Combining Texts
Ideas for
'Letter to Herodotus', 'Necessary Beings' and 'Introduction to Zermelo's 1930 paper'
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5 ideas
4. Formal Logic / D. Modal Logic ML / 7. Barcan Formula
19297
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The two Barcan principles are easily proved in fairly basic modal logic [Hale]
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19301
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With a negative free logic, we can dispense with the Barcan formulae [Hale]
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4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / a. Axioms for sets
17833
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The first-order ZF axiomatisation is highly non-categorical [Hallett,M]
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17834
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Non-categoricity reveals a sort of incompleteness, with sets existing that the axioms don't reveal [Hallett,M]
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4. Formal Logic / F. Set Theory ST / 7. Natural Sets
17837
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Zermelo allows ur-elements, to enable the widespread application of set-theory [Hallett,M]
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