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    In NFU, only stratified definitions give rise to sets. — Carmelics
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    Supports→The apparent bijection x ↦ {x} between ℘₁(V) and V cannot be a set in NFU.

    In NFU, only stratified definitions give rise to sets.

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    Related propositions within the same area of thought.
    The apparent bijection x ↦ {x} between ℘₁(V) and V cannot be a set in NFU.The map x ↦ {x} has an unstratified definition.There is no expectation that an unstratified definition yields a set.

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    Axioms implicitly define mathematical concepts without a positive pred...77%There is no expectation that an unstratified definition yields a set.75%The implicit definition of sets is problematic because it permits defi...74%There are many distinct concepts of set, each determining its own univ...74%

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    The Cantor theorem of the usual set theory asserts that \(|A| \lt |\wp(A)|\). This is clearly not true in NFU, since | \(V|\) is the cardinality of the universe and \(|\wp(V)|\) is the cardinality of the set of sets, and in fact \(|V| \gt \gt |\wp(V)|\) in all known models of NFU (there are many intervening cardinals in all such models). But \(|A| \lt |\wp(A)|\) does not make sense in TST: it is ill-typed. The correct theorem in TST, which is inherited by NFU, is \(|\wp_1 (A)| \lt |\wp(A)|\), wh

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