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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 286 32

  2. Catalogue Catalogue Public

    Catalogue of FFL

    Lean 1 1

Repositories

Showing 10 of 27 repositories
  • Foundation Public

    Formalization of Mathematical Logic

    FormalizedFormalLogic/Foundation's past year of commit activity
    Lean 286 Apache-2.0 32 27 14 Updated Oct 1, 2026
  • AlphaCentauri Public

    Auto-formalization by AI/LLM in scope of metamathematics of arithmetic

    FormalizedFormalLogic/AlphaCentauri's past year of commit activity
    Lean 0 Apache-2.0 0 40 2 Updated Oct 1, 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 1 Updated Sep 29, 2026
  • forgive Public

    Check the sorry for Lean4 library

    FormalizedFormalLogic/forgive's past year of commit activity
    Lean 0 Apache-2.0 1 0 0 Updated Sep 26, 2026
  • formalizedformallogic.github.io Public

    FFL website

    FormalizedFormalLogic/formalizedformallogic.github.io's past year of commit activity
    0 CC-BY-4.0 0 0 0 Updated Sep 23, 2026
  • ProvabilityLogic Public

    Lean 4 Mechanization about Provability Logics

    FormalizedFormalLogic/ProvabilityLogic's past year of commit activity
    Lean 6 Apache-2.0 1 4 3 Updated Sep 23, 2026
  • FormalizedFormalLogic/Mechanizing-Godels-Incompleteness-Theorems-and-Provability-Logic's past year of commit activity
    Typst 1 CC-BY-SA-4.0 0 0 0 Updated Sep 23, 2026
  • .github Public

    Formalized Formal Logic

    FormalizedFormalLogic/.github's past year of commit activity
    0 0 0 0 Updated Sep 22, 2026
  • LinearLogic Public

    Formalization of Linear Logic

    FormalizedFormalLogic/LinearLogic's past year of commit activity
    Lean 0 Apache-2.0 1 0 2 Updated Sep 12, 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

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