Unprovable flon
LO.FirstOrder.ProvabilityAbstraction.unprovable_flon
Project documentation
Formalized law of noncontradiction cannot be proved. Alternative formulation of GΓΆdel's second incompleteness theorem.
Exact Lean statement
lemma unprovable_flon [consis : Consistent T] [π .FormalizedCompleteOn π] : T β¬ flon π π
Formal artifact
Lean source
lemma unprovable_flon [consis : Consistent T] [π
.FormalizedCompleteOn π] : T β¬ flon π
π := by contrapose! consis; replace consis : T β’ βΒΉ safe π
π := by simpa [flon] using consis; have hβ : T β’ βΌ(π
π β π π) := by simpa [safe] using! FirstOrder.Theory.Proof.specialize _ _ β¨ consis; have hβ : T β’ βΌπ := (contra! jeroslow_not_safe) β¨ hβ; have hβ : T β’ π π‘ π π := jeroslow_def'; have hβ : T β’ π π := R1' hβ; have hβ
: T β’ π π π‘ π := by cl_prover [hβ]; have hβ : T β’ π := hβ
β¨ hβ; exact not_consistent_iff_inconsistent.mpr <| inconsistent_iff_provable_bot.mpr $ (N!_iff_CO!.mp hβ) β¨ hβ;- Project
- Foundation
- License
- Apache-2.0
- Commit
- 8dcdb3196454
- Source
- Foundation/FirstOrder/Incompleteness/ProvabilityAbstraction/Refutability.lean:116-125
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