this is the proper class V with the ∈ relation
    model-relative(describing properties in logic and mathematics)
    Dependent on which particular version or interpretation of a system you're looking at; something can be true in one model but not in another.

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    Proof of definition segments1 linkedTruth & Knowledge1 linked

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    Sentences proved from first-order axioms are true in all models of those axioms,...

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