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@FormalizedFormalLogic

Formalized Formal Logic

Formalize Formal Logic in Lean4

Formalized Formal Logic

Formalize formal logic (mathematical logic) in Lean Theorem Prover.

Our main repository is Foundation. See Catalogue (In progress) and Doc for more results and details.

  • Propositional Logic
    • Completeness for Classical Logic
    • Kripke Semantics for Intuitionistic Logics and Superintuitionistic Logics.
  • Intuitionistic and Classical First-Order Logic
    • Arithmetic and Set Theory
    • Completeness Theorem
    • Cut-elimination of First-Order Sequent Calculus (Gentzen's Hauptsatz)
    • Gödel's First and Second Incompleteness Theorems
    • Solovay's Arithmetical Completeness Theorem
  • Basic Modal Logic (with modal operators $\Box, \Diamond$)
    • Kripke Semantics and Completeness
    • Modal Cube
    • Modal Companion
    • Provability Logic
  • Interpretability Logic

Developers

  • Palalansoukî (Shogo Saito, @iehality, ✉️:palalansouki@gmail.com)
    • Overall design and maintenance.
    • First-order logic.
    • Intuitionistic first-order logic.
    • Proof automation.
    • Provability logic.
  • SnO2WMaN (Mashu Noguchi, @SnO2WMaN, ✉️:me@sno2wman.net)
    • Modal logic.
    • Propositional logic (including intermediate logic).
    • Provability logic.
    • Interpretability Logic.
    • Miscellaneous repository maintenance (e.g. GitHub Actions)

Financial Supports

Any financial supports would be grateful for us. If you found this project valuable, to sustain our OSS development, please consider support us.

Open Collective

Open Collective

We would like to thanks the following backers.

Open Collective Backers

Previous Backers

Individuals and organizations that have supported us in the past.

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  1. Foundation Foundation Public

    Formalization of Mathematical Logic

    Lean 272 31

  2. Catalogue Catalogue Public

    Catalogue of FFL

    Lean 1 1

Repositories

Showing 10 of 25 repositories
  • AlphaCentauri Public

    Auto-formalization by AI in scope of Arithmetic

    FormalizedFormalLogic/AlphaCentauri's past year of commit activity
    Lean 0 1 18 2 Updated Sep 10, 2026
  • LinearLogic Public

    Formalization of Linear Logic

    FormalizedFormalLogic/LinearLogic's past year of commit activity
    Lean 0 Apache-2.0 0 0 1 Updated Sep 10, 2026
  • Foundation Public

    Formalization of Mathematical Logic

    FormalizedFormalLogic/Foundation's past year of commit activity
    Lean 272 Apache-2.0 31 25 9 Updated Sep 10, 2026
  • ProvabilityLogic Public

    Lean 4 Mechanization about Provability Logics

    FormalizedFormalLogic/ProvabilityLogic's past year of commit activity
    Lean 6 Apache-2.0 1 0 1 Updated Sep 7, 2026
  • VeryWeakSubintuitionistic Public

    Formalization of Very Weak Subintuitionistic Logics

    FormalizedFormalLogic/VeryWeakSubintuitionistic's past year of commit activity
    Lean 0 Apache-2.0 0 0 0 Updated Aug 28, 2026
  • goodstein-independence Public

    EXPERIMENTAL: Kirby-Paris Theorem formalized in Lean 4

    FormalizedFormalLogic/goodstein-independence's past year of commit activity
    Lean 4 Apache-2.0 2 1 2 Updated Aug 23, 2026
  • NonClassicalModalLogic Public

    Lean4 Formalization of Non-Classical Modal Logic

    FormalizedFormalLogic/NonClassicalModalLogic's past year of commit activity
    Lean 1 Apache-2.0 0 0 1 Updated Aug 22, 2026
  • ModalLogic Public

    Formalization of Modal Logic

    FormalizedFormalLogic/ModalLogic's past year of commit activity
    Lean 0 Apache-2.0 0 23 0 Updated Aug 1, 2026
  • YabloParadox Public

    Formalization of Yablo's paradox and arithmetized Version

    FormalizedFormalLogic/YabloParadox's past year of commit activity
    Lean 0 0 0 0 Updated Jul 12, 2026
  • FormalizedFormalLogic/InterpretabilityLogic's past year of commit activity
    Lean 0 Apache-2.0 0 0 0 Updated Jul 8, 2026