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Proof of incompleteness theorem via derivability conditions #1

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@SnO2WMaN SnO2WMaN force-pushed the provability branch 4 times, most recently from 07a1657 to 18b3d19 Compare November 23, 2023 17:20
@iehality iehality marked this pull request as ready for review December 4, 2023 16:19
@SnO2WMaN SnO2WMaN force-pushed the provability branch 2 times, most recently from bcf6845 to 8ea471c Compare December 5, 2023 23:57
Comment on lines +30 to +33
have : Subtheory T₀ (T ∪ {~σ}) := by sorry;
have : Derivability1 T₀ (T ∪ {~σ}) := by sorry;
have : Derivability2 T₀ (T ∪ {~σ}) := by sorry;
have : Derivability3 T₀ (T ∪ {~σ}) := by sorry;
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明らかに導出可能性条件は保存されるはず

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PropositionalCalculusの部分はLogic.Logic.HilbertStyleに移してもいいと思う

Comment on lines 147 to 148
lemma existsKreiselSentence [hdef : Definable.Sigma T n] (σ)
: ∃ (K : Sentence ℒₒᵣ), IsKrieselSentence T₀ T K σ := by sorry
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@SnO2WMaN SnO2WMaN Dec 6, 2023

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Löbの定理を第2不完全性定理を用いずに示すためにこの補題が必要だが,代入に関する問題(Subsentenceの束縛されていない変数の数が合わない?)で上手く出来なかった記憶がある

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HilbertStyleの補題を使っている証明をhttps://github.com/iehality/lean4-logic/blob/master/Logic/AutoProver/Prover.leanby prover [ ... ]タクティックで置き換えられないだろうか?

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