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Results tagged with lo.logic
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user 142409
first-order and higher-order logic, model theory, set theory, proof theory, computability theory, formal languages, definability, interplay of syntax and semantics, constructive logic, intuitionism, philosophical logic, modal logic, completeness, Gödel incompleteness, decidability, undecidability, theories of truth, truth revision, consistency.
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Are there quantifiers that require multiple "steps" to define?
The quantifier $\exists^\infty$ is not definable over $\mathcal{L}_0$.
To prove it, we show that a sentence $S$ tautologised by $\exists^\infty$ is also a tautology for the "always false" quantifier $ …
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